Hubble and ESO's VLT provide unique 3D views of remote galaxies

NASA Astrophysics Data System (ADS)

2009-03-01

Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age, by combining the twin strengths of the NASA/ESA Hubble Space Telescope's acute eye, and the capacity of ESO's Very Large Telescope to probe the motions of gas in tiny objects. By looking at this unique "history book" of our Universe, at an epoch when the Sun and the Earth did not yet exist, scientists hope to solve the puzzle of how galaxies formed in the remote past. ESO PR Photo 10a/09 A 3D view of remote galaxies ESO PR Photo 10b/09 Measuring motions in 3 distant galaxies ESO PR Video 10a/09 Galaxies in collision For decades, distant galaxies that emitted their light six billion years ago were no more than small specks of light on the sky. With the launch of the Hubble Space Telescope in the early 1990s, astronomers were able to scrutinise the structure of distant galaxies in some detail for the first time. Under the superb skies of Paranal, the VLT's FLAMES/GIRAFFE spectrograph (ESO 13/02) -- which obtains simultaneous spectra from small areas of extended objects -- can now also resolve the motions of the gas in these distant galaxies (ESO 10/06). "This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones," says François Hammer, who led the team. "In effect, FLAMES/GIRAFFE now allows us to measure the velocity of the gas at various locations in these objects. This means that we can see how the gas is moving, which provides us with a three-dimensional view of galaxies halfway across the Universe." The team has undertaken the Herculean task of reconstituting the history of about one hundred remote galaxies that have been observed with both Hubble and GIRAFFE on the VLT. The first results are coming in and have already provided useful insights for three galaxies. In one galaxy, GIRAFFE revealed a region full of ionised gas, that is, hot gas composed of atoms that have been stripped of one or several electrons. This is normally due to the presence of very hot, young stars. However, even after staring at the region for more than 11 days, Hubble did not detect any stars! "Clearly this unusual galaxy has some hidden secrets," says Mathieu Puech, lead author of one of the papers reporting this study. Comparisons with computer simulations suggest that the explanation lies in the collision of two very gas-rich spiral galaxies. The heat produced by the collision would ionise the gas, making it too hot for stars to form. Another galaxy that the astronomers studied showed the opposite effect. There they discovered a bluish central region enshrouded in a reddish disc, almost completely hidden by dust. "The models indicate that gas and stars could be spiralling inwards rapidly," says Hammer. This might be the first example of a disc rebuilt after a major merger (ESO 01/05). Finally, in a third galaxy, the astronomers identified a very unusual, extremely blue, elongated structure -- a bar -- composed of young, massive stars, rarely observed in nearby galaxies. Comparisons with computer simulations showed the astronomers that the properties of this object are well reproduced by a collision between two galaxies of unequal mass. "The unique combination of Hubble and FLAMES/GIRAFFE at the VLT makes it possible to model distant galaxies in great detail, and reach a consensus on the crucial role of galaxy collisions for the formation of stars in a remote past," says Puech. "It is because we can now see how the gas is moving that we can trace back the mass and the orbits of the ancestral galaxies relatively accurately. Hubble and the VLT are real ‘time machines' for probing the Universe's history", adds Sébastien Peirani, lead author of another paper reporting on this study. The astronomers are now extending their analysis to the whole sample of galaxies observed. "The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over the past six to eight billion years, that is, over half the age of the Universe," concludes Hammer.

Galaxies Gather at Great Distances

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Distant Galaxy Cluster Infrared Survey Poster [figure removed for brevity, see original site] [figure removed for brevity, see original site] Bird's Eye View Mosaic Bird's Eye View Mosaic with Clusters [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] 9.1 Billion Light-Years 8.7 Billion Light-Years 8.6 Billion Light-Years

Astronomers have discovered nearly 300 galaxy clusters and groups, including almost 100 located 8 to 10 billion light-years away, using the space-based Spitzer Space Telescope and the ground-based Mayall 4-meter telescope at Kitt Peak National Observatory in Tucson, Ariz. The new sample represents a six-fold increase in the number of known galaxy clusters and groups at such extreme distances, and will allow astronomers to systematically study massive galaxies two-thirds of the way back to the Big Bang.

A mosaic portraying a bird's eye view of the field in which the distant clusters were found is shown at upper left. It spans a region of sky 40 times larger than that covered by the full moon as seen from Earth. Thousands of individual images from Spitzer's infrared array camera instrument were stitched together to create this mosaic. The distant clusters are marked with orange dots.

Close-up images of three of the distant galaxy clusters are shown in the adjoining panels. The clusters appear as a concentration of red dots near the center of each image. These images reveal the galaxies as they were over 8 billion years ago, since that's how long their light took to reach Earth and Spitzer's infrared eyes.

These pictures are false-color composites, combining ground-based optical images captured by the Mosaic-I camera on the Mayall 4-meter telescope at Kitt Peak, with infrared pictures taken by Spitzer's infrared array camera. Blue and green represent visible light at wavelengths of 0.4 microns and 0.8 microns, respectively, while red indicates infrared light at 4.5 microns.

Kitt Peak National Observatory is part of the National Optical Astronomy Observatory in Tuscon, Ariz.

Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5

NASA Astrophysics Data System (ADS)

Ebeling, Harald

2017-08-01

Truly massive galaxy clusters play a pivotal role for a wealth of extragalactic and cosmological research topics, and SNAPshot observations of these systems are ideally suited to identify the most promising cluster targets for further, in-depth study. The power of this approach was demonstrated by ACS/WFC3 SNAPshots of X-ray selected MACS and eMACS clusters at z>0.3 obtained by us in previous Cycles (44 of them in all of F606W, F814W, F110W, and F140W). Based on these data, the CLASH MCT program selected 16 out of 25 of their targets to be MACS clusters. Similarly, all but one of the six most powerful cluster lenses selected for in-depth study by the HST Frontier Fields initiative are MACS detections, and so are 16 of the 29 z>0.3 clusters targeted by the RELICS legacy program.We propose to extend our spectacularly successful SNAPshot survey of the most X-ray luminous distant clusters to a redshift-mass regime that is poorly sampled by any other project. Targeting only extremely massive clusters at z>0.5 from the X-ray selected eMACS sample (median velocity dispersion: 1180 km/s), the proposed program will (a) identify the most powerful gravitational telescopes at yet higher redshift for the next generation of in-depth studies of the distant Universe with HST and JWST, (b) provide constraints on the mass distribution within these extreme systems, (c) help improve our understanding of the physical nature of galaxy-galaxy and galaxy-gas interactions in cluster cores, and (d) unveil Balmer Break Galaxies at z 2 and Lyman-break galaxies at z>6 as F814W dropouts.Acknowledging the broad community interest in our sample we waive our data rights for these observations.

MOSAIC: A Multi-Object Spectrograph for the E-ELT

NASA Astrophysics Data System (ADS)

Kelz, A.; Hammer, F.; Jagourel, P.; MOSAIC Consortium

2016-10-01

The instrumentation plan for the European Extremely Large Telescope foresees a Multi-Object Spectrograph (E-ELT MOS). The MOSAIC project is proposed by a European-Brazilian consortium, to provide a unique MOS facility for astrophysics, studies of the inter-galactic medium and for cosmology. The science cases range from spectroscopy of the most distant galaxies, mass assembly and evolution of galaxies, via resolved stellar populations and galactic archaeology, to planet formation studies. A further strong driver is spectroscopic follow-up observations of targets that will be discovered with the James Webb Space Telescope.

TEMPLATES: Targeting Extremely Magnified Panchromatic Lensed Arcs and Their Extended Star formation

NASA Astrophysics Data System (ADS)

Spilker, Justin; Rigby, Jane R.; Vieira, Joaquin D.; TEMPLATES Team

2018-06-01

TEMPLATES is a JWST Early Release Science program designed to produce high signal-to-noise imaging and IFU spectroscopic data cubes for four gravitationally lensed galaxies at high redshift. The program will spatially resolve the star formation in galaxies across the peak of cosmic star formation in an extinction-robust manner. Lensing magnification pushes JWST to the highest spatial resolutions possible at these redshifts, to map the key spectral diagnostics of star formation and dust extinction: H-alpha, Pa-alpha, and 3.3um PAH emission within individual distant galaxies. Our targets are among the brightest, best-characterized lensed systems known, and include both UV-bright 'normal' galaxies and heavily dust-obscured submillimeter galaxies, at a range of stellar masses and luminosities. I will describe the scientific motivation for this program, detail the targeted galaxies, and describe the planned data products to be delivered to the community in advance of JWST Cycle 2.

Estimating sizes of faint, distant galaxies in the submillimetre regime

NASA Astrophysics Data System (ADS)

Lindroos, L.; Knudsen, K. K.; Fan, L.; Conway, J.; Coppin, K.; Decarli, R.; Drouart, G.; Hodge, J. A.; Karim, A.; Simpson, J. M.; Wardlow, J.

2016-10-01

We measure the sizes of redshift ˜2 star-forming galaxies by stacking data from the Atacama Large Millimeter/submillimeter Array (ALMA). We use a uv-stacking algorithm in combination with model fitting in the uv-domain and show that this allows for robust measures of the sizes of marginally resolved sources. The analysis is primarily based on the 344 GHz ALMA continuum observations centred on 88 submillimetre galaxies in the LABOCA ECDFS Submillimeter Survey (ALESS). We study several samples of galaxies at z ≈ 2 with M* ≈ 5 × 1010 M⊙, selected using near-infrared photometry (distant red galaxies, extremely red objects, sBzK-galaxies, and galaxies selected on photometric redshift). We find that the typical sizes of these galaxies are ˜0.6 arcsec which corresponds to ˜5 kpc at z = 2, this agrees well with the median sizes measured in the near-infrared z band (˜0.6 arcsec). We find errors on our size estimates of ˜0.1-0.2 arcsec, which agree well with the expected errors for model fitting at the given signal-to-noise ratio. With the uv-coverage of our observations (18-160 m), the size and flux density measurements are sensitive to scales out to 2 arcsec. We compare this to a simulated ALMA Cycle 3 data set with intermediate length baseline coverage, and we find that, using only these baselines, the measured stacked flux density would be an order of magnitude fainter. This highlights the importance of short baselines to recover the full flux density of high-redshift galaxies.

A VLT Large Programme to Study Galaxies at z ~ 2: GMASS — the Galaxy Mass Assembly Ultra-deep Spectroscopic Survey

NASA Astrophysics Data System (ADS)

Kurk, Jaron; Cimatti, Andrea; Daddi, Emanuele; Mignoli, Marco; Bolzonella, Micol; Pozzetti, Lucia; Cassata, Paolo; Halliday, Claire; Zamorani, Gianni; Berta, Stefano; Brusa, Marcella; Dickinson, Mark; Franceschini, Alberto; Rodighiero, Guilia; Rosati, Piero; Renzini, Alvio

2009-03-01

We report on the motivation, sample selection and first results of our VLT FORS2 Large Programme (173.A-0687), which has obtained the longest targeted spectra of distant galaxies obtained so far with the VLT. These long exposures, up to 77 hours for objects included in three masks, were required to detect spectral features of extremely faint galaxies, such as absorption lines of passive galaxies at z > 1.4, a population that had previously escaped attention due to its faintness in the optical wavelength regime, but which represents a critical phase in the evolution of massive galaxies. The ultra-deep spectroscopy allowed us to estimate the stellar metallicity of star-forming galaxies at z ~ 2, to trace colour bimodality up to z = 2 and to characterise a galaxy cluster progenitor at z = 1.6. The approximately 200 spectra produced by GMASS constitute a lasting legacy, populating the “redshift desert” in GOODS-S.

Hubble’s cross-section of the cosmos

NASA Image and Video Library

2014-04-17

This new Hubble image showcases a remarkable variety of objects at different distances from us, extending back over halfway to the edge of the observable Universe. The galaxies in this image mostly lie about five billion light-years from Earth but the field also contains other objects, both significantly closer and far more distant. Studies of this region of the sky have shown that many of the objects that appear to lie close together may actually be billions of light-years apart. This is because several groups of galaxies lie along our line of sight, creating something of an optical illusion. Hubble’s cross-section of the Universe is completed by distorted images of galaxies in the very distant background. These objects are sometimes distorted due to a process called gravitational lensing, an extremely valuable technique in astronomy for studying very distant objects [1]. This lensing is caused by the bending of the space-time continuum by massive galaxies lying close to our line of sight to distant objects. One of the lens systems visible here is called CLASS B1608+656, which appears as a small loop in the centre of the image. It features two foreground galaxies distorting and amplifying the light of a distant quasar the known as QSO-160913+653228. The light from this bright disc of matter, which is currently falling into a black hole, has taken nine billion years to reach us — two thirds of the age of the Universe. As well as CLASS B1608+656, astronomers have identified two other gravitational lenses within this image. Two galaxies, dubbed Fred and Ginger by the researchers who studied them, contain enough mass to visibly distort the light from objects behind them. Fred, also known more prosaically as [FMK2006] ACS J160919+6532, lies near the lens galaxies in CLASS B1608+656, while Ginger ([FMK2006] ACS J160910+6532) is markedly closer to us. Despite their different distances from us, both can be seen near to CLASS B1608+656 in the central region of this Hubble image. To capture distant and dim objects like these, Hubble required a long exposure. The image is made up of visible and infrared observations with a total exposure time of 14 hours. More info: www.spacetelescope.org/news/heic1408/ Credit: NASA/ESA/Hubble NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

HST Observations of the Luminous IRAS Source FSC10214+4724: A gravitationally Lensed Infrared Quasar

NASA Technical Reports Server (NTRS)

Eisenhardt, P. R.; Armus, L.; Hogg, D. W.; Soifer, B. T.; Neugebauer, G.; Werner, M. W.

1995-01-01

Observations of a distant object in space with the data being taken by the Hubble Space Telescope (HST) Wide Field Planetary Camera. Scientific examination and hypothesis related to this object which appears to be either an extremely luminous dust embedded quasar, or a representative of a new class of astronomical objects (a primeval galaxy).

Evolutional schemes for objects with active nuclei

NASA Technical Reports Server (NTRS)

Komberg, B. V.

1979-01-01

The observational properties of quasistellar objects (QSO) reveal that they are extremely violent nuclei of distant galaxies, but the evolutionary stage of these galaxies is still undetermined. Various published attempts to classify QSO under different criteria - including the one based on the morphological type of the surrounding galaxy E- or S- are analyzed. There are evidences that radioactive quasars reside in E-, while radio-quiet quasars reside in both E- and S- systems. The latter may be evolutionary connected to Seyfert-like objects. A correlation between the nuclei activity level in systems of different morphological type and the relative amount of gas in them is noted. From the point of view of activity level and the duration of active stage of nuclei it is concluded that an interaction of galaxies with the intergalactic medium is of particular importance and must be most conspicuous in spheriodal systems of central regions of rich clusters, in tight groups and binary galaxies.

DUSTiNGS. III. Distribution of Intermediate-age and Old Stellar Populations in Disks and Outer Extremities of Dwarf Galaxies

NASA Astrophysics Data System (ADS)

McQuinn, Kristen B. W.; Boyer, Martha L.; Mitchell, Mallory B.; Skillman, Evan D.; Gehrz, R. D.; Groenewegen, Martin A. T.; McDonald, Iain; Sloan, G. C.; van Loon, Jacco Th.; Whitelock, Patricia A.; Zijlstra, Albert A.

2017-01-01

We have traced the spatial distributions of intermediate-age and old stars in nine dwarf galaxies in the distant parts of the Local Group, using multi-epoch 3.6 and 4.5 μm data from the DUST in Nearby Galaxies with Spitzer (DUSTiNGS) survey. Using complementary optical imaging from the Hubble Space Telescope, we identify the tip of the red giant branch (TRGB) in the 3.6 μm photometry, separating thermally pulsating asymptotic giant branch stars from the larger red giant branch populations. Unlike the constant TRGB in the I band, at 3.6 μm, the TRGB magnitude varies by ˜0.7 mag, making it unreliable as a distance indicator. The intermediate-age and old stars are well mixed in two-thirds of the sample, with no evidence of a gradient in the ratio of the intermediate-age to old stellar populations outside the central ˜1‧-2‧. Variable AGB stars are detected in the outer extremities of the galaxies, indicating that chemical enrichment from these dust-producing stars may occur in the outer regions of galaxies with some frequency. Theories of structure formation in dwarf galaxies must account for the lack of radial gradients in intermediate-age populations and the presence of these stars in the outer extremities of dwarfs. Finally, we identify unique features in individual galaxies, such as extended tidal features in Sex A and Sag DIG and a central concentration of AGB stars in the inner regions of NGC 185 and NGC 147.

HUBBLE OPENS ITS EYE ON THE UNIVERSE AND CAPTURES A COSMIC MAGNIFYING GLASS

NASA Technical Reports Server (NTRS)

2002-01-01

Scanning the heavens for the first time since the successful December 1999 servicing mission, NASA's Hubble Space Telescope has imaged a giant, cosmic magnifying glass, a massive cluster of galaxies called Abell 2218. This 'hefty' cluster resides in the constellation Draco, some 2 billion light-years from Earth. The cluster is so massive that its enormous gravitational field deflects light rays passing through it, much as an optical lens bends light to form an image. This phenomenon, called gravitational lensing, magnifies, brightens, and distorts images from faraway objects. The cluster's magnifying powers provides a powerful 'zoom lens' for viewing distant galaxies that could not normally be observed with the largest telescopes. This useful phenomenon has produced the arc-shaped patterns found throughout the Hubble picture. These 'arcs' are the distorted images of very distant galaxies, which lie 5 to 10 times farther than the lensing cluster. This distant population existed when the universe was just a quarter of its present age. Through gravitational lensing these remote objects are magnified, enabling scientists to study them in more detail. This analysis provides a direct glimpse of how star-forming regions are distributed in remote galaxies and yields other clues to the early evolution of galaxies. The picture is dominated by spiral and elliptical galaxies. Resembling a string of tree lights, the biggest and brightest galaxies are members of the foreground cluster. Researchers are intrigued by a tiny red dot just left of top center. This dot may be an extremely remote object made visible by the cluster's magnifying powers. Further investigation is needed to confirm the object's identity. The Hubble telescope first viewed this cluster in 1994, producing one of the most spectacular demonstrations of gravitational lensing up to that time. Scientists who analyzed that black-and-white picture discovered more than 50 remote, young galaxies. Hubble's latest multicolor image of the cluster will allow astronomers to probe in greater detail the internal structure of these early galaxies. The color picture already reveals several arc-shaped features that are embedded in the cluster and cannot be easily seen in the black-and-white image. The colors in this picture yield clues to the ages, distances, and temperatures of stars, the stuff of galaxies. Blue pinpoints hot young stars. The yellow-white color of several of the galaxies represents the combined light of many stars. Red identifies cool stars, old stars, and the glow of stars in distant galaxies. This view is only possible by combining Hubble's unique image quality with the rare lensing effect provided by the magnifying cluster. The picture was taken Jan. 11 to 13, 2000, with the Wide Field and Planetary Camera 2. Credits: NASA, Andrew Fruchter (STScI), and the ERO team (STScI, ST-ECF)

Faint Compact Galaxy in the Early Universe

NASA Image and Video Library

2015-12-03

This is a Hubble Space Telescope view of a very massive cluster of galaxies, MACS J0416.1-2403, located roughly 4 billion light-years away and weighing as much as a million billion suns. The cluster's immense gravitational field magnifies the image of galaxies far behind it, in a phenomenon called gravitational lensing. The inset is an image of an extremely faint and distant galaxy that existed only 400 million years after the big bang. It was discovered by Hubble and NASA's Spitzer Space Telescope. The gravitational lens makes the galaxy appear 20 times brighter than normal. The galaxy is comparable in size to the Large Magellanic Cloud (LMC), a diminutive satellite galaxy of our Milky Way. It is rapidly making stars at a rate ten times faster than the LMC. This might be the growing core of what was to eventually evolve into a full-sized galaxy. The research team has nicknamed the object Tayna, which means "first-born" in Aymara, a language spoken in the Andes and Altiplano regions of South America. http://photojournal.jpl.nasa.gov/catalog/PIA20054

Distant galaxy formed stars only 250 million years after the Big Bang

NASA Astrophysics Data System (ADS)

Bouwens, Rychard

2018-05-01

Little is known about the star-birth activity of the earliest galaxies. Observations of a particularly distant galaxy provide evidence for such activity when the Universe was just 2% of its current age.

Distant Galaxy Bursts with Stars

NASA Image and Video Library

2011-12-21

This image from NASA Hubble telescope shows one of the most distant galaxies known, called GN-108036, dating back to 750 million years after the Big Bang that created our universe. The galaxy light took 12.9 billion years to reach us.

The Cosmic Dance of Distant Galaxies

NASA Astrophysics Data System (ADS)

2006-03-01

GIRAFFE at VLT reveals the turbulent life of distant galaxies Studying several tens of distant galaxies, an international team of astronomers found that galaxies had the same amount of dark matter relative to stars 6 billion years ago as they have now. If confirmed, this suggests a much closer interplay between dark and normal matter than previously believed. The scientists also found that as many as 4 out of 10 galaxies are out of balance. These results shed a new light on how galaxies form and evolve since the Universe was only half its current age. ESO PR Photo 10a/06 ESO PR Photo 10a/06 Collision Between Galaxies (Artist's Impression) "This may imply that collisions and merging are important in the formation and evolution of galaxies", said François Hammer, Paris Observatory, France, and one of the leaders of the team [1]. The scientists were interested in finding out how galaxies that are far away - thus seen as they were when the Universe was younger - evolved into the ones nearby. In particular, they wanted to study the importance of dark matter in galaxies. "Dark matter, which composes about 25% of the Universe, is a simple word to describe something we really don't understand," said Hector Flores, co-leader. "From looking at how galaxies rotate, we know that dark matter must be present, as otherwise these gigantic structures would just dissolve." In nearby galaxies, and in our own Milky Way for that matter, astronomers have found that there exists a relation between the amount of dark matter and ordinary stars: for every kilogram of material within a star there is roughly 30 kilograms of dark matter. But does this relation between dark and ordinary matter still hold in the Universe's past? ESO PR Photo 10b/06 ESO PR Photo 10b/06 Mapping Distant Galaxies (FLAMES-GIRAFFE/VLT) This required measuring the velocity in different parts of distant galaxies, a rather tricky experiment: previous measurements were indeed unable to probe these galaxies in sufficient detail, since they had to select a single slit, i.e. a single direction, across the galaxy. Things changed with the availability of the multi-object GIRAFFE spectrograph [2], now installed on the 8.2-m Kueyen Unit Telescope of ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile). In one mode, known as "3-D spectroscopy" or "integral field", this instrument can obtain simultaneous spectra of smaller areas of extended objects like galaxies or nebulae. For this, 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) , cf. ESO PR 01/02 , are used to make meticulous measurements of distant galaxies. Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec2 on the sky. It is like an insect's eye, with twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph. ESO PR Photo 10c/06 ESO PR Photo 10c/06 Dark Matter and Stellar Mass in Distant Galaxies "GIRAFFE on ESO's VLT is the only instrument in the world that is able to analyze simultaneously the light coming from 15 galaxies covering a field of view almost as large as the full moon," said Mathieu Puech, lead author of one the papers presenting the results [3]. "Every galaxy observed in this mode is split into continuous smaller areas where spectra are obtained at the same time." The astronomers used GIRAFFE to measure the velocity fields of several tens of distant galaxies, leading to the surprising discovery that as much as 40% of distant galaxies were "out of balance" - their internal motions were very disturbed - a possible sign that they are still showing the aftermath of collisions between galaxies. When they limited themselves to only those galaxies that have apparently reached their equilibrium, the scientists found that the relation between the dark matter and the stellar content did not appear to have evolved during the last 6 billions years. Thanks to its exquisite spectral resolution, GIRAFFE also allows for the first time to study the distribution of gas as a function of its density in such distant galaxies. The most spectacular results reveal a possible outflow of gas and energy driven by the intense star-formation within the galaxy and a giant region of very hot gas (HII region) in a galaxy in equilibrium that produces many stars. "Such a technique can be expanded to obtain maps of many physical and chemical characteristics of distant galaxies, enabling us to study in detail how they assembled their mass during their entire life," said François Hammer. "In many respects, GIRAFFE and its multi-integral field mode gives us a first flavour of what will be achieved with future extremely large telescopes." Notes [1]: The team comprises: François Hammer, Hector Flores, Mathieu Puech, Chantal Balkowski (GEPI - Observatoire de Paris), Philippe Amram (LAM - Observatoire Astronomique Marseille-Provence), Göran Östlin (Stockholm Observatory), Thomas Marquart (Dept. of Astronomy and Space Physics - Uppsala, Sweden) and Matthew D. Lehnert (MPE, Germany). [2]: This complex and unique instrument allows obtaining high-quality spectra of a large variety of celestial objects, from individual stars in the Milky Way and other nearby galaxies, to very distant galaxies. It functions by means of multiple optical fibres that guide the light from the telescope's focal plane into the entry slit of the spectrograph. Here the light is dispersed into its different colours. GIRAFFE and these fibres are an integral part of the advanced Fibre Large Array Multi-Element Spectrograph (FLAMES) facility which also includes the OzPoz positioner and an optical field corrector. It is the outcome of a collaboration between ESO, Observatoire de Paris-Meudon, Observatoire de Genève-Lausanne and the Anglo Australian Observatory (AAO). More details are available in ESO PR 01/02. The principle of this instrument involves the positioning in the telescope's focal plane of a large number of optical fibres. This is done in such a way that each of them guides the light from one particular celestial object towards the spectrograph that records the spectra of all these objects simultaneously. The size of the available field-of-view is no less than about 25 arcmin across, i.e. almost as large as the full moon. The individual fibres are moved and positioned "on the objects" in the field by means of the OzPoz positioner. See also ESO PR 13/02. [3]: The results will be published in a series of three papers in the leading research journal, Astronomy and Astrophysics (click on the title to access the papers): "3D spectroscopy with VLT/GIRAFFE - I: The true Tully-Fisher relationship at z~ 0.6" (Flores H., Hammer F., Puech M. et al.); "3D spectroscopy with VLT/GIRAFFE - II: Are Luminous Compact Galaxies merger remnants?" (Puech M., Hammer F., Flores H. et al.); and "3D spectroscopy with VLT/GIRAFFE - III: Mapping electron densities in distant galaxies" (Puech M., Flores H., Hammer F. & Lehnert M.D.).

Unveiling the extreme nature of the hyper faint galaxy Virgo I

NASA Astrophysics Data System (ADS)

Crnojevic, Denija

2017-08-01

We request HST/ACS imaging to obtain a deep color-magnitude diagram of the newly discovered candidate Milky Way satellite Virgo I. With an estimated absolute magnitude of only M_V -0.8 and a Galactocentric radius of 90 kpc, Virgo I is one of the faintest and most distant dwarfs ever observed, and could be identified as a prototype ''hyper'' faint galaxy. The detailed characterization of the smallest inhabited dark matter subhalos is crucial to guide hierarchical galaxy formation models, and in particular to constrain reionization, the nature of the dark matter particle, etc. With the advent of deep wide-field, ground-based surveys, the potential of uncovering these lowest-mass galaxies is quickly turning into reality, as demonstrated by the discovery in the past two years of tens of new Local Group members in the ultra-faint regime (M_V>-8). Virgo I represents a new record in galaxy physical properties, and urges us to be prepared for the likely emergence of an entirely new class of such objects in the era of future wide-field surveys (e.g., LSST). Only high resolution HST observations can enable us to confirm the nature of Virgo I, providing significantly more accurate estimates for its distance and structural properties, when compared to the discovery Subaru/HyperSuprimeCam imaging. Our proposed dataset will constitute a fundamental step in the upcoming hunt for galaxies with similarly extreme properties.

Galaxy Evolution Across The Redshift Desert

NASA Astrophysics Data System (ADS)

Kotulla, Ralf

2010-01-01

GALEV evolutionary synthesis models are an ideal tool to study the formation and evolution of galaxies. I present a large model grid that contains undisturbed E and Sa-Sd type galaxies as well as a wide range of models undergoing starbursts of various strengths and at different times and also includes the subsequent post-starburst phases for these galaxies. This model grid not only allows to describe and refine currently used color selection criteria for Lyman Break Galaxies, BzK galaxies, Extremely Red Objects (ERO) and both Distant and Luminous Red Galaxies (DRG, LRG). It also gives accurate stellar masses, gas fractions, star formation rates, metallicities and burst strengths for an unprecedentedly large sample of galaxies with multi-band photometry. We find, amongst other things, that LBGs are most likely progenitors of local early type spiral galaxies and low-mass ellipticals. We are for the first time able to reproduce E+A features in EROs by post-starbursts as an alternative to dusty starforming galaxies and predict how to discriminate between these scenarios. Our results from photometric analyses perfectly agree with all available spectroscopic information and open up a much wider perspective, including the bulk of the less luminous and more typical galaxy population, in the redshift desert and beyond. All model data are available online at http://www.galev.org.

Outskirts of Distant Galaxies in Absorption

NASA Astrophysics Data System (ADS)

Chen, Hsiao-Wen

QSO absorption spectroscopy provides a sensitive probe of both the neutral medium and diffuse ionized gas in the distant Universe. It extends 21 cm maps of gaseous structures around low-redshift galaxies both to lower gas column densities and to higher redshifts. Combining galaxy surveys with absorption-line observations of gas around galaxies enables comprehensive studies of baryon cycles in galaxy outskirts over cosmic time. This chapter presents a review of the empirical understanding of the cosmic neutral gas reservoir from studies of damped Lyα absorbers (DLAs). It describes the constraints on the star formation relation and chemical enrichment history in the outskirts of distant galaxies from DLA studies. A brief discussion of available constraints on the ionized circumgalactic gas from studies of lower column density Lyα absorbers and associated ionic absorption transitions is presented at the end.

The SCUBA HAlf Degree Extragalactic Survey (SHADES) - V. Submillimetre properties of near-infrared-selected galaxies in the Subaru/XMM -Newton deep field

NASA Astrophysics Data System (ADS)

Takagi, T.; Mortier, A. M. J.; Shimasaku, K.; Coppin, K.; Pope, A.; Ivison, R. J.; Hanami, H.; Serjeant, S.; Clements, D. L.; Priddey, R. S.; Dunlop, J. S.; Takata, T.; Aretxaga, I.; Chapman, S. C.; Eales, S. A.; Farrah, D.; Granato, G. L.; Halpern, M.; Hughes, D. H.; van Kampen, E.; Scott, D.; Sekiguchi, K.; Smail, I.; Vaccari, M.

2007-11-01

We have studied the submillimetre (submm) properties of the following classes of near-infrared-selected (NIR-selected) massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs); distant red galaxies (DRGs); and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Partial overlap of SIRIUS/NIR images and SHADES in Subaru/XMM-Newton deep field has allowed us to identify four submm-bright NIR-selected galaxies, which are detected in the mid-IR, 24μ m, and the radio, 1.4GHz. We find that all of our submm-bright NIR-selected galaxies satisfy the BzK selection criteria, i.e. BzK ≡ (z - K)AB - (B - z)AB >= -0.2, except for one galaxy whose B - z and z - K colours are however close to the BzK colour boundary. Two of the submm-bright NIR-selected galaxies satisfy all of the selection criteria we considered, i.e. they belong to the BzK-DRG-ERO overlapping population, or `extremely red' BzKs. Although these extremely red BzKs are rare (0.25 arcmin-2), up to 20 per cent of this population could be submm galaxies. This fraction is significantly higher than that found for other galaxy populations studied here. Via a stacking analysis, we have detected the 850-μ m flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution of z ~ 2 BzKs to the submm background is about 10-15 per cent and similar to that from EROs typically at z ~ 1, BzKs have a higher fraction (~30 per cent) of submm flux in resolved sources compared with EROs and submm sources as a whole. From the spectral energy distribution (SED) fitting analysis for both submm-bright and submm-faint BzKs, we found no clear signature that submm-bright BzKs are experiencing a specifically luminous evolutionary phase, compared with submm-faint BzKs. An alternative explanation might be that submm-bright BzKs are more massive than submm-faint ones.

The nature of radio emission from distant galaxies

NASA Astrophysics Data System (ADS)

Richards, Eric A.

I describe an observational program aimed at understanding the radio emission from distant, rapidly evolving galaxy populations. These observations were carried out at 1.4 and 8.5 GHz with the VLA centered on the Hubble Deep Field. Further MERLIN observations of the HDF region at 1.4 GHz provided an angular resolution of 0.2'' and when combined with the VLA data produced an image with an unprecedented rms noise of 4 μJy. All radio sources detected in the VLA complete sample are resolved with a median angular size of 1-2''. The differential count of the radio sources is marginally sub-Euclidean (γ = -2.4 +/- 0.1) and fluctuation analysis suggests nearly 60 sources per armin2 are present at the 1 μJy level. A correlation analysis indicates spatial clustering among the 371 radio sources on angular scales of 1-40 arcmin. Optical identifications are made primarily with bright (I = 22) disk systems composed of irregulars, peculiars, interacting/merging galaxies, and a few isolated field spirals. Available redshifts span the range 0.2-3. These clues coupled with the steep spectral index of the 1.4 GHz selected sample are indicative of diffuse synchrotron radiation in distant galactic disks. Thus the evolution in the microjansky radio population is driven principally by star-formation. I have isolated a number of optically faint radio sources (about 25% of the overall sample) which remain unidentified to I = 26-28 in the HDF and flanking optical fields. Several of these objects have extremely red counterparts and constitute a new class of radio sources which are candidate high redshift dusty protogalaxies.

Recovering Galaxy Properties Using Gaussian Process SED Fitting

NASA Astrophysics Data System (ADS)

Iyer, Kartheik; Awan, Humna

2018-01-01

Information about physical quantities like the stellar mass, star formation rates, and ages for distant galaxies is contained in their spectral energy distributions (SEDs), obtained through photometric surveys like SDSS, CANDELS, LSST etc. However, noise in the photometric observations often is a problem, and using naive machine learning methods to estimate physical quantities can result in overfitting the noise, or converging on solutions that lie outside the physical regime of parameter space.We use Gaussian Process regression trained on a sample of SEDs corresponding to galaxies from a Semi-Analytic model (Somerville+15a) to estimate their stellar masses, and compare its performance to a variety of different methods, including simple linear regression, Random Forests, and k-Nearest Neighbours. We find that the Gaussian Process method is robust to noise and predicts not only stellar masses but also their uncertainties. The method is also robust in the cases where the distribution of the training data is not identical to the target data, which can be extremely useful when generalized to more subtle galaxy properties.

Galaxy Cluster Smashes Distance Record

NASA Astrophysics Data System (ADS)

2009-10-01

he most distant galaxy cluster yet has been discovered by combining data from NASA's Chandra X-ray Observatory and optical and infrared telescopes. The cluster is located about 10.2 billion light years away, and is observed as it was when the Universe was only about a quarter of its present age. The galaxy cluster, known as JKCS041, beats the previous record holder by about a billion light years. Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage. JKCS041 is found at the cusp of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics - such as composition, mass, and temperature - will reveal more about how the Universe took shape. "This object is close to the distance limit expected for a galaxy cluster," said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. "We don't think gravity can work fast enough to make galaxy clusters much earlier." Distant galaxy clusters are often detected first with optical and infrared observations that reveal their component galaxies dominated by old, red stars. JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA's Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe. The Chandra data were the final - but crucial - piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected between the galaxies, as expected for a true galaxy cluster rather than one that has been caught in the act of forming. Also, without the X-ray observations, the possibility remained that this object could have been a blend of different groups of galaxies along the line of sight, or a filament, a long stream of galaxies and gas, viewed front on. The mass and temperature of the hot gas detected estimated from the Chandra observations rule out both of those alternatives. The extent and shape of the X-ray emission, along with the lack of a central radio source argue against the possibility that the X-ray emission is caused by scattering of cosmic microwave background light by particles emitting radio waves. It is not yet possible, with the detection of just one extremely distant galaxy cluster, to test cosmological models, but searches are underway to find other galaxy clusters at extreme distances. "This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known," said co-author Ben Maughan, from the University of Bristol in the United Kingdom. "One fossil might just fit in with our understanding of dinosaurs, but if you found many more, you would have to start rethinking how dinosaurs evolved. The same is true for galaxy clusters and our understanding of cosmology." The previous record holder for a galaxy cluster was 9.2 billion light years away, XMMXCS J2215.9-1738, discovered by ESA's XMM-Newton in 2006. This broke the previous distance record by only about 0.1 billion light years, while JKCS041 surpasses XMMXCS J2215.9 by about ten times that. "What's exciting about this discovery is the astrophysics that can be done with detailed follow-up studies," said Andreon. Among the questions scientists hope to address by further studying JKCS041 are: What is the build-up of elements (such as iron) like in such a young object? Are there signs that the cluster is still forming? Do the temperature and X-ray brightness of such a distant cluster relate to its mass in the same simple way as they do for nearby clusters? The paper describing the results on JKCS041 from Andreon and his colleagues will appear in an upcoming issue of the journal Astronomy and Astrophysics. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington, DC. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

SPECTROSCOPY OF LUMINOUS COMPACT BLUE GALAXIES IN DISTANT CLUSTERS. II. PHYSICAL PROPERTIES OF dE PROGENITOR CANDIDATES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crawford, S. M.; Wirth, Gregory D.; Bershady, M. A.

2016-02-01

Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10{sup 15} M{sub ⊙}), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size–luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs atmore » the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.« less

Chandra X-Ray Observatory Image of the Distant Galaxy, 3C294

NASA Technical Reports Server (NTRS)

2000-01-01

This most distant x-ray cluster of galaxies yet has been found by astronomers using Chandra X-ray Observatory (CXO). Approximately 10 billion light-years from Earth, the cluster 3C294 is 40 percent farther than the next most distant x-ray galaxy cluster. The existence of such a faraway cluster is important for understanding how the universe evolved. CXO's image reveals an hourglass-shaped region of x-ray emissions centered on the previously known central radio source (seen in this image as the blue central object) that extends outward for 60,000 light- years. The vast clouds of hot gas that surround such galaxies in clusters are thought to be heated by collapse toward the center of the cluster. Until CXO, x-ray telescopes have not had the needed sensitivity to identify such distant clusters of galaxies. Galaxy clusters are the largest gravitationally bound structures in the universe. The intensity of the x-rays in this CXO image of 3C294 is shown as red for low energy x-rays, green for intermediate, and blue for the most energetic x-rays. (Photo credit: NASA/loA/A. Fabian et al)

HUBBLE'S ULTRAVIOLET VIEWS OF NEARBY GALAXIES YIELD CLUES TO EARLY UNIVERSE

NASA Technical Reports Server (NTRS)

2002-01-01

Astronomers are using these three NASA Hubble Space Telescope images to help tackle the question of why distant galaxies have such odd shapes, appearing markedly different from the typical elliptical and spiral galaxies seen in the nearby universe. Do faraway galaxies look weird because they are truly weird? Or, are they actually normal galaxies that look like oddballs, because astronomers are getting an incomplete picture of them, seeing only the brightest pieces? Light from these galaxies travels great distances (billions of light-years) to reach Earth. During its journey, the light is 'stretched' due to the expansion of space. As a result, the light is no longer visible, but has been shifted to the infrared where present instruments are less sensitive. About the only light astronomers can see comes from regions where hot, young stars reside. These stars emit mostly ultraviolet light. But this light is stretched, appearing as visible light by the time it reaches Earth. Studying these distant galaxies is like trying to put together a puzzle with some of the pieces missing. What, then, do distant galaxies really look like? Astronomers studied 37 nearby galaxies to find out. By viewing these galaxies in ultraviolet light, astronomers can compare their shapes with those of their distant relatives. These three Hubble telescope pictures, taken with the Wide Field and Planetary Camera 2, represent a sampling from that survey. Astronomers observed the galaxies in ultraviolet and visible light to study all the stars that make up these 'cities of stars.' The results of their survey support the idea that astronomers are detecting the 'tip of the iceberg' of very distant galaxies. Based on these Hubble ultraviolet images, not all the faraway galaxies necessarily possess intrinsically odd shapes. The results are being presented today at the 197th meeting of the American Astronomical Society in San Diego, CA. The central region of the 'star-burst' spiral galaxy at far left, NGC 3310, shows young and old stars evenly distributed. If this were the case with most galaxies, astronomers would be able to recognize faraway galaxies fairly easily. In most galaxies, however, the stars are segregated by age, making classifying the distant ones more difficult. NGC 3310 is 46 million light-years from Earth in the constellation Ursa Major. The image was taken Sept. 12-13, 2000. The middle image is an example of a tiny, youthful spiral galaxy. ESO 418-008 is representative of the myriad of dwarf galaxies astronomers have seen in deep surveys. These galaxies are much smaller than typical ones like our Milky Way. In this galaxy, the population of stars is more strongly segregated by age. The older stars [red] reside in the center; the younger [blue], in the developing spiral arms. These small, young galaxies may be the building blocks of galaxy formation. ESO 418-008 is 56 million light-years from Earth in the southern constellation Fornax. The image was taken Oct. 10, 2000. The picture at right shows a cosmic collision between two galaxies, UGC 06471 and UGC 06472. These collisions occurred frequently in the early universe, producing galaxies of unusual shapes. The Hubble telescope has spied many such galaxies in the deep field surveys. The ultraviolet images of this galaxy merger suggest the presence of large amounts of dust, which were produced by massive stars that formed before or during this dramatic collision. This dust reddens the starlight in many places, just like a dusty atmosphere reddens the sunset. Studying the effects of this nearby collision could help astronomers explain the peculiar shapes seen in some of the distant galaxies. UGC 06471 and UGC 06472 are 145 million light-years from Earth in the constellation Ursa Major. The image was taken July 11, 2000. Photo credits: NASA, Rogier Windhorst (Arizona State University, Tempe, AZ), and the Hubble mid-UV team

Chandra Finds Most Distant X-ray Galaxy Cluster

NASA Astrophysics Data System (ADS)

2001-02-01

The most distant X-ray cluster of galaxies yet has been found by astronomers using NASA’s Chandra X-ray Observatory. Approximately 10 billion light years from Earth, the cluster 3C294 is 40 percent farther than the next most distant X-ray galaxy cluster. The existence of such a distant galaxy cluster is important for understanding how the universe evolved. "Distant objects like 3C294 provide snapshots to how these galaxy clusters looked billions of years ago," said Andrew Fabian of the Institute of Astronomy, Cambridge, England and lead author of the paper accepted for publication in the Monthly Notices of Britain’s Royal Astronomical Society. "These latest results help us better understand what the universe was like when it was only 20 percent of its current age." Chandra’s image reveals an hourglass-shaped region of X-ray emission centered on the previously known central radio source. This X-ray emission extends outward from the central galaxy for at least 300,000 light years and shows that the known radio source is in the central galaxy of a massive cluster. Scientists have long suspected that distant radio-emitting galaxies like 3C294 are part of larger groups of galaxies known as "clusters." However, radio data provides astronomers with only a partial picture of these distant objects. Confirmation of the existence of clusters at great distances - and, hence, at early stages of the universe - requires information from other wavelengths. Optical observations can be used to pinpoint individual galaxies, but X-ray data are needed to detect the hot gas that fills the space within the cluster. "Galaxy clusters are the largest gravitationally bound structures in the universe," said Fabian. "We do not expect to find many massive objects, such as the 3C294 cluster, in early times because structure is thought to grow from small scales to large scales." The vast clouds of hot gas that envelope galaxies in clusters are thought to be heated by collapse toward the center of the cluster. Until Chandra, X-ray telescopes have not had the needed sensitivity to identify and measure hot gas clouds in distant clusters. Carolin Crawford, Stefano Ettori and Jeremy Sanders of the Institute of Astronomy were also members of the team that observed 3C294 for 5.4 hours on October 29, 2000 with the Advanced CCD Imaging Spectrometer (ACIS). The ACIS X-ray camera was developed for NASA by Pennsylvania State University and Massachusetts Institute of Technology. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program for the Office of Space Science in Washington, DC. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA. Images associated with this release are available on the World Wide Web at: http://chandra.harvard.edu AND http://chandra.nasa.gov

The Andromeda Optical and Infrared Disk Survey

NASA Astrophysics Data System (ADS)

Sick, Jonathan

The spectral energy distributions of galaxies inform us about a galaxy's stellar populations and interstellar medium, revealing stories of galaxy formation and evolution. How we interpret this light depends in part on our proximity to the galaxy. For nearby galaxies, detailed star formation histories can be extracted from the resolved stellar populations, while more distant galaxies feature the contributions of entire stellar populations within their integrated spectral energy distribution (SED). This thesis aims to resolve whether the techniques used to investigate stellar populations in distant galaxies are consistent with those available for nearby galaxies. As the nearest spiral galaxy, the Andromeda Galaxy (M31) is the ideal testbed for the joint study of resolved stellar populations and panchromatic SEDs. We present the Andromeda Optical and Infrared Disk Survey (ANDROIDS), which adds new near-UV to near-IR (u*g'r'i'JKs) imaging using the MegaCam and WIRCam cameras at the Canada-France-Hawaii telescope to the available M31 panchromatic dataset. To accurately subtract photometric background from our extremely wide-field (14 square degree) mosaics, we present observing and data reduction techniques with sky-target nodding, optimization of image-to-image surface brightness, and a novel hierarchical Bayesian model to trace the background signal while modelling the astrophysical SED. We model the spectral energy distributions of M31 pixels with MAGPHYS (da Cunha et al. 2008) and compare those results to resolved stellar population models of the same pixels from the Panchromatic Hubble Andromeda Treasury (PHAT) survey (Williams et al. 2017). We find substantial (0.3 dex) differences in stellar mass estimates despite a common use of the Chabrier (2003) initial mass function. Stellar mass estimated from the resolved stellar population is larger than any mass estimate from SED models or colour-M/L relations (CMLRs). There is also considerable diversity among CMLR estimators, largely driven by differences in the star formation history prior distribution. We find broad consistency between the star formation history estimated by integrated spectral energy distributions and resolved stars. Generally, spectral energy distribution models yield a stronger inside-out radial metallicity gradient and bias towards younger mean ages than resolved stellar population models.

ASCA observations of distant clusters of galaxies.

NASA Astrophysics Data System (ADS)

Tsuru, T.; Koyama, K.; Hughes, J. P.; Arimoto, N.; Kii, T.; Hattori, M.

It is important not only in studies of clusters of galaxies but also in cosmological aspects to investigate the evolution of X-ray properties of clusters of galaxies. ASCA enables detailed spectral studies on distant clusters and the evolution of temperature for the first time. The authors present here "preliminary" results of ASCA observation of 17 distant (z = 0.14 - 0.55) clusters of galaxies. The sample includes: Cl0016+16 Abell 370, Abell 1995, Abell 959, ACGG 118, Zw 3136, EMSS 1305.4+2941, Abell 1851, Abell 963, Abell 2163, EMSS 0839.8+2938, Abell 665, Abell 1689, Abell 2218, Abell 586, Abell 1413, Abell 1895. The cosmological constants of H0 = 50 km/s/Mpc and q0 = 0.5 are adopted in this paper.

A search for X-ray bright distant clusters of galaxies

NASA Technical Reports Server (NTRS)

Nichol, R. C.; Ulmer, M. P.; Kron, R. G.; Wirth, G. D.; Koo, D. C.

1994-01-01

We present the results of a search for X-ray luminous distant clusters of galaxies. We found extended X-ray emission characteristic of a cluster toward two of our candidate clusters of galaxies. They both have a luminosity in the ROSAT bandpass of approximately equals 10(exp 44) ergs/s and a redshift greater than 0.5; thus making them two of the most distant X-ray clusters ever observed. Furthermore, we show that both clusters are optically rich and have a known radio source associated with them. We compare our result with other recent searches for distant X-ray luminous clusters and present a lower limit of 1.2 x 10(exp -7)/cu Mpc for the number density of such high-redshift clusters. This limit is consistent with the expected abundance of such clusters in a standard (b = 2) cold dark matter universe. Finally, our clusters provide important high-redshift targets for further study into the origin and evolution of massive clusters of galaxies.

A new giant luminous arc gravitational lens associated with a z = 0.62 galaxy cluster, and the environments of distant radio galaxies

NASA Technical Reports Server (NTRS)

Dickinson, Mark

1993-01-01

In the course of a survey investigating the cluster environments of distant 3CR radio galaxies, I have identified a previously unknown 'giant luminous arc' gravitational lens. The lensing cluster is associated with the radio galaxy 3C 220.1 at z = 0.62 and is the most distant cluster now known to produce such arcs. I present imaging and spectroscopic observations of the cluster and the arc, and discuss the implications for the cluster mass. At z greater than 0.6 the cluster velocity dispersions implied by such giant arcs may provide an interesting constraint on theories of large scale structure formation. The parent investigation in which this arc was identified concerns galaxy clusters and radio galaxy environments at 0.35 less than z less than 0.8. At the present epoch, powerful FR 2 radio galaxies tend to be found in environments of poor or average galaxy density. In contrast, at the higher redshifts investigated here, richer group and cluster environments are common. I present additional data on other clusters from this survey, and discuss its extension to z greater than 1 through a program of near-infrared and optical imaging.

Physics of Galaxy Clusters and How it Affects Cosmological Tests

NASA Technical Reports Server (NTRS)

Vikhlinin, Alexey; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

We have worked on the analysis of the Chandra observations of the nearby and distant clusters of galaxies, and on the expansion of the sample of distant X-ray clusters based on the archival ROSAT PSPC data. Some of the scientific results are discussed.

CFHT and VLT Identify Extremely Remote Galaxy

NASA Astrophysics Data System (ADS)

2003-05-01

Top Telescopes Peer into the Distant Past Summary With improved telescopes and instruments, observations of extremely remote and faint galaxies have become possible that were until recently astronomers' dreams. One such object was found by a team of astronomers [2] with a wide-field camera installed at the Canada-France-Hawaii telescope at Mauna Kea (Hawaii, USA) during a search for extremely distant galaxies. Designated "z6VDF J022803-041618" , it was detected because of its unusual colour , being visible only on images obtained through a special optical filter isolating light in a narrow near-infrared band. A follow-up spectrum of this object with the FORS2 multi-mode instrument at the ESO Very Large Telescope (VLT) confirmed that it is a very distant galaxy (the redshift is 6.17 [3]). It is seen as it was when the Universe was only about 900 million years old . z6VDF J022803-041618 is one of the most distant galaxies for which spectra have been obtained so far. Interestingly, it was discovered because of the light emitted by its massive stars and not, as originally expected, from emission by hydrogen gas. PR Photo 13a/03 : Emission from the Earth's atmosphere. PR Photo 13b/03 : CHFT images of the very remote galaxy z6VDF J022803-041618. PR Photo 13c/03 : VLT spectrum of very remote galaxy z6VDF J022803-041618. PR Photo 13d/03 : Cleaned tracing of the VLT spectrum. A brief history of the early Universe Most scientists agree that the Universe emanated from a hot and extremely dense initial state in a Big Bang . The latest observations indicate that this crucial event took place about 13,700 million years ago . During the first few minutes, enormous quantities of hydrogen and helium nuclei with protons and neutrons were produced. There were also lots of free electrons and during the following epoch, the numerous photons were scattered from these and the atomic nuclei. At this stage, the Universe was completely opaque. After some 100,000 years, the Universe had cooled down to a few thousand degrees and the nuclei and electrons now combined to form atoms. The photons were then no longer scattered from these and the Universe suddenly became transparent . Cosmologists refer to this moment as the "recombination epoch" . The microwave background radiation we now observe from all directions depicts the state of great uniformity in the Universe at that distant epoch. In the next phase, the primeval atoms - more than 99% of which were of hydrogen and helium - moved together and began to form huge clouds from which stars and galaxies later emerged . The first generation of stars and, somewhat later, the first galaxies and quasars [4], produced intensive ultraviolet radiation. That radiation did not travel very far, however, despite the fact that the Universe had become transparent a long time ago. This is because the ultraviolet (short-wavelength) photons would be immediately absorbed by the hydrogen atoms, "knocking" electrons off those atoms, while longer-wavelength photons could travel much farther. The intergalactic gas thus again became ionized in steadily growing spheres around the ionizing sources. At some moment, these spheres had become so big that they overlapped completely; this is referred to as the "epoch of re-ionization" . Until then, the ultraviolet radiation was absorbed by the atoms, but the Universe now also became transparent to this radiation. Before, the ultraviolet light from those first stars and galaxies could not be seen over large distances, but now the Universe suddenly appeared to be full of bright objects. It is for this reason that the time interval between the epochs of "recombination" and "re-ionization" is referred to as the "Dark Ages" . When was the end of the "Dark Ages"? The exact epoch of re-ionization is a subject of active debate among astronomers, but recent results from ground and space observations indicate that the "Dark Ages" lasted a few hundred million years . Various research programmes are now underway which attempt to determine better when these early events happened. For this, it is necesary to find and study in detail the earliest and hence, most distant, objects in the Universe - and this is a very demanding observational endeavour. Light is dimmed by the square of the distance and the further we look out in space to observe an object - and therefore the further back in time we see it - the fainter it appears. At the same time, its dim light is shifted towards the red region of the spectrum due to the expansion of the Universe - the larger the distance, the larger the observed redshift [3]. The Lyman-alpha emission line With ground-based telescopes, the faintest detection limits are achieved by observations in the visible part of the spectrum. The detection of very distant objects therefore requires observations of ultraviolet spectral signatures which have been redshifted into the visible region. Normally, the astronomers use for this the redshifted Lyman-alpha spectral emission line with rest wavelength 121.6 nm; it corresponds to photons emitted by hydrogen atoms when they change from an excited state to their fundamental state. One obvious way of searching for the most distant galaxies is therefore to search for Lyman-alpha emission at the reddest (longest) possible wavelengths . The longer the wavelength of the observed Lyman-alpha line, the larger is the redshift and the distance, and the earlier is the epoch at which we see the galaxy and the closer we come towards the moment that marked the end of the "Dark Ages". CCD-detectors used in astronomical instruments (as well as in commercial digital cameras) are sensitive to light of wavelengths up to about 1000 nm (1 µm), i.e., in the very near-infrared spectral region, beyond the reddest light that can be perceived by the human eye at about 700-750 nm. The bright near-infrared night sky ESO PR Photo 13a/03 ESO PR Photo 13a/03 [Preview - JPEG: 759 x 400 pix - 37k [Normal - JPEG: 1518 x 800 pix - 248k] Caption : PR Photo 13a/03 shows a spectrum of emission by the terrestrial atmosphere. In the spectral region above 700 nm, this emission is dominated by strong lines from the OH molecule. By observing in "windows" of low OH emission, such as those around 820 or 920 nm, the "noise" caused by the OH-emission is strongly reduced and it is possible to detect fainter celestial objects. There is another problem, however, for this kind of work. The search for faint Lyman-alpha emission from distant galaxies is complicated by the fact that the terrestrial atmosphere - through which all ground-based telescopes must look - also emits light . This is particularly so in the red and near-infrared part of the spectrum where hundreds of discrete emission lines originate from the hydroxyl molecule (the OH radical) that is present in the upper terrestrial atmosphere at an altitude of about 80 km (see PR Photo 13a/03 ). This strong emission which the astronomers refer to as the "sky background" is responsible for the faintness limit at which celestial objects can be detected with ground-based telescopes at near-infrared wavelengths. However, there are fortunately spectral intervals of "low OH-background" where these emission lines are much fainter, thus allowing a fainter detection limit from ground observations. Two such "dark-sky windows" are evident in PR Photo 13a/03 near wavelengths of 820 and 920 nm. Considering these aspects, a promising way to search efficiently for the most distant galaxies is therefore to observe at wavelengths near 920 nm by means of a narrow-band optical filter. Adapting the spectral width of this filter to about 10 nm allows the detection of as much light from the celestial objects as possible when emitted in a spectral line matching the filter, while minimizing the adverse influence of the sky emission. In other words, with a maximum of light collected from the distant objects and a minimum of disturbing light from the terrestrial atmosphere, the chances for detecting those distant objects are optimal. The astronomers talk about "maximizing the contrast" of objects showing emission lines at this wavelength. The CFHT Search Programme ESO PR Photo 13b/03 ESO PR Photo 13b/03 [Preview - JPEG: 494 x 400 pix - 83k [Normal - JPEG: 987 x 800 pix - 920k] Caption : PR Photo 13b/03 displays the image of a particular object (at the center), as seen at various wavelengths (colours) on CCD-frames obtained through different optical filters with the CFH12K camera at the CFHT. The object is only visible in the NB920 frame in which emission at the near-infrared wavelength 920 nm is registered (upper left). It is not seen in any of the others ( B lue [450 nm], V isual [550 nm], R ed [650 nm], I [800 nm]), nor in a combination of these (the "sum" of BVRI , the so-called "detection" image, here labeled as "Det"; it is used to detect closer objects from their optical colours for spectroscopic follow-up observations). The indicated object was later shown to be an extremely distant galaxy and has been designated z6VDF J022803-041618 . Each of the six photos covers 20 x 20 arcsec 2 ; North is up, East is right. Based on the above considerations, an international team of astronomers [2] installed a narrow-band optical filter centered at the near-infrared wavelength 920 nm on the CFH12K instrument at the Canada-France-Hawaii telescope on Mauna Kea (Hawaii, USA) to search for extremely distant galaxies. The CFH12K is a wide-field camera used at the prime focus of the CFHT, providing a field-of-view of approx. 30 x 40 arcmin 2 , somewhat larger than the full moon [5]. By comparing images of the same sky field taken through different filters, the astronomers were able to identify objects which appear comparatively "bright" in the NB920 image and "faint" (or are even not visible) in the corresponding images obtained through the other filters. A striking example is shown in PR Photo 13b/03 - the object at the center is well visible in the 920nm image, but not at all in the other images. The most probable explanation for an object with such an unusual colour is that it is a very distant galaxy for which the observed wavelength of the strong Lyman-alpha emission line is close to 920 nm, due to the redshift. Any light emitted by the galaxy at wavelengths shorter than Lyman-alpha is strongly absorbed by intervening interstellar and intergalactic hydrogen gas; this is the reason that the object is not visible in all the other filters. The VLT spectrum ESO PR Photo 13c/03 ESO PR Photo 13c/03 [Preview - JPEG: 756 x 300 pix - 68k [Normal - JPEG: 1512 x 600 pix - 552k] ESO PR Photo 13d/03 ESO PR Photo 13d/03 [Preview - JPEG: 479 x 400 pix - 41k [Normal - JPEG: 957 x 800 pix - 272k] Captions : PR Photo 13c/03 shows a spectroscopic image (between the horizontal arrows) of the very distant galaxy z6VDF J022803-041618 at the center of PR Photo 13b/03 , obtained with the multi-mode FORS2 instrument at the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. The horizontal axis shows the dispersed light, with wavelengths increasing from left to right. In this spectral image, the bright emission lines from OH molecules in the terrestrial atmosphere, cf. PR Photo 13a/03 , have been subtracted, but they still leave residual "imprints", visible as strong and "noisy" vertical bars. The "window" at wavelength 920 nm is clearly visible on the right side of the image; in this region, there is much less "noise" from the OH-lines. The dark spot at the bottom left of the image is the Lyman-alpha line of the object. The adjacent "continuum" emission from the object, although very faint, is clearly visible on the long-wavelength side (to the right) of the Lyman-alpha line. There is no such continuum emission detected on the short-wavelength side (to the left) of the Lyman alpha line. Together with the observed asymmetry of the line, this is a clear spectral fingerprint of the redshifted Lyman-alpha emission line from a distant galaxy. PR Photo 13d/03 shows a tracing of the spectrum of this galaxy, as extracted from the image in PR Photo 13c/03 . The strong emission line at wavelength 872 nm is the redshifted Lyman-alpha spectral line from the galaxy; it is shown in more detail in the insert panel. In order to learn the true nature of this object, it is necessary to perform a spectroscopic follow-up, by observing its spectrum. This was accomplished with the FORS 2 multi-mode instrument at the 8.2-m VLT YEPUN telescope at the ESO Paranal Observatory. This facility provides a perfect combination of moderate spectral resolution and high sensitivity in the red for this kind of very demanding observation. The resulting (faint) spectrum is shown in PR Photo 13c/03 . PR Photo 13d/03 shows a tracing of the final ("cleaned") spectrum of the object after extraction from the image shown in PR Photo 13c/03 . One broad emission line is clearly detected (to the left of the center; enlarged in the insert). It is asymmetric, being depressed on its blue (left) side. This, combined with the fact that no continuum light is detected to the left of the line, is a clear spectral signature of the Lyman-alpha line: photons "bluer" than Lyman-alpha are heavily absorbed by the gas present in the galaxy itself, and in the intergalactic medium along the line-of-sight between the Earth and the object. The spectroscopic observations therefore allowed the astronomers to identify unambiguously this line as Lyman-alpha, and therefore to confirm the great distance (high redshift) of this particular object. The measured redshift is 6.17, making this object one of the most distant galaxies ever detected . It received the designation "z6VDF J022803-041618" - the first part of this somewhat unwieldy name refers to the survey and the second indicates the position of this galaxy in the sky. Starlight in the early Universe However, these observations did not come without surprise! The astronomers had hoped (and expected) to detect the Lyman-alpha line from the object at the center of the 920 nm spectral window. However, while the Lyman-alpha line was found, it was positioned at a somewhat shorter wavelength. Thus, it was not the Lyman-alpha emission that caused this galaxy to be "bright" in the narrow-band (NB920) image, but "continuum" emission at wavelengths longer than that of Lyman-alpha . This radiation is very faintly visible as a horizontal, diffuse line in PR Photo 13c/03 . One consequence is that the measured redshift of 6.17 is lower than the originally predicted redshift of about 6.5. Another is that z6VDF J022803-041618 was detected by light from its massive stars (the "continuum") and not by emission from hydrogen gas (the Lyman-alpha line). This interesting conclusion is of particular interest as it shows that it is in principle possible to detect galaxies at this enormous distance without having to rely on the Lyman-alpha emission line, which may not always be present in the spectra of the distant galaxies. This will provide the astronomers with a more complete picture of the galaxy population in the early Universe. Moreover, observing more and more of these distant galaxies will help to better understand the ionization state of the Universe at this age: the ultraviolet light emitted by these galaxies should not reach us in a "neutral" Universe, i.e., before re-ionization occurred. The hunt for more such galaxies is now on to clarify how the transition from the Dark Ages happened!

The Detection and Photometric Redshift Determination of Distant Galaxies using SIRTF's Infrared Array Camera

NASA Technical Reports Server (NTRS)

Simpson, C.; Eisenhardt, P.

1998-01-01

We investigate the ability of the Space Infrared Telescope Facility's Infrared Array Camera to detect distant (z3) galaxies and measure their photometric redshifts. Our analysis shows that changing the original long wavelength filter specifications provides significant improvements in performance in this and other areas.

Space Shuttle Projects

NASA Image and Video Library

1996-11-01

This STS-80 onboard photograph shows the Orbiting Retrievable Far and Extreme Ultraviolet Spectrometer-Shuttle Pallet Satellite II (ORFEUS-SPAS II), photographed during approach by the Space Shuttle Orbiter Columbia for retrieval. Built by the German Space Agency, DARA, the ORFEUS-SPAS II, a free-flying satellite, was dedicated to astronomical observations at very short wavelengths to: investigate the nature of hot stellar atmospheres, investigate the cooling mechanisms of white dwarf stars, determine the nature of accretion disks around collapsed stars, investigate supernova remnants, and investigate the interstellar medium and potential star-forming regions. Some 422 observations of almost 150 astronomical objects were completed, including the Moon, nearby stars, distant Milky Way stars, stars in other galaxies, active galaxies, and quasar 3C273. The STS-80 mission was launched November 19, 1996.

The detection of distant cooling flows and the formation of dark matter

NASA Technical Reports Server (NTRS)

Fabian, A. C.; Arnaud, K. A.; Nulsen, P. E. J.; Mushotzky, R. F.

1986-01-01

Cooling flows involving substantial mass inflow rates appear to be common in many nearby rich and poor clusters and in isolated galaxies. The extensive optical and ultraviolet filaments produced by the thermal instability of large flows are detectable out to redshifts greater than 1. It is proposed that this may explain the extended optical line emission reported in, and around, many distant radio galaxies, narrow-line quasars, and even nearby normal and active galaxies. An important diagnostic to distinguish cooling flows from other possible origins of emission line filaments is the presence of extensive regions at high thermal pressure. Other evidence for distant cooling flows and the resultant star formation is further discussed, together with the implications of cooling flow initial-mass functions for galaxy formation and the nature of 'dark' matter.

An analytic resolution to the competition between Lyman-Werner radiation and metal winds in direct collapse black hole hosts

NASA Astrophysics Data System (ADS)

Agarwal, Bhaskar; Regan, John; Klessen, Ralf S.; Downes, Turlough P.; Zackrisson, Erik

2017-10-01

A near pristine atomic cooling halo close to a star forming galaxy offers a natural pathway for forming massive direct collapse black hole (DCBH) seeds, which could be the progenitors of the z > 6 redshift quasars. The close proximity of the haloes enables a sufficient Lyman-Werner flux to effectively dissociate H2 in the core of the atomic cooling halo. A mild background may also be required to delay star formation in the atomic cooling halo, often attributed to distant background galaxies. In this paper, we investigate the impact of metal pollution from both the background galaxies and the close star forming galaxy under extremely unfavourable conditions such as instantaneous metal mixing. We find that within the time window of DCBH formation, the level of pollution never exceeds the critical threshold (Zcr ˜ 1 × 10-5 Z⊙) and attains a maximum metallicity of Z ˜ 2 × 10- 6 Z⊙. As the system evolves, the metallicity eventually exceeds the critical threshold, long after the DCBH has formed.

Chandra X-Ray Observatory Image NGC 3603

NASA Technical Reports Server (NTRS)

2001-01-01

NGC 3603 is a bustling region of star birth in the Carina spiral arm of the Milky Way galaxy, about 20,000 light-years from Earth. For the first time, this Chandra image resolves the multitude of individual x-ray sources in this star-forming region. (The intensity of the x-rays observed by Chandra are depicted by the various colors in this image. Green represents lower intensity sources, while purple and red indicate increasing x-ray intensity.) Specifically, the Chandra image reveals dozens of extremely massive stars born in a burst of star formation about 2 million years ago. This region's activities may be indicative of what is happening in other distant 'starburst' galaxies (bright galaxies flush with new stars). In the case of NGC 3603, scientists now believe that these x-rays are emitted from massive stars and stellar winds, since the stars are too young to have produced supernovae or have evolved into neutron stars. The Chandra observations of NGC 3603 may provide new clues about x-ray emission in starburst galaxies as well as star formation itself. (Photo credit: NASA/GSFC/M. Corcoran et al)

History of Chandra X-Ray Observatory

NASA Image and Video Library

2001-01-01

NGC 3603 is a bustling region of star birth in the Carina spiral arm of the Milky Way galaxy, about 20,000 light-years from Earth. For the first time, this Chandra image resolves the multitude of individual x-ray sources in this star-forming region. (The intensity of the x-rays observed by Chandra are depicted by the various colors in this image. Green represents lower intensity sources, while purple and red indicate increasing x-ray intensity.) Specifically, the Chandra image reveals dozens of extremely massive stars born in a burst of star formation about 2 million years ago. This region's activities may be indicative of what is happening in other distant "starburst" galaxies (bright galaxies flush with new stars). In the case of NGC 3603, scientists now believe that these x-rays are emitted from massive stars and stellar winds, since the stars are too young to have produced supernovae or have evolved into neutron stars. The Chandra observations of NGC 3603 may provide new clues about x-ray emission in starburst galaxies as well as star formation itself. (Photo credit: NASA/GSFC/M. Corcoran et al)

Galactic Hearts of Glass

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] Click on image for larger graph

This artist's concept shows delicate greenish crystals sprinkled throughout the violent core of a pair of colliding galaxies. The white spots represent a thriving population of stars of all sizes and ages. NASA's Spitzer Space Telescope detected more than 20 bright and dusty galactic mergers like the one depicted here, all teeming with the tiny gem-like crystals.

When galaxies collide, they trigger the birth of large numbers of massive stars. Astronomers believe these blazing hot stars act like furnaces to produce silicate crystals in the same way that glass is made from sand. The stars probably shed the crystals as they age, and as they blow apart in supernovae explosions.

At the same time the crystals are being churned out, they are also being destroyed. Fast-moving particles from supernova blasts easily convert silicates crystals back to their amorphous, or shapeless, form.

How is Spitzer seeing the crystals if they are rapidly disappearing? Astronomers say that, for a short period of time at the beginning of galactic mergers, massive stars might be producing silicate crystals faster than they are eliminating them. When our own galaxy merges with the Andromeda galaxy in a few billion years, a similar burst of massive stars and silicate crystals might occur.

Crystal Storm in Distant Galaxy The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells astronomers that a distant galaxy called IRAS 08752+3915 is experiencing a storm of tiny crystals made up of silicates. The crystals are similar to the glass-like grains of sand found on Earth's many beaches.

The data were taken by Spitzer's infrared spectrograph, which splits light open to reveal its rainbow-like components. The resulting spectrum shown here reveals the signatures of both crystalline (green) and non-crystalline (brown) silicates.

Spitzer detected the same crystals in 20 additional galaxies, all belonging to a class called ultraluminous infrared galaxies. These extremely bright and dusty galaxies usually consist of two galaxies in the process of smashing into each other. Astronomers believe massive stars at the hearts of the galaxies are churning out clouds of silicate crystals. This phenomenon may represent a short-lived phase in the evolution of galactic mergers.

MAD Adaptive Optics Imaging of High-luminosity Quasars: A Pilot Project

NASA Astrophysics Data System (ADS)

Liuzzo, E.; Falomo, R.; Paiano, S.; Treves, A.; Uslenghi, M.; Arcidiacono, C.; Baruffolo, A.; Diolaiti, E.; Farinato, J.; Lombini, M.; Moretti, A.; Ragazzoni, R.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

2016-08-01

We present near-IR images of five luminous quasars at z ˜ 2 and one at z ˜ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ˜ 0.2 arcsec. We are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2-3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K-magnitude spanning from 15 to 20 (corresponding to absolute magnitude -31 to -26) and host galaxies that are 4 mag fainter than their nuclei.

NASA Galaxy Mission Celebrates Sixth Anniversary

NASA Image and Video Library

2009-04-28

NASA Galaxy Evolution Explorer Mission celebrates its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space. The mission studies the shape, brightness, size and distance of distant galaxies across 10 billion years of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC598, more commonly known as M33. The image shows a map of the recent star formation history of M33. The bright blue and white areas are where star formation has been extremely active over the past few million years. The patches of yellow and gold are regions where star formation was more active 100 million years ago. In addition, the ultraviolet image shows the most massive young stars in M33. These stars burn their large supply of hydrogen fuel quickly, burning hot and bright while emitting most of their energy at ultraviolet wavelengths. Compared with low-mass stars like our sun, which live for billions of years, these massive stars never reach old age, having a lifespan as short as a few million years. http://photojournal.jpl.nasa.gov/catalog/PIA12000

HST Imaging of the Eye of Horus, a Double Source Plane Gravitational Lens

NASA Astrophysics Data System (ADS)

Wong, Kenneth

2017-08-01

Double source plane (DSP) gravitational lenses are extremely rare alignments of a massive lens galaxy with two background sources at distinct redshifts. The presence of two source planes provides important constraints on cosmology and galaxy structure beyond that of typical lens systems by breaking degeneracies between parameters that vary with source redshift. While these systems are extremely valuable, only a handful are known. We have discovered the first DSP lens, the Eye of Horus, in the Hyper Suprime-Cam survey and have confirmed both source redshifts with follow-up spectroscopy, making this the only known DSP lens with both source redshifts measured. Furthermore, the brightest image of the most distant source (S2) is split into a pair of images by a mass component that is undetected in our ground-based data, suggesting the presence of a satellite or line-of-sight galaxy causing this splitting. In order to better understand this system and use it for cosmology and galaxy studies, we must construct an accurate lens model, accounting for the lensing effects of both the main lens galaxy and the intermediate source. Only with deep, high-resolution imaging from HST/ACS can we accurately model this system. Our proposed multiband imaging will clearly separate out the two sources by their distinct colors, allowing us to use their extended surface brightness distributions as constraints on our lens model. These data may also reveal the satellite galaxy responsible for the splitting of the brightest image of S2. With these observations, we will be able to take full advantage of the wealth of information provided by this system.

A search for N-type galaxies

NASA Technical Reports Server (NTRS)

Jefferies, J. T.

1971-01-01

A large number of distant clusters of galaxies was examined for the presence of a bright compact galaxy or blue stellar object. Nearly 600 square degrees of sky were searched using glass copies of the National Geographic Society-Palomar Observatory Sky Survey plates, and over 20 fields were selected for observation. The objects were examined for infrared and ultraviolet excesses, using wideband filter photography and spectroscopy. Initial findings include a faint, distant cluster of galaxies near the quasi-stellar radio source 4C 37.43 with a red shift of 0.370. One of these galaxies has an emission line at 6895 A, indicating a possible red shift of 0.377 of the 5007 A line of (0 III).

Exploring the Extreme Universe with the Fermi Gamma-Ray Space Telescope

NASA Technical Reports Server (NTRS)

Thompson, David J.; Digel, Seth W.; Racusin, Judith L.

2012-01-01

In ways similar to experiments in nuclear and particle physics, high-energy astrophysics usesgamma rays and energetic charged particles toprobe processes that involve large energy transfers.Since its launch in 2008, the international Fermi Gamma-Ray Space Telescope has been exploringnatural particle accelerators and the interactionsof high-energy particles in the universe. Withsources ranging from thunderstorms on Earth to galaxies and exploding stars in distant parts of the cosmos, the telescopes subjects of study are almostas diverse as were those of the scientist whose name it bears.

IRAS 14348-1447, an ultraluminous pair of colliding, gas-rich galaxies - The birth of a quasar?

NASA Technical Reports Server (NTRS)

Sanders, D. B.; Soifer, B. T.; Scoville, N. Z.

1988-01-01

Ground-baed observations of the object IRAS 14348-1447, which was discovered with the Infrared Astronomical Satellite, show that it is an extremely luminous colliding galaxy system that emits more than 95 percent of its energy at FIR wavelengths. IRAS 14348-1447, which is receeding from the sun at 8 percent of the speed of light, has a bolometric luminosity more than 100 times larger than that of the Galaxy, and is therefore as luminous as optical quasars. New optical, infrared, and spectroscopic measurements suggest that the dominant luminosity source is a dust-enshrouded quasar. The fuel for the intense activity is an enormous supply of molecular gas. Carbon monoxide emission has been detected at a wavelength of 2.6 millimeters by means of a new, more sensitive receiver recently installed on the 12-meter telescope of the National Radio Astronomy Observatory. IRAS 14348-1447 is the most distant and luminous source of carbon monoxide line emission yet detected.

Jekyll & Hyde: quiescence and extreme obscuration in a pair of massive galaxies 1.5 Gyr after the Big Bang

NASA Astrophysics Data System (ADS)

Schreiber, C.; Labbé, I.; Glazebrook, K.; Bekiaris, G.; Papovich, C.; Costa, T.; Elbaz, D.; Kacprzak, G. G.; Nanayakkara, T.; Oesch, P.; Pannella, M.; Spitler, L.; Straatman, C.; Tran, K.-V.; Wang, T.

2018-03-01

We obtained ALMA spectroscopy and deep imaging to investigate the origin of the unexpected sub-millimeter emission toward the most distant quiescent galaxy known to date, ZF-COSMOS-20115 at z = 3.717. We show here that this sub-millimeter emission is produced by another massive (M* 1011 M⊙), compact (r1/2 = 0.67 ± 0.14 kpc) and extremely obscured galaxy (AV 3.5), located only 0.43'' (3.1 kpc) away from the quiescent galaxy. We dub the quiescent and dusty galaxies Jekyll and Hyde, respectively. No dust emission is detected at the location of the quiescent galaxy, implying SFR < 13 M⊙ yr-1 which is the most stringent upper limit ever obtained for a quiescent galaxy at these redshifts. The two sources are spectroscopically confirmed to lie at the same redshift thanks to the detection of [C II]158 in Hyde (z = 3.709), which provides one the few robust redshifts for a highly-obscured "H-dropout" galaxy (H - [4.5] = 5.1 ± 0.8). The [C II] line shows a clear rotating-disk velocity profile which is blueshifted compared to the Balmer lines of Jekyll by 549 ± 60 km s-1, demonstrating that it is produced by another galaxy. Careful de-blending of the Spitzer imaging confirms the existence of this new massive galaxy, and its non-detection in the Hubble images requires extremely red colors and strong attenuation by dust. Full modeling of the UV-to-far-IR emission of both galaxies shows that Jekyll has fully quenched at least 200Myr prior to observation and still presents a challenge for models, while Hyde only harbors moderate star-formation with SFR ≲ 120 M⊙ yr-1, and is located at least a factor 1.4 below the z 4 main sequence. Hyde could also have stopped forming stars less than 200 Myr before being observed; this interpretation is also suggested by its compactness comparable to that of z 4 quiescent galaxies and its low [C II]/FIR ratio, but significant on-going star-formation cannot be ruled out. Lastly, we find that despite its moderate SFR, Hyde hosts a dense reservoir of gas comparable to that of the most extreme starbursts. This suggests that whatever mechanism has stopped or reduced its star-formation must have done so without expelling the gas outside of the galaxy. Because of their surprisingly similar mass, compactness, environment and star-formation history, we argue that Jekyll and Hyde can be seen as two stages of the same quenching process, and provide a unique laboratory to study this poorly understood phenomenon. The reduced ALMA image, spectrum, and data cube are available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A22

A dusty, normal galaxy in the epoch of reionization.

PubMed

Watson, Darach; Christensen, Lise; Knudsen, Kirsten Kraiberg; Richard, Johan; Gallazzi, Anna; Michałowski, Michał Jerzy

2015-03-19

Candidates for the modest galaxies that formed most of the stars in the early Universe, at redshifts z > 7, have been found in large numbers with extremely deep restframe-ultraviolet imaging. But it has proved difficult for existing spectrographs to characterize them using their ultraviolet light. The detailed properties of these galaxies could be measured from dust and cool gas emission at far-infrared wavelengths if the galaxies have become sufficiently enriched in dust and metals. So far, however, the most distant galaxy discovered via its ultraviolet emission and subsequently detected in dust emission is only at z = 3.2 (ref. 5), and recent results have cast doubt on whether dust and molecules can be found in typical galaxies at z ≥ 7. Here we report thermal dust emission from an archetypal early Universe star-forming galaxy, A1689-zD1. We detect its stellar continuum in spectroscopy and determine its redshift to be z = 7.5 ± 0.2 from a spectroscopic detection of the Lyman-α break. A1689-zD1 is representative of the star-forming population during the epoch of reionization, with a total star-formation rate of about 12 solar masses per year. The galaxy is highly evolved: it has a large stellar mass and is heavily enriched in dust, with a dust-to-gas ratio close to that of the Milky Way. Dusty, evolved galaxies are thus present among the fainter star-forming population at z > 7.

Nearby Hot Stars May Change Our View of Distant Sources

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

As if it werent enough that quasars distant and bright nuclei of galaxies twinkle of their own accord due to internal processes, nature also provides another complication: these distant radio sources can also appear to twinkle because of intervening material between them and us. A new study has identified a possible source for the material getting in the way.Unexplained VariabilityA Spitzer infrared view of the Helix nebula, which contains ionized streamers of gas extending radially outward from the central star. [NASA/JPL-Caltech/Univ. of Ariz.]Distant quasars occasionally display extreme scintillation, twinkling with variability timescales shorter than a day. This intra-day variability is much greater than we can account for with standard models of the interstellar medium lying between the quasar and us. So what could cause this extreme scattering instead?The first clue to this mystery came from the discovery of strong variability in the radio source PKS 1322110. In setting up follow-up observations of this object, Mark Walker (Manly Astrophysics, Australia) and collaborators noticed that, in the plane of the sky, PKS 1322110 lies very near the bright star Spica. Could this be coincidence, or might this bright foreground star have something to do with the extreme scattering observed?Diagram explaining the source of the intra-day radio source variability as intervening filaments surrounding a hot star. [M. Walker/CSIRO/Manly Astrophysics]Swarms of ClumpsWalker and collaborators put forward a hypothesis: perhaps the ultraviolet photons of nearby hot stars ionize plasma around them, which in turn causes the extreme scattering of the distant background sources.As a model, the authors consider the Helix Nebula, in which a hot, evolved star is surrounded by cool globules of molecular hydrogen gas. The radiation from the star hits these molecular clumps, dragging them into long radial streamers and ionizing their outer skins.Though the molecular clumps in the Helix Nebula were thought to have formed only as the star evolved late into its lifetime, Walker and collaborators are now suggesting that all stars regardless of spectral type or evolutionary stage may be surrounded by swarms of tiny molecular clumps. Aroundstars that are hot enough, these clumps become the ionized plasma streamers that can cause interference with the light traveling to us from distant sources.Significant MassTo test this theory, Walker and collaborators explore observations of two distant radio quasars that have both exhibited intra-day variability over many years of observations. The team identified a hot A-type star near each of these two sources: J1819+3845 has Vega nearby, and PKS 1257326 has Alhakim.Locations of stars along the line of site to two distant quasars, J1819+3845 (top panel) and PKS 1257326 (bottom panel). Both have a nearby, hot star (blue markers) radially within 2 pc: Vega (z = 7.7 pc) and Alhakim (z = 18 pc), respectively. [Walker et al. 2017]By modeling the systems of the sources and stars, the authors show that the size, location, orientation, and numbers of plasma concentrations necessary to explain observations are all consistent with an environment similar to that of the Helix Nebula. Walker and collaborators find that the total mass in the molecular clumps surrounding the two stars would need to be comparable to the mass of the stars themselves.If this picture is correct, and if all stars are indeed surrounded by molecular clumps like these, then a substantial fraction of the mass of ourgalaxy could be contained in these clumps. Besides explaining distant quasar scintillation, this idea would therefore have a significant impact on our overall understanding of how mass in galaxies is distributed. More observations of twinkling quasars are the next step toward confirming this picture.CitationMark A. Walker et al 2017 ApJ 843 15. doi:10.3847/1538-4357/aa705c

A direct measurement of the high-mass end of the velocity dispersion function at z ~ 0.55 from SDSS-III/BOSS

DOE PAGES

Montero-Dorta, Antonio D.; Bolton, Adam S.; Shu, Yiping

2017-02-24

When two galaxies that are distant from one another (and also distant from Earth) happen to lie along a single line of sight in the sky, the resulting phenomenon is known as a “gravitational lens.” The gravity of the more nearby galaxy warps the image of the more distant galaxy into multiple images or complete rings (know as “Einstein rings” since the quantitative description of the gravitational lensing effect relies on Einstein’s theory of gravity.) Strong gravitational lens systems have multiple scientific applications. If the more distant galaxy happens to contain a time-varying quasar (bright emission powered by a supermassivemore » black hole at the galaxy’s center) or supernova explosion, the time delay between multiple images can be used as a probe of the expansion rate of the universe (and other cosmological parameters.) Forecasting the incidence of gravitational lenses in future large-scale sky surveys relies on quantifying the population of potential lens galaxies in the universe in terms of their abundance and their lensing efficiency. The lensing efficiency is most directly correlated with the galaxy’s “velocity dispersion:” the characteristic speed with which stars in the galaxy are orbiting under the influence of the galaxy’s overall gravitational field. This paper uses previous results quantifying the combined demographics of galaxies in brightness and velocity dispersion to compute the demographics of massive “elliptical” galaxies in velocity dispersion alone, thereby providing the essential ingredient for forecasting the expected incidence of strong gravitational lensing by these types of galaxies in future sky surveys such as DESI and LSST. These results are also applicable to the association of massive galaxies with their associated dark-matter “halos,” which is an essential ingredient for the most accurate and informative extraction of cosmological parameters from the data sets produced by large-scale surveys of the universe.« less

High molecular gas fractions in normal massive star-forming galaxies in the young Universe.

PubMed

Tacconi, L J; Genzel, R; Neri, R; Cox, P; Cooper, M C; Shapiro, K; Bolatto, A; Bouché, N; Bournaud, F; Burkert, A; Combes, F; Comerford, J; Davis, M; Schreiber, N M Förster; Garcia-Burillo, S; Gracia-Carpio, J; Lutz, D; Naab, T; Omont, A; Shapley, A; Sternberg, A; Weiner, B

2010-02-11

Stars form from cold molecular interstellar gas. As this is relatively rare in the local Universe, galaxies like the Milky Way form only a few new stars per year. Typical massive galaxies in the distant Universe formed stars an order of magnitude more rapidly. Unless star formation was significantly more efficient, this difference suggests that young galaxies were much more molecular-gas rich. Molecular gas observations in the distant Universe have so far largely been restricted to very luminous, rare objects, including mergers and quasars, and accordingly we do not yet have a clear idea about the gas content of more normal (albeit massive) galaxies. Here we report the results of a survey of molecular gas in samples of typical massive-star-forming galaxies at mean redshifts of about 1.2 and 2.3, when the Universe was respectively 40% and 24% of its current age. Our measurements reveal that distant star forming galaxies were indeed gas rich, and that the star formation efficiency is not strongly dependent on cosmic epoch. The average fraction of cold gas relative to total galaxy baryonic mass at z = 2.3 and z = 1.2 is respectively about 44% and 34%, three to ten times higher than in today's massive spiral galaxies. The slow decrease between z approximately 2 and z approximately 1 probably requires a mechanism of semi-continuous replenishment of fresh gas to the young galaxies.

Dwarfs in the Deepest Fields at Noon: Studying Size and Shape of Low-mass Galaxies out to z 3 in Five HST Legacy Fields

NASA Astrophysics Data System (ADS)

Guo, Yicheng

2017-08-01

Galaxies with stellar mass 100x-1000x times smaller than our Milky Way (hereafter dwarf galaxies or DGs) are important for understanding galaxy formation and evolution by being the most sensitive probes of both the macro-physics of dark matter halos and the micro-physics of the different physical mechanisms that regulate star formation and shape galaxies. Currently, however, observations of distant DGs have been hampered by small samples and poor quality due to their faintness. We propose an archival study of the size, morphology, and structures of DGs out to z 3.0 by combining the archived data from five of the deepest regions that HST has ever observed: eXtreme Deep Field (XDF, updated from HUDF) and the Hubble Legacy Fields (HLFs). Our program would be the first to advance the morphology studies of DGs to the Cosmic Noon (z 2), and hence place unprecedented constraints on models of galaxy structure formation. Equally important is the data product of our program: multi-wavelength photometry and morphology catalogs for all detected galaxies in these fields. These catalogs would be a timely treasure for the public to prepare for the coming JWST era by providing detailed information of small, faint, but important objects in some deepest HST fields for JWST observations.

NIR Spectroscopic Observation of Massive Galaxies in the Protocluster at z = 3.09

NASA Astrophysics Data System (ADS)

Kubo, Mariko; Yamada, Toru; Ichikawa, Takashi; Kajisawa, Masaru; Matsuda, Yuichi; Tanaka, Ichi

2015-01-01

We present the results of near-infrared spectroscopic observations of the K-band-selected candidate galaxies in the protocluster at z = 3.09 in the SSA22 field. We observed 67 candidates with K AB < 24 and confirmed redshifts of the 39 galaxies at 2.0 < z spec < 3.4. Of the 67 candidates, 24 are certainly protocluster members with 3.04 <= z spec <= 3.12, which are massive red galaxies that have been unidentified in previous optical observations of the SSA22 protocluster. Many distant red galaxies (J - K AB > 1.4), hyper extremely red objects (J - K AB > 2.1), Spitzer MIPS 24 μm sources, active galactic nuclei (AGNs) as well as the counterparts of Lyα blobs and the AzTEC/ASTE 1.1 mm sources in the SSA22 field are also found to be protocluster members. The mass of the SSA22 protocluster is estimated to be ~2-5 × 1014 M ⊙, and this system is plausibly a progenitor of the most massive clusters of galaxies in the current universe. The reddest (J - K AB >= 2.4) protocluster galaxies are massive galaxies with M star ~ 1011 M ⊙ showing quiescent star formation activities and plausibly dominated by old stellar populations. Most of these massive quiescent galaxies host moderately luminous AGNs detected by X-ray. There are no significant differences in the [O III] λ5007/Hβ emission line ratios and [O III] λ5007 line widths and spatial extents of the protocluster galaxies from those of massive galaxies at z ~ 2-3 in the general field.

Finding the First Galaxies

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.

2009-01-01

Astronomers study distant galaxies by taking long exposures in deep survey fields. They choose fields that are empty of known sources, so that they are statistically representative of the Universe as a whole. Astronomers can compare the distribution of the detected galaxies in brightness, color, morphology and redshift to theoretical models, in order to puzzle out the processes of galaxy evolution. In 2004, the Hubble Space Telescope was pointed at a small, deep-survey field in the southern constellation Fornax for more than 500 hours of exposure time. The resulting Hubble Ultra-Deep Field could see the faintest and most distant galaxies that the telescope is capable of viewing. These galaxies emitted their light less than 1 billion years after the Big Bang. From the Ultra Deep Field and other galaxy surveys, astronomers have built up a history of star formation in the universe. the peak occurred about7 billion years ago, about half of the age of the current universe, then the number of stars that were forming was about 15 time the rate today. Going backward in time to when the very first starts and galaxies formed, the average star-formation rate should drop to zero. but when looking at the most distant galaxies in the Ultra Deep field, the star formation rate is still higher than it is today. The faintest galaxies seen by Hubble are not the first galaxies that formed in the early universe. To detect these galaxies NASA is planning the James Webb Space Telescope for launch in 2013. Webb will have a 6.5-meter diameter primary mirror, much bigger than Hubble's 2.4-meter primary, and will be optimized for infrared observations to see the highly redshifted galaxies.

Multi-conjugated adaptive optics imaging of distant galaxies - a comparison of Gemini/GSAOI and VLT/HAWK-I data

NASA Astrophysics Data System (ADS)

Schirmer, Mischa; Garrel, Vincent; Sivo, Gaetano; Marin, Eduardo; Carrasco, Eleazar R.

2017-11-01

Multi-conjugated adaptive optics (MCAO) yield nearly diffraction-limited images at 2 μm wavelengths. Currently, Gemini Multi-Conjugate Adaptive Optics System (GeMS)/Gemini South Adaptive Optics Imager (GSAOI) at Gemini South is the only MCAO facility instrument at an 8-m telescope. Using real data, and for the first time, we investigate the gain in depth and signal-to-noise ratios (S/N) when MCAO is employed for Ks-band observations of distant galaxies. Our analysis is based on the Frontier Fields cluster MACS J0416.1-2403, observed with GeMS/GSAOI (near diffraction-limited) and compared against Very Large Telescope/HAWK-I (natural seeing) data. Using galaxy number counts, we show that the substantially increased thermal background and lower optical throughput of the MCAO unit are fully compensated for by the wavefront correction because the galaxy images can be measured in smaller apertures with less sky noise. We also performed a direct comparison of the S/N of sources detected in both data sets. For objects with intrinsic angular sizes corresponding to half the HAWK-I image seeing, the gain in S/N is 40 per cent. Even smaller objects experience a boost in S/N by up to a factor of 2.5 despite our suboptimal natural guide star configuration. The depth of the near diffraction limited images is more difficult to quantify than that of seeing limited images, due to a strong dependence on the intrinsic source profiles. Our results emphasize the importance of cooled MCAO systems for Ks-band observations with future, extremely large telescopes.

History of Chandra X-Ray Observatory

NASA Image and Video Library

2000-10-01

This most distant x-ray cluster of galaxies yet has been found by astronomers using Chandra X-ray Observatory (CXO). Approximately 10 billion light-years from Earth, the cluster 3C294 is 40 percent farther than the next most distant x-ray galaxy cluster. The existence of such a faraway cluster is important for understanding how the universe evolved. CXO's image reveals an hourglass-shaped region of x-ray emissions centered on the previously known central radio source (seen in this image as the blue central object) that extends outward for 60,000 light- years. The vast clouds of hot gas that surround such galaxies in clusters are thought to be heated by collapse toward the center of the cluster. Until CXO, x-ray telescopes have not had the needed sensitivity to identify such distant clusters of galaxies. Galaxy clusters are the largest gravitationally bound structures in the universe. The intensity of the x-rays in this CXO image of 3C294 is shown as red for low energy x-rays, green for intermediate, and blue for the most energetic x-rays. (Photo credit: NASA/loA/A. Fabian et al)

Astronomers Discover Six-Image Gravitational Lens

NASA Astrophysics Data System (ADS)

2001-08-01

An international team of astronomers has used the National Science Foundation's Very Long Baseline Array (VLBA) radio telescope and NASA's Hubble Space Telescope (HST) to discover the first gravitational lens in which the single image of a very distant galaxy has been split into six different images. The unique configuration is produced by the gravitational effect of three galaxies along the line of sight between the more-distant galaxy and Earth. Optical and Radio Images of Gravitational Lens "This is the first gravitational lens with more than four images of the background object that is produced by a small group of galaxies rather than a large cluster of galaxies," said David Rusin, who just received his Ph.D. from the University of Pennsylvania. "Such systems are expected to be extremely rare, so this discovery is an important stepping stone. Because this is an intermediate case between gravitational lenses produced by single galaxies and lenses produced by large clusters of galaxies, it will give us insights we can't get from other types of lenses," Rusin added. The gravitational lens, called CLASS B1359+154, consists of a galaxy more than 11 billion light-years away in the constellation Bootes, with a trio of galaxies more than 7 billion light-years away along the same line of sight. The more-distant galaxy shows signs that it contains a massive black hole at its core and also has regions in which new stars are forming. The gravitational effect of the intervening galaxies has caused the light and radio waves from the single, more-distant galaxy to be "bent" to form six images as seen from Earth. Four of these images appear outside the triangle formed by the three intermediate galaxies and two appear inside that triangle. "This lens system is a very interesting case to study because it is more complicated than lenses produced by single galaxies, and yet simpler than lenses produced by clusters of numerous galaxies," said Chris Kochanek of the Harvard-Smithsonian Center for Astrophysics (CfA). "When we understand this system, we will have a much clearer picture of how galaxies are changed by being part of a bigger cluster of galaxies," he added. B1359+154 was discovered in 1999 by the Cosmic Lens All-Sky Survey, an international collaboration of astronomers who use radio telescopes to search the sky for gravitational lenses. Images made by the NSF's Very Large Array in New Mexico and by Britain's MERLIN radio telescope showed six objects suspected of being gravitational-lens images, but the results were inconclusive. Rusin and his team used the VLBA and HST in 1999 and 2000 to make more-detailed studies of B1359+154. The combination of data from the VLBA and HST convinced the astronomers that B1359+154 actually consists of six lensed images of a single background galaxy. The VLBA images were made from data collected during observations at a radio frequency of 1.7 GHz. "This is a great example of modern, multi-wavelength astronomy," said Rusin. "We need the radio telescopes to detect the gravitational lenses in the first place, then we need the visible-light information from Hubble to show us additional detail about the structure of the system." Armed with the combined VLBA and HST data about the positions and brightnesses of the six images of the background galaxy as well as the positions of the three intermediate galaxies, the astronomers did computer simulations to show how the gravitation of the three galaxies could produce the lens effect. They were able to design a computer model of the system that, in fact, produces the six images seen in B1359+154. "Our computer model certainly is not perfect, and we need to do more observations of this system to refine it, but we have clearly demonstrated that the three galaxies we see can produce a six-image lens system," said Martin Norbury, a graduate student at Jodrell Bank Observatory in Britain. "We think this work will give us an excellent tool for studying much-denser clusters of galaxies and the relationships of the individual cluster galaxies to the 'halo' of dark matter in which they are embedded," he added. Clusters of galaxies are known to produce gravitational lenses with up to eight images of a single background object. However, the number of galaxies in such a cluster makes it difficult for astronomers to decipher just how their gravitational effects have combined to produce the multiple images. Researchers hope to be able to understand the lensing effect well enough to use the lenses to show them how galaxies, gas and unseen dark matter in clusters are distributed. A system such as B1359+154, with only three galaxies involved in the lensing, can help astronomers learn how complex gravitational lenses work. "The next big step is to use HST to see the pattern of rings produced by the galaxy surrounding the black hole. We already see hints of them, but with the upgrades to HST in the next servicing mission we should be able to trace it completely both to pin down the structure of the lens and to have an enormously magnified image for studying the distant host galaxy," Kochanek said. In addition to Rusin, Kochanek and Norbury, the researchers are: Emilio Falco of the CfA; Chris Impey of Steward Observatory at the University of Arizona; Joseph Lehar of the CfA; Brian McLeod of the CfA; Hans-Walter Rix of the Max Planck Institute for Astronomy in Germany; Chuck Keeton of Steward Observatory; Jose Munoz of the Astrophysical Institute of the Canaries in Tenerife, Spain; and Chien Peng of Steward Observatory. The team published its results in the Astrophysical Journal. The VLBA is a system of 10 radio-telescope antennas that work together as a single astronomical instrument. The antennas are spread across the United States, from Hawaii in the west to the U.S. Virgin Islands in the east. A radio telescope system more than 5,000 miles across, the VLBA produces extremely detailed images. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA,, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international Cooperation between NASA and the European Space Agency.

Massive and Distant Clusters of WISE Survey (MaDCoWS)

NASA Astrophysics Data System (ADS)

Brodwin, Mark; MaDCoWS Collaboration

2018-06-01

The Massive and Distant Clusters of WISE Survey (MaDCoWS) is a comprehensive program to detect and characterize the most massive galaxy clusters in the Universe at z ~ 1, and is the only all-sky survey sensitive to galaxy clusters at this epoch. The foundation for this program is data from the NASA Wide-field Infrared Survey Explorer (WISE). The primary goal is to study the evolution of massive galaxies in the most overdense environments at z > 1 when star formation and AGN activity may be peaking in these structures. Spitzer follow-up imaging of 2000 MaDCoWS clusters has allowed us to select the richest and/or most distant clusters for detailed study. To date we have spectroscopically confirmed over 35 MaDCoWS clusters, spanning a wide range of masses (2-11 x 10^14 Msun), out to z = 1.5. This includes the discovery of the most massive z > 1.15 cluster found to date, as well as a cluster at z = 1.23 that is lensing a z = 2.22 supernova Ia. Multiwavelength follow-up observations of these distant clusters, currently underway, will permit several novel studies of galaxy evolution in rich cluster environments at z > 1.

Violence in the hearts of galaxies: aberration or adolescence?

PubMed

Mundell, Carole G

2002-12-15

Violent activity in the nuclei of galaxies has long been considered a curiosity in its own right; manifestations of this phenomenon include distant quasars in the early Universe and comparatively nearby Seyfert galaxies, both thought to be powered by the release of gravitational potential energy as material from the host galaxy accretes onto a central supermassive black hole (SMBH). Traditionally, the broader study of the formation, structure and evolution of galaxies has largely excluded active galactic nuclei. Recently, however, this situation has changed dramatically, both observationally and theoretically, with the realization that the growth and influence of the SMBH, the origin and development of galaxies and nuclear activity at different epochs in the Universe may be intimately related. The most spectacular fireworks seen in distant quasars may be relatively easy to explain, since the era of greatest quasar activity seems to coincide with turbulent dynamics at the epoch of galaxy formation in the young, gas-rich Universe. Ubiquitous black holes are believed to be a legacy of this violent birth. Alternatively, black holes may be the seeds that drive galaxy formation in the first place. Closer to home, and hence more recently in the history of the Universe, a fraction of comparatively ordinary galaxies, similar to our own, has reignited their central engines, albeit at a lower level of activity. Since these galaxies are more established than their younger and more distant counterparts, the activity here is all the more puzzling. Whatever the mechanisms involved, they are likely to play an important role in galaxy evolution. I review the intriguing evidence for causal links between SMBHs, nuclear activity and the formation and evolution of galaxies, and describe opportunities for testing these relationships using the next generation of earthbound and space-borne astronomical facilities.

The Evolution of the Observed Hubble Sequence over the past 6Gyr

NASA Astrophysics Data System (ADS)

Delgado-Serrano, R.; Hammer, F.; Yang, Y. B.; Puech, M.; Flores, H.; Rodrigues, M.

2011-10-01

During the past years we have confronted serious problems of methodology concerning the morphological and kinematic classification of distant galaxies. This has forced us to create a new simple and effective morphological classification methodology, in order to guarantee a morpho-kinematic correlation, make the reproducibility easier and restrict the classification subjectivity. Giving the characteristic of our morphological classification, we have thus been able to apply the same methodology, using equivalent observations, to representative samples of local and distant galaxies. It has allowed us to derive, for the first time, the distant Hubble sequence (~6 Gyr ago), and determine a morphological evolution of galaxies over the past 6 Gyr. Our results strongly suggest that more than half of the present-day spirals had peculiar morphologies, 6 Gyr ago.

Extended Source/Galaxy All Sky 1

NASA Image and Video Library

2003-03-27

This panoramic view of the entire sky reveals the distribution of galaxies beyond our Milky Way galaxy, which astronomers call extended sources, as observed by Two Micron All-Sky Survey. The image is constructed from a database of over 1.6 million galaxies listed in the survey's Extended Source Catalog; more than half of the galaxies have never before been catalogued. The image is a representation of the relative brightnesses of these million-plus galaxies, all observed at a wavelength of 2.2 microns. The brightest and nearest galaxies are represented in blue, and the faintest, most distant ones are in red. This color scheme gives insights into the three dimensional large-scale structure of the nearby universe with the brightest, closest clusters and superclusters showing up as the blue and bluish-white features. The dark band in this image shows the area of the sky where our Milky Way galaxy blocks our view of distant objects, which, in this projection, lies predominantly along the edges of the image. http://photojournal.jpl.nasa.gov/catalog/PIA04252

Probing the Evolution of the Galaxy Interaction/Merger Rate Using Distant Collisional Ring Galaxies

NASA Astrophysics Data System (ADS)

Lavery, Russell J.; Remijan, Anthony J.

We present the initial results from our long-term program of identifying distant collisional ring galaxies (CRGS) in deep HST WFPC-2 images. The unique morphological characteristics of these galaxies make them easily identifiable out to a redshift of z = 1. To date, we have visually scanned 100 WFPC-2 fields and identified 14 excellent collisional ring galaxy (CRG) candidates. Based on estimated redshifts, these 14 galaxies are expected to lie in the redshift interval of 0.1 to 1. We have used this sample of CRGs to estimate the evolution of the galaxy interaction/merger rate with redshift. To account for the number of CRGs we have identified in these fields, the galaxy interaction/merger rate, parameterized as (1 + z)m, must increase steeply with redshift, with m = 5.7 +/- 1.5. We can rule out a non-evolving galaxy merger rate (m = 0) at greater than the 3σ level. We compare our results with other programs to determine the value of m using the evolution of galaxy pairs.

MAD ADAPTIVE OPTICS IMAGING OF HIGH-LUMINOSITY QUASARS: A PILOT PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liuzzo, E.; Falomo, R.; Paiano, S.

2016-08-01

We present near-IR images of five luminous quasars at z ∼ 2 and one at z ∼ 4 obtained with an experimental adaptive optics (AO) instrument at the European Southern Observatory Very Large Telescope. The observations are part of a program aimed at demonstrating the capabilities of multi-conjugated adaptive optics imaging combined with the use of natural guide stars for high spatial resolution studies on large telescopes. The observations were mostly obtained under poor seeing conditions but in two cases. In spite of these nonoptimal conditions, the resulting images of point sources have cores of FWHM ∼ 0.2 arcsec. Wemore » are able to characterize the host galaxy properties for two sources and set stringent upper limits to the galaxy luminosity for the others. We also report on the expected capabilities for investigating the host galaxies of distant quasars with AO systems coupled with future Extremely Large Telescopes. Detailed simulations show that it will be possible to characterize compact (2–3 kpc) quasar host galaxies for quasi-stellar objects at z = 2 with nucleus K -magnitude spanning from 15 to 20 (corresponding to absolute magnitude −31 to −26) and host galaxies that are 4 mag fainter than their nuclei.« less

Fingerprints in the Light

NASA Image and Video Library

2005-03-01

This spectrum shows the light from a dusty, distant galaxy located 11 billion light-years away. The galaxy is invisible to optical telescopes, but NASA Spitzer Space Telescope captured the light from it and dozens of other similar galaxies.

Automatic Approach to Morphological Classification of Galaxies With Analysis of Galaxy Populations in Clusters

NASA Astrophysics Data System (ADS)

Sultanova, Madina; Barkhouse, Wayne; Rude, Cody

2018-01-01

The classification of galaxies based on their morphology is a field in astrophysics that aims to understand galaxy formation and evolution based on their physical differences. Whether structural differences are due to internal factors or a result of local environment, the dominate mechanism that determines galaxy type needs to be robustly quantified in order to have a thorough grasp of the origin of the different types of galaxies. The main subject of my Ph.D. dissertation is to explore the use of computers to automatically classify and analyze large numbers of galaxies according to their morphology, and to analyze sub-samples of galaxies selected by type to understand galaxy formation in various environments. I have developed a computer code to classify galaxies by measuring five parameters from their images in FITS format. The code was trained and tested using visually classified SDSS galaxies from Galaxy Zoo and the EFIGI data set. I apply my morphology software to numerous galaxies from diverse data sets. Among the data analyzed are the 15 Abell galaxy clusters (0.03 < z < 0.184) from Rude et al. 2017 (in preparation), which were observed by the Canada-France-Hawaii Telescope. Additionally, I studied 57 galaxy clusters from Barkhouse et al. (2007), 77 clusters from the WINGS survey (Fasano et al. 2006), and the six Hubble Space Telescope (HST) Frontier Field galaxy clusters. The high resolution of HST allows me to compare distant clusters with those nearby to look for evolutionary changes in the galaxy cluster population. I use the results from the software to examine the properties (e.g. luminosity functions, radial dependencies, star formation rates) of selected galaxies. Due to the large amount of data that will be available from wide-area surveys in the future, the use of computer software to classify and analyze the morphology of galaxies will be extremely important in terms of efficiency. This research aims to contribute to the solution of this problem.

A young source of optical emission from distant radio galaxies.

PubMed

Hammer, F; Fèvre, O Le; Angonin, M C

1993-03-25

DISTANT radio galaxies provide valuable insights into the properties of the young Universe-they are the only known extended optical sources at high redshift and might represent an early stage in the formation and evolution of galaxies in general. This extended optical emission often has very complex morphologies, but the origin of the light is still unclear. Here we report spectroscopic observations for several distant radio galaxies (0.75≤ z ≤ 1.1) in which the rest-frame spectra exhibit featureless continua between 2,500 Å and 5,000 Å. We see no evidence for the break in the spectrum at 4,000 Å expected for an old stellar population 1-3 , and suggest that young stars or scattered emissions from the active nuclei are responsible for most of the observed light. In either case, this implies that the source of the optical emission is com-parable in age to the associated radio source, namely 10 7 years or less.

ALMA Examines a Distant Quasar Host

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-04-01

The dust continuum (top) and the [CII] emission (bottom) maps for the region around J1120+0641. [Adapted from Venemans et al. 2017]A team of scientists has used the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the host galaxy of the most distant quasar known. Their observations may help us to build a picture of how the first supermassive black holes in the universe formed and evolved.Faraway Monsters and Their GalaxiesWe know that quasars the incredibly luminous and active centers of some distant galaxies are powered by accreting, supermassive black holes. These monstrous powerhouses have been detected out to redshifts of z 7, when the universe was younger than a billion years old.Though weve observed over a hundred quasars at high redshift, we still dont understand how these early supermassive black holes formed, or whether the black holes and the galaxies that host them co-evolved. In order to answer questions like these, however, we first need to gather information about the properties and behavior of various supermassive black holes and their host galaxies.A team of scientists led by Bram Venemans (Max-Planck Institute for Astronomy, Germany) recently used the unprecedented sensitivity and angular resolution of ALMA as well as the Very Large Array and the IRAM Plateau de Bure Interferometer to examine the most distant quasar currently known, J1120+0641, located at a redshift of z = 7.1.A High-Resolution LookThe teams observations of the dust and gas emission from the quasars host galaxy revealed a number of intriguing things:The red and blue sides of the [CII] emission line are shown here as contours, demonstrating that theres no ordered rotational motion of the gas on kpc scales. [Adapted from Venemans et al. 2017]The majority of the galaxys emission is very compact. Around 80% of the observed flux came from a region of only 11.5 kpc in diameter.Despite the fact that the 2.4-billion-solar-mass black hole at the galaxys center is accreting at a high rate, the heating in the galaxy is dominated not by the black holes accretion, but by star formation.Theres no sign of the expected structure of a rotating disk on kpc scales.The authors estimate a dynamical mass of the host galaxy of 43 billion solar masses and the black hole at the galaxys center makes up 6% of that. This ratio is roughly 10x higher than the black-hole-to-bulge mass ratio in local early-type galaxies.In the very central region, the black hole accounts for around 20% of the galaxys dynamical mass, and gas and dust likely accounts for most of the remainder. This doesnt leave much room for massive stars in the center of the galaxy.ALMAs capabilities have enabled these first efforts to spatially resolve the host galaxy of the most distant quasar known, resulting new and unexpected information. The authors now look hopefully to the future, when even longer baselines of ALMA may allow us a still-higher-resolution look at this distant quasar, possibly providing answers to some of the questions it has raised.CitationBram P. Venemans et al 2017 ApJ 837 146. doi:10.3847/1538-4357/aa62ac

The far-infrared view on the distant Universe

NASA Astrophysics Data System (ADS)

Elbaz, David

2015-08-01

I will review what we have learnt on distant galaxies from far infrared surveys and present news ways to identify z>2 highly star-forming galaxies, often missed by standard techniques such as LBGs, that may represent the missing progenitors of passive z~2 galaxies. I will also discuss inconsistencies between SFR indicators that can be linked to the starburstiness and compactness of star-forming galaxies. Based on these results we will discuss the evidence in favor/against the existence of a SFR-M* main sequence up to z=4. The impact of the spatial distribution of star formation and its evolution with redshift will be discussed on the basis of newly obtained ALMA data.

Modeling the Internal Kinematics (Rotation and Dispersion) of Distant Galaxies (z ~ 1.0) Using Multi-PA Keck DEIMOS Slit Spectra

NASA Astrophysics Data System (ADS)

Miao, Connie; Chen, Jerry; Torres Hernandez, Jose; Guhathakurta, Puragra; Jang, Hyerin

2017-01-01

The stark difference between the chaotic internal motion of distant galaxies and the ordered rotation of typical local spiral galaxies suggests that disordered galaxies at high redshifts (i.e., early times in the Universe's history) gradually settle into well ordered disk morphologies with ordered rotation. We have used slit spectra obtained with Keck DEIMOS at four different position angles for 133 distant objects (z ~ 1.0) in the GOODS-N field. The emission lines in the 2D spectra of the galaxies were used to calculate the redshift/velocity at each spatial location. For each slit row, the distribution of flux over velocity was modeled as a Gaussian curve from which we obtained the radial velocity and spread of radial velocity. Rotation curves and velocity dispersions for each galaxy at each slit angle were plotted at these values. We qualitatively classified galaxies as regularly rotating, merging, face-on, or unable to be determined by examining overlays of the rotation curves from the four slit angles. We found that regular rotating galaxies tended to have peak velocity dispersion at the center while mergers had fairly constant velocity dispersions. Face-on galaxies had chaotic and inconsistent velocity dispersions between different slit angles. Regularly rotation galaxies represented 45% of our sample and mergers represented 27%. The relative percentage of galaxies that were either regularly rotating or mergers roughly matched those of the literature. This research was supported by NASA and the National Science Foundation. Most of this work was carried out by high school students working under the auspices of the Science Internship Program at UC Santa Cruz.

Have We Finally Found Pop III Stars?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-08-01

Elusive Population: Population III stars — the theoretical generation of extremely metal-poor stars that should have been formed in the early universe before metals existed — have been conspicuously absent in observations. But a team led by David Sobral (Institute of Astrophysics and Space Sciences, University of Lisbon, and Leiden Observatory) may have changed this paradigm with their recent detection of an extremely bright galaxy in the early universe. The team's broad survey of distant galaxies using ESO's Very Large Telescope provides a glimpse of the universe as it was only 800 million years after the Big Bang. The survey uncovered several unusually bright galaxies — including the brightest galaxy ever seen at this distance, an important discovery by itself. But further scrutiny of this galaxy, named CR7, produced an even more exciting find: a bright pocket of the galaxy contained no sign of any metals. Follow-up with other telescopes confirmed this initial detection. Formation Waves: Sobral and his team postulate that we are observing this galaxy at just the right time to have caught a cluster of Population III stars — the bright, metal-free region of the galaxy — at the end of a wave of early star formation. The observations of CR7 also suggest the presence of regular stars in clumps around the metal-free pocket. These older, surrounding clusters may have formed stars first, helping to ionize a local bubble in the galaxy and allowing us to now observe the light from CR7. It was previously thought that Population III stars might only be found in small, dim galaxies, making them impossible for us to detect. But CR7 provides an interesting alternative: this galaxy is bright, and the candidate Population III stars are surrounded by clusters of normal stars. This suggests that these first-generation stars might in fact be easier to detect than was originally thought. Additional follow-up observations with other telescopes will help to confirm the identity of these stars. In particular, the James Webb Space Telescope is expected to further advance the pursuit of the earliest galaxies and stars in the universe. Citation: David Sobral et al. 2015, ApJ, 808, 139. doi:10.1088/0004-637X/808/2/139

Galaxies Near and Far Artist Concept

NASA Image and Video Library

2011-06-30

This artist concept shows how a normal spiral galaxy around our local universe left might have looked back in the distant universe, when astronomers think galaxies would have been filled with larger populations of hot, bright stars right.

NIR SPECTROSCOPIC OBSERVATION OF MASSIVE GALAXIES IN THE PROTOCLUSTER AT z = 3.09

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubo, Mariko; Yamada, Toru; Ichikawa, Takashi

2015-01-20

We present the results of near-infrared spectroscopic observations of the K-band-selected candidate galaxies in the protocluster at z = 3.09 in the SSA22 field. We observed 67 candidates with K {sub AB} < 24 and confirmed redshifts of the 39 galaxies at 2.0 < z {sub spec} < 3.4. Of the 67 candidates, 24 are certainly protocluster members with 3.04 ≤ z {sub spec} ≤ 3.12, which are massive red galaxies that have been unidentified in previous optical observations of the SSA22 protocluster. Many distant red galaxies (J – K {sub AB} > 1.4), hyper extremely red objects (J –more » K {sub AB} > 2.1), Spitzer MIPS 24 μm sources, active galactic nuclei (AGNs) as well as the counterparts of Lyα blobs and the AzTEC/ASTE 1.1 mm sources in the SSA22 field are also found to be protocluster members. The mass of the SSA22 protocluster is estimated to be ∼2-5 × 10{sup 14} M {sub ☉}, and this system is plausibly a progenitor of the most massive clusters of galaxies in the current universe. The reddest (J – K {sub AB} ≥ 2.4) protocluster galaxies are massive galaxies with M {sub star} ∼ 10{sup 11} M {sub ☉} showing quiescent star formation activities and plausibly dominated by old stellar populations. Most of these massive quiescent galaxies host moderately luminous AGNs detected by X-ray. There are no significant differences in the [O III] λ5007/Hβ emission line ratios and [O III] λ5007 line widths and spatial extents of the protocluster galaxies from those of massive galaxies at z ∼ 2-3 in the general field.« less

A close-pair binary in a distant triple supermassive black hole system.

PubMed

Deane, R P; Paragi, Z; Jarvis, M J; Coriat, M; Bernardi, G; Fender, R P; Frey, S; Heywood, I; Klöckner, H-R; Grainge, K; Rumsey, C

2014-07-03

Galaxies are believed to evolve through merging, which should lead to some hosting multiple supermassive black holes. There are four known triple black hole systems, with the closest black hole pair being 2.4 kiloparsecs apart (the third component in this system is at 3 kiloparsecs), which is far from the gravitational sphere of influence (about 100 parsecs for a black hole with mass one billion times that of the Sun). Previous searches for compact black hole systems concluded that they were rare, with the tightest binary system having a separation of 7 parsecs (ref. 10). Here we report observations of a triple black hole system at redshift z = 0.39, with the closest pair separated by about 140 parsecs and significantly more distant from Earth than any other known binary of comparable orbital separation. The effect of the tight pair is to introduce a rotationally symmetric helical modulation on the structure of the large-scale radio jets, which provides a useful way to search for other tight pairs without needing extremely high resolution observations. As we found this tight pair after searching only six galaxies, we conclude that tight pairs are more common than hitherto believed, which is an important observational constraint for low-frequency gravitational wave experiments.

The CfA-Rosat Survey of Distant Clusters of Galaxies

NASA Technical Reports Server (NTRS)

McNamara, Brian

1998-01-01

We (Vikhlinin, McNamara, Forman, Jones, Hornstrup, Quintana) have completed a new survey of distant clusters of galaxies, which we use to to study cluster evolution over cosmological timescales. The clusters were identified as extended X-ray sources in 650 ROSAT PSPC images of high Galactic latitude fields. Our catalog of approximately 230 extended X-ray sources covers 160 square degrees on the sky. Ours is the largest of the several ROSAT serendipitous cluster surveys in progress (e.g. SHARC, Rosati, WARPS etc.). Using V,R,I imagery obtained at several observatories, we find that greater than 90% of the X-ray sources are associated with distant clusters of galaxies. We have obtained spectroscopic redshifts for nearly 80 clusters in our catalog, and we have measured photometric redshifts for the remaining clusters. Our sample contains more than 20 clusters at z > 0.5. I will discuss the logN-logS relationship for our clusters. Because our large survey area, we are able to confirm the evolution of the most luminous distant clusters first seen in the Einstein Extended Medium Sensitivity Survey. In addition, I will discuss the relationships between optical richness, core radius, and X-ray luminosity for distant, X-ray-selected clusters.

Gravitational Lensing by Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Tyson, J.; Murdin, P.

2000-11-01

CLUSTERS OF GALAXIES are massive and relatively rare objects containing hundreds of galaxies. Their huge mass—dominated by DARK MATTER—bends light from all background objects, systematically distorting the images of thousands of distant galaxies (shear). This observed gravitational lens distortion can be inverted to produce an `image' of the mass in the foreground cluster of galaxies. Most of the...

RELICS: A Candidate Galaxy Arc at z~10 and Other Brightly Lensed z>6 Galaxies

NASA Astrophysics Data System (ADS)

Salmon, Brett; Coe, Dan; Bradley, Larry; Bradac, Marusa; Huang, Kuang-Han; Oesch, Pascal; Brammer, Gabriel; Stark, Daniel P.; Sharon, Keren; Trenti, Michele; Avila, Roberto J.; Ogaz, Sara; Acebron, Ana; Andrade-Santos, Felipe; Carrasco, Daniela; Cerny, Catherine; Cibirka, Nathália; Dawson, William; Frye, Brenda; Hoag, Austin; Jones, Christine; Mainali, Ramesh; Ouchi, Masami; Paterno-Mahler, Rachel; Rodney, Steven; Umetsu, Keiichi; Zitrin, Adi; RELICS

2018-01-01

Massive foreground galaxy clusters magnify and distort the light of objects behind them, permitting a view into both the extremely distant and intrinsically faint galaxy populations. We present here some of the most brightly lensed z>6 galaxy candidates known from the Reionization Lensing Cluster Survey (RELICS) and the discovery of a particularly fortuitous z~10 galaxy candidate which has been arced by the effects of strong gravitational lensing. The z~10 candidate has a lensed H-band magnitude of 25.8 AB mag and a high lensing magnification (~4-7). The inferred upper limits on the stellar mass (log [M_star /M_Sun]=9.5) and star formation rate (log [SFR/(M_Sun/yr)]=1.5) indicate that this candidate is a typical star-forming galaxy on the z>6 SFR-M_star relation. We rule out the only low-z solution as unphysical based on the required stellar mass, dust attenuation, size, and [OIII] EW needed for a z~2 SED to match the data. Finally, we reconstruct the source-plane image and estimate the candidate's physical size at z~10, finding a half-light radius of r_e < 0.8 kpc that is in line with the sizes of other z>9 candidates. While the James Webb Space Telescope will detect z>10 with ease, this rare candidate offers the potential for unprecedented spatial resolution less than 500 Myr after the Big Bang.

Pandora Cluster Seen by Spitzer

NASA Image and Video Library

2016-09-28

This image of galaxy cluster Abell 2744, also called Pandora's Cluster, was taken by the Spitzer Space Telescope. The gravity of this galaxy cluster is strong enough that it acts as a lens to magnify images of more distant background galaxies. This technique is called gravitational lensing. The fuzzy blobs in this Spitzer image are the massive galaxies at the core of this cluster, but astronomers will be poring over the images in search of the faint streaks of light created where the cluster magnifies a distant background galaxy. The cluster is also being studied by NASA's Hubble Space Telescope and Chandra X-Ray Observatory in a collaboration called the Frontier Fields project. In this image, light from Spitzer's infrared channels is colored blue at 3.6 microns and green at 4.5 microns. http://photojournal.jpl.nasa.gov/catalog/PIA20920

Deep Spitzer/IRAC Imaging of the Subaru Deep Field

NASA Astrophysics Data System (ADS)

Jiang, Linhua; Egami, Eiichi; Cohen, Seth; Fan, Xiaohui; Ly, Chun; Mechtley, Matthew; Windhorst, Rogier

2013-10-01

The last decade saw great progress in our understanding of the distant Universe as a number of objects at z > 6 were discovered. The Subaru Deep Field (SDF) project has played an important role on study of high-z galaxies. The SDF is unique: it covers a large area of 850 sq arcmin; it has extremely deep optical images in a series of broad and narrow bands; it has the largest sample of spectroscopically-confirmed galaxies known at z >= 6, including ~100 Lyman alpha emitters (LAEs) and ~50 Lyman break galaxies (LBGs). Here we propose to carry out deep IRAC imaging observations of the central 75% of the SDF. The proposed observations together with those from our previous Spitzer programs will reach a depth of ~10 hours, and enable the first complete census of physical properties and stellar populations of spectroscopically-confirmed galaxies at the end of cosmic reionization. IRAC data is the key to measure stellar masses and constrain stellar populations in high-z galaxies. From SED modeling with secure redshifts, we will characterize the physical properties of these galaxies, and trace their mass assembly and star formation history. In particular, it allows us, for the first time, to study stellar populations in a large sample of z >=6 LAEs. We will also address some critical questions, such as whether LAEs and LBGs represent physically different galaxy populations. All these will help us to understand the earliest galaxy formation and evolution, and better constrain the galaxy contribution to reionization. The IRAC data will also cover 10,000 emission-line selected galaxies at z < 1.5, 50,000 UV and mass selected LBGs at 1.5 < z < 3, and more than 5,000 LBGs at 3 < z < 6. It will have a legacy value for SDF-related programs.

Sub-millimetre properties of massive star-forming galaxies at z ~ 2 in SHADES/SXDF

NASA Astrophysics Data System (ADS)

Takagi, T.; Mortier, A. M. J.; Shimasaku, K.; Coppin, K.; Pope, A.; Ivison, R. J.; Hanami, H.; Serjeant, S.; Dunlop, J. S.

2007-05-01

We study the submillimetre (submm) properties of the following NIR-selected massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs), distant red galaxies (DRGs) and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. We detected 6 NIR-selected galaxies in our SCUBA map. Four submm-detected galaxies out of six are found to be detected both at 24 micron and in radio (1.4 GHz), and therefore confirmed as genuine submm-bright galaxies. We identify two submm-bright NIR-selected galaxies are the BzK-DRG-ERO overlapping population. Although this overlapping population is rare, about 12% of this population could be submm galaxies. With a stacking analysis, we detected the 850-micron flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution from BzKs at z˜2 to submm background is about 10 - 15 % and similar to that from EROs typically at z˜1, BzKs have a higher fraction (˜30%) of flux in resolved sources than EROs do. Therefore, submm flux of BzKs seems to be biased high. From the SED fitting using an evolutionary model of starbursts with radiative transfer, submm-bright NIR-selected galaxies, mostly BzKs, are found to have the stellar mass of >5x1010M[sun] with the bolometric luminosity of >3x1012L[sun]. On the other hand, an average SED of submm-faint BzKs indicates the typical stellar mass of <6x1010M[sun] and therefore less massive.

Spectrum from Faint Galaxy IRAS F00183-7111

NASA Technical Reports Server (NTRS)

2003-01-01

NASA's Spitzer Space Telescope has detected the building blocks of life in the distant universe, albeit in a violent milieu. Training its powerful infrared eye on a faint object located at a distance of 3.2 billion light-years, Spitzer has observed the presence of water and organic molecules in the galaxy IRAS F00183-7111. With an active galactic nucleus, this is one of the most luminous galaxies in the universe, rivaling the energy output of a quasar. Because it is heavily obscured by dust (see visible-light image in the inset), most of its luminosity is radiated at infrared wavelengths.

The infrared spectrograph instrument onboard Spitzer breaks light into its constituent colors, much as a prism does for visible light. The image shows a low-resolution spectrum of the galaxy obtained by the spectrograph at wavelengths between 4 and 20 microns. Spectra are graphical representations of a celestial object's unique blend of light. Characteristic patterns, or fingerprints, within the spectra allow astronomers to identify the object's chemical composition and to determine such physical properties as temperature and density.

The broad depression in the center of the spectrum denotes the presence of silicates (chemically similar to beach sand) in the galaxy. An emission peak within the bottom of the trough is the chemical signature for molecular hydrogen. The hydrocarbons (orange) are organic molecules comprised of carbon and hydrogen, two of the most common elements on Earth. Since it has taken more than three billion years for the light from the galaxy to reach Earth, it is intriguing to note the presence of organics in a distant galaxy at a time when life is thought to have started forming on our home planet.

Additional features in the spectrum reveal the presence of water ice (blue), carbon dioxide ice (green) and carbon monoxide (purple) in both gas and solid forms. The magenta peak corresponds to singly ionized neon gas, a spectral line often used by astronomers as a diagnostic of star formation rates in distant galaxies.

The Spitzer spectrum is the result of only 14 minutes of integration time, highlighting the power of the infrared spectrograph to unlock the secrets of distant galaxies.

Galaxies 800 million years after the Big Bang seen with the Atacama Large Millimetre Array

NASA Astrophysics Data System (ADS)

Smit, Renske

2018-01-01

The identification of galaxies in the first billion years after the Big Bang presents a challenge for even the largest optical telescopes. When the Atacama Large Millimetre Array (ALMA) started science operations in 2011 it presented a tantalising opportunity to identify and characterise these first sources of light in a new window of the electromagnetic spectrum. I will present new sources successfully identified at z=6.8 using ALMA; the first spectroscopic confirmations of typical star-forming galaxies during the Epoch or Reionization using a sub-millimetre telescope. Moreover, these observations reveal the gas kinematics of such distant sources for the first time. The velocity gradient in these galaxies indicate that these galaxies likely have similar dynamical properties as the turbulent, yet rotation-dominated disks that have been observed for Hα emitting galaxies 2 billion years later at cosmic noon. This novel approach for confirming galaxies during Reionization paves the way for larger studies of distant galaxies with spectroscopic redshifts. Particularly important, this opens up opportunities for the measurement of high angular-resolution dynamics in galaxies less than one billion years after the Big Bang.

Charting Ingredients for Life

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Figure 1: Spectrum Charts Light from a Faraway Galaxy

This graph, or spectrum, charts light from a faraway galaxy located 10 billion light years from Earth. It tracks mid-infrared light from an extremely luminous galaxy when the universe was only 1/4 of its current age.

Spectra are created when an instrument called a spectrograph spreads light out into its basic parts, like a prism turning sunlight into a rainbow. They reveal the signatures, or 'fingerprints,' of molecules that make up a galaxy and contribute to its light.

Spitzer's infrared spectrometer identified characteristic fingerprints of complex organic molecules called polycyclic aromatic hydrocarbons, illustrated in the artist's concept in the inset. These large molecules comprised of carbon and hydrogen, are considered among the building blocks of life.

Scientists determined it took 10 billion years for photons from this galaxy to reach Spitzer's infrared eyes. These complex carbon and hydrogen molecules are from a young galaxy which is undergoing intense star formation, at the time the universe was only 3.5 billion years old.

These distant galaxies with enormous amounts of gas being converted into young stars are some of the most luminous objects in the sky. Enshrouded by dust, they are only faint, inconspicuous little dots in optical images. They are as bright as 10 trillion suns put together and 10 times brighter than starburst galaxies seen in our local universe.

This prompts a fascinating question as to what physical process is driving such enormous energy production in these galaxies when the universe is so young.

These data were taken by Spitzer's infrared spectrograph in August and September 2004.

Era of Galaxy and Black Hole Growth Spurt Discovered

NASA Astrophysics Data System (ADS)

2005-04-01

Distant galaxies undergoing intense bursts of star formation have been shown by NASA's Chandra X-ray Observatory to be fertile growing grounds for the largest black holes in the Universe. Collisions between galaxies in the early Universe may be the ultimate cause for both the accelerated star formation and black hole growth. By combining the deepest X-ray image ever obtained with submillimeter and optical observations, an international team of scientists has found evidence that some extremely luminous adolescent galaxies and their central black holes underwent a phenomenal spurt of growth more than 10 billion years ago. This concurrent black hole and galaxy growth spurt is only seen in these galaxies and may have set the stage for the birth of quasars - distant galaxies that contain the largest and most active black holes in the Universe. Simulation of a Galaxy Collision Simulation of a Galaxy Collision "The extreme distances of these galaxies allow us to look back in time, and take a snapshot of how today's largest galaxies looked when they were producing most of their stars and growing black holes," said David Alexander of the University of Cambridge, UK, and lead author of a paper in the April 7, 2005 issue of Nature that describes this work. The galaxies studied by Alexander and his colleagues are known as submillimeter galaxies, so-called because they were originally identified by the James Clerk Maxwell submillimeter telescope (JCMT) on Mauna Kea in Hawaii. The submillimeter observations along with optical data from Keck indicate these galaxies had an unusually large amount of gas. The gas in each galaxy was forming into stars at a rate of about one per day, or 100 times the present rate in the Milky Way galaxy. The Chandra X-ray data show that the supermassive black holes in the galaxies were also growing at the same time. Chandra X-ray Image of CDFN Chandra X-ray Image of CDFN These galaxies are very faint and it is only with the deepest observations of the Universe that they can be detected at all. "The deeper we look into the Universe with Chandra, the more fascinating things we find" says Niel Brandt of Penn State University in University Park. "Who knows what nature has in store for us as we push the boundaries yet further." The X-ray observations also showed that the black holes are surrounded by a dense shroud of gas and dust. This is probably the material that will be consumed by the growing black holes. Hubble Space Telescope observations indicate that most of the submillimeter galaxies are actually two galaxies that are colliding and merging. Recent sophisticated computer simulations performed by Tiziana Di Matteo of Carnegie Mellon University in Pittsburgh, Penn., and her collaborators have shown that such mergers drive gas toward the central regions of galaxies, triggering a burst of star formation and providing fuel for the growth of a central black hole. Chandra's X-ray Image of Black Holes in the Early Universe Chandra's X-ray Image of Black Holes in the Early Universe "It is exciting that these recent observations are in good agreement with our simulation," says Di Matteo, "We seem to be converging on a consistent picture of galaxy formation with both observations and theory." In particular, this work will help scientists to understand the observed link in the present epoch between the total mass of stars in the central bulges of large galaxies and the size of their central, supermassive black holes. The James Clerk Maxwell Telescope (JCMT) is operated on behalf of the United Kingdom, Canada & Netherlands by the Joint Astronomy Centre. With its 15-meter (50-foot) diameter dish the JCMT detects light with "submillimeter" wavelengths, between infrared light and radio waves on the wavelength scale. The W. M. Keck Observatory is operated by the California Association for Research in Astronomy. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate, Washington. Northrop Grumman of Redondo Beach, Calif., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

DDT_nnesvadb_4: C+ and H2 spectroscopy of a single star-forming region at z=2.599 recently discovered with Planck/SUCBA2/SPIRE

NASA Astrophysics Data System (ADS)

Nesvadba, N.

2013-02-01

We request DD time to observe a highly magnified starburst at z=2.599 recently discovered with Planck, which has CO line widths like those of giant molecular clouds in the Milky Way! The velocity gradient and narrowness of the CO lines indicates that we are observing small (a few 10s pc) star forming regions in a distant galaxy due to its extreme magnification and fortuitous alignment with the lensing mass. This is a UNIQUE opportunity to probe a starburst at z=2.5 AT THE SCALE OF SINGLE STAR-FORMING REGIONS. We will measure [CII]158, the main coolant of UV-heated gas and thus, a prime tracer of star formation, and the H2 0-0 S(1) line, the main coolant of shocked gas, a tracer of turbulence dissipation and the warm molecular mass. Only Herschel can observe these important lines. ALMA cannot, and SOFIA cannot. During the formation process of galaxies, strong turbulence is generated with potentially dramatic consequences for the nature of star formation in distant galaxies. For example, if the gas remains turbulent on scales <100 pc, then the global galaxy kinematics (i.e., Toomre stability) no longer stabilizes the gas. What are the consequences for the star formation in such an environment and how does this high level of turbulence during galaxy formation change the nature of galaxies? Through a unique synergy of the Planck all-sky survey, Herschel, and IRAM sub-arcsec DDT interferometry, we have just caught a unique source at z=2.599, G80.3+49.8, with bright FIR continuum akin to dusty high-z starbursts, and surprisingly narrow CO line widths like GMCs in the Milky Way! G80.3+49.8 is truly unique and will become a benchmark for studying the physics regulating intense star formation at high-z. Herschel "last-minute" observations are our only way to quantify the global budgets of UV and shock heating estimated from the main IR cooling lines, both of which are unobservable from the ground, and both critical in linking the details of star formation with the generalities of galaxy formation.

Bursting with Stars and Black Holes

NASA Technical Reports Server (NTRS)

2007-01-01

A growing black hole, called a quasar, can be seen at the center of a faraway galaxy in this artist's concept. Astronomers using NASA's Spitzer and Chandra space telescopes discovered swarms of similar quasars hiding in dusty galaxies in the distant universe.

The quasar is the orange object at the center of the large, irregular-shaped galaxy. It consists of a dusty, doughnut-shaped cloud of gas and dust that feeds a central supermassive black hole. As the black hole feeds, the gas and dust heat up and spray out X-rays, as illustrated by the white rays. Beyond the quasar, stars can be seen forming in clumps throughout the galaxy. Other similar galaxies hosting quasars are visible in the background.

The newfound quasars belong to a long-lost population that had been theorized to be buried inside dusty, distant galaxies, but were never actually seen. While some quasars are easy to detect because they are oriented in such a way that their X-rays point toward Earth, others are oriented with their surrounding doughnut-clouds blocking the X-rays from our point of view. In addition, dust and gas in the galaxy itself can block the X-rays.

Astronomers had observed the most energetic of this dusty, or obscured, bunch before, but the 'masses,' or more typical members of the population, remained missing. Using data from Spitzer and Chandra, the scientists uncovered many of these lost quasars in the bellies of massive galaxies between 9 and 11 billion light-years away. Because the galaxies were also busy making stars, the scientists now believe most massive galaxies spent their adolescence building up their stars and black holes simultaneously.

The Spitzer observations were made as part of the Great Observatories Origins Deep Survey program, which aims to image the faintest distant galaxies using a variety of wavelengths.

Power Spacewalk on This Week @NASA - October 17, 2014

NASA Image and Video Library

2014-10-17

During an October 15 spacewalk outside the International Space Station – the second U.S. spacewalk in as many weeks – Expedition 41 Flight Engineers Reid Wiseman and Barry Wilmore of NASA, replaced a failed voltage regulation device to restore the station’s electrical power output to full capacity. The pair also relocated camera and TV equipment as part of a major reconfiguration to accommodate new docking adapters for use by U.S. commercial crew spacecraft in the next few years. Also, MAVEN’s “First Light”, Hubble finds extremely distant galaxy, Possible bonus destination for New Horizons, New information about volcanic activity on our moon and more!

Glimpsing Matter at the Brink

NASA Astrophysics Data System (ADS)

Morris, Mark R.

2004-04-01

Most astronomers are comfortable with the notion of a black hole at the center of our Galaxy, but defining and measuring its size is an extremely difficult matter, mostly because it is so small from our distant vantage point. In his Perspective, Morris discusses results reported in the same issue by Bower et al. on new measurements of the size of the radio-emitting region immediately surrounding the Galactic black hole. By observing at the shortest possible wavelengths with very long baseline interferometry, the authors have been able to resolve the intrinsic size of the black hole region in spite of the interstellar interference that has plagued previous attempts.

Accretion of low-metallicity gas by the Milky Way.

PubMed

Wakker, B P; Howk, J C; Savage, B D; van Woerden, H; Tufte, S L; Schwarz, U J; Benjamin, R; Reynolds, R J; Peletier, R F; Kalberla, P M

1999-11-25

Models of the chemical evolution of the Milky Way suggest that the observed abundances of elements heavier than helium ('metals') require a continuous infall of gas with metallicity (metal abundance) about 0.1 times the solar value. An infall rate integrated over the entire disk of the Milky Way of approximately 1 solar mass per year can solve the 'G-dwarf problem'--the observational fact that the metallicities of most long-lived stars near the Sun lie in a relatively narrow range. This infall dilutes the enrichment arising from the production of heavy elements in stars, and thereby prevents the metallicity of the interstellar medium from increasing steadily with time. However, in other spiral galaxies, the low-metallicity gas needed to provide this infall has been observed only in associated dwarf galaxies and in the extreme outer disk of the Milky Way. In the distant Universe, low-metallicity hydrogen clouds (known as 'damped Ly alpha absorbers') are sometimes seen near galaxies. Here we report a metallicity of 0.09 times solar for a massive cloud that is falling into the disk of the Milky Way. The mass flow associated with this cloud represents an infall per unit area of about the theoretically expected rate, and approximately 0.1-0.2 times the amount required for the whole Galaxy.

Galactic Teamwork Makes Distant Bubbles

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-03-01

During the period of reionization that followed the dark ages of our universe, hydrogen was transformed from a neutral state, which is opaque to radiation, to an ionized one, which is transparent to radiation. But what generated the initial ionizing radiation? The recent discovery of multiple distant galaxies offers evidence for how this process occurred.Two Distant GalaxiesWe believe reionization occurred somewhere between a redshift of z = 6 and 7, because Ly-emitting galaxies drop out at roughly this redshift. Beyond this distance, were generally unable to see the light from these galaxies, because the universe is no longer transparent to their emission. This is not always the case, however: if a bubble of ionized gas exists around a distant galaxy, the radiation can escape, allowing us to see the galaxy.This is true of two recently-discovered Ly-emitting galaxies, confirmed to be at a redshift of z~7 and located near one another in a region known as the Bremer Deep Field. The fact that were able to see the radiation from these galaxies means that they are in an ionized HII region presumably one of the earlier regions to have become reionized in the universe.But on their own, neither of these galaxies is capable of generating an ionized bubble large enough for their light to escape. So what ionized the region around them, and what does this mean for our understanding of how reionization occurred in the universe?A Little Help From FriendsLocation in different filters of the objects in the Hubble Bremer Deep Field catalog. The z~7 selection region is outlined by the grey box. BDF-521 and BDF-3299 were the two originally discovered galaxies; the remaining red markers indicate the additional six galaxies discovered in the same region. [Castellano et al. 2016]A team of scientists led by Marco Castellano (Rome Observatory, INAF) investigated the possibility that there are other, faint galaxies near these two that have helped to ionize the region. Performing a survey using deep field Hubble observations, Castellano and collaborators found an additional 6 galaxies in the same region as the first two, also at a redshift of z~7!The authors believe these galaxies provide a simple explanation of the ionized bubble: each of these faint, normal galaxies produced a small ionized bubble. The overlap of these many small bubbles provided the larger ionized region from which the light of the two originally discovered galaxies was able to escape.How normal is this clustering of galaxies found by Castellano and collaborators? The team demonstrates via cosmological modeling that the number density of galaxies in this region is a factor of 34 greater than would be expected at this distance in a random pointing of the same size.These results greatly support the theoretical prediction that the first ionization fronts in the universe were formed in regions with significant galaxy overdensities. The discovery of this deep-field collection of galaxies strongly suggests that reionization was driven by faint, normal star-forming galaxies in a clumpy process.CitationM. Castellano et al 2016 ApJ 818 L3. doi:10.3847/2041-8205/818/1/L3

Spatial distribution of dust in galaxies from the Integral field unit data

NASA Astrophysics Data System (ADS)

Zafar, Tayyaba; Sophie Dubber, Andrew Hopkins

2018-01-01

An important characteristic of the dust is it can be used as a tracer of stars (and gas) and tell us about the composition of galaxies. Sub-mm and infrared studies can accurately determine the total dust mass and its spatial distribution in massive, bright galaxies. However, faint and distant galaxies are hampered by resolution to dust spatial dust distribution. In the era of integral-field spectrographs (IFS), Balmer decrement is a useful quantity to infer the spatial extent of the dust in distant and low-mass galaxies. We conducted a study to estimate the spatial distribution of dust using the Sydney-Australian Astronomical Observatory (AAO) Multi-object Integral field spectrograph (SAMI) galaxies. Our methodology is unique to exploit the potential of IFS and using the spatial and spectral information together to study dust in galaxies of various morphological types. The spatial extent and content of dust are compared with the star-formation rate, reddening, and inclination of galaxies. We find a right correlation of dust spatial extent with the star-formation rate. The results also indicate a decrease in dust extent radius from Late Spirals to Early Spirals.

GALAXIES IN THE YOUNG UNIVERSE [left

NASA Technical Reports Server (NTRS)

2002-01-01

This image of a small region of the constellation Sculptor, taken with a ground-based photographic sky survey camera, illustrates the extremely small angular size of a distant galaxy cluster in the night sky. Though this picture encompasses a piece of the sky about the width of the bowl of the Big Dipper, the cluster is so far away it fills a sky area only 1/10th the diameter of the Full Moon. The cluster members are not visible because they are so much fainter than foreground stars. [center] A NASA Hubble Space Telescope (HST) image of the farthest cluster of galaxies in the universe, located at a distance of 12 billion light-years. Because the light from these remote galaxies has taken 12 billion years to reach us, this image is a remarkable glimpse of the primeval universe, at it looked about two billion years after the Big Bang. The cluster contains 14 galaxies, the other objects are largely foreground galaxies. The galaxy cluster lies in front of quasar Q0000-263 in the constellation Sculptor. Presumably the brilliant core of an active galaxy, the quasar provides a beacon for searching for primordial galaxy clusters. The image is the full field view of the Wide Field and Planetary Camera-2, taken on September 6, 1994. The 4.7-hour exposure reveals objects down to 28.5 magnitude. [right] This enlargement shows one of the farthest normal galaxies yet detected, (blob at center right) at a distance of 12 billion light-years (redshift of z=3.330). The galaxy lies 300 million light-years in front of the quasar Q0000-263 (z=4.11, large white blob and spike on left side of frame) and was detected because it absorbs some light from the quasar. The galaxy's spectrum reveals that vigorous star formation is taking place. Credit: Duccio Macchetto (ESA/STScI), Mauro Giavalisco (STScI), and NASA

CANDELS: A Cosmic Quest for Distant Galaxies Offering Live Views of Galaxy Evolution

NASA Astrophysics Data System (ADS)

Koo, David C.; CANDELS

2017-06-01

For decades, the study of distant galaxies has been pushing the frontiers of extra-galactic research, with observations from the best suite of telescopes and instruments and with theory from the most advanced computer simulations. This talk will focus on observations taken within the CANDELS fields to reveal the richness and complexity of this still-growing field. CANDELS (Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey) itself is the largest project ever taken by Hubble and is composed of optical and near-infrared images of five tiny regions of sky containing over 200,000 distant galaxies. All these regions, two of which are GOODS North and South, were already outstanding in possessing years of prior surveys taken by many teams worldwide and have continued to attract more and better spectra and panchromatic images from Keck, Hubble, Chandra, Spitzer, and other telescopes ranging from X-ray to radio. Combined together, the rich data within the CANDELS fields offer live views of galaxy evolution from “Cosmic Dawn” when the first infant galaxies and cosmic black holes were born, through “Cosmic Noon” during the peak of galaxy and black hole growth, and then to “Cosmic Afternoon” when star formation and black hole activities, morphologies, motions, and contents settled to those of our Milky Way and its zoo of cousins today. The talk will highlight some interesting discoveries from the last two periods and close with new mysteries challenging our field in the 21st century and future prospects for solving them.

Stellar Populations and Physical Conditions at 100 pc Resolution in a Lensed Galaxy at z 4

NASA Astrophysics Data System (ADS)

Berg, Danielle

2015-10-01

Large surveys of star-forming galaxies at high redshift (z > 1.5) have provided us with a broad understanding of how galaxies assemble and evolve, but the spatial and spectral limitations inherent in observing faint, distant objects mean that many of the physical processes regulating this dynamic evolution are poorly constrained. Much of our most detailed knowledge of the physical conditions in distant galaxies comes from careful studies of gravitationally lensed sources, few of which are at z>3.5. FOR J0332-3557 is a gravitationally lensed galaxy at z 4 for which we and other groups have obtained a total of 37.3 hours of VLT spectroscopy. The rest-frame UV spectrum is notable for its unusual combination of both strong emission lines in the rest-frame UV and strong Lya and interstellar absorption, and for the unusual spatial variation seen in the nebular emission lines, which are less extended than the underlying stellar continuum. We propose high spatial resolution imaging of FOR J0332-3557 with four broadband filters on WFC3, taking advantage of both the HST resolution and the lensing magnification to study star formation and extinction on 100 pc scales. Because the interpretation of our unusual rest-frame UV and optical spectra requires an accurate reddening estimate, combining these observations with ground-based spectroscopy will give the most complete picture to date of chemical evolution in a distant galaxy.

Observational Searches for Star-Forming Galaxies at z > 6

NASA Astrophysics Data System (ADS)

Finkelstein, Steven L.

2016-08-01

Although the universe at redshifts greater than six represents only the first one billion years (< 10%) of cosmic time, the dense nature of the early universe led to vigorous galaxy formation and evolution activity which we are only now starting to piece together. Technological improvements have, over only the past decade, allowed large samples of galaxies at such high redshifts to be collected, providing a glimpse into the epoch of formation of the first stars and galaxies. A wide variety of observational techniques have led to the discovery of thousands of galaxy candidates at z > 6, with spectroscopically confirmed galaxies out to nearly z = 9. Using these large samples, we have begun to gain a physical insight into the processes inherent in galaxy evolution at early times. In this review, I will discuss (i) the selection techniques for finding distant galaxies, including a summary of previous and ongoing ground and space-based searches, and spectroscopic follow-up efforts, (ii) insights into galaxy evolution gleaned from measures such as the rest-frame ultraviolet luminosity function, the stellar mass function, and galaxy star-formation rates, and (iii) the effect of galaxies on their surrounding environment, including the chemical enrichment of the universe, and the reionisation of the intergalactic medium. Finally, I conclude with prospects for future observational study of the distant universe, using a bevy of new state-of-the-art facilities coming online over the next decade and beyond.

GRAVITATIONAL LENS CAPTURES IMAGE OF PRIMEVAL GALAXY

NASA Technical Reports Server (NTRS)

2002-01-01

This Hubble Space Telescope image shows several blue, loop-shaped objects that actually are multiple images of the same galaxy. They have been duplicated by the gravitational lens of the cluster of yellow, elliptical and spiral galaxies - called 0024+1654 - near the photograph's center. The gravitational lens is produced by the cluster's tremendous gravitational field that bends light to magnify, brighten and distort the image of a more distant object. How distorted the image becomes and how many copies are made depends on the alignment between the foreground cluster and the more distant galaxy, which is behind the cluster. In this photograph, light from the distant galaxy bends as it passes through the cluster, dividing the galaxy into five separate images. One image is near the center of the photograph; the others are at 6, 7, 8, and 2 o'clock. The light also has distorted the galaxy's image from a normal spiral shape into a more arc-shaped object. Astronomers are certain the blue-shaped objects are copies of the same galaxy because the shapes are similar. The cluster is 5 billion light-years away in the constellation Pisces, and the blue-shaped galaxy is about 2 times farther away. Though the gravitational light-bending process is not new, Hubble's high resolution image reveals structures within the blue-shaped galaxy that astronomers have never seen before. Some of the structures are as small as 300 light-years across. The bits of white imbedded in the blue galaxy represent young stars; the dark core inside the ring is dust, the material used to make stars. This information, together with the blue color and unusual 'lumpy' appearance, suggests a young, star-making galaxy. The picture was taken October 14, 1994 with the Wide Field Planetary Camera-2. Separate exposures in blue and red wavelengths were taken to construct this color picture. CREDIT: W.N. Colley and E. Turner (Princeton University), J.A. Tyson (Bell Labs, Lucent Technologies) and NASA Image files in GIF and JPEG format and captions may be accessed on Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

First Results from the ISO-IRAS Faint Galaxy Survey

NASA Technical Reports Server (NTRS)

Wolstencroft, R. D.; Wehrle, A. E.; Levine, D. A.

1997-01-01

We present the first result from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12um ISOCAM AND 90um ISOPHOT observation.

A complex multi-notch astronomical filter to suppress the bright infrared sky.

PubMed

Bland-Hawthorn, J; Ellis, S C; Leon-Saval, S G; Haynes, R; Roth, M M; Löhmannsröben, H-G; Horton, A J; Cuby, J-G; Birks, T A; Lawrence, J S; Gillingham, P; Ryder, S D; Trinh, C

2011-12-06

A long-standing and profound problem in astronomy is the difficulty in obtaining deep near-infrared observations due to the extreme brightness and variability of the night sky at these wavelengths. A solution to this problem is crucial if we are to obtain the deepest possible observations of the early Universe, as redshifted starlight from distant galaxies appears at these wavelengths. The atmospheric emission between 1,000 and 1,800 nm arises almost entirely from a forest of extremely bright, very narrow hydroxyl emission lines that varies on timescales of minutes. The astronomical community has long envisaged the prospect of selectively removing these lines, while retaining high throughput between them. Here we demonstrate such a filter for the first time, presenting results from the first on-sky tests. Its use on current 8 m telescopes and future 30 m telescopes will open up many new research avenues in the years to come.

Astronomers Discover Most Distant Galaxy Showing Key Evidence For Furious Star Formation

NASA Astrophysics Data System (ADS)

2003-12-01

Astronomers have discovered a key signpost of rapid star formation in a galaxy 11 billion light-years from Earth, seen as it was when the Universe was only 20 percent of its current age. Using the National Science Foundation's Very Large Array (VLA) radio telescope, the scientists found a huge quantity of dense interstellar gas -- the environment required for active star formation -- at the greatest distance yet detected. A furious spawning of the equivalent of 1,000 Suns per year in a distant galaxy dubbed the Cloverleaf may be typical of galaxies in the early Universe, the scientists say. Cloverleaf galaxy VLA image (green) of radio emission from HCN gas, superimposed on Hubble Space Telescope image of the Cloverleaf galaxy. The four images of the Cloverleaf are the result of gravitational lensing. CREDIT: NRAO/AUI/NSF, STScI (Click on Image for Larger Version) "This is a rate of star formation more than 300 times greater than that in our own Milky Way and similar spiral galaxies, and our discovery may provide important information about the formation and evolution of galaxies throughout the Universe," said Philip Solomon, of Stony Brook University in New York. While the raw material for star formation has been found in galaxies at even greater distances, the Cloverleaf is by far the most distant galaxy showing this essential signature of star formation. That essential signature comes in the form of a specific frequency of radio waves emitted by molecules of the gas hydrogen cyanide (HCN). "If you see HCN, you are seeing gas with the high density required to form stars," said Paul Vanden Bout of the National Radio Astronomy Observatory (NRAO). Solomon and Vanden Bout worked with Chris Carilli of NRAO and Michel Guelin of the Institute for Millimeter Astronomy in France. They reported their results in the December 11 issue of the scientific journal Nature. In galaxies like the Milky Way, dense gas traced by HCN but composed mainly of hydrogen molecules is always associated with regions of active star formation. What is different about the Cloverleaf is the huge quantity of dense gas along with very powerful infrared radiation from the star formation. Ten billion times the mass of the Sun is contained in dense, star-forming gas clouds. "At the rate this galaxy is seen to be forming stars, that dense gas will be used up in only about 10 million years," Solomon said. In addition to giving astronomers a fascinating glimpse of a huge burst of star formation in the early Universe, the new information about the Cloverleaf helps answer a longstanding question about bright galaxies of that era. Many distant galaxies have supermassive black holes at their cores, and those black holes power "central engines" that produce bright emission. Astronomers have wondered specifically about those distant galaxies that emit large amounts of infrared light, galaxies like the Cloverleaf which has a black hole and central engine. "Is this bright infrared light caused by the black-hole-powered core of the galaxy or by a huge burst of star formation? That has been the question. Now we know that, in at least one case, much of the infrared light is produced by intense star formation," Carilli said. The rapid star formation, called a starburst, and the black hole are both generating the bright infrared light in the Cloverleaf. The starburst is a major event in the formation and evolution of this galaxy. "This detection of HCN gives us a unique new window through which we can study star formation in the early Universe," Carilli said. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

An Exploration of Dusty Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-04-01

Submillimeter galaxies i.e., galaxies that we detect in the submillimeter wavelength range are mysterious creatures. Its only within the last couple decades that weve had telescope technology capable of observing them, and were only now getting to the point where angular resolution limits allow us to examine them closely. A new study has taken advantage of new capabilities to explore the properties of a sample of 52 of thesegalaxies.Dusty Star FormationSubmillimeter galaxies are generally observed in the early universe. Though theyre faint in other wavebands, theyre extremely luminous in infrared and submillimeter their infrared luminosities are typically trillions of times the Suns luminosity. This is thought to be because these galaxies are very actively forming stars at rates of hundreds of times that of the Milky Way!Example 10 10 true-color images of ten submillimeter galaxies in the authors ALMA-identified sample. [Simpson et al. 2017]Submillimeter galaxies are also extremely dusty, so we dont see their star formation directly in optical wavelengths. Instead, we see the stellar light after its been absorbed and reemitted by interstellar dust lanes were indirectly observing heavily obscured star formation.Why look for submillimeter galaxies? Studying them can help us to learn about galaxy and star formation early in our universes history, and help us to understand how the universe has evolved into what we see locally today.Submillimeter StrugglesDue to angular resolution limitations in the past, we often couldnt pin down the exact locations of submillimeter galaxies, preventing us from examining them properly. But now a team of scientists has used the Atacama Large Millimeter/submillimeter array (ALMA) to precisely locate 52 submillimeter galaxies identified by the Submillimeter Common-User Bolometer Array (SCUBA-2) in the UKIDSS Ultra Deep Survey field.The precise locations made possible by ALMA allowed the team led by James Simpson (University of Edinburgh and Durham University) to identify the multi-wavelength properties of these galaxies in a pilot study that they hope to extend to many more similar galaxies in the future.Lessons from Distant GalaxiesWhat did Simpson and collaborators learn in this study?Photometric redshift distribution of the ALMA-identified submillimeter galaxies in the authors sample (grey). [Simpson et al. 2017]For the set of galaxies for which the team could measure photometric redshifts, the median redshift was z 2.65 (though redshifts ranged up to z 5).Submillimeter galaxies are cooler and larger than local far-infrared galaxies (known as ULIRGs). The authors therefore argue that its unlikely that ULIRGs are evolved versions of submillimeter galaxies.Estimates of dust mass in these galaxies suggest that effectively all of the optical-to-near-infrared light from colocated stars is obscured by dust.Estimates of the future stellar mass of these galaxies suggest that they cannot evolve into lenticular or spiral galaxies. Instead, the authors conclude, submillimeter galaxies must be the progenitors of local elliptical galaxies.CitationJ. M. Simpson et al 2017 ApJ 839 58. doi:10.3847/1538-4357/aa65d0

Direct Measurement of Dust Attenuation in z approx. 1.5 Star-Forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

NASA Technical Reports Server (NTRS)

Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B; Conroy, Charlie; Schreiber, Natascha M. Foerster; Franx, Marijn; Fumagalli, Mattia; Lundren, Britt; Momcheva, Ivelina; Nelson, Erica J.;

The distant red galaxy neighbour population of 1

NASA Astrophysics Data System (ADS)

Bornancini, C.; García Lambas, D.

We study the Distant Red Galaxy (DRG, J-Ks > 2.3) neighbour population of Quasi Stellar Objects (QSOs) selected from the Sloan Digital Sky Survey (SDSS) in the redshift range 1 < z < 2. We perform a similar analysis for optically obscured AGNs (i.e. with a limiting magnitude I > 24) detected in the mid-infrared (24 microns) with the Spitzer Space Telescope and a mean redshift z~2.2 in the Flamingos Extragalactic Survey (FLAMEX). We present results on the cross-correlation function of DRGs around QSOs and optically faint mid-infrared sources. The corresponding correlation length obtained for the QSO sample targets is r_0=5.4+/-1.6 Mpc. For the optically obscured galaxy sample we find r_0=8.9+/-1.4 Mpc. These results indicate that optically faint obscured sources are located in denser environment of evolved red galaxies compare to QSOs.

A DISTANT QUASAR'S BRILLIANT LIGHT

NASA Technical Reports Server (NTRS)

2002-01-01

The arrow in this image, taken by a ground-based telescope, points to a distant quasar, the brilliant core of an active galaxy residing billions of light-years from Earth. As light from this faraway object travels across space, it picks up information on galaxies and the vast clouds of material between galaxies as it moves through them. The Space Telescope Imaging Spectrograph aboard NASA's Hubble Space Telescope decoded the quasar's light to find the spectral 'fingerprints' of highly ionized (energized) oxygen, which had mixed with invisible clouds of hydrogen in intergalactic space. The quasar's brilliant beam pierced at least four separate filaments of the invisible hydrogen laced with the telltale oxygen. The presence of oxygen between the galaxies implies there are huge quantities of hydrogen in the universe. Credits: WIYN Telescope at Kitt Peak National Observatory in Arizona. The telescope is owned and operated by the University of Wisconsin, Indiana University, Yale University, and the National Optical Astronomy Observatories.

Photometric Signatures of Starbursts in Interacting Galaxies and the Butcher-Oemler Effect

NASA Technical Reports Server (NTRS)

Rakos, Karl D.; Maindl, Thomas I.; Schombert, James M.

1996-01-01

This paper presents new and synthetic narrow band photometry of ellipticals, spirals, Seyferts and interacting galaxies in an attempt to identify the cause of the unusually high fraction of blue cluster galaxies in distant clusters (the Butcher-Oemler Effect). The properties and distribution of the low redshift sample specifically points to starbursts as the origin of the blue narrow band colors in interacting Arp galaxies.

Physical properties and H-ionizing-photon production rates of extreme nearby star-forming regions

NASA Astrophysics Data System (ADS)

Chevallard, Jacopo; Charlot, Stéphane; Senchyna, Peter; Stark, Daniel P.; Vidal-García, Alba; Feltre, Anna; Gutkin, Julia; Jones, Tucker; Mainali, Ramesh; Wofford, Aida

2018-06-01

Measurements of the galaxy UV luminosity function at z ≳ 6 suggest that young stars hosted in low-mass star-forming galaxies produced the bulk of hydrogen-ionizing photons necessary to reionize the intergalactic medium (IGM) by redshift z ˜ 6. Whether star-forming galaxies dominated cosmic reionization, however, also depends on their stellar populations and interstellar medium properties, which set, among other things, the production rate of H-ionizing photons, ξ _{ion}^\\star, and the fraction of these escaping into the IGM. Given the difficulty of constraining with existing observatories the physical properties of z ≳ 6 galaxies, in this work we focus on a sample of ten nearby objects showing UV spectral features comparable to those observed at z ≳ 6. We use the new-generation BEAGLE tool to model the UV-to-optical photometry and UV/optical emission lines of these Local `analogues' of high-redshift galaxies, finding that our relatively simple, yet fully self-consistent, physical model can successfully reproduce the different observables considered. Our galaxies span a broad range of metallicities and are characterised by high ionization parameters, low dust attenuation, and very young stellar populations. Through our analysis, we derive a novel diagnostic of the production rate of H-ionizing photons per unit UV luminosity, ξ _{ion}^\\star, based on the equivalent width of the bright [O III]49595007 line doublet, which does not require measurements of H-recombination lines. This new diagnostic can be used to estimate ξ _{ion}^\\star from future direct measurements of the [O III]49595007 line using JWST/NIRSpec (out to z ˜ 9.5), and by exploiting the contamination by Hβ +[O III]{4959}{5007}} of photometric observations of distant galaxies, for instance from existing Spitzer/IRAC data and from future ones with JWST/NIRCam.

Structure and substructure analysis of DAFT/FADA galaxy clusters in the [0.4–0.9] redshift range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guennou, L.; et al.

2014-01-17

Context. The DAFT/FADA survey is based on the study of ~90 rich(masses found in the literature >2 x 10^14 M_⊙)and moderately distant clusters (redshifts 0.4 < z < 0.9), all withHST imaging data available. This survey has two main objectives: to constrain dark energy(DE) using weak lensing tomography on galaxy clusters and to build a database (deepmulti-band imaging allowing photometric redshift estimates, spectroscopic data, X-raydata) of rich distant clusters to study their properties.

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 ( z = 0.902)

DOE PAGES

Tholken, Sophia; Schrabback, Tim; Reiprich, Thomas H.; ...

2018-03-05

Here, observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased.

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 ( z = 0.902)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tholken, Sophia; Schrabback, Tim; Reiprich, Thomas H.

Here, observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased.

Shedding Light on the Cosmic Skeleton

NASA Astrophysics Data System (ADS)

2009-11-01

Astronomers have tracked down a gigantic, previously unknown assembly of galaxies located almost seven billion light-years away from us. The discovery, made possible by combining two of the most powerful ground-based telescopes in the world, is the first observation of such a prominent galaxy structure in the distant Universe, providing further insight into the cosmic web and how it formed. "Matter is not distributed uniformly in the Universe," says Masayuki Tanaka from ESO, who led the new study. "In our cosmic vicinity, stars form in galaxies and galaxies usually form groups and clusters of galaxies. The most widely accepted cosmological theories predict that matter also clumps on a larger scale in the so-called 'cosmic web', in which galaxies, embedded in filaments stretching between voids, create a gigantic wispy structure." These filaments are millions of light years long and constitute the skeleton of the Universe: galaxies gather around them, and immense galaxy clusters form at their intersections, lurking like giant spiders waiting for more matter to digest. Scientists are struggling to determine how they swirl into existence. Although massive filamentary structures have been often observed at relatively small distances from us, solid proof of their existence in the more distant Universe has been lacking until now. The team led by Tanaka discovered a large structure around a distant cluster of galaxies in images they obtained earlier. They have now used two major ground-based telescopes to study this structure in greater detail, measuring the distances from Earth of over 150 galaxies, and, hence, obtaining a three-dimensional view of the structure. The spectroscopic observations were performed using the VIMOS instrument on ESO's Very Large Telescope and FOCAS on the Subaru Telescope, operated by the National Astronomical Observatory of Japan. Thanks to these and other observations, the astronomers were able to make a real demographic study of this structure, and have identified several groups of galaxies surrounding the main galaxy cluster. They could distinguish tens of such clumps, each typically ten times as massive as our own Milky Way galaxy - and some as much as a thousand times more massive - while they estimate that the mass of the cluster amounts to at least ten thousand times the mass of the Milky Way. Some of the clumps are feeling the fatal gravitational pull of the cluster, and will eventually fall into it. "This is the first time that we have observed such a rich and prominent structure in the distant Universe," says Tanaka. "We can now move from demography to sociology and study how the properties of galaxies depend on their environment, at a time when the Universe was only two thirds of its present age." The filament is located about 6.7 billion light-years away from us and extends over at least 60 million light-years. The newly uncovered structure does probably extend further, beyond the field probed by the team, and hence future observations have already been planned to obtain a definite measure of its size. More information This research was presented in a paper published as a letter in the Astronomy & Astrophysics Journal: The spectroscopically confirmed huge cosmic structure at z = 0.55, by Tanaka et al. The team is composed of Masayuki Tanaka (ESO), Alexis Finoguenov (Max-Planck-Institute for Extraterrestrial Physics, Garching, Germany and University of Maryland, Baltimore, USA), Tadayuki Kodama (National Astronomical Observatory of Japan, Tokyo, Japan), Yusei Koyama (Department of Astronomy, University of Tokyo, Japan), Ben Maughan (H.H. Wills Physics Laboratory, University of Bristol, UK) and Fumiaki Nakata (Subaru Telescope, National Astronomical Observatory of Japan). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Explained: Why many surveys of distant galaxies miss 90% of their targets

NASA Astrophysics Data System (ADS)

2010-03-01

Astronomers have long known that in many surveys of the very distant Universe, a large fraction of the total intrinsic light was not being observed. Now, thanks to an extremely deep survey using two of the four giant 8.2-metre telescopes that make up ESO's Very Large Telescope (VLT) and a unique custom-built filter, astronomers have determined that a large fraction of galaxies whose light took 10 billion years to reach us have gone undiscovered. The survey also helped uncover some of the faintest galaxies ever found at this early stage of the Universe. Astronomers frequently use the strong, characteristic "fingerprint" of light emitted by hydrogen known as the Lyman-alpha line, to probe the amount of stars formed in the very distant Universe [1]. Yet there have long been suspicions that many distant galaxies go unnoticed in these surveys. A new VLT survey demonstrates for the first time that this is exactly what is happening. Most of the Lyman-alpha light is trapped within the galaxy that emits it, and 90% of galaxies do not show up in Lyman-alpha surveys. "Astronomers always knew they were missing some fraction of the galaxies in Lyman-alpha surveys," explains Matthew Hayes, the lead author of the paper, published this week in Nature, "but for the first time we now have a measurement. The number of missed galaxies is substantial." To figure out how much of the total luminosity was missed, Hayes and his team used the FORS camera at the VLT and a custom-built narrowband filter [2] to measure this Lyman-alpha light, following the methodology of standard Lyman-alpha surveys. Then, using the new HAWK-I camera, attached to another VLT Unit Telescope, they surveyed the same area of space for light emitted at a different wavelength, also by glowing hydrogen, and known as the H-alpha line. They specifically looked at galaxies whose light has been travelling for 10 billion years (redshift 2.2 [3]), in a well-studied area of the sky, known as the GOODS-South field. "This is the first time we have observed a patch of the sky so deeply in light coming from hydrogen at these two very specific wavelengths, and this proved crucial," says team member Göran Östlin. The survey was extremely deep, and uncovered some of the faintest galaxies known at this early epoch in the life of the Universe. The astronomers could thereby conclude that traditional surveys done using Lyman-alpha only see a tiny part of the total light that is produced, since most of the Lyman-alpha photons are destroyed by interaction with the interstellar clouds of gas and dust. This effect is dramatically more significant for Lyman-alpha than for H-alpha light. As a result, many galaxies, a proportion as high as 90%, go unseen by these surveys. "If there are ten galaxies seen, there could be a hundred there," Hayes says. Different observational methods, targeting the light emitted at different wavelengths, will always lead to a view of the Universe that is only partially complete. The results of this survey issue a stark warning for cosmologists, as the strong Lyman-alpha signature becomes increasingly relied upon in examining the very first galaxies to form in the history of the Universe. "Now that we know how much light we've been missing, we can start to create far more accurate representations of the cosmos, understanding better how quickly stars have formed at different times in the life of the Universe," says co-author Miguel Mas-Hesse. The breakthrough was made possible thanks to the unique camera used. HAWK-I, which saw first light in 2007, is a state-of-the-art instrument. "There are only a few other cameras with a wider field of view than HAWK-I, and they are on telescopes less than half the size of the VLT. So only VLT/HAWK-I, really, is capable of efficiently finding galaxies this faint at these distances," says team member Daniel Schaerer. Notes [1] Lyman-alpha light corresponds to light emitted by excited hydrogen (more specifically, when the electron around the nucleus jumps from the first excited level to the fundamental, or ground, level). This light is emitted in the ultraviolet, at 121.6 nm. The Lyman-alpha line is the first in the so-called Lyman series, named after its discoverer, Theodore Lyman. The Balmer series, named after Johann Balmer, also corresponds to light emitted by excited hydrogen. In this case, the electron falls into the first excited level. The first line in this series is the H-alpha line, emitted at 656.3 nm. As most hydrogen atoms present in a galaxy are in the ground level, Lyman-alpha light is more efficiently absorbed than H-alpha light, which requires atoms having an electron in the second level. As this is very uncommon in the cold interstellar hydrogen permeating galaxies, the gas is almost perfectly transparent to H-alpha light. [2] A narrowband filter is an optical filter designed to let pass only a narrow bandwidth of light, centred on a specific wavelength. Traditional narrowband filters include those centred on the lines of the Balmer series, such as H-alpha. [3] Because the Universe expands, the light of a distant object is redshifted by an amount depending on its distance. This means its light is moved towards longer wavelengths. A redshift of 2.2 - corresponding to galaxies whose light has taken approximately 10 billion years to reach us - means that the light is stretched by a factor 3.2. Thus the Lyman-alpha light is now seen at about 390 nm, near the visible domain, and can be observed with the FORS instrument on ESO's VLT, while the H-alpha line is moved towards 2.1 microns, in the near-infrared. It can thus be observed with the HAWK-I instrument on the VLT. More information This research was presented in a paper to appear in Nature ("Escape of about five per cent of Lyman-a photons from high-redshift star-forming galaxies", by M. Hayes et al.). The team is composed of Matthew Hayes, Daniel Schaerer, and Stéphane de Barros (Observatoire Astronomique de l'Université de Genève, Switzerland), Göran Östlin and Jens Melinder (Stockholm University, Sweden), J. Miguel Mas-Hesse (CSIC-INTA, Madrid, Spain), Claus Leitherer (Space Telescope Science Institute, Baltimore, USA), Hakim Atek and Daniel Kunth (Institut d'Astrophysique de Paris, France), and Anne Verhamme (Oxford Astrophysics, U.K.). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Recent Structural Evolution of Early-Type Galaxies: Size Growth from z = 1 to z = 0

NASA Astrophysics Data System (ADS)

van der Wel, Arjen; Holden, Bradford P.; Zirm, Andrew W.; Franx, Marijn; Rettura, Alessandro; Illingworth, Garth D.; Ford, Holland C.

2008-11-01

Strong size and internal density evolution of early-type galaxies between z ~ 2 and the present has been reported by several authors. Here we analyze samples of nearby and distant (z ~ 1) galaxies with dynamically measured masses in order to confirm the previous, model-dependent results and constrain the uncertainties that may play a role. Velocity dispersion (σ) measurements are taken from the literature for 50 morphologically selected 0.8 < z < 1.2 field and cluster early-type galaxies with typical masses Mdyn = 2 × 1011 M⊙. Sizes (Reff) are determined with Advanced Camera for Surveys imaging. We compare the distant sample with a large sample of nearby (0.04 < z < 0.08) early-type galaxies extracted from the Sloan Digital Sky Survey for which we determine sizes, masses, and densities in a consistent manner, using simulations to quantify systematic differences between the size measurements of nearby and distant galaxies. We find a highly significant difference between the σ - Reff distributions of the nearby and distant samples, regardless of sample selection effects. The implied evolution in Reff at fixed mass between z = 1 and the present is a factor of 1.97 +/- 0.15. This is in qualitative agreement with semianalytic models; however, the observed evolution is much faster than the predicted evolution. Our results reinforce and are quantitatively consistent with previous, photometric studies that found size evolution of up to a factor of 5 since z ~ 2. A combination of structural evolution of individual galaxies through the accretion of companions and the continuous formation of early-type galaxies through increasingly gas-poor mergers is one plausible explanation of the observations. Based on observations with the Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555, and observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Based on observations collected at the European Southern Observatory, Chile (169.A-0458). Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

STAR FORMATION AT Z = 2.481 IN THE LENSED GALAXY SDSS J1110+6459: STAR FORMATION DOWN TO 30 PARSEC SCALES.

PubMed

Johnson, Traci L; Rigby, Jane R; Sharon, Keren; Gladders, Michael D; Florian, Michael; Bayliss, Matthew B; Wuyts, Eva; Whitaker, Katherine E; Livermore, Rachael; Murray, Katherine T

2017-07-10

We present measurements of the surface density of star formation, the star-forming clump luminosity function, and the clump size distribution function, for the lensed galaxy SGAS J111020.0+645950.8 at a redshift of z =2.481. The physical size scales that we probe, radii r = 30-50 pc, are considerably smaller scales than have yet been studied at these redshifts. The star formation surface density we find within these small clumps is consistent with surface densities measured previously for other lensed galaxies at similar redshift. Twenty-two percent of the rest-frame ultraviolet light in this lensed galaxy arises from small clumps, with r <100 pc. Within the range of overlap, the clump luminosity function measured for this lensed galaxy is remarkably similar to those of z ∼ 0 galaxies. In this galaxy, star-forming regions smaller than 100 pc-physical scales not usually resolved at these redshifts by current telescopes-are important locations of star formation in the distant universe. If this galaxy is representative, this may contradict the theoretical picture in which the critical size scale for star formation in the distant universe is of order 1 kiloparsec. Instead, our results suggest that current telescopes have not yet resolved the critical size scales of star-forming activity in galaxies over most of cosmic time.

IRAS 14348-1447, an Ultraluminous Pair of Colliding, Gas-Rich Galaxies: The Birth of a Quasar?

PubMed

Sanders, D B; Scoville, N Z; Soifer, B T

1988-02-05

Ground-based observations of the object IRAS 14348-1447, which was discovered with the Infrared Astronomical Satellite, show that it is an extremely luminous colliding galaxy system that emits more than 95 percent of its energy at far-infrared wavelengths. IRAS 14348-1447, which is receeding from the sun at 8 percent of the speed of light, has a bolometric luminosity more than 100 times larger than that of our galaxy, and is therefore as luminous as optical quasars. New optical, infrared, and spectroscopic measurements suggest that the dominant luminosity source is a dustenshrouded quasar. The fuel for the intense activity is an enormous supply of molecular gas. Carbon monoxide emission has been detected at a wavelength of 2.6 millimeters by means of a new, more sensitive receiver recently installed on the 12-meter telescope of the National Radio Astronomy Observatory. IRAS 14348-1447 is the most distant and luminous source of carbon monoxide line emission yet detected. The derived mass of interstellar molecular hydrogen is 6 x 10(10) solar masses. This value is approximately 20 times that of the molecular gas content of the Milky Way and is similar to the largest masses of atomic hydrogen found in galaxies. A large mass of molecular gas may be a prerequisite for the formation of quasars during strong galactic collisions.

The Search for RR Lyrae Variables in the Dark Energy Survey

NASA Astrophysics Data System (ADS)

Nielsen, Chandler; Marshall, Jennifer L.; Long, James

2017-01-01

RR Lyrae variables are stars with a characteristic relationship between magnitude and phase and whose distances can be easily determined, making them extremely valuable in mapping and analyzing galactic substructure. We present our method of searching for RR Lyrae variable stars using data extracted from the Dark Energy Survey (DES). The DES probes for stars as faint as i = 24.3. Finding such distant RR Lyrae allows for the discovery of objects such as dwarf spheroidal tidal streams and dwarf galaxies; in fact, at least one RR Lyrae has been discovered in each of the probed dwarf spheroidal galaxies orbiting the Milky Way (Baker & Willman 2015). In turn, these discoveries may ultimately resolve the well-known missing satellite problem, in which theoretical simulations predict many more dwarf satellites than are observed in the local Universe. Using the Lomb-Scargle periodogram to determine the period of the star being analyzed, we could display the relationship between magnitude and phase and visually determine if the star being analyzed was an RR Lyrae. We began the search in frequently observed regions of the DES footprint, known as the supernova fields. We then moved our search to known dwarf galaxies found during the second year of the DES. Unfortunately, we did not discover RR Lyrae in the probed dwarf galaxies; this method should be tried again once more observations are taken in the DES.

Dusty Feedback from Massive Black Holes in Two Elliptical Galaxies

NASA Technical Reports Server (NTRS)

Temi, P.; Brighenti, F.; Mathews, W. G.; Amblard, A.; Riguccini, L.

2013-01-01

Far-infrared dust emission from elliptical galaxies informs us about galaxy mergers, feedback energy outbursts from supermassive black holes and the age of galactic stars. We report on the role of AGN feedback observationally by looking for its signatures in elliptical galaxies at recent epochs in the nearby universe. We present Herschel observations of two elliptical galaxies with strong and spatially extended FIR emission from colder grains 5-10 kpc distant from the galaxy cores. Extended excess cold dust emission is interpreted as evidence of recent feedback-generated AGN energy outbursts in these galaxies, visible only in the FIR, from buoyant gaseous outflows from the galaxy cores.

Bursting with Stars and Black Holes Artist Concept

NASA Image and Video Library

2007-10-25

A growing black hole, called a quasar, is seen at the center of a faraway galaxy in this artist concept. Astronomers using NASA Spitzer and Chandra space telescopes discovered swarms of similar quasars hiding in dusty galaxies in the distant universe.

Statistical properties of Faraday rotation measure in external galaxies - I. Intervening disc galaxies

NASA Astrophysics Data System (ADS)

Basu, Aritra; Mao, S. A.; Fletcher, Andrew; Kanekar, Nissim; Shukurov, Anvar; Schnitzeler, Dominic; Vacca, Valentina; Junklewitz, Henrik

2018-06-01

Deriving the Faraday rotation measure (RM) of quasar absorption line systems, which are tracers of high-redshift galaxies intervening background quasars, is a powerful tool for probing magnetic fields in distant galaxies. Statistically comparing the RM distributions of two quasar samples, with and without absorption line systems, allows one to infer magnetic field properties of the intervening galaxy population. Here, we have derived the analytical form of the probability distribution function (PDF) of RM produced by a single galaxy with an axisymmetric large-scale magnetic field. We then further determine the PDF of RM for one random sight line traversing each galaxy in a population with a large-scale magnetic field prescription. We find that the resulting PDF of RM is dominated by a Lorentzian with a width that is directly related to the mean axisymmetric large-scale field strength of the galaxy population if the dispersion of B0 within the population is smaller than . Provided that RMs produced by the intervening galaxies have been successfully isolated from other RM contributions along the line of sight, our simple model suggests that in galaxies probed by quasar absorption line systems can be measured within ≈50 per cent accuracy without additional constraints on the magneto-ionic medium properties of the galaxies. Finally, we discuss quasar sample selection criteria that are crucial to reliably interpret observations, and argue that within the limitations of the current data base of absorption line systems, high-metallicity damped Lyman-α absorbers are best suited to study galactic dynamo action in distant disc galaxies.

Constraining the excitation conditions of the molecular gas in the most distant submillimetre galaxy at z=4.76

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Weiss, Axel; van der Werf, Paul; Menten, Karl; De Breuck, Carlos; Walter, Fabian; Loenen, Edo; Edge, Alastair; Emonts, Bjorn; Huynh, Minh; Swinbank, Mark; Smail, Ian; Schinnerer, Eva; Greve, Thomas; Chapman, Scott; Danielson, Alice; Knudsen, Kirsten; Dannerbauer, Helmut; Brandt, Niel; Berciano Alba, Alicia; Strom, Allison

2010-10-01

We propose to use ATCA to measure CO(5-4) emission in the currently highest redshift submm-selected galaxy (SMG) known: LESS J033229 at z=4.755. Combined with our previous successful ATCA observations of the CO(2-1) transition in this SMG, we will be able to start building up the CO SED excitation ladder and so gain new insight on the excitation conditions of the molecular gas which is fuelling a massive burst of star formation at a time when the Universe was only 1 Gyr old. ATCA is currently the only available facility that can provide these data, giving us a sneak-preview of the capabilities of ALMA for studying the youngest galaxies in the very distant Universe.

Tracing the Fuel for Forming Stars

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-11-01

Huge reservoirs of cold hydrogen gas the raw fuel for star formation lurk in galaxies throughout the universe. A new study examines whether these reservoirs have always been similar, or whether those in distant galaxies are very different from those in local galaxies today.Left: Optical SLOAN images of the five HIGHz galaxies in this study. Right: ALMA images of the molecular gas in these galaxies. Both images are 30 wide. [Adapted from Cortese et al. 2017]Molecular or Atomic?The formation of stars is a crucial process that determines how galaxies are built and evolve over time. Weve observed that star formation takes place in cold clouds of molecular gas, and that star-formation rates increase in galaxies with a larger surface density of molecular hydrogen so we know that molecular hydrogen feeds the star-forming process.But not all cold gas in the interstellar medium of galaxies exists in molecular form. In the local universe, only around 30% of cold gas is found in molecular form (H2) and able to directly feed star formation; the rest is atomic hydrogen (H I). But is this true of galaxies earlier in the universe as well?Studying Distant GalaxiesCosmological simulations have predicted that earlier in our universes history, the ratio of molecular to atomic hydrogen could be larger i.e., more cold hydrogen may be in a form ready to fuel star formation but this prediction is difficult to test observationally. Currently, radio telescopes are not able to measure the atomic hydrogen in very distant galaxies, such as those at the peak of star formation in the universe, 10 billion years ago.Recently, however, we have measured atomic hydrogen in closer galaxies: those at a redshift of about z 0.20.4, a few billion years ago. One recent study of seven galaxies at this distance, usinga sample from a survey known as COOL BUDHIES, showed that the hydrogen reservoirs of these galaxies are dominated by molecular hydrogen, unlike in the local universe. If this is true of most galaxies at this distance, it would suggest that gas reservoirs have drastically changed in the short time between then and now.But a team of scientists from the International Centre for Radio Astronomy Research in Australia, led by Luca Cortese, has now challenged this conclusion.Top: molecular vs. atomic hydrogen gas in galaxies between z = 0 and z = 1.5. Bottom: the evolution of the molecular-to-atomic mass ratio with redshift. [Adapted from Cortese et al. 2017]Adding to the SampleCortese and collaborators combined observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and Arecibo to estimate the ratio of molecular to atomic hydrogen in five HIGHz-survey massive star-forming galaxies at a redshift of z 0.2. They then combine these results with those of the COOL BUDHIES survey; they argue that, since the two surveys use different selection criteria, the combination of the two samples provides a fairer view of the overall population of star-forming galaxies at z 0.2.Intriguingly, the HIGHz galaxies do not show the molecular-gas dominance that the COOL BUDHIES galaxies do. Cortese and collaborators demonstrate that the addition of the HIGHz galaxies to the sample reveals that the gas reservoirs of star-forming disks 3 billion years ago are, in fact, still the same as what we see today, suggesting that star formation in galaxies at z 0.2 is likely fueled in much the same way as it is today.As telescope capabilities increase, we may be able to explore whether this continues to hold true for more distant galaxies. In the meantime, increasing our sample size within the range that we can observe will help us to further explore how galaxies have formed stars over time.CitationLuca Cortese et al 2017 ApJL 848 L7. doi:10.3847/2041-8213/aa8cc3

Giant Cosmic Lens Reveals Secrets of Distant Galaxy

NASA Astrophysics Data System (ADS)

2003-04-01

Using the National Science Foundation's Very Large Array (VLA) radio telescope and helped by a gigantic cosmic lens conveniently provided by nature, an international team of astronomers has discovered that a young galaxy had a central disk of gas in which hundreds of new stars were being born every year -- at a time when the Universe was only a fraction of its current age. Artist's Conception of the Star-Forming Disk (Click on Image for Larger Version) VLA Image of PSS J2322+1944 (Click on Image for Larger Version) "This unique look into a very distant, young galaxy gives us unprecedented insight into the process that produced both tremendous numbers of stars and supermassive black holes in forming galaxies," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM, leader of the research team. "This work strongly supports the idea that the stars and the black holes formed simultaneously," he added. The research was published in the April 4 issue of Science Express. The astronomers studied a quasar called PSS J2322+1944, about 12 billion light-years from Earth. The quasar is an extremely luminous object powered by the supermassive black hole at the core of a galaxy. At the distance of this quasar, the scientists see the object as it was when the Universe was less than 2 billion years old, about 15 percent of its current age. The discovery required a huge assist from nature. To find the star-forming disk, the astronomers needed to observe natural radio emission from the carbon monoxide (CO) molecule, an important component of the gas that forms stars. However, this molecule emits radio waves at frequencies much higher than the VLA is capable of receiving. At PSS J2322+1944's distance of 12 billion light-years, however, the expansion of the Universe stretched the radio waves, reducing their frequency. CO emission at 230 GigaHertz was shifted to 45 GigaHertz, within the VLA's range. That alone was not enough. The distance that made it possible to receive the radio waves from the quasar also meant that the object was too far away for the VLA to discern the detail required to show the disk. Once again, nature stepped in to help, providing another galaxy directly between the quasar and Earth to form a gravitational lens. "What we needed wasn't just any old gravitational lens, but a nearly-perfect alignment of the distant quasar, mid-distance galaxy, and Earth -- and that's what we got," said Geraint Lewis of the University of Sydney in Australia, another member of the team. With such a perfect alignment, the quasar image was distorted into a ring, called an "Einstein Ring." The VLA images were the first to show the Einstein Ring of PSS J2322+1944. "We never would have seen the disk of CO gas near the center of this galaxy without the gravitational lens," said Carilli. "The lens boosted the signal and magnified the image to reveal the disk's structure in unprecedented detail," he added. For several years, astronomers have noted that the masses of black holes are directly proportional to the sizes of central bulges of stars in galaxies. This led to the speculation that formation of the black holes and of the stars are somehow related to each other. Scientists hypothesized that gas being drawn towards a galaxy's central black hole is the same gas from which large numbers of stars are forming. Studies of more-nearby galaxies supported such speculation, but the question remained whether the idea could be applied to the very early Universe, when the first galaxies and black holes formed. "This new observation gives strong support to the idea that large numbers of stars were forming in young galaxies at the same time that their central black holes were pulling in additional mass," said Pierre Cox, of the Institute for Space Astrophysics of the University of Paris. The astronomers believe that galaxies in the early Universe were frequently disrupted by nearby encounters with other galaxies, "feeding" the central black hole with gas. The gas formed an extensive, spinning disk around the galaxy's center, some of it eventually falling into the black hole and some of it forming new stars. In PSS J2322+1944, the astronomers believe that new stars with a total mass equal to some 900 times that of the Sun were forming in the 13,000-light-year-diameter disk every year. At that rate, the scientists say, most of the stars in a large elliptical galaxy could form in only about 100 million years. PSS J2322+1944 is one of the most luminous quasars in the Universe. It was first discovered by George Djorgovski and his collaborators from the California Institute of Technology (Caltech), using the digitized Palomar Observatory Sky Survey. Later studies led by Cox and Alain Omont of the Astrophysical Institute of Paris using the IRAM millimeter-wave facilities in Europe (the 30-meter telescope and the Plateau de Bure Interferometer) showed that it had a huge reservoir of dust and molecular gas, the fuel for star formation. Optical observation at the W.M. Keck Observatory in Hawaii showed a double image that indicated gravitational lensing. All these factors, the scientists said, made it an ideal candidate for study with the VLA. "Our guess paid off handsomely. Finding that Einstein Ring with the VLA gave us the tool we needed to see what was going on inside that very distant galaxy," said Carilli. "There are fewer than 100 gravitational lenses known so far, and we were extremely lucky to find one that allowed us to help resolve the specific scientific question we were studying." Gravitational lenses were predicted, based on Albert Einstein's General Theory of Relativity, in 1919. Einstein himself showed in 1936 that a perfectly-aligned gravitational lens would produce a circular image, but felt that the chances of actually observing such an object were nearly zero. The first gravitational lens was discovered in 1979, and the first Einstein Ring was discovered by researchers using the VLA in 1987. PSS J2322+1944 is the first Einstein Ring detected through the signature emission of a molecule and the most distant yet found. PSS J2322+1944 may be able to make another contribution to science. Astronomers believe that gravitational lenses may serve as a tool for precisely measuring great distances in the Universe. If a distant quasar varies in brightness over time, the multiple images formed by a gravitational lens would show that variation at different times. By monitoring such time differences and using a mathematical model of the specific gravitational lens, the distance to the quasar can be measured. "This quasar, if it shows brightness variations in the future, may be such a 'Golden Lens,' long sought to refine our measurement of very great distances," said Lewis. In addition to Carilli, Lewis, Djorgovski, Cox and Omont, the research team includes Ashish Mahabal of Caltech and Frank Bertoldi of the Max-Planck Institute for Radio Astronomy in Bonn, Germany. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Spectroscopic confirmation of a galaxy at redshift z = 8.6.

PubMed

Lehnert, M D; Nesvadba, N P H; Cuby, J-G; Swinbank, A M; Morris, S; Clément, B; Evans, C J; Bremer, M N; Basa, S

2010-10-21

Galaxies had their most significant impact on the Universe when they assembled their first generations of stars. Energetic photons emitted by young, massive stars in primeval galaxies ionized the intergalactic medium surrounding their host galaxies, cleared sightlines along which the light of the young galaxies could escape, and fundamentally altered the physical state of the intergalactic gas in the Universe continuously until the present day. Observations of the cosmic microwave background, and of galaxies and quasars at the highest redshifts, suggest that the Universe was reionized through a complex process that was completed about a billion years after the Big Bang, by redshift z ≈ 6. Detecting ionizing Lyman-α photons from increasingly distant galaxies places important constraints on the timing, location and nature of the sources responsible for reionization. Here we report the detection of Lyα photons emitted less than 600 million years after the Big Bang. UDFy-38135539 (ref. 5) is at a redshift of z = 8.5549 ± 0.0002, which is greater than those of the previously known most distant objects, at z = 8.2 (refs 6 and 7) and z = 6.96 (ref. 8). We find that this single source is unlikely to provide enough photons to ionize the volume necessary for the emission line to escape, requiring a significant contribution from other, probably fainter galaxies nearby.

Groth Deep Locations Image

NASA Image and Video Library

2003-07-25

NASA's Galaxy Evolution Explorer photographed this ultraviolet color blowup of the Groth Deep Image on June 22 and June 23, 2003. Hundreds of galaxies are detected in this portion of the image, and the faint red galaxies are believed to be 6 billion light years away. The white boxes show the location of these distant galaxies, of which more than a 100 can be detected in this image. NASA astronomers expect to detect 10,000 such galaxies after extrapolating to the full image at a deeper exposure level. http://photojournal.jpl.nasa.gov/catalog/PIA04626

X-ray versus infrared selection of distant galaxy clusters: a case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-07-01

We present a comparison of two samples of z> 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray-selected XMM Large Scale Structure (LSS) distant cluster survey and 92 clusters from the optical-mid-infrared (MIR)-selected Spitzer Adaptation of the Red Sequence Cluster survey (SpARCS) cluster survey. Both samples are selected from the same approximately 9 sq deg sky area and we examine them using common XMM-Newton, Spitizer Wide-Area Infrared Extra-galactic (SWIRE) survey, and Canada-France-Hawaii Telescope Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: (i) X-ray bright, (ii) X-ray faint, MIR bright, and (iii) X-ray faint, MIR faint clusters. We determine that X-ray- and MIR-selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray- and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of brightest cluster galaxy-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

Galaxy Transformation Under Extreme Conditions: The Evolution of Galaxies in the Largest Structures in the High Redshift Universe

NASA Astrophysics Data System (ADS)

Lemaux, Brian Clark

This dissertation describes research performed in the field of observational astrophysics as part of the Observations of Redshift Evolution in Large Scale Environment (ORELSE) survey. The general motivation of the research presented in this dissertation is to investigate the processes responsible for the evolution of galaxies in a wide range of physical conditions over cosmic time. Throughout this dissertation, galaxy populations will be considered in the very nearby universe (i.e., within one billion light years from Earth), the middle-aged universe (i.e., eight billion years ago), and in the very early universe (i.e., just one billion years after the beginning of the universe). In each chapter I present unique data from observations taken and analyzed specifically for the ORELSE survey. In the first part of this dissertation I describe the context, aims, and current state of the ORELSE survey. The studies presented in this dissertation span a large range of galaxy samples and investigate a variety of different astrophysical phenomena. As all of these studies fall under the context of galaxy evolution, these initial sections will set the framework for the variety of studies presented in this thesis. In the second part of this dissertation I present four studies undertaken to investigate various aspects of galaxy evolution. The first of these studies is an investigation of a large population of very distant galaxies detected in one of the ORELSE fields. The survey in this field represents the deepest survey of a particular kind of very distant galaxy population known as Lymanalpha Emitter (LAEs). The number of LAEs found in this survey far exceeded expectations for such galaxies and are shown to be in excess of every other survey of similar galaxies at similar distances. This result has important consequences for galaxy evolution studies, as it suggests that faint LAEs may be much more numerous than previously thought. This work also has important consequences for a process in the early universe known as reionization, which is the subject of much debate amongst astronomers. The second and third of these studies are investigations using near-infrared spectroscopy of X-ray bright and red galaxies that exhibit optical spectra with prominent emission features. These studies are the first systematic investigations of both galaxy populations in the middle-aged universe using near-infrared spectroscopy. In both studies I conclude the dominant mechanism giving rise to optical emission line features are processes associated with the presence of an Active Galactic Nuclei (AGN) rather than normal star formation. This result has important consequences for galaxy evolutionary scenarios, as the two processes are typically difficult to separate observationally and are thought to be related. The final study in this presentation is a full investigation of the processes driving galaxy evolution in one of the ORELSE fields, the Cl1604 supercluster. In this study I present the wealth of astronomical observations available to the ORELSE survey on the member galaxies of this supercluster. Several transitional populations of galaxies are detected in the supercluster environment, and their properties are analyzed in the context of galaxy evolution. Processing of the galaxy population is found to be significant in both the densest environments in the supercluster and the lower-density regions. One of the major conclusions of this work relates to the efficiency of these transformative processes and the global environment in which a galaxy resides. I present evidence for a process termed "dynamical downsizing", in which efficient transforming of galaxies occurs earliest in structures of galaxies that are observed to be relaxed (i.e., virialized) in their dynamics.

Galaxy Evolution Viewed as Functions of Environment and Mass

NASA Astrophysics Data System (ADS)

Kodama, Tadayuki; Tanaka, Masayuki; Tanaka, Ichi; Kajisawa, Masaru

We present two large surveys of distant clusters currently being carried out with Subaru, making use of its great capability of wide-field study both in the optical and in the near-infrared. The optical surveys, called PISCES, have mapped out large scale structures in and around 8 distant clusters at 0.4 < z <1.3, composed of multiple filaments and clumps extended over 15-30 Mpc scale. From the photometric and spectroscopic properties of galaxies over a wide range in environment, we find that the truncation of galaxies is seen in the outskirts of clusters rather than in the cluster cores.We also see a clear environmental dependence of the down-sizing (progressively later quenching of star formation in smaller galaxies). The near-infrared surveys are being conducted with a new wide-field instrument targeting proto-clusters around high-zradio-loud galaxies up to z ~4. Most of these field are known to show a large number of Lyαand/or Hαemitters at the same redshifts of the radio galaxies. We see a clear excess of near-infrared selected galaxies (JHK s -selected galaxies as well as DRG) in these fields, and they are indeed proto-clusters with not only young emitters but also evolved populations. Spatial distribution of such NIR selected galaxies is filamentary and track similar structures traced by the emitters. There is an hint that the bright-end of the red sequence first appeared between z= 3 and 2.

When Bad Masks Turn Good

NASA Astrophysics Data System (ADS)

Abraham, Roberto G.

In keeping with the spirit of a meeting on ‘masks,' this talk presents two short stories on the theme of dust. In the first, dust plays the familiar role of the evil obscurer, the enemy to bedefeated by the cunning observer in order to allow a key future technology (adaptive optics) to be exploited fully by heroic astronomers. In the second story, dust itself emerges as the improbable hero, in the form of a circumstellar debris disks. I will present evidence of a puzzling near-infrared excess in the continuum of high-redshift galaxies and will argue that the seemingly improbable origin of this IR excess is a population of young circumstellar disks formed around high-mass stars in distant galaxies. Assuming circumstellar disks extend down to lower masses,as they do in our own Galaxy, the excess emission presents us with an exciting opportunity to measure the formation rate of planetary systems in distant galaxies at cosmic epochs before our own solar system formed.

Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe.

PubMed

Hennawi, Joseph F; Prochaska, J Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

2015-05-15

All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations. Copyright © 2015, American Association for the Advancement of Science.

The essential signature of a massive starburst in a distant quasar.

PubMed

Solomon, P; Vanden Bout, P; Carilli, C; Guelin, M

2003-12-11

Observations of carbon monoxide emission in high-redshift (zeta > 2) galaxies indicate the presence of large amounts of molecular gas. Many of these galaxies contain an active galactic nucleus powered by accretion of gas onto a supermassive black hole, and a key question is whether their extremely high infrared luminosities result from the active galactic nucleus, from bursts of massive star formation (associated with the molecular gas), or both. In the Milky Way, high-mass stars form in the dense cores of interstellar molecular clouds, where gas densities are n(H2) > 10(5) cm(-3) (refs 1, 2). Recent surveys show that virtually all galactic sites of high-mass star formation have similarly high densities. The bulk of the cloud material traced by CO observations, however, is at a much lower density. For galaxies in the local Universe, the HCN molecule is an effective tracer of high-density molecular gas. Here we report observations of HCN emission from the infrared-luminous 'Cloverleaf' quasar (at a redshift zeta = 2.5579). The HCN line luminosity indicates the presence of 10 billion solar masses of very dense gas, an essential feature of an immense starburst, which contributes, together with the active galactic nucleus it harbours, to its high infrared luminosity.

The Space Density of Luminous Dusty Star-forming Galaxies at z > 4: SCUBA-2 and LABOCA Imaging of Ultrared Galaxies from Herschel-ATLAS

NASA Astrophysics Data System (ADS)

Ivison, R. J.; Lewis, A. J. R.; Weiss, A.; Arumugam, V.; Simpson, J. M.; Holland, W. S.; Maddox, S.; Dunne, L.; Valiante, E.; van der Werf, P.; Omont, A.; Dannerbauer, H.; Smail, Ian; Bertoldi, F.; Bremer, M.; Bussmann, R. S.; Cai, Z.-Y.; Clements, D. L.; Cooray, A.; De Zotti, G.; Eales, S. A.; Fuller, C.; Gonzalez-Nuevo, J.; Ibar, E.; Negrello, M.; Oteo, I.; Pérez-Fournon, I.; Riechers, D.; Stevens, J. A.; Swinbank, A. M.; Wardlow, J.

2016-11-01

Until recently, only a handful of dusty, star-forming galaxies (DSFGs) were known at z > 4, most of them significantly amplified by gravitational lensing. Here, we have increased the number of such DSFGs substantially, selecting galaxies from the uniquely wide 250, 350, and 500 μm Herschel-ATLAS imaging survey on the basis of their extremely red far-infrared colors and faint 350 and 500 μm flux densities, based on which, they are expected to be largely unlensed, luminous, rare, and very distant. The addition of ground-based continuum photometry at longer wavelengths from the James Clerk Maxwell Telescope and the Atacama Pathfinder Experiment allows us to identify the dust peak in their spectral energy distributions (SEDs), with which we can better constrain their redshifts. We select the SED templates that are best able to determine photometric redshifts using a sample of 69 high-redshift, lensed DSFGs, then perform checks to assess the impact of the CMB on our technique, and to quantify the systematic uncertainty associated with our photometric redshifts, σ = 0.14 (1 + z), using a sample of 25 galaxies with spectroscopic redshifts, each consistent with our color selection. For Herschel-selected ultrared galaxies with typical colors of S 500/S 250 ˜ 2.2 and S 500/S 350 ˜ 1.3 and flux densities, S 500 ˜ 50 mJy, we determine a median redshift, {\\hat{z}}{phot}=3.66, an interquartile redshift range, 3.30-4.27, with a median rest-frame 8-1000 μm luminosity, {\\hat{L}}{IR}, of 1.3 × 1013 L ⊙. A third of the galaxies lie at z > 4, suggesting a space density, ρ z > 4, of ≈6 × 10-7 Mpc-3. Our sample contains the most luminous known star-forming galaxies, and the most overdense cluster of starbursting proto-ellipticals found to date.

A Magellan M2FS Spectroscopic Survey of Galaxies at 5.5 < z < 6.8: Program Overview and a Sample of the Brightest Lyα Emitters

NASA Astrophysics Data System (ADS)

Jiang, Linhua; Shen, Yue; Bian, Fuyan; Zheng, Zhen-Ya; Wu, Jin; Oyarzún, Grecco A.; Blanc, Guillermo A.; Fan, Xiaohui; Ho, Luis C.; Infante, Leopoldo; Wang, Ran; Wu, Xue-Bing; Mateo, Mario; Bailey, John I., III; Crane, Jeffrey D.; Olszewski, Edward W.; Shectman, Stephen; Thompson, Ian; Walker, Matthew G.

2017-09-01

We present a spectroscopic survey of high-redshift, luminous galaxies over four square degrees on the sky, aiming to build a large and homogeneous sample of Lyα emitters (LAEs) at z≈ 5.7 and 6.5, and Lyman-break galaxies (LBGs) at 5.5< z< 6.8. The fields that we choose to observe are well studied, such as by the Subaru XMM-Newton Deep Survey and COSMOS. They have deep optical imaging data in a series of broad and narrow bands, allowing for the efficient selection of galaxy candidates. Spectroscopic observations are being carried out using the multi-object spectrograph M2FS on the Magellan Clay telescope. M2FS is efficient enough to identify high-redshift galaxies, owing to its 256 optical fibers deployed over a circular field of view 30\\prime in diameter. We have observed ˜2.5 square degrees. When the program is completed, we expect to identify more than 400 bright LAEs at z≈ 5.7 and 6.5, and a substantial number of LBGs at z≥slant 6. This unique sample will be used to study a variety of galaxy properties and to search for large protoclusters. Furthermore, the statistical properties of these galaxies will be used to probe cosmic reionization. We describe the motivation, program design, target selection, and M2FS observations. We also outline our science goals, and present a sample of the brightest LAEs at z≈ 5.7 and 6.5. This sample contains 32 LAEs with Lyα luminosities higher than 1043 erg s-1. A few of them reach ≥3 × 1043 erg s-1, comparable to the two most luminous LAEs known at z≥slant 6, “CR7” and “COLA1.” These LAEs provide ideal targets to study extreme galaxies in the distant universe.

NEW CONSTRAINTS ON THE FAINT END OF THE UV LUMINOSITY FUNCTION AT z ∼ 7-8 USING THE GRAVITATIONAL LENSING OF THE HUBBLE FRONTIER FIELDS CLUSTER A2744

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atek, Hakim; Kneib, Jean-Paul; Richard, Johan

2015-02-10

Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ∼ 7 and eight candidates at z ∼ 8 in a total survey area of 0.96 arcmin{sup 2} in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we weremore » able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ∼ 7 UV LF down to an absolute magnitude of M {sub UV} ∼ –15.5. We find a characteristic magnitude of M{sub UV}{sup ⋆}=−20.90{sub −0.73}{sup +0.90} mag and a faint-end slope α=−2.01{sub −0.28}{sup +0.20}, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L {sup *}. Although prone to large uncertainties, our results at z ∼ 8 also seem to confirm a steep faint-end slope below 0.1 L {sup *}. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization.« less

X-ray versus infrared selection of distant galaxy clusters: A case study using the XMM-LSS and SpARCS cluster samples

NASA Astrophysics Data System (ADS)

Willis, J. P.; Ramos-Ceja, M. E.; Muzzin, A.; Pacaud, F.; Yee, H. K. C.; Wilson, G.

2018-04-01

We present a comparison of two samples of z > 0.8 galaxy clusters selected using different wavelength-dependent techniques and examine the physical differences between them. We consider 18 clusters from the X-ray selected XMM-LSS distant cluster survey and 92 clusters from the optical-MIR selected SpARCS cluster survey. Both samples are selected from the same approximately 9 square degree sky area and we examine them using common XMM-Newton, Spitzer-SWIRE and CFHT Legacy Survey data. Clusters from each sample are compared employing aperture measures of X-ray and MIR emission. We divide the SpARCS distant cluster sample into three sub-samples: a) X-ray bright, b) X-ray faint, MIR bright, and c) X-ray faint, MIR faint clusters. We determine that X-ray and MIR selected clusters display very similar surface brightness distributions of galaxy MIR light. In addition, the average location and amplitude of the galaxy red sequence as measured from stacked colour histograms is very similar in the X-ray and MIR-selected samples. The sub-sample of X-ray faint, MIR bright clusters displays a distribution of BCG-barycentre position offsets which extends to higher values than all other samples. This observation indicates that such clusters may exist in a more disturbed state compared to the majority of the distant cluster population sampled by XMM-LSS and SpARCS. This conclusion is supported by stacked X-ray images for the X-ray faint, MIR bright cluster sub-sample that display weak, centrally-concentrated X-ray emission, consistent with a population of growing clusters accreting from an extended envelope of material.

Selections from 2017: Hubble Survey Explores Distant Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.CANDELS Multi-Wavelength Catalogs: Source Identification and Photometry in the CANDELS COSMOSSurvey FieldPublished January2017Main takeaway:A publication led byHooshang Nayyeri(UC Irvine and UC Riverside) early this year details acatalog of sources built using the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey(CANDELS), a survey carried out by cameras on board the Hubble Space Telescope. The catalogliststhe properties of 38,000 distant galaxies visiblewithin the COSMOS field, a two-square-degree equatorial field explored in depthto answer cosmological questions.Why its interesting:Illustration showing the three-dimensional map of the dark matter distribution in theCOSMOS field. [Adapted from NASA/ESA/R. Massey(California Institute of Technology)]The depth and resolution of the CANDELS observations areuseful for addressingseveral major science goals, including the following:Studying the most distant objects in the universe at the epoch of reionization in the cosmic dawn.Understanding galaxy formation and evolution during the peak epoch of star formation in the cosmic high noon.Studying star formation from deep ultravioletobservations and studying cosmology from supernova observations.Why CANDELS is a major endeavor:CANDELS isthe largest multi-cycle treasury program ever approved on the Hubble Space Telescope using over 900 orbits between 2010 and 2013 withtwo cameras on board the spacecraftto study galaxy formation and evolution throughout cosmic time. The CANDELS images are all publicly available, and the new catalogrepresents an enormous source of information about distant objectsin our universe.CitationH. Nayyeri et al 2017 ApJS 228 7. doi:10.3847/1538-4365/228/1/7

An infrared jet in Centaurus A - A link to the extranuclear activity in distant radio galaxies?

NASA Technical Reports Server (NTRS)

Joy, Marshall; Harvey, P. M.; Tollestrup, E. V.; Sellgren, K.; Mcgregor, P. J.

1991-01-01

High-resolution NIR images of the visually obscured central region of Centaurus A (NGC 5128) were obtained with the University of Texas array camera on the AAT in June 1988, in order to investigate the effect of the active nucleus on the surrounding galaxy. The J (1.25 micron), H (1.65 micron), and K (2.2 micron) images of the central 40 arcsec of the galaxy revealed an emission feature extending about 10 arcsec northeast of the nucleus at the same position angle as the X-ray and radio jets. This jet is most prominent at the 1.25 micron wavelength, where its brightness was comparable to that of the nucleus. The observed properties of the 'infrared jet' were found to be similar to those seen in distant radio sources.

Space Science

NASA Image and Video Library

1978-12-01

The Andromeda Galaxy, also known as M31 since it is the 31st object on Messier's list of diffuse sky objects, is the nearest large galaxy to our own Milky Way galaxy. Our galaxy is thought to look much like Andromeda, but it is about four times as massive as the Milky Way. Together these two galaxies dominate the Local Group of galaxies. The diffused light from Andromeda is caused by hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our galaxy that are well in front of the background object. Andromeda is so distant that it takes approximately two millions years for light to reach us from there.

Reconstructing galaxy histories from globular clusters.

PubMed

West, Michael J; Côté, Patrick; Marzke, Ronald O; Jordán, Andrés

2004-01-01

Nearly a century after the true nature of galaxies as distant 'island universes' was established, their origin and evolution remain great unsolved problems of modern astrophysics. One of the most promising ways to investigate galaxy formation is to study the ubiquitous globular star clusters that surround most galaxies. Globular clusters are compact groups of up to a few million stars. They generally formed early in the history of the Universe, but have survived the interactions and mergers that alter substantially their parent galaxies. Recent advances in our understanding of the globular cluster systems of the Milky Way and other galaxies point to a complex picture of galaxy genesis driven by cannibalism, collisions, bursts of star formation and other tumultuous events.

Hubble Goes to the eXtreme to Assemble Farthest-Ever View of the Universe

NASA Image and Video Library

2017-12-08

NASA image release September 25, 2012 Like photographers assembling a portfolio of best shots, astronomers have assembled a new, improved portrait of mankind's deepest-ever view of the universe. Called the eXtreme Deep Field, or XDF, the photo was assembled by combining 10 years of NASA Hubble Space Telescope photographs taken of a patch of sky at the center of the original Hubble Ultra Deep Field. The XDF is a small fraction of the angular diameter of the full moon. The Hubble Ultra Deep Field is an image of a small area of space in the constellation Fornax, created using Hubble Space Telescope data from 2003 and 2004. By collecting faint light over many hours of observation, it revealed thousands of galaxies, both nearby and very distant, making it the deepest image of the universe ever taken at that time. The new full-color XDF image is even more sensitive, and contains about 5,500 galaxies even within its smaller field of view. The faintest galaxies are one ten-billionth the brightness of what the human eye can see. To read more go to:http://www.nasa.gov/mission_pages/hubble/science/xdf.html Credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Dust-obscured star formation and the contribution of galaxies escaping UV/optical color selections at z ~ 2

NASA Astrophysics Data System (ADS)

Riguccini, L.; Le Floc'h, E.; Ilbert, O.; Aussel, H.; Salvato, M.; Capak, P.; McCracken, H.; Kartaltepe, J.; Sanders, D.; Scoville, N.

2011-10-01

Context. A substantial amount of the stellar mass growth across cosmic time occurred within dust-enshrouded environments. So far, identification of complete samples of distant star-forming galaxies from the short wavelength range has been strongly biased by the effect of dust extinction. Nevertheless, the exact amount of star-forming activity that took place in high-redshift dusty galaxies but that has currently been missed by optical surveys has barely been explored. Aims: Our goal is to determine the number of luminous star-forming galaxies at 1.5 ≲ z ≲ 3 that are potentially missed by the traditional color selection techniques because of dust extinction. We also aim at quantifying the contribution of these sources to the IR luminosity and cosmic star formation density at high redshift. Methods: We based our work on a sample of 24 μm sources brighter than 80 μJy and taken from the Spitzer survey of the COSMOS field. Almost all of these sources have accurate photometric redshifts. We applied to this mid-IR selected sample the BzK and BM/BX criteria, as well as the selections of the IRAC peakers and the Optically-Faint IR-bright (OFIR) galaxies. We analyzed the fraction of sources identified with these techniques. We also computed 8 μm rest-frame luminosity from the 24 μm fluxes of our sources, and considering the relationships between L8 μm and LPaα and between L8 μm and LIR, we derived ρIR and then ρSFR for our MIPS sources. Results: The BzK criterion offers an almost complete (~90%) identification of the 24 μm sources at 1.4 < z < 2.5. In contrast, the BM/BX criterion misses 50% of the MIPS sources. We attribute this bias to the effect of extinction, which reddens the typical colors of galaxies. The contribution of these two selections to the IR luminosity density produced by all the sources brighter than 80 μJy are on the same order. Moreover the criterion based on the presence of a stellar bump in their spectra (IRAC peakers) misses up to 40% of the IR luminosity density, while only 25% of the IR luminosity density at z ~ 2 is produced by OFIR galaxies characterized by extreme mid-IR to optical flux ratios. Conclusions: Color selections of distant star-forming galaxies must be used with care given the substantial bias they can suffer. In particular, the effect of dust extinction strongly affects the completeness of identifications at the bright end of the bolometric luminosity function, which implies large and uncertain extrapolations to account for the contribution of dusty galaxies missed by these selections. In the context of forthcoming facilities that will operate at long wavelengths (e.g., JWST, ALMA, SAFARI, EVLA, SKA), this emphasizes the importance of minimizing the extinction biases when probing the activity of star formation in the early Universe.

First Year Results from the Fermi Gamma-Ray Space Telescope

NASA Technical Reports Server (NTRS)

Hays, Elizabeth

2009-01-01

After one year of survey observations and more than 70 billion triggers, Fermi is revealing an unprecedented view of the high energy gamma-ray sky. The observatory .carries two instruments, the Gamma-ray Burst Monitor (GB, 8 keV - 40 MeV) and the Large Area Telescope (LAT, 20 MeV greater than or equal to 300 GeV), which in combination cover over 7 orders of magnitude in energy for transient phenomena. The LAT provides substantially more sensitivity than previous instruments in this waveband and has opened up the energy window from 10-100 GeV. The first year has produced many important results, from detections of extremely energetic and distant gamma-ray bursts, to monitoring daily variations in emission caused by massive black holes at the cores of galaxies, to identifying a new population of gamma-ray bright pulsars, to measuring the spectrum of diffuse emission from our own. Galaxy and the spectrum of the local cosmic electrons. I'll review highlights from the first year and discuss how the data are answering questions from the past and raising new ones for the future.

Fast radio burst tied to distant dwarf galaxy (Image 2)

NSF Multimedia

2017-06-07

Radio telescope at Arecibo only localized the fast radio burst to the area inside the two circles in this image, but the Very Large Array was able to pinpoint it as a dwarf galaxy within the square (shown at intersection of cross hairs in enlarged box)

Cosmic String Searches

NASA Astrophysics Data System (ADS)

Hoffman, Y.; Hogan, C.

The author discusses observational strategies for finding effects associated with the gravitational lensing of distant objects by strings. In particular, the requirements of a survey to find chains of galaxy image pairs or single galaxies with sharp edges are studied in some detail, and a proposed search program at Steward Observatory is described.

Molecular gas in the halo fuels the growth of a massive cluster galaxy at high redshift.

PubMed

Emonts, B H C; Lehnert, M D; Villar-Martín, M; Norris, R P; Ekers, R D; van Moorsel, G A; Dannerbauer, H; Pentericci, L; Miley, G K; Allison, J R; Sadler, E M; Guillard, P; Carilli, C L; Mao, M Y; Röttgering, H J A; De Breuck, C; Seymour, N; Gullberg, B; Ceverino, D; Jagannathan, P; Vernet, J; Indermuehle, B T

2016-12-02

The largest galaxies in the universe reside in galaxy clusters. Using sensitive observations of carbon monoxide, we show that the Spiderweb galaxy-a massive galaxy in a distant protocluster-is forming from a large reservoir of molecular gas. Most of this molecular gas lies between the protocluster galaxies and has low velocity dispersion, indicating that it is part of an enriched intergalactic medium. This may constitute the reservoir of gas that fuels the widespread star formation seen in earlier ultraviolet observations of the Spiderweb galaxy. Our results support the notion that giant galaxies in clusters formed from extended regions of recycled gas at high redshift. Copyright © 2016, American Association for the Advancement of Science.

Determining accurate distances to nearby galaxies

NASA Astrophysics Data System (ADS)

Bonanos, Alceste Zoe

2005-11-01

Determining accurate distances to nearby or distant galaxies is a very simple conceptually, yet complicated in practice, task. Presently, distances to nearby galaxies are only known to an accuracy of 10-15%. The current anchor galaxy of the extragalactic distance scale is the Large Magellanic Cloud, which has large (10-15%) systematic uncertainties associated with it, because of its morphology, its non-uniform reddening and the unknown metallicity dependence of the Cepheid period-luminosity relation. This work aims to determine accurate distances to some nearby galaxies, and subsequently help reduce the error in the extragalactic distance scale and the Hubble constant H 0 . In particular, this work presents the first distance determination of the DIRECT Project to M33 with detached eclipsing binaries. DIRECT aims to obtain a new anchor galaxy for the extragalactic distance scale by measuring direct, accurate (to 5%) distances to two Local Group galaxies, M31 and M33, with detached eclipsing binaries. It involves a massive variability survey of these galaxies and subsequent photometric and spectroscopic follow-up of the detached binaries discovered. In this work, I also present a catalog of variable stars discovered in one of the DIRECT fields, M31Y, which includes 41 eclipsing binaries. Additionally, we derive the distance to the Draco Dwarf Spheroidal galaxy, with ~100 RR Lyrae found in our first CCD variability study of this galaxy. A "hybrid" method of discovering Cepheids with ground-based telescopes is described next. It involves applying the image subtraction technique on the images obtained from ground-based telescopes and then following them up with the Hubble Space Telescope to derive Cepheid period-luminosity distances. By re-analyzing ESO Very Large Telescope data on M83 (NGC 5236), we demonstrate that this method is much more powerful for detecting variability, especially in crowded fields. I finally present photometry for the Wolf-Rayet binary WR 20a, which confirmed that the system consists of two extremely massive stars and refined the values of the masses. It is the most massive binary known with an accurate mass determination.

A green flash from the Moon; BOSS measures the distant universe in 3D; Cuts in Parliament; When asteroids collide; SpaceX to beat China

NASA Astrophysics Data System (ADS)

2011-06-01

The biggest 3D map of the distant universe, based on the intergalactic hydrogen distribution as well as on the distribution of visible galaxies, has been produced by the Sloan Digital Sky Survey (SDSS-III).

ASCA Observations of Distant Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Tsuru, T. G.

We present results from ASCA observation of distant clusters of galaxies. The observed clusters are as follows; CL0016+16, A370, A959, AC118, Zw3136, MS1305.4+2941, A1851, A963, A2163, MS0839.8+2938, A665, A1689, A2218, A586 and A1413. The covering range of the redshifts is 0.14-0.55 and their average red-shift is 0.245. The negative correlation between the metal abundance and the plasma temperature seen in near clusters is also detected in the distant clusters. No apparent difference between the two correlation. It suggests no strong metal evolution has been made from z = 0.2-0.3 to z = 0. Data of velocity dispersion is available for seven clusters among our samples. All the betaspec of them are above the average of near clusters. The average betaspec for the distant clusters obtained to be betaspec = 1.85 with an rms scatter of 0.62. The value is significantly higher than the near clusters' value of betaspec = 0.94 plus or minus 0.08 with an rms scatter of 0.46.

Star Formation in Distant Red Galaxies: Spitzer Observations in the Hubble Deep Field-South

NASA Astrophysics Data System (ADS)

Webb, Tracy M. A.; van Dokkum, Pieter; Egami, Eiichi; Fazio, Giovanni; Franx, Marijn; Gawiser, Eric; Herrera, David; Huang, Jiasheng; Labbé, Ivo; Lira, Paulina; Marchesini, Danilo; Maza, José; Quadri, Ryan; Rudnick, Gregory; van der Werf, Paul

2006-01-01

We present Spitzer 24 μm imaging of 1.5~40 μJy and conclude that the bulk of the DRG population is dusty active galaxies. A mid-infrared (MIR) color analysis with IRAC data suggests that the MIR fluxes are not dominated by buried AGNs, and we interpret the high detection rate as evidence for a high average star formation rate of =130+/-30 Msolar yr-1. From this, we infer that DRGs are important contributors to the cosmic star formation rate density at z~2, at a level of ~0.02 Msolar yr-1 Mpc-3 to our completeness limit of KAB=22.9 mag.

A Flight Through the Universe, by the Sloan Digital Sky Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aragon, Miguel; Subbarao, Mark; Szalay, Alex

This animated flight through the universe was made by Miguel Aragon of Johns Hopkins University with Mark Subbarao of the Adler Planetarium and Alex Szalay of Johns Hopkins. There are close to 400,000 galaxies in the animation, with images of the actual galaxies in these positions (or in some cases their near cousins in type) derived from the Sloan Digital Sky Survey (SDSS) Data Release 7. Vast as this slice of the universe seems, its most distant reach is to redshift 0.1, corresponding to roughly 1.3 billion light years from Earth. SDSS Data Release 9 from the Baryon Oscillation Spectroscopicmore » Survey (BOSS), led by Berkeley Lab scientists, includes spectroscopic data for well over half a million galaxies at redshifts up to 0.8 -- roughly 7 billion light years distant -- and over a hundred thousand quasars to redshift 3.0 and beyond.« less

Division Viii: Galaxies and the Universe

NASA Astrophysics Data System (ADS)

Sadler, Elaine M.; Combes, Françoise; Okamura, Sadanori; Davies, Roger L.; Gallagher, John S.; Padmanabhan, Thanu; Schmidt, Brian P.

2012-04-01

The fields of extragalactic research and cosmology have continued to progress rapidly over the past three years, as detailed in the reports of the Commission Presidents, and we are pleased to acknowledge the award of the 2011 Nobel Prize in Physics to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess for ``the discovery of the accelerating expansion of the Universe through observations of distant supernovae''. The Gruber Cosmology Prize was awarded in 2009 to Wendy L. Freedman, Robert C. Kennicutt and Jeremy Mould for their leadership of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale, in 2010 to Charles Steidel for the identification and study of galaxies in the very distant universe, and in 2011 to Marc Davis, George Efstathiou, Carlos Frenk and Simon D.M. White for pioneering the use of numerical simulations as a tool to model and interpret the large-scale distribution of galaxies and dark matter.

Serendipitous Discovery of RR Lyrae Stars in the Leo V Ultra-faint Galaxy

NASA Astrophysics Data System (ADS)

Medina, Gustavo E.; Muñoz, Ricardo R.; Vivas, A. Katherina; Förster, Francisco; Carlin, Jeffrey L.; Martinez, Jorge; Galbany, Lluis; González-Gaitán, Santiago; Hamuy, Mario; de Jaeger, Thomas; Maureira, Juan Carlos; San Martín, Jaime

2017-08-01

During the analysis of RR Lyrae stars (RRLs) discovered in the High Cadence Transient Survey (HiTS) taken with the Dark Energy Camera at the 4 m telescope at Cerro Tololo Inter-American Observatory, we found a group of three very distant, fundamental mode pulsator RR Lyrae (type ab). The location of these stars agrees with them belonging to the Leo V ultra-faint satellite galaxy, for which no variable stars have been reported to date. The heliocentric distance derived for Leo V based on these stars is 173 ± 5 kpc. The pulsational properties (amplitudes and periods) of these stars locate them within the locus of the Oosterhoff II group, similar to most other ultra-faint galaxies with known RRLs. This serendipitous discovery shows that distant RRLs may be used to search for unknown faint stellar systems in the outskirts of the Milky Way.

Chandra X-ray observations of the hyper-luminous infrared galaxy IRAS F15307+3252

NASA Astrophysics Data System (ADS)

Hlavacek-Larrondo, J.; Gandhi, P.; Hogan, M. T.; Gendron-Marsolais, M.-L.; Edge, A. C.; Fabian, A. C.; Russell, H. R.; Iwasawa, K.; Mezcua, M.

2017-01-01

Hyper-luminous infrared galaxies (HyLIRGs) lie at the extreme luminosity end of the IR galaxy population with LIR > 1013 L⊙. They are thought to be closer counterparts of the more distant sub-millimeter galaxies, and should therefore be optimal targets to study the most massive systems in formation. We present deep Chandra observations of IRAS F15307+3252 (100 ks), a classical HyLIRG located at z = 0.93 and hosting a radio-loud AGN (L1.4 GHz ˜ 3.5 × 1025 W Hz-1). The Chandra images reveal the presence of extended (r = 160 kpc), asymmetric X-ray emission in the soft 0.3-2.0 keV band that has no radio counterpart. We therefore argue that the emission is of thermal origin originating from a hot intragroup or intracluster medium virializing in the potential. We find that the temperature (˜2 keV) and bolometric X-ray luminosity (˜3 × 1043 erg s-1) of the gas follow the expected LX-ray-T correlation for groups and clusters, and that the gas has a remarkably short cooling time of 1.2 Gyr. In addition, VLA radio observations reveal that the galaxy hosts an unresolved compact steep-spectrum (CSS) source, most likely indicating the presence of a young radio source similar to 3C186. We also confirm that the nucleus is dominated by a redshifted 6.4 keV Fe Kα line, strongly suggesting that the AGN is Compton-thick. Finally, Hubble images reveal an overdensity of galaxies and sub-structure in the galaxy that correlates with soft X-ray emission. This could be a snapshot view of on-going groupings expected in a growing cluster environment. IRAS F15307+3252 might therefore be a rare example of a group in the process of transforming into a cluster.

ESA's XMM-Newton gains deep insights into the distant Universe

NASA Astrophysics Data System (ADS)

2003-07-01

First image from the XMM-LSS survey hi-res Size hi-res: 87 kb Credits: ESA First image from the XMM-LSS survey The first image from the XMM-LSS survey is actually a combination of fourteen separate 'pointings' of the space observatory. It represents a region of the sky eight times larger than the full Moon and contains around 25 clusters. The circles represent the sources previously known from the 1991 ROSAT All-Sky Survey. A computer programme zooms in on an interesting region hi-res Size hi-res: 86 kb Credits: ESA A computer programme zooms in on an interesting region A computer programme zooms in on an interesting region of the image and identifies the possible cluster. Each point on this graph represents a single X-ray photons detected by XMM-Newton. Most come from distant actie galaxies and the computer must perform a sophisticated, statistical computation to determine which X-ray come from clusters. Contour map of clusters hi-res Size hi-res: 139 kb Credits: ESA Contour map of clusters The computer programme transforms the XMM-Newton data into a contour map of the cluster's probable extent and superimposes it over the CFHT snapshot, allowing the individual galaxies in the cluster to be targeted for further observations with ESO's VLT, to measure its distance and locate the cluster in the universe. Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies like our own which themselves congregate into clusters. These clusters are 'strung' throughout the Universe in a web-like structure. Astronomers have studied this large-scale structure of the nearby Universe but have lacked the instruments to extend the search to the large volumes of the distant Universe. Thanks to its unrivalled sensitivity, in less than three hours, ESA's X-ray observatory XMM-Newton can see back about 7000 million years to a cosmological era when the Universe was about half its present size, and clusters of galaxies more tightly packed. Marguerite Pierre, CEA Saclay, France, with a European and Chilean team, used this ability to search for remote clusters of galaxies and map out their distribution. The work heralds a new era of studying the distant Universe. The optical identification of clusters shows only the galaxies themselves. However, X-rays show the gas in between the galaxies - which is where most of the matter in a cluster resides. This is like going from seeing a city at night, where you only see the lighted windows, to seeing it during the daytime, when you finally get to see the buildings themselves. Tracking down the clusters is a painstaking, multi-step process. In tandem with XMM-Newton, the team uses the four-metre Canada-France-Hawaii Telescope (CFHT), on Mauna Kea, Hawaii, to take an optical snapshot of the same region of space. A tailor-made computer programme combs the XMM-Newton data looking for concentrations of X-rays that suggest large, extended structures. These are the clusters and they represent only about 10% of the detected X-ray sources (the others are mostly distant active galaxies). When the program finds a cluster, it zooms in on that region and converts the XMM-Newton data into a contour map of X-ray intensity, which it then superimposes on the CFHT optical image. The astronomers use this to check if anything is visible within the X-ray emission. If it is, the work then shifts to one of the world's largest telescopes, the European Southern Observatory (ESO) Very Large Telescope where the astronomers identify the individual galaxies in the cluster and take 'redshift' measurements. These give a measurement of the cluster's distance. In this way, Pierre and colleagues are mapping the distribution of galaxy clusters of the distant Universe, for the first time in astronomy. "Galaxy clusters are the largest concentrations of matter in the Universe and XMM-Newton is extremely efficient at finding them," says Pierre. Although the task is still a work in progress, first results seem to confirm that the number of clusters 7000 million years ago is little different from that of today. This behaviour is predicted by models of the Universe that expand forever and drive the galaxy clusters further and further apart. Eventually, it will be possible for the team to use their results to determine whether the expansion of the Universe is accelerating, as indicated by some other recent observations, or decelerating, as traditionally thought. Note to Editors: This is a coordinated ESA/ESO release. The presented results have been obtained by the XMM-LSS consortium, led by Service d'Astrophysique du CEA (France) and consisting of Co-I institutes from the United Kingdom, Ireland, Denmark, The Netherlands, Belgium, France, Italy, Germany, Spain and Chile. The home page of the XMM-LSS project can be found at: http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/index_e.html This work is based on two papers to be published in the professional astronomy journal, Astronomy and Astrophysics (The XMM-LSS survey:I. Scientific motivations, design and first results by Marguerite Pierre et al., astro-ph/0305191 and The XMM-LSS survey:II. First high redshift galaxy clusters: relaxed and collapsing systems by Ivan Valtchanov et al.,astro-ph/0305192). More about XMM-Newton XMM-Newton can detect more X-ray sources than any previous satellite and is helping to solve many cosmic mysteries of the violent Universe, from black holes to the formation of galaxies. It was launched on 10 December 1999, using an Ariane-5 rocket from French Guiana. It is expected to return data for a decade. XMM-Newton's high-tech design uses over 170 wafer-thin cylindrical mirrors spread over three telescopes. Its orbit takes it almost a third of the way to the Moon, so that astronomers can enjoy long, uninterrupted views of celestial objects.

Growing Galaxies Gently

NASA Astrophysics Data System (ADS)

2010-10-01

New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence of the flow of pristine gas from the surrounding space and the associated formation of new stars. They were very careful to make sure that their specimen galaxies had not been disturbed by interactions with other galaxies. The selected galaxies were very regular, smoothly rotating discs, similar to the Milky Way, and they were seen about two billion years after the Big Bang (at a redshift of around three). In galaxies in the modern Universe the heavy elements [1] are more abundant close to the centre. But when Cresci's team mapped their selected distant galaxies with the SINFONI spectrograph on the VLT [2] they were excited to see that in all three cases there was a patch of the galaxy, close to the centre, with fewer heavy elements, but hosting vigorously forming stars, suggesting that the material to fuel the star formation was coming from the surrounding pristine gas that is low in heavy elements. This was the smoking gun that provided the best evidence yet of young galaxies accreting primitive gas and using it to form new generations of stars. As Cresci concludes: "This study has only been possible because of the outstanding performance of the SINFONI instrument on the VLT. It has opened a new window for studying the chemical properties of very distant galaxies. SINFONI provides information not only in two spatial dimensions, but also in a third, spectral dimension, which allows us to see the internal motions inside galaxies and study the chemical composition of the interstellar gas." Notes [1] The gas filling the early Universe was almost all hydrogen and helium. The first generations of stars processed this primitive material to create heavier elements such as oxygen, nitrogen and carbon by nuclear fusion. When this material was subsequently spewed back into space by intense particle winds from massive young stars and supernova explosions the amounts of heavy elements in the galaxy gradually increased. Astronomers refer to elements other than hydrogen and helium as "heavy elements". [2] By carefully splitting up the faint light coming from a galaxy into its component colours using powerful telescopes and spectrographs, astronomers can identify the fingerprints of different chemicals in remote galaxies, and measure the amounts of heavy elements present. With the SINFONI instrument on the VLT astronomers can go one better and get a separate spectrum for each part of an object. This allows them to make a map that shows the quantity of heavy elements present in different parts of a galaxy and also determine where in the galaxy star formation is occurring most vigorously. More information This research was presented in a paper, Gas accretion in distant galaxies as the origin of chemical abundance gradients, by Cresci et al., to appear in Nature on 14 October 2010. The team is composed of G. Cresci (Osservatorio Astrofisico di Arcetri, Italy), F. Mannucci (Osservatorio Astrofisico di Arcetri, Italy), R. Maiolino (INAF, Osservatorio Astronomico di Roma, Italy), A. Marconi (Universitá di Firenze, Italy), A. Gnerucci (Universitá di Firenze, Italy) and L. Magrini (Osservatorio Astrofisico di Arcetri, Italy). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

The Most Distant X-Ray Clusters

NASA Technical Reports Server (NTRS)

Dickinson, Mark

1999-01-01

In this program we have used ROSAT (Roentgen Satellite Mission) to observe X-ray emission around several high redshift radio galaxies in a search for extended, hot plasma which may indicate the presence of a rich galaxy cluster. When this program was begun, massive, X-ray emitting galaxy clusters were known to exist out to to z=0.8, but no more distant examples had been identified. However, we had identified several apparently rich clusters around 3CR radio galaxies at z greater than 0.8, and hoped to use ROSAT to confirm the nature of these structures as massive, virialized clusters. We have written up our results and submitted them as a paper to the Astrophysical Journal. This paper has been refereed and requires some significant revisions to accommodate the referees comments. We are in the process of doing this, adding some additional analysis as well. We will resubmit the paper early in 2000, and hopefully will meet with the referee's approval. We are including three copies of the submitted paper here, although it has not yet been accepted for publication.

A cooling flow in a high-redshift, X-ray-selected cluster of galaxies

NASA Astrophysics Data System (ADS)

Nesci, Roberto; Gioia, Isabella M.; Maccacaro, Tommaso; Morris, Simon L.; Perola, Giuseppe C.; Schild, Rudolph E.; Wolter, Anna

1989-09-01

The X-ray cluster of galaxies IE 0839.9 + 2938 was serendipitously discovered with the Einstein Observatory. CCD imaging at R and V wavelengths show that the color of the dominant elliptical galaxy of this cluster is significantly bluer than the colors of the next brightest cluster galaxies. Strong emission lines, typical of cD galaxies with cooling flows, are present in the spectrum of the dominant galaxy, from which a redshift of 0.193 is derived. The emitting line region is spatially resolved with an extension of about 13 kpc. All the collected data suggest that this cluster is one of the most distant cooling flow clusters known to date.

A cooling flow in a high-redshift, X-ray-selected cluster of galaxies

NASA Technical Reports Server (NTRS)

Nesci, Roberto; Perola, Giuseppe C.; Gioia, Isabella M.; Maccacaro, Tommaso; Morris, Simon L.

1989-01-01

The X-ray cluster of galaxies IE 0839.9 + 2938 was serendipitously discovered with the Einstein Observatory. CCD imaging at R and V wavelengths show that the color of the dominant elliptical galaxy of this cluster is significantly bluer than the colors of the next brightest cluster galaxies. Strong emission lines, typical of cD galaxies with cooling flows, are present in the spectrum of the dominant galaxy, from which a redshift of 0.193 is derived. The emitting line region is spatially resolved with an extension of about 13 kpc. All the collected data suggest that this cluster is one of the most distant cooling flow clusters known to date.

Supernovae - A new selection effect. [statistical distribution in and radial distance from center of parent galaxy

NASA Technical Reports Server (NTRS)

Shaw, R. L.

1979-01-01

A sample of 228 supernovae that occurred in galaxies with known redshifts is used to show that the mean projected linear supernova distance from the center of the parent galaxy increases with increasing redshift. This effect is interpreted as an observational bias: the discovery rate of supernovae is reduced in the inner parts of distant, poorly resolved galaxies. Even under the optimistic assumption that no selection effects work in galaxies closer than 33 Mpc, about 50% of all supernovae are lost in the inner regions of galaxies beyond 150 Mpc. This observational bias must be taken into account in the derivation of statistical properties of supernovae.

Most Distant Group of Galaxies Known in the Universe

NASA Astrophysics Data System (ADS)

2002-04-01

New VLT Discovery Pushes Back the Beginnings Summary Using the ESO Very Large Telescope (VLT) , a team of astronomers from The Netherlands, Germany, France and the USA [1] have discovered the most distant group of galaxies ever seen , about 13.5 billion light-years away. It has taken the light now recorded by the VLT about nine-tenths of the age of the Universe to cover the huge distance. We therefore observe those galaxies as they were at a time when the Universe was only about 10% of its present age . The astronomers conclude that this group of early galaxies will develop into a rich cluster of galaxies, such as those seen in the nearby Universe. The newly discovered structure provides the best opportunity so far for studying when and how galaxies began to form clusters after the initial Big Bang , one of the greatest puzzles in modern cosmology. PR Photo 11a/02 : Sky field with the distant cluster of galaxies. PR Photo 11b/02 : Spectra of some of the galaxies in the cluster. Radio Galaxies as cosmic signposts A most intriguing question in modern astronomy is how the first groupings or "clusters" of galaxies emerged from the gas produced in the Big Bang. Some theoretical models predict that densely populated galaxy clusters ("rich clusters" in current astronomical terminology) are built up through a step-wise process. Clumps develop in the primeval gas, and stars condense out of these clumps to form small galaxies. Then these small galaxies merge together to form larger units. The peculiar class of "radio galaxies" is particularly important for investigating such scenarios. They are called so because their radio emission - a result of violent processes believed to be related to massive black holes located at the centres of these galaxies - is stronger by 5 - 10 orders of magnitude than that of our own Milky Way galaxy. In fact, this radio emission is often so intense that the galaxies can be spotted at extremely large distances, and thus at the remote epoch when the Universe was very young, just a small fraction of its present age. The radio galaxies are amongst the most massive objects in the early Universe and there has long been circumstantial evidence that they are located at the heart of young clusters of galaxies, still in the process of formation. In this sense, they act as signposts of early cosmic "meeting points" . Radio galaxies are therefore potential beacons for pinpointing regions of the Universe in which large galaxies and clusters of galaxies are being formed. VLT observations of the environment of radio galaxy TN J1338-1942 ESO PR Photo 11a/02 ESO PR Photo 11a/02 [Preview - JPEG: 400 x 493 pix - 336k] [Normal - JPEG: 1250 x 1541 pix - 2.3M] Caption : PR Photo 11a/02 shows the sky region near the powerful radio galaxy TN J1338-1942 at a redshift of 4.1 [2], i.e. at a distance of about 13.5 billion light-years from the Earth (we see it as it was when the Universe was just 1.5 billion years old). The photo is a "negative" rendering (the objects are dark on a bright background) of an image obtained with the FORS2 multi-mode instrument on the 8.2-m VLT KUEYEN telescope (ESO Paranal Observatory, Chile) through a narrow-band optical filter, centered at the wavelength of the redshifted Lyman-alpha line. The 20 galaxies that have been confirmed to be emitting the sharp colours due to glowing hydrogen gas at the distance of the radio galaxy are encircled in blue. The green rectangle marks the radio galaxy, from which a stream of hydrogen gas stretches to the northwest, over a distance of about 300,000 light-years. The size of the sky field corresponds to about 10 million light-years at the distance of these galaxies. North is up and East is left. Technical information about the photo is available below. ESO PR Photo 11b/02 ESO PR Photo 11b/02 [Preview - JPEG: 515 x 400 pix - 136k] [Normal - JPEG: 1000 x 777 pix - 320k] Caption : PR Photo 11b/02 shows the spectra (brightness as a function of wavelength) for ten of the confirmed galaxies in the very distant, young cluster found near the radio galaxy TN J1338-1942 . Each galaxy displays a sharp peak in colour showing the signature of its hydrogen gas - this is the redshifted Lyman-alpha emission line [2]. Technical information about the photo is available below. Following up this conjecture, the Leiden astronomers and their colleagues in the USA and Germany [1] proposed a large observing programme with the ESO VLT at Paranal (Chile) to search for groupings of galaxies in the vicinity of distant radio galaxies that might be the ancestors of rich clusters. For this, they first used the FORS2 multi-mode instrument on the 8.2-m VLT KUEYEN telescope to take very "deep" pictures of sky regions around several radio galaxies, each field measuring about one-fifth of the diameter of the full moon. The most distant of these was an object called TN J1338-1942 , a radio galaxy at a distance of about 13.5 billion light years from the Earth. To search for galaxies at the same distance as the radio galaxy, the pictures were optimised in sensitivity for the sharp colour emitted by glowing hydrogen gas at the distance of the radio galaxy [2]. Images were taken through two red filters, one that is "tuned" to light produced by the hydrogen gas (the redshifted Lyman-alpha line) and the other that is dominated by light from stars (the R-band), cf. PR Photo 11a/02 . An earlier example of this observational technique is described in ESO PR 13/99. These images revealed 28 galaxies that are likely to be at the distance of the radio galaxy. More detailed information was obtained for 23 of these with the FORS2 instrument in the spectrographic mode, now confirming 20 of them to be indeed located at the same distance as the radio galaxy, cf. PR Photo 11b/02 . Earliest known group of galaxies The spectra also showed that the galaxies are moving around with speeds of a few hundred kilometers per second. The observed structure of galaxies is more than 10 million light-years across and its existence means that galaxies must have begun to form groups already at this early epoch, i.e. still within the first 10% of the history of the Universe . From the excess number of detected galaxies and the observed volume of the structure, its combined mass can be estimated. The derived number is 1000 million million (10 15 ) times the mass of the Sun - this is comparable with the masses of nearby rich clusters of galaxies. For the present structure to evolve into a nearby rich cluster, it must contract in volume by an order of magnitude in about one billion years. This newly discovered group of galaxies is the most remote discovered so far and hence the earliest known at this moment - another, less distant one was recently described in ESO PR 03/02. The VLT observations also establish a crucial link between the ancestors of rich galaxy clusters and the bright galaxies whose active nuclei produce the bright radio emission. Based on the 4 radio galaxies surveyed by the VLT so far, the team concludes that every forming cluster may house a bright galaxy that is or has been a powerful radio source . The radio sources are believed to be powered by massive black holes located deep within their nuclei. Next steps The next step in the present project will be to use the VLT to establish the boundaries of the proto-cluster. Also, the colours and shapes of galaxies in the structure will be studied intensively by the Advanced Camera for Surveys (ACS), recently fitted to the Hubble Space Telescope (HST) . George Miley , also a member of the ACS Science Team, is enthusiastic: "We have now scheduled this particular target for one of the deepest observations ever to be made with the HST. Our project is an example of the great possibilities now opening to astronomers by combining the complementary strengths of the wonderful new ground- and space-based observational facilities!" More information The results described in this Press Release are about to appear in print in the research journal Astrophysical Journal ("The Most Distant Structure of Galaxies Known: a Protocluster at z = 4.1" by B.P. Venemans and co-authors), cf. astro-ph/0203249. Notes [1]: The team is led by George Miley (Leiden University, The Netherlands) and the first author of the resulting research paper is Bram Venemans , a graduate student of Miley's. Other members are Jaron Kurk and Huub Röttgering (also Leiden University), Laura Pentericci (MPIA, Heidelberg, Germany), Wil van Breugel (Lawrence Livermore National Laboratory, USA), Chris Carilli (US National Radio Astronomy Observatory, Charlottesville, USA), Carlos De Breuck (Institut d'Astrophysique, Paris, France) Holland Ford and Tim Heckman (Johns Hopkins University, Baltimore, USA) and Pat McCarthy (Carnegie Institute, Pasadena, USA). [2]: The measured redshift of TN J1338-1942 is z = 4.1. In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a remote galaxy provides an estimate of its distance. The distances indicated in the present text are based on an age of the Universe of 15 billion years. At the indicated redshift, the Lyman-alpha line of atomic hydrogen (rest wavelength 121.6 nm) is observed at 620 nm, i.e. in the red spectral region. Contact George Miley Leiden University Observatory The Netherlands Tel.: +31-715275849 email: miley@strw.leidenuniv.nl Technical information about the photos PR Photo 11a/02 is reproduced from FORS2-exposures, obtained on March 25 and 26, 2001, using a narrow-band optical filter (peak at 619.5 nm with transmission 80%, FWHM 6.0 nm). The total exposure time was 33300 sec (9 hrs 15 min). The field-of-view of the final image is 6.4 x 6.2 arcmin 2 , corresponding to about 3 Mpc on each side. The frames were obtained in photometric conditions, and the image quality in the combined frame is 0.65 arcsec. The galaxy spectra shown in PR Photo 11b/02 were obtained by FORS2 in the MXU-mode on May 20, 21 and 22, 2001. Exposures of 31500 sec and 35100 sec, respectively, were made through two masks under photometric conditions, with seeing 1.0 arcsec and slit sizes of 1 arcsec. The 600RI grism was used; it has peak efficiency 87%, resolution R = 1011 at 663.0 nm and spectral dispersion of 0.132 nm/pixel, corresponding to 290 km/s at z = 4.1.

NASA Telescopes Help Identify Most Distant Galaxy Cluster

NASA Astrophysics Data System (ADS)

2011-01-01

WASHINGTON -- Astronomers have uncovered a burgeoning galactic metropolis, the most distant known in the early universe. This ancient collection of galaxies presumably grew into a modern galaxy cluster similar to the massive ones seen today. The developing cluster, named COSMOS-AzTEC3, was discovered and characterized by multi-wavelength telescopes, including NASA's Spitzer, Chandra and Hubble space telescopes, and the ground-based W.M. Keck Observatory and Japan's Subaru Telescope. "This exciting discovery showcases the exceptional science made possible through collaboration among NASA projects and our international partners," said Jon Morse, NASA's Astrophysics Division director at NASA Headquarters in Washington. Scientists refer to this growing lump of galaxies as a proto-cluster. COSMOS-AzTEC3 is the most distant massive proto-cluster known, and also one of the youngest, because it is being seen when the universe itself was young. The cluster is roughly 12.6 billion light-years away from Earth. Our universe is estimated to be 13.7 billion years old. Previously, more mature versions of these clusters had been spotted at 10 billion light-years away. The astronomers also found that this cluster is buzzing with extreme bursts of star formation and one enormous feeding black hole. "We think the starbursts and black holes are the seeds of the cluster," said Peter Capak of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena. "These seeds will eventually grow into a giant, central galaxy that will dominate the cluster -- a trait found in modern-day galaxy clusters." Capak is first author of a paper appearing in the Jan. 13 issue of the journal Nature. Most galaxies in our universe are bound together into clusters that dot the cosmic landscape like urban sprawls, usually centered around one old, monstrous galaxy containing a massive black hole. Astronomers thought that primitive versions of these clusters, still forming and clumping together, should exist in the early universe. But locating one proved difficult -- until now. Capak and his colleagues first used the Chandra X-ray Observatory and the United Kingdom's James Clerk Maxwell Telescope on Mauna Kea, Hawaii, to search for the black holes and bursts of star formation needed to form the massive galaxies at the centers of modern galaxy cities. The astronomers then used Hubble and the Subaru telescopes to estimate the distances to these objects, and look for higher densities of galaxies around them. Finally, the Keck telescope was used to confirm that these galaxies were at the same distance and part of the same galactic sprawl. Once the scientists found this lumping of galaxies, they measured the combined mass with the help of Spitzer. At this distance the optical light from stars is shifted, or stretched, to infrared wavelengths that can only be observed in outer space by Spitzer. The lump sum of the mass turned out to be a minimum of 400 billion suns -- enough to indicate that the astronomers had indeed uncovered a massive proto-cluster. The Spitzer observations also helped confirm a massive galaxy at the center of the cluster was forming stars at an impressive rate. Chandra X-ray observations were used to find and characterize the whopping black hole with a mass of more than 30 million suns. Massive black holes are common in present-day galaxy clusters, but this is the first time a feeding black hole of this heft has been linked to a cluster that is so young. Finally, the Institut de Radioastronomie Millimétrique's interferometer telescope in France and 30-meter telescope in Spain, along with the National Radio Astronomy Observatory's Very Large Array telescope in New Mexico, measured the amount of gas, or fuel for future star formation, in the cluster. The results indicate the cluster will keep growing into a modern city of galaxies. "It really did take a village of telescopes to nail this cluster," said Capak. "Observations across the electromagnetic spectrum, from X-ray to millimeter wavelengths, were all critical in providing a comprehensive view of the cluster's many facets." COSMOS-AzTEC3, located in the constellation Sextans, is named after the region where it was found, called COSMOS after the Cosmic Evolution Survey. AzTEC is the name of the camera used on the James Clerk Maxwell Telescope -- this camera is now on its way to the Large Millimeter Telescope located in Mexico's Puebla state. For more information about NASA's Spitzer, Chandra and Hubble space telescopes, visit: http://www.nasa.gov/chandra http://www.nasa.gov/spitzer http://www.nasa.gov/hubble

Unbiased Large Spectroscopic Surveys of Galaxies Selected by SPICA Using Dust Bands

NASA Astrophysics Data System (ADS)

Kaneda, H.; Ishihara, D.; Oyabu, S.; Yamagishi, M.; Wada, T.; Armus, L.; Baes, M.; Charmandaris, V.; Czerny, B.; Efstathiou, A.; Fernández-Ontiveros, J. A.; Ferrara, A.; González-Alfonso, E.; Griffin, M.; Gruppioni, C.; Hatziminaoglou, E.; Imanishi, M.; Kohno, K.; Kwon, J.; Nakagawa, T.; Onaka, T.; Pozzi, F.; Scott, D.; Smith, J.-D. T.; Spinoglio, L.; Suzuki, T.; van der Tak, F.; Vaccari, M.; Vignali, C.; Wang, L.

2017-11-01

The mid-infrared range contains many spectral features associated with large molecules and dust grains such as polycyclic aromatic hydrocarbons and silicates. These are usually very strong compared to fine-structure gas lines, and thus valuable in studying the spectral properties of faint distant galaxies. In this paper, we evaluate the capability of low-resolution mid-infrared spectroscopic surveys of galaxies that could be performed by SPICA. The surveys are designed to address the question how star formation and black hole accretion activities evolved over cosmic time through spectral diagnostics of the physical conditions of the interstellar/circumnuclear media in galaxies. On the basis of results obtained with Herschel far-infrared photometric surveys of distant galaxies and Spitzer and AKARI near- to mid-infrared spectroscopic observations of nearby galaxies, we estimate the numbers of the galaxies at redshift z > 0.5, which are expected to be detected in the polycyclic aromatic hydrocarbon features or dust continuum by a wide (10 deg2) or deep (1 deg2) blind survey, both for a given observation time of 600 h. As by-products of the wide blind survey, we also expect to detect debris disks, through the mid-infrared excess above the photospheric emission of nearby main-sequence stars, and we estimate their number. We demonstrate that the SPICA mid-infrared surveys will efficiently provide us with unprecedentedly large spectral samples, which can be studied further in the far-infrared with SPICA.

Mapping Extinction and Star Formation Rates of Nearby Galaxies

NASA Astrophysics Data System (ADS)

Ridenour, Anthony; Takamiya, M.

2010-01-01

Star Formation Rate (SFR) is a physical characteristic of galaxies vital to our understanding of such problems as the evolution of the Universe. In computing SFRs obscuring dust systematically lowers them at shorter wavelengths compared to longer wavelengths. This issue of dust extinction has been handled well by multi-wavelength studies of nearby galaxies. Star Formation Rate measurements of distant galaxies are currently reliant on the emission of visible spectroscopic lines like Hα and [OII] after correction for extinction. However, if the visible light is completely obscured an incorrect assumption may be drawn; namely that there is neither SFR nor extinction. The work purposed here is to calibrate the SFR ascertained from Hα emission in nearby galaxies and compare it to radio and infrared emission. The Balmer decrement, or the ratio of Hβ to Hα emission, used to determine extinction, will also be studied and compared to infrared images. 30 nearby galaxies will be sampled and 2-D maps and Balmer decrements will be formed to do two things: measure SFRs and determine differences between Hα and infrared emission, and explore in what ways this difference corresponds with such things as the radio SFR, galaxy luminosity and morphological type. The accuracy of Hα as a SFR indicator and its determination as a sound tool in measuring SFRs of distant galaxies can both be quantified by interpreting these maps. Dr. Marianne Takamiya, the principal investigator and my mentor, secured funds through a grant to the University of Hawai'i at Hilo from The Research Corporation for Science Advancement Cottrell College Science Awards for this research.

A Proposal to Investigate Outstanding Problems in Astronomy

NASA Technical Reports Server (NTRS)

Ford, Holland

2003-01-01

During the past year the ACS science team has concentrated on analyzing ACS observations, writing papers, and disseminating our results to the astronomy community at conferences and workshops around the world. We also have put considerable effort in getting our results to the public via public lectures and through press releases. Taking a very broad view of our program, we are investigating the evolution of galaxies and clusters of galaxies from their birth, approximately one billion years after the beginning of the Universe, to the present. We have found and characterized a population of galaxies that are no more than 1.4 billion years old. These may well be the Universe s first generation of infant galaxies. Looking at the Universe 500,000 years later, we see what appears to be a cluster of galaxies just beginning to form (a proto-cluster) around a luminous radio galaxy. Moving forward in time and closer to the present, we are studying clusters of galaxies that are less than half the age of the Universe. Our observations and analysis lead us to the important conclusion that the elliptical galaxies in these clusters must have had their last significant star formation some three billion years earlier, which is about the time when the proto-cluster was forming. Coming still closer to home, we are observing nearby massive clusters of galaxies that are approximately 12 billion years old. The gravity from these large aggregates of dark and luminous matter is so strong it warps space-time itself, and makes the cluster act as a cosmic telescope that magnifies the distant galaxies behind the cluster. We used the magnified (or lensed) galaxies to map the distribution of the dominant matter within the clusters, which is the so-called dark matter (the matter is invisible, and its nature is unknown). We also are using these cosmic telescopes to study the distant lensed galaxies that would otherwise be too small and too faint to be seen even by Hubble and the ACS.

What can the occult do for you?

NASA Astrophysics Data System (ADS)

Holwerda, B. W.; Keel, W. C.

2017-03-01

Interstellar dust is still a dominant uncertainty in Astronomy, limiting precision in e.g., cosmological distance estimates and models of how light is re-processed within a galaxy. When a foreground galaxy serendipitously overlaps a more distant one, the latter backlights the dusty structures in the nearer foreground galaxy. Such an overlapping or occulting galaxy pair can be used to measure the distribution of dust in the closest galaxy with great accuracy. The STARSMOG program uses Hubble to map the distribution of dust in foreground galaxies in fine (<100 pc) detail. Integral Field Unit (IFU) observations will map the effective extinction curve, disentangling the role of fine-scale geometry and grain composition on the path of light through a galaxy. The overlapping galaxy technique promises to deliver a clear understanding of the dust in galaxies: geometry, a probability function of dimming as a function of galaxy mass and radius, and its dependence on wavelength.

Interpreting the Clustering of Distant Red Galaxies

NASA Astrophysics Data System (ADS)

Tinker, Jeremy L.; Wechsler, Risa H.; Zheng, Zheng

2010-01-01

We analyze the angular clustering of z ~ 2.3 distant red galaxies (DRGs) measured by Quardi et al. We find that, with robust estimates of the measurement errors and realistic halo occupation distribution modeling, the measured clustering can be well fit within standard halo occupation models, in contrast to previous results. However, in order to fit the strong break in w(θ) at θ = 10'', nearly all satellite galaxies in the DRG luminosity range are required to be DRGs. Within this luminosity-threshold sample, the fraction of galaxies that are DRGs is ~44%, implying that the formation of DRGs is more efficient for satellite galaxies than for central galaxies. Despite the evolved stellar populations contained within DRGs at z = 2.3, 90% of satellite galaxies in the DRG luminosity range have been accreted within 500 Myr. Thus, satellite DRGs must have known they would become satellites well before the time of their accretion. This implies that the formation of DRGs correlates with large-scale environment at fixed halo mass, although the large-scale bias of DRGs can be well fit without such assumptions. Further data are required to resolve this issue. Using the observational estimate that ~30% of DRGs have no ongoing star formation, we infer a timescale for star formation quenching for satellite galaxies of 450 Myr, although the uncertainty on this number is large. However, unless all non-star-forming satellite DRGs were quenched before accretion, the quenching timescale is significantly shorter than z ~ 0 estimates. Down to the completeness limit of the Quadri et al. sample, we find that the halo masses of central DRGs are ~50% higher than non-DRGs in the same luminosity range, but at the highest halo masses the central galaxies are DRGs only ~2/3 of the time.

Star Formation at z = 2.481 in the Lensed Galaxy SDSS J1110+6459: Star Formation Down to 30 pc Scales

NASA Astrophysics Data System (ADS)

Johnson, Traci L.; Rigby, Jane R.; Sharon, Keren; Gladders, Michael D.; Florian, Michael; Bayliss, Matthew B.; Wuyts, Eva; Whitaker, Katherine E.; Livermore, Rachael; Murray, Katherine T.

2017-07-01

We present measurements of the surface density of star formation, the star-forming clump luminosity function, and the clump size distribution function, for the lensed galaxy SGAS J111020.0+645950.8 at a redshift of z = 2.481. The physical size scales that we probe, radii r = 30-50 pc, are considerably smaller scales than have yet been studied at these redshifts. The star formation surface density we find within these small clumps is consistent with surface densities measured previously for other lensed galaxies at similar redshift. Twenty-two percent of the rest-frame ultraviolet light in this lensed galaxy arises from small clumps, with r< 100 pc. Within the range of overlap, the clump luminosity function measured for this lensed galaxy is remarkably similar to those of z˜ 0 galaxies. In this galaxy, star-forming regions smaller than 100 pc—physical scales not usually resolved at these redshifts by current telescopes—are important locations of star formation in the distant universe. If this galaxy is representative, this may contradict the theoretical picture in which the critical size scale for star formation in the distant universe is of the order of 1 kpc. Instead, our results suggest that current telescopes have not yet resolved the critical size scales of star-forming activity in galaxies over most of cosmic time. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13003.

Analysis and Interpretation of Hard X-ray Emission fromthe Bullet Cluster (1E0657-56), the Most Distant Cluster of Galaxies Observed by the RXTE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrosian, Vahe; /Stanford U., Phys. Dept. /SLAC /Stanford U., Appl. Phys. Dept.; Madejski, Greg

2006-08-16

Evidence for non-thermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons. New windows in the Extreme Ultraviolet and Hard X-ray ranges have provided for more powerful tools for the investigation of this phenomenon. Detection of hard X-rays in the 20 to 100 keV range have been reported from several clusters of galaxies, notably from Coma and others. Based on these earlier observations we identified the relatively high redshift cluster 1E0657-56 (also known as RX J0658-5557) as a good candidate for hard X-ray observations. This cluster, also known as the bullet cluster,more » has many other interesting and unusual features, most notably that it is undergoing a merger, clearly visible in the X-ray images. Here we present results from a successful RXTE observations of this cluster. We summarize past observations and their theoretical interpretation which guided us in the selection process. We describe the new observations and present the constraints we can set on the flux and spectrum of the hard X-rays. Finally we discuss the constraints one can set on the characteristics of accelerated electrons which produce the hard X-rays and the radio radiation.« less

The Euclid mission design

NASA Astrophysics Data System (ADS)

Racca, Giuseppe D.; Laureijs, René; Stagnaro, Luca; Salvignol, Jean-Christophe; Lorenzo Alvarez, José; Saavedra Criado, Gonzalo; Gaspar Venancio, Luis; Short, Alex; Strada, Paolo; Bönke, Tobias; Colombo, Cyril; Calvi, Adriano; Maiorano, Elena; Piersanti, Osvaldo; Prezelus, Sylvain; Rosato, Pierluigi; Pinel, Jacques; Rozemeijer, Hans; Lesna, Valentina; Musi, Paolo; Sias, Marco; Anselmi, Alberto; Cazaubiel, Vincent; Vaillon, Ludovic; Mellier, Yannick; Amiaux, Jérôme; Berthé, Michel; Sauvage, Marc; Azzollini, Ruyman; Cropper, Mark; Pottinger, Sabrina; Jahnke, Knud; Ealet, Anne; Maciaszek, Thierry; Pasian, Fabio; Zacchei, Andrea; Scaramella, Roberto; Hoar, John; Kohley, Ralf; Vavrek, Roland; Rudolph, Andreas; Schmidt, Micha

2016-07-01

Euclid is a space-based optical/near-infrared survey mission of the European Space Agency (ESA) to investigate the nature of dark energy, dark matter and gravity by observing the geometry of the Universe and on the formation of structures over cosmological timescales. Euclid will use two probes of the signature of dark matter and energy: Weak gravitational Lensing, which requires the measurement of the shape and photometric redshifts of distant galaxies, and Galaxy Clustering, based on the measurement of the 3-dimensional distribution of galaxies through their spectroscopic redshifts. The mission is scheduled for launch in 2020 and is designed for 6 years of nominal survey operations. The Euclid Spacecraft is composed of a Service Module and a Payload Module. The Service Module comprises all the conventional spacecraft subsystems, the instruments warm electronics units, the sun shield and the solar arrays. In particular the Service Module provides the extremely challenging pointing accuracy required by the scientific objectives. The Payload Module consists of a 1.2 m three-mirror Korsch type telescope and of two instruments, the visible imager and the near-infrared spectro-photometer, both covering a large common field-of-view enabling to survey more than 35% of the entire sky. All sensor data are downlinked using K-band transmission and processed by a dedicated ground segment for science data processing. The Euclid data and catalogues will be made available to the public at the ESA Science Data Centre.

Chandra Provides New View of Biggest Construction Sites in Universe

NASA Astrophysics Data System (ADS)

2003-05-01

Images made by NASA's Chandra X-ray Observatory have revealed two distant cosmic construction sites buzzing with activity. This discovery shows how super massive black holes control the growth of massive galaxies in the distant universe. X-rays were detected from vast clouds of high-energy particles around the galaxies 3C294 and 4C41.17, which are 10 and 12 billion light years from Earth, respectively. The energetic particles were left over from past explosive events that can be traced through the X-ray and radio jets back to the super massive black holes located in the centers of the galaxies. "These galaxies are revealing an energetic phase in which a super massive black hole transfers considerable energy into the gas surrounding the galaxies," said Andrew Fabian of England's Cambridge University, lead author of a paper on 3C294 to appear in an upcoming issue of the Monthly Notices of the Royal Astronomical Society. "This appears to be crucial in explaining the puzzling properties of present-day galaxies, especially those that group together in large clusters," he said. The picture that is emerging is of a grand cosmic cycle. A dense region of intergalactic gas cools to form several smaller galaxies, which merge to form a larger galaxy with a super massive black hole. The galaxy and its central black hole continue to grow until the energy generated by jets from the vicinity of the voracious black hole stops the fall of matter into the black hole. Millions of years after the jet activity subsides, matter will resume falling into the black hole and the cycle begins anew. 4C41.17 and 3C294 4C41.17 Both 3C294 and 4C41.17 reside in regions of space containing unusually high numbers of galaxies. The gas and galaxies surrounding these galaxies will eventually collapse to form galaxy clusters, some of the most massive objects in the universe. Although 3C294 and 4C41.17 will grow to gargantuan sizes, through the accumulation of surrounding matter that forms hundreds of billions of stars, their growth does not go unchecked. "It's as if nature tries to impose a weight limit on the size of the most massive galaxies," said Caleb Scharf of Columbia University, N.Y., and lead author of a paper on 4C41.17 to be published in The Astrophysical Journal. "The Chandra observations have given us an important clue as to how this occurs. The high energy jets give the super massive black holes an extended reach to regulate the growth of these galaxies," he said. In 3C294 and 4C41.17, the hot swirling infernos around their super massive black holes have launched magnetized jets of high energy particles first identified by radio telescopes. These jets, which were also detected by Chandra, have swept up clouds of dust and gas and have helped trigger the formation of billions of new stars. The dusty, star-forming clouds of 4C41.17, the most powerful source of infrared radiation ever observed, are embedded in even larger clouds of gas. Astronomers recently used the Keck Observatory to observe these larger clouds, which have a temperature of 10,000 degree Celsius gas. These clouds are leftover material from the galaxy's formation and should have cooled rapidly by radiation in the absence of a heat source. Animation of How Supermassive Black Holes Affect the Formation of Massive Galaxies Animation of How Supermassive Black Holes Affect the Formation of Massive Galaxies "Significantly, the warm gas clouds coincide closely with the largest extent of the X-ray emission," said Michiel Reuland of Lawrence Livermore National Laboratory, Livermore, Calif., a coauthor on the 4C41.17 paper and a paper describing Keck Observatory work. "The Chandra results show that high energy particles or radiation can supply the necessary energy to light up these clouds," he said. Most of the X-rays from 4C41.17 and 3C294 are due to collisions of energetic electrons with the cosmic background of photons produced in the hot early universe. Because these galaxies are far away, their observed radiation originated when the universe was younger and the background was more intense. This effect enhances the X-radiation and helps astronomers to study extremely distant galaxies. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass., for the Office of Space Science, NASA Headquarters, Washington. Images and additional information about this result are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

A SWIRE Picture is Worth Billions of Years

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Figure 1: SWIRE View of Distant Galaxies [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 2Figure 3 Figure 4

These spectacular images, taken by the Spitzer Wide-area Infrared Extragalactic (SWIRE) Legacy project, encapsulate one of the primary objectives of the Spitzer mission: to connect the evolution of galaxies from the distant, or early, universe to the nearby, or present day, universe.

The Tadpole galaxy (main image) is the result of a recent galactic interaction in the local universe. Although these galactic mergers are rare in the universe's recent history, astronomers believe that they were much more common in the early universe. Thus, SWIRE team members will use this detailed image of the Tadpole galaxy to help understand the nature of the 'faint red-orange specks' of the early universe.

The larger picture (figure 2) depicts one-sixteenth of the SWIRE survey field called ELAIS-N1. In this image, the bright blue sources are hot stars in our own Milky Way, which range anywhere from 3 to 60 times the mass of our Sun. The fainter green spots are cooler stars and galaxies beyond the Milky Way whose light is dominated by older stellar populations. The red dots are dusty galaxies that are undergoing intense star formation. The faintest specks of red-orange are galaxies billions of light-years away in the distant universe.

Figure 3 features an unusual ring-like galaxy called CGCG 275-022. The red spiral arms indicate that this galaxy is very dusty and perhaps undergoing intense star formation. The star-forming activity could have been initiated by a near head-on collision with another galaxy.

The most distant galaxies that SWIRE is able to detect are revealed in a zoom of deep space (figure 4). The colors in this feature represent the same objects as those in the larger field image of ELAIS-N1.

The observed SWIRE fields were chosen on the basis of being 'empty' or as free as possible from the obscuring dust, gas, and stars of our own Milky Way. Because Earth is located within the Milky Way galaxy, there is always a screen of Milky Way objects blocking our view of the rest of the universe. In some places, our view of the larger universe is less obscured than others and for the most part is considered 'empty.' These are prime observing spots for astronomers interested in studying objects beyond the Milky Way. ELAIS-N1 is only one of six SWIRE survey fields. The full survey covers 49 square degrees of the sky, equivalent to the area covered by about 250 full moons.

The SWIRE images are 3-channel false-color composites, where blue represents visible green light (light that would appear to be blue/green to the human eye), green captures infrared light of 3.6 microns, and red represents infrared emissions of 8 microns. The infrared data are from Spitzer's infrared array camera and the visible-light data are from the Isaac Newton Telescope, Spain.

The Search for Lensed Supernovae

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-01-01

Type Ia supernovae that have multiple images due to gravitational lensing can provide us with a wealth of information both about the supernovae themselves and about our surrounding universe. But how can we find these rare explosions?Clues from Multiple ImagesWhen light from a distant object passes by a massive foreground galaxy, the galaxys strong gravitational pull can bend the light, distorting our view of the backgroundobject. In severe cases, this process can cause multiple images of the distant object to appear in the foreground lensing galaxy.An illustration of gravitational lensing. Light from the distant supernova is bent as it passes through a giant elliptical galaxy in the foreground, causing multiple images of the supernova to appear to be hosted by the elliptical galaxy. [Adapted from image by NASA/ESA/A. Feild (STScI)]Observations of multiply-imaged Type Ia supernovae (explosions that occur when white dwarfs in binary systems exceed their maximum allowed mass) could answer a number of astronomical questions. Because Type Ia supernovae are standard candles, distant, lensed Type Ia supernovae can be used to extend the Hubble diagram to high redshifts. Furthermore, the lensing time delays from the multiply-imaged explosion can provide high-precision constraints on cosmological parameters.The catch? So far, weve only found one multiply-imaged Type Ia supernova: iPTF16geu, discovered late last year. Were going to need a lot more of them to develop a useful sample! So how do we identify themutiply-imaged Type Ias among the many billions of fleeting events discovered in current and future surveys of transients?Searching for AnomaliesAbsolute magnitudes for Type Ia supernovae in elliptical galaxies. None are expected to be above -20 in the B band, so if we calculate a magnitude for a Type Ia supernova thats larger than this, its probably not hosted by the galaxy we think it is! [Goldstein Nugent 2017]Two scientists from University of California, Berkeley and Lawrence Berkeley National Laboratory have a plan. In a recent publication, Daniel Goldstein and Peter Nugent propose the following clever procedure to apply to data from transient surveys:From the data, select only the supernova candidates that appear to be hosted by quiescent elliptical galaxies.Use the host galaxies photometric redshifts to calculate absolute magnitudes for the supernovae in this sample.Select from this only the supernovae above the maximum absolute magnitude expected for Type Ia supernovae.Supernovae selected in this way are likely tricking us: their apparent hosts are probably not their hosts at all! Instead, the supernova is likely behind the galaxy, and the galaxy is just lensing its light. Using this strategy therefore allows us to select supernova candidates that are most likely to be distant, gravitationally lensed Type Ia supernovae.Redshift distribution of the multiply-imaged Type Ia supernovae the authors estimate will be detectable by ZTF and LSST in their respective 3- and 10-year survey durations. [Goldstein Nugent 2017]A convenient aspect of Goldstein and Nugents technique is that we dont need to be able to resolve the lensed multiple images for discovery. This is useful, because ground-based optical surveys dont have the resolution to see the separate images yet theyll still be useful for discovering multiply-imaged supernovae.Future ProspectsHow useful? Goldstein and Nugent use Monte Carlo simulations to estimate how many multiply-imaged Type Ia supernovae will be discoverable with future survey projects. They find that theZwicky Transient Facility (ZTF), which will begin operating this year, should be able to find up to 10 using this technique in a 3-year search. The Large Synoptic Survey Telescope (LSST), which should start operating in 2022, will be able to find around 500 multiply-imaged Type Ia supernovae in a 10-year survey.CitationDaniel A. Goldstein and Peter E. Nugent 2017 ApJL 834 L5. doi:10.3847/2041-8213/834/1/L5

Nearby Quasars Result From Galactic Encounters, VLA Studies Indicate

NASA Astrophysics Data System (ADS)

1998-12-01

Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have found previously unseen evidence that galaxy collisions trigger energetic quasar activity in relatively nearby galaxies. New radio images of galaxies with bright quasar cores show that, though the galaxies appear normal in visible-light images, their gas has been disrupted by encounters with other galaxies. "This is what theorists have believed for years, but even the best images from optical telescopes, including the Hubble Space Telescope, failed to show any direct evidence of interactions with other galaxies in many cases," said Jeremy Lim, of the Academia Sinica Institute of Astronomy & Astrophysics in Taipei, Taiwan. Lim, along with Paul Ho of the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA, reported their findings in the January 1 issue of Astrophysical Journal Letters. Quasars are among the most luminous objects in the universe, and generally are believed to be powered by material being drawn into a supermassive black hole at the center of a galaxy, releasing large amounts of energy. Many quasars are found at extremely great distances from Earth, billions of light-years away. Because the light from these quasars took billions of years to reach our telescopes, we see them as they were when they were much younger objects. These distant quasars are thought to "turn on" when the host galaxy's central black hole is "fueled" by material drawn in during an early stage of the galaxy's development, before the galaxy "settles down" to a more sedate life. However, other galaxies with quasar cores are much closer, and thus are older, more mature galaxies. Their quasar activity has been attributed to encounters with nearby galaxies -- encounters that disrupt material and provide new "fuel" to the black hole. The problem for this scenario was the lack of evidence for such galactic encounters in optical images of many nearby quasars. "Our VLA studies are the first to image the neutral atomic hydrogen gas in nearby quasar galaxies," said Ho. "This is important, because, in any galactic encounter, the gas is more easily disrupted than the stars in the galaxies, and the gas takes longer to return to normal after the encounter. This means we have a better chance of finding evidence of galactic encounters by imaging the gas using radio telescopes." The VLA can image the gas in such galaxies because it is particularly sensitive to the radio waves naturally emitted by hydrogen atoms. The researchers chose three quasars at distances of 670 million to 830 million light-years. The three galaxies surrounding these quasars had different appearances in optical images: one showed evidence of mild interaction with a neighboring galaxy; one appeared undisturbed but had a nearby neighbor; and the third appeared undisturbed and alone. When imaged with the VLA, all three showed strong evidence that their gas had been disrupted by an encounter with another galaxy. "This shows how well such radio images of the gas distribution in galaxies can reveal evidence of galactic interactions," Lim said. "We hope to make further studies and learn more about how these galaxy mergers actually stimulate the quasar activity." Quasars are among the most enigmatic objects in the universe. Though they appear on photographic plates made by astronomers more than a century ago, they looked like ordinary stars, and raised no curiosity. When radio telescopes were first used to make detailed maps of the sky in the 1950s, many strong sources of radio emission seemed to have no counterparts in visible light. In 1960, one of these bright radio-emitting objects was identified as a faint, bluish-looking "star" by astronomers using the 200-inch telescope on Palomar Mountain in California. That first quasar and others identified later puzzled astronomers because, when their light was analyzed to find the characteristic "signature" of emission at specific wavelengths shown by particular atoms, the pattern was at first indecipherable. In 1963, Maarten Schmidt of Caltech realized that the pattern made sense if the light's wavelength had been shifted through the Doppler effect by the object's motion away from Earth at greater velocities than had yet been seen. Because the universe is expanding, objects are moving away from Earth with greater speed at greater distances. The speeds seen in the quasars indicated that they were the most distant objects yet found, and, because they appear bright even at those great distances, must be extremely energetic. The idea that the tremendous amounts of energy released by quasars results from material being drawn into a black hole at the center of a galaxy quickly rose as the leading explanation. Galactic interactions were first proposed as an explanation for nearby quasar activity in 1972. Today, quasars are thought to be one of several types of active galactic nuclei, all of which are powered by central black holes. The VLA is an instrument of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. Radio-Optical Image of Quasar and Companion Galaxy CAPTION: A combined optical-radio image of the quasar IRAS 17596+4221 and a companion galaxy. The orange areas are the hydrogen gas imaged by the VLA. In the optical image, there is no direct evidence for an interaction between the galaxy hosting the quasar and the companion galaxy. The extensions in the hydrogen gas, however, are a clear indication of disruption resulting from an interaction between the two galaxies.

Deepest Infrared View of the Universe

NASA Astrophysics Data System (ADS)

2002-12-01

VLT Images Progenitors of Today's Large Galaxies Summary An international team of astronomers [2] has made the deepest-ever near-infrared Ks-band image of the sky, using the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope. For this, the VLT was pointed for more than 100 hours under optimal observing conditions at the Hubble Deep Field South (HDF-S) and obtained images in three near-infrared filters. The resulting images reveal extremely distant galaxies, which appear at infrared wavelengths, but are barely detected in the deepest optical images acquired with the Hubble Space Telescope (HST). Astronomer Marijn Franx from the University of Leiden and leader of the team concludes: "These results demonstrate that very deep observations in the near-infrared are essential to obtain a proper census of the earliest phases of the universe. The new VLT images have opened a new research domain which has not been observationally accessible before". The HDF-S is a tiny field on the sky in the southern constellation Tucana (The Toucan) - only about 1% of the area of the full moon. The NASA/ESA Hubble Space Telescope (HST) observed it with a total exposure time of about 1 week, yielding the deepest optical images ever taken of the sky, similar to those made earlier on the Hubble Deep Field North (HDF-N). The VLT infrared images of the same field were obtained in the course of a major research project, the Faint InfraRed Extragalactic Survey (FIRES). They were made at wavelengths up to 2.3 µm where the HST is not competitive. Ivo Labbé, another team member from the University of Leiden, is certain: "Without the unique capabilities of the VLT and ISAAC we would never have been able to observe these very remote galaxies. In fact, the image in the Ks-band is the deepest which has ever been made at that wavelength". The optical light emitted by the distant galaxies has been redshifted to the near-infrared spectral region [3]. Indeed, some of the galaxies found in the new images are so remote that - due to the finite speed of light - they are observed as they were when the Universe was still extremely young, less than 2 billion years old. From these observations, two interesting conclusions have been drawn so far. One is that although the newly identified galaxies do not appear to form stars very actively they probably account for about half the mass of normal matter present at this epoch. This is in sharp contrast to the galaxies at this early time found during optical surveys - they are very blue because of young and hot stars. Another is that galaxies existed already at that epoch which are clearly rather large, and some show spiral structure similar to that seen in very nearby galaxies. This new important insight is having profound impact on the current attempts to understand the formation and evolution of galaxies. PR Photo 28a/02: Composite colour image of the sky field observed by HST and VLT. PR Photo 28b/02: The ISAAC K s -band image , the deepest of its kind ever obtained. PR Photo 28c/02: Images of very red, very distant compact galaxies in different wavebands. PR Photo 28d/02: Images of very distant extended galaxies in different wavebands. Formation and evolution of galaxies How did galaxies form in the early Universe? How did they evolve and when did the first stars form in those systems? These are some of the key questions in present-day astronomy. Thanks to powerful ground- and space-based telescopes, astronomers are now able to actively pursue studies in this direction. Recent front-line observational results are helping them to gain new insights into these fundamental issues. Light emitted by distant galaxies travels a long time before we observe it with our telescopes. In this way, astronomers can look back in time and directly study galaxies as they were when the universe was still very young. However, this is technically difficult, as the galaxies are extremely faint. Another complication is that, due to the expansion of the universe, their light is shifted towards longer wavelengths [3]. In order to study those early galaxies in some detail, astronomers thus need to use the largest ground-based telescopes, collecting their faint light during very long integrations. And they must work in the infrared region of the spectrum which is not visible to the human eye. The Hubble Deep Field South (HDF-S) was selected to be studied in great detail with the Hubble Space Telescope (HST) and other powerful telescopes. The HST images of this field represent a total exposure time of 140 hours. Many ground-based telescopes have obtained additional photos and spectra, in particular telescopes at the European Southern Observatory in Chile. The ISAAC observations The sky field in the direction of HDF-S observed in the present study (the Faint InfraRed Extragalactic Survey (FIRES)), measures 2.5 x 2.5 arcmin2. It is slightly larger than the field covered by the WFPC2 camera on the HST, but still 100 times smaller than the full moon. Whenever the field was visible from Paranal and the atmospheric conditions were optimal, ESO astronomers pointed the 8.2-m VLT ANTU telescope in the direction of this field, taking near-infrared images with the ISAAC multi-mode instrument. The data were transmitted by Internet to the astronomers of the team in Europe, who then combined them to construct some of the deepest infrared astronomical images ever taken from the ground. Colours and distance A crucial feature of the new observations is that they were made in three infrared bands (Js, H, Ks), allowing a 3-dimensional view of a small region of the Universe. This is because, by comparing the brightness of the galaxies in these colours with that in optical light, as measured by the HST, it is possible to estimate their redshifts [3] and thus how long ago the light we now see has been emitted. For the reddest of the galaxies the answer is that we are seeing them as they were when the Universe was only about 2 billion years old. The nature of the galaxies Two conclusions drawn so far about the nature of these galaxies are therefore all the more important in the context of formation and evolution of galaxies. One is that a few of them are clearly rather large and show spiral structure similar to that seen in very nearby galaxies, cf. PR Photo 28d/02. It is not obvious that current theoretical models can easily account for such galaxies having evolved to this stage so early in the life of the Universe. Another conclusion is that, in contrast to the galaxies at similar redshifts (and hence, at this early epoch) found most commonly in surveys at optical wavelengths, most of the 'infrared-selected' galaxies show relatively little visible star-forming activity. They appear in fact to have already formed most of their stars and in quantities sufficient to account for at least half the total luminous mass of the Universe at that time. Given the time to reach this state they must clearly have formed even earlier in the life of the Universe and are thus probably amongst the "oldest" galaxies now known. Rather than being randomly distributed in space, these red galaxies are also found to prefer company, i.e., they tend to cluster close to each other. In general terms this can be taken as support for the latest theoretical models in which galaxies, which consist of "normal" matter, form in the highest-density regions of the much more pervasive "dark" matter. Although the latter accounts for most of the mass of the universe, its origin so far is completely unknown. These new observations may, therefore, also add new insight into one of the biggest mysteries currently confronting cosmologists. Marijn Franx agrees, but also cautions against drawing firm conclusions on this aspect too quickly: "We now need similar images of a considerably larger region of the sky. We will soon follow-up these first, tantalizing results with more observations of other sky fields." More information The information presented in this Press Release is based on a research article ("Ultradeep Near-Infrared ISAAC Observations of the Hubble Deep Field South: Observations, Reduction, Multicolor Catalog, and Photometric Redshifts" by Ivo Labbé et al.) that will soon appear in the research journal "Astronomical Journal" (cf. astro-ph/0212236). A shorter account will appear in the December 2002 issue of ESO's house journal "The Messenger". Information, including photos and reduced data, is also available at the website of the FIRES project. Notes [1]: This press release is issued in coordination between ESO, Leiden Observatory, the Netherlands Research School for Research in Astronomy (NOVA) and the Netherlands Foundation for Research (NWO). A Dutch-language version is available here. [2]: The team consists of Ivo Labbé, Marijn Franx, Natascha M. Förster Schreiber, Paul van der Werf, Huub Röttgering, Lottie van Starkenburg, Arjen van de Wel and Konrad Kuijken (Leiden Observatory, The Netherlands), Gregory Rudnick (Max-Planck-Institut für Astrophysik, Garching, Germany), Hans-Walter Rix (Max-Planck-Institut für Astronomie, Heidelberg, Germany), Alan Moorwood and Emanuele Daddi (ESO, Garching, Germany) and Pieter G. van Dokkum (California Institute of Technology, Pasadena, USA). [3]: In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a remote galaxy provides an estimate of its distance.

Ten billion years of brightest cluster galaxy alignments

NASA Astrophysics Data System (ADS)

West, Michael J.; de Propris, Roberto; Bremer, Malcolm N.; Phillipps, Steven

2017-07-01

A galaxy's orientation is one of its most basic observable properties. Astronomers once assumed that galaxies are randomly oriented in space; however, it is now clear that some have preferred orientations with respect to their surroundings. Chief among these are giant elliptical galaxies found in the centres of rich galaxy clusters. Numerous studies have shown that the major axes of these galaxies often share the same orientation as the surrounding matter distribution on larger scales1,2,3,4,5,6. Using Hubble Space Telescope observations of 65 distant galaxy clusters, we show that similar alignments are seen at earlier epochs when the Universe was only one-third of its current age. These results suggest that the brightest galaxies in clusters are the product of a special formation history, one influenced by development of the cosmic web over billions of years.

Infrared images of distant 3C radio galaxies

NASA Technical Reports Server (NTRS)

Eisenhardt, Peter; Chokshi, Arati

1990-01-01

J (1.2-micron) and K (2.2 micron) images have been obtained for eight 3CR radio galaxies with redshifts from 0.7 to 1.8. Most of the objects were known to have extended asymmetric optical continuum or line emission aligned with the radio lobe axis. In general, the IR morphologies of these galaxies are just as peculiar as their optical morphologies. For all the galaxies, when asymmetric structure is present in the optical, structure with the same orientation is seen in the IR and must be accounted for in any model to explain the alignment of optical and radio emission.

Disk galaxy scaling relations at intermediate redshifts. I. The Tully-Fisher and velocity-size relations

NASA Astrophysics Data System (ADS)

Böhm, Asmus; Ziegler, Bodo L.

2016-07-01

Aims: Galaxy scaling relations such as the Tully-Fisher relation (between the maximum rotation velocity Vmax and luminosity) and the velocity-size relation (between Vmax and the disk scale length) are powerful tools to quantify the evolution of disk galaxies with cosmic time. Methods: We took spatially resolved slit spectra of 261 field disk galaxies at redshifts up to z ≈ 1 using the FORS instruments of the ESO Very Large Telescope. The targets were selected from the FORS Deep Field and William Herschel Deep Field. Our spectroscopy was complemented with HST/ACS imaging in the F814W filter. We analyzed the ionized gas kinematics by extracting rotation curves from the two-dimensional spectra. Taking into account all geometrical, observational, and instrumental effects, these rotation curves were used to derive the intrinsic Vmax. Results: Neglecting galaxies with disturbed kinematics or insufficient spatial rotation curve extent, Vmax was reliably determined for 124 galaxies covering redshifts 0.05 < z < 0.97. This is one of the largest kinematic samples of distant disk galaxies to date. We compared this data set to the local B-band Tully-Fisher relation and the local velocity-size relation. The scatter in both scaling relations is a factor of ~2 larger at z ≈ 0.5 than at z ≈ 0. The deviations of individual distant galaxies from the local Tully-Fisher relation are systematic in the sense that the galaxies are increasingly overluminous toward higher redshifts, corresponding to an overluminosity ΔMB = -(1.2 ± 0.5) mag at z = 1. This luminosity evolution at given Vmax is probably driven by younger stellar populations of distant galaxies with respect to their local counterparts, potentially combined with modest changes in dark matter mass fractions. The analysis of the velocity-size relation reveals that disk galaxies of a given Vmax have grown in size by a factor of ~1.5 over the past ~8 Gyr, most likely through accretion of cold gas and/or small satellites. From scrutinizing the combined evolution in luminosity and size, we find that the galaxies that show the strongest evolution toward smaller sizes at z ≈ 1 are not those that feature the strongest evolution in luminosity, and vice versa. Based on observations with the European Southern Observatory Very Large Telescope (ESO-VLT), observing run IDs 65.O-0049, 66.A-0547, 68.A-0013, 69.B-0278B, 70.B-0251A and 081.B-0107A.The full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A64

A cooling flow in a high-redshift, X-ray-selected cluster of galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nesci, R.; Perola, G.C.; Gioia, I.M.

The X-ray cluster of galaxies IE 0839.9 + 2938 was serendipitously discovered with the Einstein Observatory. CCD imaging at R and V wavelengths show that the color of the dominant elliptical galaxy of this cluster is significantly bluer than the colors of the next brightest cluster galaxies. Strong emission lines, typical of cD galaxies with cooling flows, are present in the spectrum of the dominant galaxy, from which a redshift of 0.193 is derived. The emitting line region is spatially resolved with an extension of about 13 kpc. All the collected data suggest that this cluster is one of themore » most distant cooling flow clusters known to date. 28 refs.« less

Most Massive Spiral Galaxy Known in the Universe

NASA Astrophysics Data System (ADS)

2000-12-01

The VLT Observes Rapid Motion in Distant Object Summary The most massive spiral galaxy known so far in the Universe has been discovered by a team of astronomers from Garching, Padova, Leiden, ESO and London [1]. They base their conclusion on recent observations with ISAAC , an infrared-sensitive, multi-mode instrument on ESO's Very Large Telescope at the Paranal Observatory. This galaxy has been designated ISOHDFS 27 and is located at a distance of approx. 6 billion light-years (the redshift is 0.58). Its measured mass is more than 1000 billion times that of the Sun [2]. It is thus about four times more massive than our own galaxy, the Milky Way, and twice as heavy as the heaviest spiral galaxy known so far. The determination of the mass of ISOHDFS 27 is based on a unique measurement of the motions of its stars and nebulae around the center. The faster the motion is, the greater is the mass. It is, in essence, the same method that allows determining the mass of the Earth from the orbital speed and distance of the Moon. This is the first time a "rotation curve" has been observed in such a distant galaxy by means of infrared observations, allowing a very detailed dynamical study. Other observations by the team concern a pair of distant, interacting galaxies that were also found to possess comparably high masses. They also have observations of a third galaxy at a distance of about 10 billion light-years, with a mass that approaches that of ISOHDFS 27 . The new result has important cosmological implications, as it demonstrates that very heavy structures had already been formed in the Universe at a comparatively early epoch . PR Photo 33a/00 : ISOHDFS 27 , the heaviest spiral galaxy known. PR Photo 33b/00 : The "raw" ISAAC spectrum of ISOHDFS 27 . PR Photo 33c/00 : H-alpha profile of ISOHDFS 27 . Star formation in young galaxies It is of fundamental importance to current cosmological studies to understand how stars evolve within galaxies and how the galaxies themselves evolve into the various shapes we observe. Some are elliptical, others have the form of single or multiple spirals. Quite a few, especially smaller ones, appear to have no particular structure at all and are referred to as "irregular". With the advent of large optical/infrared telescopes like the ESO VLT, astronomers are now able to observe extremely distant objects and hence to "look back" to the time when galaxies were being formed in the young Universe. They have found it particularly useful to observe in the infrared part of the spectrum during the present search for "young galaxies". Such observations minimize the effects of dust obscuration and serve to trace the active phases of galaxy evolution , i.e. those specific periods of time when there is particularly intense star-formation in a galaxy. It is still not well known what triggers such phases of enhanced star-forming activity, but it is suspected that galaxy collisions and mergers may play an important role. The formation of stars usually takes place deep inside thick dust clouds that absorb the optical and UV light from the young stars and re-emit it in the infrared region of the spectrum. The imprints of this type of activity are thus best observed in that spectral band. Indeed, the infrared spectra of such objects have been found to undergo huge variations that relate to the related, complex processes. Infrared observations are therefore crucial for the study of these most violent episodes in the Universe. By means of detailed observations of distant galaxies, we may hope to learn how they occurred at earlier times and, in particular, how the major structures (e.g., spirals, bulges) that we now see in most galaxies were formed. Dusty Infrared-Luminous Galaxies In 1995-98, the infrared camera ISOCAM onboard the ESA Infrared Space Observatory (ISO) , with its unique imaging capabilities, provided astronomers with the first deep, overall "infrared view" of the Universe. Through various deep surveys with ISO, a new class of objects was discovered: luminous, distant galaxies detected during transient phases of enhanced infrared emission and undergoing rapid evolution with cosmic time. One of the sky areas surveyed by ISO was the Hubble Deep Field South (HDF-S) , that has also been observed with various ESO telescopes including the VLT, cf. ESO PR 20/98. The present team of astronomers decided to investigate some of the luminous galaxies that were detected by ISOCAM in the HDF-S area. Their goal was to better understand the enigmatic nature of these unsual objects and to try to learn which processes are really behind those huge amounts of energy that are emitted by these galaxies in the infrared region of the spectrum. However, all of the galaxies in HDF-S are at very large distances - several billion light-years away (i.e. with redshifts between 0.6 and 1.5) and they are rather faint. They refer to these objects as ISOHDFS galaxies and their colours are quite red. The astronomers therefore decided to use one of the most efficient astronomical infrared instruments now available, the multi-mode ISAAC on the 8.2-m VLT ANTU telescope. VLT Observations of ISOHDFS galaxies In September 1999, the team began to obtain low-resolution spectra of about one dozen of these galaxies. This initial observing run at Paranal was very successful and it provided a first clue towards the true nature of these systems. It was found, in particular, that ISOHDFS galaxies emit strongly in the H-alpha spectral line from hydrogen atoms and that this emission originates in dusty regions with intense star formation activity in these galaxies. The astronomers determined accurate redshifts (and hence, distances to the individual galaxies) by measuring the Doppler shifts of the H-alpha lines in their infrared spectra (an example of an early observation of this type is shown in ESO PR 19/98 ). Inspired by the excellent quality of these first VLT observations, they were ready to take the next, challenging step in August 2000. They now attempted to get a deeper insight into the nature and dynamical stage of the ISOHDFS galaxies, by means of measurements of the stellar masses in the nuclear regions of these objects. The spectrum of ISOHDFS 27 ESO PR Photo 33a/00 ESO PR Photo 33a/00 [Preview - JPEG: 400 x 358 pix - 74k] [Normal - JPEG: 800 x 715 pix - 240ak] [Hi-Res - JPEG: 3000 x 2683 pix - 1.8Mb] Caption : PR Photo 33a/00 is reproduced from an optical image of the distant galaxy ISOHDFS 27 , obtained with the Hubble Space Telescope (HST). The angular size of this galaxy is about 7 arcsec, corresponding to about 130,000 light-years (40 kpc) at the distance of the galaxy, approx. 6,000 million light-years. The inclination of the galaxy's main plane to the line-of-sight is about 50°. Technical information about this photo is available below. The first target for this new study was a large spiral galaxy, designated ISOHDFS 27 and of which an HST image is shown in Photo 33a/00 . The superb observing conditions at Paranal - the seeing improved to the near-record value of only 0.2 arcsec during the acquisition of these data! - made it possible to obtain the first spatially resolved, infrared H-alpha spectra of some of the ISOHDFS galaxies, allowing for the first time a probe into the dynamical stage of these distant objects. ESO PR Photo 33b/00 ESO PR Photo 33b/00 [Preview - JPEG: 400 x 322 pix - 69k] [Normal - JPEG: 800 x 643 pix - 728k] [Hi-Res - JPEG: 3000 x 2413 pix - 944k] ESO PR Photo 33c/00 ESO PR Photo 33c/00 [Preview - JPEG: 400 x 344 pix - 19k] [Normal - JPEG: 800 x 687 pix - 76k] Caption : PR Photo 33b/00 shows the "raw" spectrum of the distant galaxy ISOHDFS 27 , obtained with the ISAAC infrared instrument at the 8.2-m VLT ANTU telescope. Light from hydrogen atoms emitted in the red spectral region (the H-alpha emission line) is visible as two prominent "blobs" on either side of the central, featureless spectrum (the galaxy "continuum"). A weaker emission line from singly ionized nitrogen ([N II]) is seen to the right; it shows exactly the same behaviour. Technical information about this photo is available below. Caption : PR Photo 33c/00 shows the extracted H-alpha profile in ISOHDFS 27 , following extensive image processing of the spectrum shown in Photo 33b/00. When corrected for the inclination of the galaxy (50°), the peak-to-peak velocity difference is about 830 km/sec, corresponding to a rotational velocity of about 415 km/sec. This is about three times more than what is typical for normal spiral galaxies and hence indicates a very large mass. Photo 33b/00 shows the "raw" ISAAC spectrum, i.e. the image of the spectrum as seen in the read-out from the detector. The derived spectral profile of the H-alpha line is shown in Photo 33c/00 . The shape is very unusual and implies that the emitting region is probably not concentrated at the centre of the galaxy, but most likely has a disk-like structure. Taking into account the inclination of the galaxy (50°), the difference in velocity between the two peaks is 830 km/sec, i.e. the rotational velocity is half of that, 415 km/sec, or significantly more than what is measured in normal spiral galaxies. This was an interesting start for an ambitious project. But the astronomers got really excited when they made the first estimate of the total mass of that galaxy. "I can't believe it, this spiral galaxy is really massive!" , said Dimitra Rigopoulou from the Garching team. And she added: "With an estimated mass of 10 12 times that of our Sun and 4 times the mass of our own Galaxy, it seems to be the most massive spiral galaxy found so far in the Universe!" Indeed, careful calculations later showed that a total mass of 1.04 10 12 solar masses is present within 4 arcsec of the central region of (an area of 8 arcsec across), corresponding to 100,000 light-years (40 kpc) in ISOHDFS 27 . This is enormous by all standards [3]. The baryonic mass which corresponds to the mass in the older stars and is estimated from the infrared spectrum, is found to be 6 x10 11 solar masses, about half the dynamical mass. During the same observing run, two other ISO-detected infrared sources were observed. One turned out to be a system of two counter-rotating galaxies with masses of about 2 x 10 11 solar masses and the other an even more distant galaxy (about 12 billion light-years) with comparably high mass. Implications and Future Plans The present programme is a fine illustration of the importance of "collaboration" between space- and ground-based telescopes. While the galaxies were first found with ISO and HST, it took the enormous light-gathering capability of the VLT to obtain a detailed spectrum and measure their masses. Clearly, these exciting results have important implications for future studies of formation and evolution of galaxies, as well as the origin of the IR background. The discovery of such massive spiral galaxies at very large distances implies that enormous structures were in place in the Universe, already some 6 billion years ago. Galaxies like ISOHDFS 27 which are strongly emitting in the infrared region of the spectrum are presumed to contribute significantly to the observed infrared background radiation. Consequently, these new observations imply that the infrared background is largely made up of massive galaxies with recent star formation activity. The team now plans to continue its work on the determination of the dynamical status of other high-redshift galaxies. These studies are indeed very timely since a plethora of future space- and ground-based missions such as NGST, SIRTF, FIRST and ALMA will be able to perform even more detailed follow-up observations of these objects. The present observations open a new and exciting era in the study of the formation of galaxies in the young Universe. Notes [1]: The project on exploring the dynamical stage of ISO-detected galaxies in the Hubble Deep Field South is being carried out by a large international collaboration led by astronomers from the Max-Planck-Institut für Extraterrestrische Physik (MPE) in Garching (Germany) and the Padova University (Italy). Besides Dimitra Rigopoulou and Alberto Franceschini , the team includes Herve Aussel (Padova), Catherine Cesarsky (ESO), Reinhard Genzel (MPE), David Elbaz (Saclay, France), Michael Rowan-Robinson (IC, UK), Niranjan Thatte (MPE), and Paul van der Werf (Leiden, The Netherlands). [2]: 1 billion = 1,000 million = 10 9. [3]: Some other distant spiral galaxies have been found with masses in the range of 1 - 5 x 10 11 solar masses. The heaviest spiral galaxy known until now is UGC 12591 , with a measured mass of 6 x10 11 solar masses. Technical information about the photos PR Photo 33a/00 covers an area of approx. 7 x 8 arcsec 2 ; North is up, East is to the left. The present results, including the spectrum shown in PR Photo 33b/00 , are based on observations that were collected in visitor mode during August 18-20, 2000. For these observations, ISAAC was used in medium resolution mode (R ~ 5000) with a slit of 0.6 arcsec x 2 arcmin. The pixel scale is 0.146 arcsec/pix. The wavelength for the H-alpha is 1.0370 µm and the SZ band was used for the observations. The seeing was very good throughout the run (from 0.2 - 0.9 arcsec). The spectrum shown in PR Photo 33b/00 was acquired under 0.2 arcsec seeing.

Blueberry Galaxies: The Lowest Mass Young Starbursts

NASA Astrophysics Data System (ADS)

Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Wang, Junxian

2017-09-01

Searching for extreme emission line galaxies allows us to find low-mass metal-poor galaxies that are good analogs of high redshift Lyα emitting galaxies. These low-mass extreme emission line galaxies are also potential Lyman-continuum leakers. Finding them at very low redshifts (z≲ 0.05) allows us to be sensitive to even lower stellar masses and metallicities. We report on a sample of extreme emission line galaxies at z≲ 0.05 (blueberry galaxies). We selected them from SDSS broadband images on the basis of their broadband colors and studied their properties with MMT spectroscopy. From the entire SDSS DR12 photometric catalog, we found 51 photometric candidates. We spectroscopically confirm 40 as blueberry galaxies. (An additional seven candidates are contaminants, and four remain without spectra.) These blueberries are dwarf starburst galaxies with very small sizes (<1 kpc) and very high ionization ([O III]/[O II] ˜ 10-60). They also have some of the lowest stellar masses ({log}(M/{M}⊙ )˜ 6.5{--}7.5) and lowest metallicities (7.1< 12+{log}({{O}}/{{H}})< 7.8) of starburst galaxies. Thus, they are small counterparts to green pea galaxies and high redshift Lyα emitting galaxies.

RELICS of the Cosmic Dawn

NASA Astrophysics Data System (ADS)

Bradac, Marusa; Coe, Dan; Bradley, Larry; Huang, Kuang-Han; Ryan, Russell; Dawson, Will; Zitrin, Adi; Hoag, Austin; Jones, Christine; Czakon, Nicole; Sharon, Keren; Trenti, Michele; Stark, Daniel; Bouwens, Rychard

2015-10-01

When did galaxies start forming stars? What is the role of distant galaxies in galaxy formation models and epoch of reionization? Recent observations indicate at least two critical puzzles in these studies. First galaxies might have started forming stars earlier than previously thought (<400Myr after the Big Bang). Furthermore, it is still unclear what is their star formation history and whether these galaxies can reionize the Universe. Accurate knowledge of stellar masses, ages, and star formation rates at this epoch requires measuring both rest-frame UV and optical light, which only Spitzer and HST can probe at z>7-11 for a large enough sample of typical galaxies. To address this cosmic puzzle, we propose Spitzer imaging of the fields behind 41 powerful cosmic telescopes selected using Planck data from the RELICS program (Reionization Lensing Cluster Survey; 190 HST orbits). This proposal will be a valuable Legacy complement to the existing IRAC deep surveys, and it will open up a new parameter space by probing the ordinary yet magnified population with much improved sample variance. The program will allow us to detect early galaxies with Spitzer and directly study stellar properties of a large number, ~20 galaxies (10 at z~7, 7 at z~8, 3 at z~9, and 1 at z~10). Spitzer data will much improve photometric redshifts of the earliest galaxies and will be crucial to ascertain the nature of any z>~10 candidate galaxies uncovered in the HST data. Spitzer also allows for an efficient selection of likely line emitters (as demonstrated by our recent spectroscopic confirmation of the most distant galaxy to date at z=8.68). Finally this proposal will establish the presence (or absence) of an unusually early established stellar population, as was recently observed in MACS1149JD at z~9. If confirmed in a larger sample, this result will require a paradigm shift in our understanding of the earliest star formation.

A comparison of LBGs, DRGs, and BzK galaxies: their contribution to the stellar mass density in the GOODS-MUSIC sample

NASA Astrophysics Data System (ADS)

Grazian, A.; Salimbeni, S.; Pentericci, L.; Fontana, A.; Nonino, M.; Vanzella, E.; Cristiani, S.; de Santis, C.; Gallozzi, S.; Giallongo, E.; Santini, P.

2007-04-01

Context: The classification scheme for high redshift galaxies is complex at the present time, with simple colour-selection criteria (i.e. EROs, IEROs, LBGs, DRGs, BzKs), resulting in ill-defined properties for the stellar mass and star formation rate of these distant galaxies. Aims: The goal of this work is to investigate the properties of different classes of high-z galaxies, focusing in particular on the stellar masses of LBGs, DRGs, and BzKs, in order to derive their contribution to the total mass budget of the distant Universe. Methods: We used the GOODS-MUSIC catalog, containing ~3000 Ks-selected (~10 000 z-selected) galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8~μm band, with spectroscopic or accurate photometric redshifts. We selected samples of BM/BX/LBGs, DRGs, and BzK galaxies to discuss the overlap and the limitations of these criteria, which can be overridden by a selection criterion based on physical parameters. We then measured the stellar masses of these galaxies and computed the stellar mass density (SMD) for the different samples up to redshift ≃4. Results: We show that the BzK-PE criterion is not optimal for selecting early type galaxies at the faint end. On the other hand, BzK-SF is highly contaminated by passively evolving galaxies at red z-Ks colours. We find that LBGs and DRGs contribute almost equally to the global SMD at z≥ 2 and, in general, that star-forming galaxies form a substantial fraction of the universal SMD. Passively evolving galaxies show a strong negative density evolution from redshift 2 to 3, indicating that we are witnessing the epoch of mass assembly of such objects. Finally we have indications that by pushing the selection to deeper magnitudes, the contribution of less massive DRGs could overtake that of LBGs. Deeper surveys, like the HUDF, are required to confirm this suggestion.

NASA Galaxy Mission Celebrates Sixth Anniversary

NASA Image and Video Library

2009-04-28

NASA Galaxy Evolution Explorer Mission celebrates its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space. The mission studies the shape, brightness, size and distance of distant galaxies across 10 billion years of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC598, more commonly known as M33. This image is a blend of the Galaxy Evolution Explorer's M33 image and another taken by NASA's Spitzer Space Telescope. M33, one of our closest galactic neighbors, is about 2.9 million light-years away in the constellation Triangulum, part of what's known as our Local Group of galaxies. Together, the Galaxy Evolution Explorer and Spitzer can see a broad spectrum of sky. Spitzer, for example, can detect mid-infrared radiation from dust that has absorbed young stars' ultraviolet light. That's something the Galaxy Evolution Explorer cannot see. This combined image shows in amazing detail the beautiful and complicated interlacing of the heated dust and young stars. In some regions of M33, dust gathers where there is very little far-ultraviolet light, suggesting that the young stars are obscured or that stars further away are heating the dust. In some of the outer regions of the galaxy, just the opposite is true: There are plenty of young stars and very little dust. Far-ultraviolet light from young stars glimmers blue, near-ultraviolet light from intermediate age stars glows green, near-infrared light from old stars burns yellow and orange, and dust rich in organic molecules burns red. The small blue flecks outside the spiral disk of M33 are most likely distant background galaxies. This image is a four-band composite that, in addition to the two ultraviolet bands, includes near infrared as yellow/orange and far infrared as red. http://photojournal.jpl.nasa.gov/catalog/PIA11999

The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA)

NASA Astrophysics Data System (ADS)

Moustakas, Leonidas A.; Bolton, Adam J.; Booth, Jeffrey T.; Bullock, James S.; Cheng, Edward; Coe, Dan; Fassnacht, Christopher D.; Gorjian, Varoujan; Heneghan, Cate; Keeton, Charles R.; Kochanek, Christopher S.; Lawrence, Charles R.; Marshall, Philip J.; Metcalf, R. Benton; Natarajan, Priyamvada; Nikzad, Shouleh; Peterson, Bradley M.; Wambsganss, Joachim

2008-07-01

Dark matter in a universe dominated by a cosmological constant seeds the formation of structure and is the scaffolding for galaxy formation. The nature of dark matter remains one of the fundamental unsolved problems in astrophysics and physics even though it represents 85% of the mass in the universe, and nearly one quarter of its total mass-energy budget. The mass function of dark matter "substructure" on sub-galactic scales may be enormously sensitive to the mass and properties of the dark matter particle. On astrophysical scales, especially at cosmological distances, dark matter substructure may only be detected through its gravitational influence on light from distant varying sources. Specifically, these are largely active galactic nuclei (AGN), which are accreting super-massive black holes in the centers of galaxies, some of the most extreme objects ever found. With enough measurements of the flux from AGN at different wavelengths, and their variability over time, the detailed structure around AGN, and even the mass of the super-massive black hole can be measured. The Observatory for Multi-Epoch Gravitational Lens Astrophysics (OMEGA) is a mission concept for a 1.5-m near-UV through near-IR space observatory that will be dedicated to frequent imaging and spectroscopic monitoring of ~100 multiply-imaged active galactic nuclei over the whole sky. Using wavelength-tailored dichroics with extremely high transmittance, efficient imaging in six channels will be done simultaneously during each visit to each target. The separate spectroscopic mode, engaged through a flip-in mirror, uses an image slicer spectrograph. After a period of many visits to all targets, the resulting multidimensional movies can then be analyzed to a) measure the mass function of dark matter substructure; b) measure precise masses of the accreting black holes as well as the structure of their accretion disks and their environments over several decades of physical scale; and c) measure a combination of Hubble's local expansion constant and cosmological distances to unprecedented precision. We present the novel OMEGA instrumentation suite, and how its integrated design is ideal for opening the time domain of known cosmologically-distant variable sources, to achieve the stated scientific goals.

Galaxy Evolution Explorer Spies Band of Stars

NASA Image and Video Library

2007-06-20

Globular star cluster NGC 362, in a false-color image from NASA's Galaxy Evolution Explorer. Image credit: NASA/JPL-Caltech/Univ. of Virginia The Galaxy Evolution Explorer's ultraviolet eyes have captured a globular star cluster, called NGC 362, in our own Milky Way galaxy. In this new image, the cluster appears next to stars from a more distant neighboring galaxy, known as the Small Magellanic Cloud. "This image is so interesting because it allows a study of the final stages of evolution of low-mass stars in NGC 362, as well as the history of star formation in the Small Magellanic Cloud," said Ricardo Schiavon of the University of Virginia, Charlottesville, Va. Globular clusters are densely packed bunches of old stars scattered in galaxies throughout the universe. NGC 362, located 30,000 light-years away, can be spotted as the dense collection of mostly yellow-tinted stars surrounding a large white-yellow spot toward the top-right of this image. The white spot is actually the core of the cluster, which is made up of stars so closely packed together that the Galaxy Evolution Explorer cannot see them individually. The light blue dots surrounding the cluster core are called extreme horizontal branch stars. These stars used to be very similar to our sun and are nearing the end of their lives. They are very hot, with temperatures reaching up to about four times that of the surface of our sun (25,000 Kelvin or 45,500 degrees Fahrenheit). A star like our sun spends most of its life fusing hydrogen atoms in its core into helium. When the star runs out of hydrogen in its core, its outer envelope will expand. The star then becomes a red giant, which burns hydrogen in a shell surrounding its inner core. Throughout its life as a red giant, the star loses a lot of mass, then begins to burn helium at its core. Some stars will have lost so much mass at the end of this process, up to 85 percent of their envelopes, that most of the envelope is gone. What is left is a very hot ultraviolet-bright core, or extreme horizontal branch star. Blue dots scattered throughout the image are hot, young stars in the Small Magellanic Cloud, a satellite galaxy of the Milky Way located approximately 200,000 light-years away. The stars in this galaxy are much brighter intrinsically than extreme horizontal branch stars, but they appear just as bright because they are farther away. The blue stars in the Small Magellanic Cloud are only about a few tens of millions of years old, much younger than the approximately 10-million-year-old stars in NGC 362. Because NGC 362 sits on the northern edge of the Small Magellanic Cloud galaxy, the blue stars are denser toward the south, or bottom, of the image. Some of the yellow spots in this image are stars in the Milky Way galaxy that are along this line of sight. Astronomers believe that some of the other spots, particularly those closer to NGC 362, might actually be a relatively ultraviolet-dim family of stars called "blue stragglers." These stars are formed from collisions or close encounters between two closely orbiting stars in a globular cluster. "This observation could only be done with the Galaxy Evolution Explorer because it is the only ultraviolet imager available to the astronomical community with such a large field of view," said Schiavon. This image is a false-color composite, where light detected by the Galaxy Evolution Explorer's far-ultraviolet detector is colored blue, and light from the telescope's near-ultraviolet detector is red. Written by Linda Vu, Spitzer Science Center Media contact: Whitney Clavin/JPL (818) 354-4673

A wide-field survey for high-redshift quasars

NASA Astrophysics Data System (ADS)

Kakazu, Yuko K. M.

2008-02-01

The present thesis reports the results from the Hawaii Quasar and T dwarf survey (HQT survey), which is a wide-field optical imaging survey conducted with Subaru/Suprime-Cam. The HQT survey was designed to search for low- luminosity quasars ( M 1450 < -22.5) at high-redshift ( z > 5.7) as well as T dwarfs, both of which are selected by their very red optical I -- z ' colors. We developed a new color selection technique using a narrowband NB 816 filter in order to break a well-known color degeneracy between quasars and foreground M and L dwarfs. The follow-up Keck/DEIMOS spectroscopy and near-IR imaging with various instruments on Mauna Kea have demonstrated the effectiveness of our technique, and have successfully revealed six faint T dwarfs ( J < 20). These dwarfs are among the most distant spectroscopically known (60 - 170 pc) and they provide an indirect support for the high binary fraction at L/ T transition. The non-detection of z > 5.7 quasars in our survey is consistent with the present picture of the cosmic reionization in which quasars are negligible contributor to the cosmic reionization. With our survey area coverage (9.3 deg 2 ) and depths ( Z AB < 23.3), we were able to set strong constraints on the faint-end slope of the quasar luminosity function. Majority of our candidate quasars turned out to be strong emission line galaxies at z < 1, whose large equivalent widths and low metal contents suggest they are very young systems which have just undergone starbursts within a few Myrs. In order to systematically search for these Ultra-Strong Emission Line galaxies (USELs), we used narrowband selected samples from Hu's ultra-deep multiwavelength data. The followup Keck/DEIMOS spectra have revealed their high star formation density (5-10% of UV measurements at z = 0-1), which is a significant contribution at a epoch when cosmic star formation is in its peak. Many of the USELs show [OIII]l4363 auroral lines and about a dozen satisfy the criteria for eXtremely Metal Poor Galaxies (XMPGs). Our XMPGs are the most distant known today. Our high yield rate of XMPGs suggests that narrowband method is powerful in finding such populations. Strikingly, a few of our XMPGs have metallities close to the most metal-poor galaxy. Our discovery indicates that galaxies are still forming in relatively chemically pristine sites at z ~ 1

Carbon monoxide in an extremely metal-poor galaxy.

PubMed

Shi, Yong; Wang, Junzhi; Zhang, Zhi-Yu; Gao, Yu; Hao, Cai-Na; Xia, Xiao-Yang; Gu, Qiusheng

2016-12-09

Extremely metal-poor galaxies with metallicity below 10% of the solar value in the local universe are the best analogues to investigating the interstellar medium at a quasi-primitive environment in the early universe. In spite of the ongoing formation of stars in these galaxies, the presence of molecular gas (which is known to provide the material reservoir for star formation in galaxies such as our Milky Way) remains unclear. Here we report the detection of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with 7% solar metallicity, with additional detections in two galaxies at higher metallicities. Such detections offer direct evidence for the existence of molecular gas in these galaxies that contain few metals. Using archived infrared data, it is shown that the molecular gas mass per CO luminosity at extremely low metallicity is approximately one-thousand times the Milky Way value.

Carbon monoxide in an extremely metal-poor galaxy

PubMed Central

Shi, Yong; Wang, Junzhi; Zhang, Zhi-Yu; Gao, Yu; Hao, Cai-Na; Xia, Xiao-Yang; Gu, Qiusheng

2016-01-01

Extremely metal-poor galaxies with metallicity below 10% of the solar value in the local universe are the best analogues to investigating the interstellar medium at a quasi-primitive environment in the early universe. In spite of the ongoing formation of stars in these galaxies, the presence of molecular gas (which is known to provide the material reservoir for star formation in galaxies such as our Milky Way) remains unclear. Here we report the detection of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with 7% solar metallicity, with additional detections in two galaxies at higher metallicities. Such detections offer direct evidence for the existence of molecular gas in these galaxies that contain few metals. Using archived infrared data, it is shown that the molecular gas mass per CO luminosity at extremely low metallicity is approximately one-thousand times the Milky Way value. PMID:27934880

Dynamics, Chemical Abundances, and ages of Globular Clusters in the Virgo Cluster of Galaxies

NASA Astrophysics Data System (ADS)

Guhathakurta, Puragra; NGVS Collaboration

2018-01-01

We present a study of the dynamics, metallicities, and ages of globular clusters (GCs) in the Next Generation Virgo cluster Survey (NGVS), a deep, multi-band (u, g, r, i, z, and Ks), wide-field (104 deg2) imaging survey carried out using the 3.6-m Canada-France-Hawaii Telescope and MegaCam imager. GC candidates were selected from the NGVS survey using photometric and image morphology criteria and these were followed up with deep, medium-resolution, multi-object spectroscopy using the Keck II 10-m telescope and DEIMOS spectrograph. The primary spectroscopic targets were candidate GC satellites of dwarf elliptical (dE) and ultra-diffuse galaxies (UDGs) in the Virgo cluster. While many objects were confirmed as GC satellites of Virgo dEs and UDGs, many turned out to be non-satellites based on their radial velocity and/or positional mismatch any identifiable Virgo cluster galaxy. We have used a combination of spectral characteristics (e.g., presence of absorption vs. emission lines), new Gaussian mixture modeling of radial velocity and sky position data, and a new extreme deconvolution analysis of ugrizKs photometry and image morphology, to classify all the objects in our sample into: (1) GC satellites of dE galaxies, (2) GC satellites of UDGs, (3) intra-cluster GCs (ICGCs) in the Virgo cluster, (4) GCs in the outer halo of the central cluster galaxy M87, (5) foreground Milky Way stars, and (6) distant background galaxies. We use these data to study the dynamics and dark matter content of dE and UDGs in the Virgo cluster, place important constraints on the nature of dE nuclei, and study the origin of ICGCs versus GCs in the remote M87 halo.We are grateful for financial support from the NSF and NASA/STScI.

New Fast Lane towards Discoveries of Clusters of Galaxies Inaugurated

NASA Astrophysics Data System (ADS)

2003-07-01

Space and Ground-Based Telescopes Cooperate to Gain Deep Cosmological Insights Summary Using the ESA XMM-Newton satellite, a team of European and Chilean astronomers [2] has obtained the world's deepest "wide-field" X-ray image of the cosmos to date. This penetrating view, when complemented with observations by some of the largest and most efficient ground-based optical telescopes, including the ESO Very Large Telescope (VLT), has resulted in the discovery of several large clusters of galaxies. These early results from an ambitious research programme are extremely promising and pave the way for a very comprehensive and thorough census of clusters of galaxies at various epochs. Relying on the foremost astronomical technology and with an unequalled observational efficiency, this project is set to provide new insights into the structure and evolution of the distant Universe. PR Photo 19a/03: First image from the XMM-LSS survey. PR Photo 19b/03: Zoom-in on PR Photo 19b/03. PR Photo 19c/03: XMM-Newton contour map of the probable extent of a cluster of galaxies, superimposed upon a CHFT I-band image. PR Photo 19d/03: Velocity distribution in the cluster field shown in PR Photo 19c/03. The universal web Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies which themselves congregate into clusters (and even clusters of clusters). These clusters are "strung" throughout the Universe in a web-like structure, cf. ESO PR 11/01. Our Galaxy, the Milky Way, for example, belongs to the so-called Local Group which also comprises "Messier 31", the Andromeda Galaxy. The Local Group contains about 30 galaxies and measures a few million light-years across. Other clusters are much larger. The Coma cluster contains thousands of galaxies and measures more than 20 million light-years. Another well known example is the Virgo cluster, covering no less than 10 degrees on the sky ! Clusters of galaxies are the most massive bound structures in the Universe. They have masses of the order of one thousand million million times the mass of our Sun. Their three-dimensional space distribution and number density change with cosmic time and provide information about the main cosmological parameters in a unique way. About one fifth of the optically invisible mass of a cluster is in the form of a diffuse hot gas in between the galaxies. This gas has a temperature of the order of several tens of million degrees and a density of the order of one atom per liter. At such high temperatures, it produces powerful X-ray emission. Observing this intergalactic gas and not just the individual galaxies is like seeing the buildings of a city in daytime, not just the lighted windows at night. This is why clusters of galaxies are best discovered using X-ray satellites. Using previous X-ray satellites, astronomers have performed limited studies of the large-scale structure of the nearby Universe. However, they so far lacked the instruments to extend the search to large volumes of the distant Universe. The XMM-Newton wide-field observations ESO PR Photo 19a/03 ESO PR Photo 19a/03 [Preview - JPEG: 575 x 400 pix - 52k [Normal - JPEG: 1130 x 800 pix - 420k] ESO PR Photo 19b/03 ESO PR Photo 19b/03 [Preview - JPEG: 400 x 489 pix - 52k [Normal - JPEG: 800 x 978 pix - 464k] Captions: PR Photo 19a/03 is the first image from the XMM-LSS X-Ray survey. It is actually a combination of fourteen separate "pointings" of this space observatory. It represents a region of the sky eight times larger than the full Moon and contains around 25 clusters. The circles represent the X-Ray sources previously known from the 1991 ROSAT All-Sky Survey. PR Photo 19b/03 zooms in on a particularly interesting region of the image shown in ESO PR Photo 19a/03 with a possible cluster identified (in box). Each point on this graph represents a single X-ray photon detected by XMM-Newton. Marguerite Pierre (CEA Saclay, France), with a European/Chilean team of astronomers known as the XMM-LSS consortium [2], used the large field-of-view and the high sensitivity of ESA's X-ray observatory XMM-Newton to search for remote clusters of galaxies and map out their distribution in space. They could see back about 7,000 million years to a cosmological era when the Universe was about half its present size and age, when clusters of galaxies were more tightly packed. Tracking down the clusters is a painstaking, multi-step process, requiring both space and ground-based telescopes. Indeed, from X-ray images with XMM, it was possible to select several tens of cluster candidate objects, identified as areas of enhanced X-radiation (cf PR Photo 19b/03). But having candidates is not enough ! They must be confirmed and further studied with ground-based telescopes. In tandem with XMM-Newton, Pierre uses the very-wide-field imager attached to the 4-m Canada-France-Hawaii Telescope, on Mauna Kea, Hawaii, to take an optical snapshot of the same region of space. A tailor-made computer programme then combs the XMM-Newton data looking for concentrations of X-rays that suggest large, extended structures. These are the clusters and represent only about 10% of the detected X-ray sources. The others are mostly distant active galaxies. Back to the Ground ESO PR Photo 19c/03 ESO PR Photo 19c/03 [Preview - JPEG: 400 x 481 pix - 84k [Normal - JPEG: 800 x 961 pix - 1M] ESO PR Photo 19d/03 ESO PR Photo 19d/03 [Preview - JPEG: 400 x 488 pix - 44k [Normal - JPEG: 800 x 976 pix - 520k] Captions: PR Photo 19c/03 represents the XMM-Newton X-ray contour map of the cluster's probable extent superimposed upon the CFHT I-band image. A concentration of distant galaxies is conspicuous, thus confirming the X-ray detection. The symbols indicate the galaxies which have been subject to a subsequent spectroscopic measurement and found to be cluster members (triangles flag emission line galaxies). The individual galaxies in the cluster can then be targeted for further observations with ESO's VLT, in order to measure its distance and locate the cluster in the universe. Following the X-ray discovery and the optical cluster identification, galaxies in the cluster field shown in ESO PR Photo 19c/03 have been spectroscopically observed at the ESO VLT using the FORS2 instrument in order to determine the cluster redshift [3]. Using two masks, each of them observed during one hour, allowing to take the spectra of 16 emission-line galaxies at a time, the cluster was found to have a redshift of 0.84, corresponding to a distance of 8,000 million light-years, and a velocity dispersion of 750 km/s. PR Photo 19d/03 shows the measured velocity distribution. This is one of the most distant known clusters of galaxies for which a velocity dispersion has been measured. When the programme finds a cluster, it zooms in on that region and converts the XMM-Newton data into a contour map of X-ray intensity, which is then superimposed upon the CFHT optical image (PR Photo 19c/03). The astronomers use this to check if anything is visible within the area of extented X-ray emission. If something is seen, the work then shifts to one of the world's prime optical/infrared telescopes, the European Southern Observatory's Very Large Telescope (VLT) at Paranal (Chile). By means of the FORS multi-mode instruments, the astronomers zoom-in on the individual galaxies in the field, taking spectral measurements that reveal their overall characteristics, in particular their redshift and hence, distance. Cluster galaxies have similar distances and these measurement ultimately provide, by averaging, the cluster's distance as well as the velocity dispersion in the cluster. The FORS instruments are among the most efficient and versatile for this type of work, taking on the average spectra of 30 galaxies at a time. The first spectroscopic observations dedicated to the identification and redshift measurement of the XMM-LSS galaxy clusters took place during three nights in the fall of 2002. As of March 2003, there were only 5 known clusters in the literature at such a large redshift with enough spectroscopically measured redshifts to allow an estimate of the velocity dispersion. But the VLT allowed obtaining the dispersion in a distant cluster in 2 hours only, raising great expectations for future work. 700 spectra... Marguerite Pierre is extremely content : Weather and working conditions at the VLT were optimal. In three nights only, 12 cluster fields were observed, yielding no less than 700 spectra of galaxies. The overall strategy proved very successful. The high observing efficiency of the VLT and FORS support our plan to perform follow-up studies of large numbers of distant clusters with relatively little observing time. This represents a most substantial increase in efficiency compared to former searches. The present research programme has begun well, clearly demonstrating the feasibility of this new multi-telescope approach and its very high efficiency. And Marguerite Pierre and her colleagues are already seeing the first tantalising results: it seems to confirm that the number of clusters 7,000 million years ago is little different from that of today. This particular behaviour is predicted by models of the Universe that expand forever, driving the galaxy clusters further and further apart. Equally important, this multi-wavelength, multi-telescope approach developed by the XMM-LSS consortium to locate clusters of galaxies also constitutes a decisive next step in the fertile synergy between space and ground-based observatories and is therefore a basic building block of the forthcoming Virtual Observatory. More information This work is based on two papers to be published in the professional astronomy journal, Astronomy and Astrophysics (The XMM-LSS survey : I. Scientific motivations, design and first results by Marguerite Pierre et al., astro-ph/0305191 and The XMM-LSS survey : II. First high redshift galaxy clusters: relaxed and collapsing systems by Ivan Valtchanov et al., astro-ph/0305192). Dr. M. Pierre will give an invited talk on this subject at the IAU Symposium 216 - Maps of the Cosmos - this Thursday July 17, 2003 during the IAU General Assembly 2003 in Sydney, Australia.

ZEUS-2: a second generation submillimeter grating spectrometer for exploring distant galaxies

NASA Astrophysics Data System (ADS)

Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Stacey, Gordon J.; Irwin, Kent D.; Cho, Hsiao-Mei; Halpern, Mark

2010-07-01

ZEUS-2, the second generation (z)Redshift and Early Universe Spectrometer, like its predecessor is a moderate resolution (R~1000) long-slit, echelle grating spectrometer optimized for the detection of faint, broad lines from distant galaxies. It is designed for studying star-formation across cosmic time. ZEUS-2 employs three TES bolometer arrays (555 pixels total) to deliver simultaneous, multi-beam spectra in up to 4 submillimeter windows. The NIST Boulder-built arrays operate at ~100mK and are readout via SQUID multiplexers and the Multi-Channel Electronics from the University of British Columbia. The instrument is cooled via a pulse-tube cooler and two-stage ADR. Various filter configurations give ZEUS-2 access to 7 different telluric windows from 200 to 850 micron enabling the simultaneous mapping of lines from extended sources or the simultaneous detection of the 158 micron [CII] line and the [NII] 122 or 205 micron lines from z = 1-2 galaxies. ZEUS-2 is designed for use on the CSO, APEX and possibly JCMT.

Emission-line galaxies in the third list of the Case Low-Dispersion Northern Sky Survey

NASA Technical Reports Server (NTRS)

Weistrop, Donna; Downes, Ronald A.

1991-01-01

Observations of 47 galaxies in the third Case list are reported. Thirty-five of the galaxies in the sample were selected for the presence of emission lines on the objective prism plates. At the higher spectral dispersion of the data, significant line emission was found in 46 of the 47 galaxies. Twenty-six galaxies are found to be undergoing significant bursts of star formation. Ten additional galaxies may be starburst galaxies with low-excitation spectra. Two galaxies are probably type Seyfert 2. The most distant object, CG 200, at a redshift of 0.144, has a strong broad H-alpha emission line, and is probably a Seyfert 1. Seventeen of the galaxies have been detected by IRAS. Eight of the IRAS galaxies have H-II-region-type spectra and eight have low-ionization starburst spectra. The galaxies represent a mixture of types, ranging from intrinsically faint dwarf galaxies with Mb equalling -16 mag, to powerful galaxies with MB equalling -23 mag. Galaxies CG 234 and CG 235 are interacting, as are galaxies CG 269 and CG 270.

Beacons in the dark: using the most distant galaxies to probe cosmic reionization

NASA Astrophysics Data System (ADS)

De Barros, Stephane

2017-08-01

One of the major unresolved problems in modern cosmology is when and how the universe was ionized. The consensus scenario is that ultra-faint, low-mass galaxies contributed most to the UV background at high-redshift and that reionization was an inhomogeneous process, with ionized bubbles created first around galaxy overdensities. The very surprising discovery of Ly-alpha emission lines around a large fraction of the most luminous galaxies at z=7.4-8.7, when we expect the universe to be highly neutral, could thus be explained by the fact that they lie in large HII bubbles which were ionized thanks to yet undetected fainter neighbors. Theoretical models indeed predict a boost of up to 6x larger galaxy counts around the brightest sources compared to the general field, when probing down to luminosities as faint as 0.1L_UV of the central source. Here we propose a direct test of these models by searching for fainter neighbors around three bright z>7.4 galaxies emitting Ly-alpha, including two sources that lie only 9 Mpc from each other and could share the same ionized bubble, as well as the most distant confirmed Ly-alpha emitter EGSY-8p7 at z=8.68. Given the expected overdensities, we have the opportunity to detect 20 (and up to 50) new z 7-9 galaxies with only a modest investment of HST time. These observations are thus maximally efficient at providing a large number of precious high-redshift targets for early JWST spectroscopy to directly study the galaxies that are in the process of ionizing the universe. Our imaging will further enhance the legacy of the CANDELS/EGS field, and we will make the reduced data available to the community immediately for JWST follow-up.

HUBBLE AND KECK DISCOVER GALAXY BUILDING BLOCK

NASA Technical Reports Server (NTRS)

2002-01-01

This NASA Hubble Space Telescope image shows a very small, faint galaxy 'building block' newly discovered by a unique collaboration between ground- and space-based telescopes. Hubble and the 10-meter Keck Telescopes in Hawaii joined forces, using a galaxy cluster which acts as gravitational lens to detect what scientists believe is one of the smallest very distant objects ever found. The galaxy cluster Abell 2218 was used by a team of European and American astronomers led by Richard Ellis (Caltech) in their systematic search for intrinsically faint distant star-forming systems. Without help from Abell 2218's exceptional magnifying power to make objects appear about 30 times brighter, the galaxy building block would have been undetectable. In the image to the right, the object is seen distorted into two nearly identical, very red 'images' by the gravitational lens. The image pair represents the magnified result of a single background object gravitationally lensed by Abell 2218 and viewed at a distance of 13.4 billion light-years. The intriguing object contains only one million stars, far fewer than a mature galaxy, and scientists believe it is very young. Such young star-forming systems of low mass at early cosmic times are likely to be the objects from which present-day galaxies have formed. In the image to the left, the full overview of the galaxy cluster Abell 2218 is seen. This image was taken by Hubble in 1999 at the completion of Hubble Servicing Mission 3A. Credit: NASA, ESA, Richard Ellis (Caltech) and Jean-Paul Kneib (Observatoire Midi-Pyrenees, France) Acknowledgment: NASA, A. Fruchter and the ERO Team (STScI and ST-ECF)

Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

NASA Technical Reports Server (NTRS)

Luppino, G. A.; Gioia, I. M.

1995-01-01

During the course of a gravitational lensing survey of distant, X-ray selected Einstein Observatory Extended Medium Sensitivity Survey (EMSS) clusters of galaxies, we have studied six X-ray-luminous (L(sub x) greater than 5 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) clusters at redshifts exceeding z = 0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z approximately 0.6 exhibit gravitationally lensed arcs. Furthermore, the highest redshift cluster in our sample, MS 1054-0321 at z = 0.826, is both extremely X-ray luminous (L(sub 0.3-3.5keV)=9.3 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) and exceedingly rich with an optical richness comparable to an Abell Richness Class 4 cluster. In this Letter, we discuss the cosmological implications of the very existence of these clusters for hierarchical structure formation theories such as standard Omega = 1 CDM (cold dark matter), hybrid Omega = 1 C + HDM (hot dark matter), and flat, low-density Lambda + CDM models.

Variable Stars in the M31 Dwarf Spheroidal Companion Cassiopeia

NASA Astrophysics Data System (ADS)

Pritzl, Barton J.; Armandroff, T. E.; Jacoby, G. H.; Da Costa, G. S.

2007-12-01

Dwarf spheroidal galaxies show very diverse star formation histories. For the Galactic dwarf spheroidal galaxies, a correlation exists between Galactocentric distance and the prominence of intermediate-age ( 2 - 10 Gyr) populations. To test whether this correlation exists for the M31 dwarf spheroidal galaxies, we observed the Cassiopeia (And VII) dwarf galaxy, which is one of the most distant M31 dwarf spheroidal galaxies. We will present the results of a variable star search using HST/ACS data, along with a preliminary color-magnitude diagram. From the RR Lyrae stars we can obtain an independent distance and metallicity estimate for the dwarf galaxy. These results will be compared to those found for the other M31 dwarf spheroidal galaxies.This research is supported in part by NASA through grant number GO-11081.11 from the Space Telescope Science Institute.

Extinction Mapping and Dust-to-Gas Ratios of Nearby Galaxies using LEGUS

NASA Astrophysics Data System (ADS)

Kahre, Lauren; Walterbos, Rene; Kim, Hwihyun; Thilker, David; Lee, Janice; LEGUS Team

2018-01-01

Dust is commonly used as a tracer for cold dense gas, either through IR and NIR emission maps or through extinction mapping, and dust abundance and gas metallicity are critical constraints for chemical and galaxy evolution models. Extinction mapping has been used to trace dust column densities in the Milky Way, the Magellanic Clouds, and M31. The maps for M31 use IR and NIR photometry of red giant branch stars, which is more difficult to obtain for more distant galaxies. Work by Kahre et al. (in prep) uses the extinctions derived for individual massive stars using the isochrone-matching method described by Kim et al. (2012) to generate extinction maps for these more distant galaxies.Isochrones of massive stars lie in the same location on a color-color diagram with little dependence on metallicity and luminosity class, so the extinction can be directly derived from the observed photometry. We generate extinction maps using photometry of massive stars from the Hubble Space Telescope for several of the nearly 50 galaxies observed by the Legacy Extragalactic Ultraviolet Survey (LEGUS). The derived extinction maps will allow us to correct ground-based and HST Halpha maps for extinction, and will be used to constrain changes in the dust-to-gas ratio across the galaxy sample and in different star formation, metallicity and morphological environments. Previous studies have found links between galaxy metallicity and the dust-to-gas mass ratio. We present a study of LEGUS galaxies spanning a range of distances, metallicities, and galaxy morphologies, expanding on our previous study of metal-poor dwarfs Holmberg I and II and giant spirals NGC 6503 and NGC 628. We see clear evidence for changes in the dust-to-gas mass ratio with changing metallicity. We also examine changes in the dust-to-gas mass ratio with galactocentric radius. Ultimately, we will provide constraints on the dust-to-gas mass ratio across a wide range of galaxy environments.

"A Richness Study of 14 Distant X-Ray Clusters from the 160 Square Degree Survey"

NASA Technical Reports Server (NTRS)

Jones, Christine; West, Donald (Technical Monitor)

2001-01-01

We have measured the surface density of galaxies toward 14 X-ray-selected cluster candidates at redshifts z(sub i) 0.46, and we show that they are associated with rich galaxy concentrations. These clusters, having X-ray luminosities of Lx(0.5-2 keV) approx. (0.5 - 2.6) x 10(exp 44) ergs/ sec are among the most distant and luminous in our 160 deg(exp 2) ROSAT Position Sensitive Proportional Counter cluster survey. We find that the clusters range between Abell richness classes 0 and 2 and have a most probable richness class of 1. We compare the richness distribution of our distant clusters to those for three samples of nearby clusters with similar X-ray luminosities. We find that the nearby and distant samples have similar richness distributions, which shows that clusters have apparently not evolved substantially in richness since redshift z=0.5. There is, however, a marginal tendency for the distant clusters to be slightly poorer than nearby clusters, although deeper multicolor data for a large sample would be required to confirm this trend. We compare the distribution of distant X-ray clusters in the L(sub X)-richness plane to the distribution of optically selected clusters from the Palomar Distant Cluster Survey. The optically selected clusters appear overly rich for their X-ray luminosities, when compared to X-ray-selected clusters. Apparently, X-ray and optical surveys do not necessarily sample identical mass concentrations at large redshifts. This may indicate the existence of a population of optically rich clusters with anomalously low X-ray emission, More likely, however, it reflects the tendency for optical surveys to select unvirialized mass concentrations, as might be expected when peering along large-scale filaments.

(Almost) Dark Galaxies in the ALFALFA Survey: HI-bearing Ultra-Diffuse Galaxies, and Beyond

NASA Astrophysics Data System (ADS)

Leisman, Luke; Haynes, Martha P.; Giovanelli, Riccardo; ALFALFA Almost Darks Team

2017-01-01

Scaling relations between HI and stars in galaxies suggest strong ties between their atomic gas content and star formation laws. The Arecibo Legacy Fast ALFA (ALFALFA) blind extragalactic HI survey is well positioned to locate very low surface brightness sources that lie off these relations, the most extreme of which may fall below optical detection limits. Thus, the ALFALFA (Almost) Darks Project has been investigating extreme outliers from these relations by studying the ~1% of ALFALFA sources without apparent stellar counterparts in major optical surveys. We have obtained deep HI and optical imaging of 25 of these candidate "dark" sources. We find that most "dark" sources are not extreme "(almost) dark" galaxies. A few are rare OH Megamasers, redshifted into the ALFALFA bandpass, and many are part of large galactic plumes, stretching as far as 600 kpc from their host galaxy. However, a small handful of sources appear to be galaxies with extreme stellar systems. We find multiple systems with HI mass to stellar mass ratios an order of magnitude larger than typical gas rich dwarfs. Further, we find an isolated population of HI-bearing "ultra diffuse" galaxies (UDGs), with stellar masses of dwarfs, but HI and optical radii of L* galaxies. We suggest that these sources may be related to recently reported gas poor, quiescent UDGs.

KSC-08pd2397

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians monitor the movement of the Wide Field Camera 3, or WFC3, as it is lowered onto a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2396

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians monitor the movement of the Wide Field Camera 3, or WFC3, as the overhead crane transfers it to a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2383

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the cover of the Wide Field Camera 3, or WFC3, shipping container is lifted away from the mobile base. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2392

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians move the base of the shipping container holding the Wide Field Camera 3, or WFC3, into the high bay. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2391

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians move the base of the shipping container holding the Wide Field Camera 3, or WFC3. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2398

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians monitor the placement of the Wide Field Camera 3, or WFC3, on a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2450

NASA Image and Video Library

2008-08-16

CAPE CANAVERAL, Fla. – Technicians in the Payload Hazardous Servicing Facility remove the protective cover from the Wide Field Camera 3, or WFC3. The WFC3 is part of the payload on space shuttle Atlantis for the fifth and final Hubble servicing mission, STS-125. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2381

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians attach an overhead crane to the cover of the Wide Field Camera 3, or WFC3, shipping container. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2449

NASA Image and Video Library

2008-08-16

CAPE CANAVERAL, Fla. – Technicians in the Payload Hazardous Servicing Facility begin removing the protective cover from the Wide Field Camera 3, or WFC3. The WFC3 is part of the payload on space shuttle Atlantis for the fifth and final Hubble servicing mission, STS-125. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2378

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – The shipping container with the Wide Field Camera 3, or WFC3, inside is removed from the truck outside the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2382

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians begin lifting the cover of the Wide Field Camera 3, or WFC3, shipping container. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2379

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians unlatch the cover of the Wide Field Camera 3, or WFC3,shipping container before removing it. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

OH megamasers in high-luminosity IRAS galaxies

NASA Technical Reports Server (NTRS)

Mirabel, I. F.; Sanders, D. B.

1987-01-01

OH megamaser emission and H I and CO profiles from the distant infrared galaxies IRAS 10173 + 0828, III Zw 035, and Zw 475.056 are reported. The OH isotropic luminosities at 1667 MHz are 463, 534, and 6.6 solar luminosities, respectively. Far-infrared pumping efficiencies of the OH greater than 1 percent are found in IRAS 10173 + 0828 and III Zw 035. These two galaxies show anomalously large 1667/1665 MHz emission line ratios. OH megamasers reside in the nuclei of superluminous far-infrared galaxies that have a high content of molecular gas, high efficiency of star formation, and in some instances, a striking deficiency of atomic hydrogen.

Clearing the Cosmic Fog - The Most Distant Galaxy Ever Measured

NASA Astrophysics Data System (ADS)

2010-10-01

A European team of astronomers using ESO's Very Large Telescope (VLT) has measured the distance to the most remote galaxy so far. By carefully analysing the very faint glow of the galaxy they have found that they are seeing it when the Universe was only about 600 million years old (a redshift of 8.6). These are the first confirmed observations of a galaxy whose light is clearing the opaque hydrogen fog that filled the cosmos at this early time. The results were presented at an online press conference with the scientists on 19 October 2010, and will appear in the 21 October issue of the journal Nature. "Using the ESO Very Large Telescope we have confirmed that a galaxy spotted earlier using Hubble is the most remote object identified so far in the Universe" [1], says Matt Lehnert (Observatoire de Paris) who is lead author of the paper reporting the results. "The power of the VLT and its SINFONI spectrograph allows us to actually measure the distance to this very faint galaxy and we find that we are seeing it when the Universe was less than 600 million years old." Studying these first galaxies is extremely difficult. By the time that their initially brilliant light gets to Earth they appear very faint and small. Furthermore, this dim light falls mostly in the infrared part of the spectrum because its wavelength has been stretched by the expansion of the Universe - an effect known as redshift. To make matters worse, at this early time, less than a billion years after the Big Bang, the Universe was not fully transparent and much of it was filled with a hydrogen fog that absorbed the fierce ultraviolet light from young galaxies. The period when the fog was still being cleared by this ultraviolet light is known as the era of reionisation [2]. Despite these challenges the new Wide Field Camera 3 on the NASA/ESA Hubble Space Telescope discovered several robust candidate objects in 2009 [3] that were thought to be galaxies shining in the era of reionisation. Confirming the distances to such faint and remote objects is an enormous challenge and can only reliably be done using spectroscopy from very large ground-based telescopes [4], by measuring the redshift of the galaxy's light. Matt Lehnert takes up the story: "After the announcement of the candidate galaxies from Hubble we did a quick calculation and were excited to find that the immense light collecting power of the VLT, when combined with the sensitivity of the infrared spectroscopic instrument, SINFONI, and a very long exposure time might just allow us to detect the extremely faint glow from one of these remote galaxies and to measure its distance." On special request to ESO's Director General they obtained telescope time on the VLT and observed a candidate galaxy called UDFy-38135539 [5] for 16 hours. After two months of very careful analysis and testing of their results, the team found that they had clearly detected the very faint glow from hydrogen at a redshift of 8.6, which makes this galaxy the most distant object ever confirmed by spectroscopy. A redshift of 8.6 corresponds to a galaxy seen just 600 million years after the Big Bang. Co-author Nicole Nesvadba (Institut d'Astrophysique Spatiale) sums up this work, "Measuring the redshift of the most distant galaxy so far is very exciting in itself, but the astrophysical implications of this detection are even more important. This is the first time we know for sure that we are looking at one of the galaxies that cleared out the fog which had filled the very early Universe." One of the surprising things about this discovery is that the glow from UDFy-38135539 seems not to be strong enough on its own to clear out the hydrogen fog. "There must be other galaxies, probably fainter and less massive nearby companions of UDFy-38135539, which also helped make the space around the galaxy transparent. Without this additional help the light from the galaxy, no matter how brilliant, would have been trapped in the surrounding hydrogen fog and we would not have been able to detect it", explains co-author Mark Swinbank (Durham University). Co-author Jean-Gabriel Cuby (Laboratoire d'Astrophysique de Marseille) remarks: "Studying the era of reionisation and galaxy formation is pushing the capability of current telescopes and instruments to the limit, but this is just the type of science that will be routine when ESO's European Extremely Large Telescope - which will be the biggest optical and near infrared telescope in the world - becomes operational." Notes [1] An earlier ESO result (eso0405) reported an object at a larger distance (a redshift of 10). However, further work failed to find an object of similar brightness at this position, and more recent observations with the NASA/Hubble Space Telescope have been inconclusive. The identification of this object with a galaxy at very high redshift is no longer considered to be valid by most astronomers. [2] When the Universe cooled down after the Big Bang, about 13.7 billion years ago, electrons and protons combined to form hydrogen gas. This cool dark gas was the main constituent of the Universe during the so-called Dark Ages, when there were no luminous objects. This phase eventually ended when the first stars formed and their intense ultraviolet radiation slowly made the hydrogen fog transparent again by splitting the hydrogen atoms back into electrons and protons, a process known as reionisation. This epoch in the Universe's early history lasted from about 150 million to 800 million years after the Big Bang. Understanding how reionisation happened and how the first galaxies formed and evolved is one of the major challenges of modern cosmology. [3] These Hubble observations are described at: http://www.spacetelescope.org/news/heic1001/ [4] Astronomers have two main ways of finding and measuring the distances to the earliest galaxies. They can take very deep images through differently coloured filters and measure the brightness of many objects at different wavelengths. They can then compare these with what is expected of galaxies of different types at different times in the Universe's history. This is the only way currently available to discover these very faint galaxies and is the technique employed by the Hubble team. But this technique is not always reliable. For example, what may seem to be a faint, very distant galaxy can sometimes turn out to be a mundane, cool star in our Milky Way. Once candidate objects are found more reliable estimates of the distance (measured as the redshift) can be obtained by splitting the light from a candidate object up into its component colours and looking for the telltale signs of emission from hydrogen or other elements in the galaxy. This spectroscopic approach is the only means by which astronomers can obtain the most reliable and accurate measurements of distance. [5] The strange name indicates that it was found in the Ultra Deep Field search area and the number gives its precise position on the sky. More information An online press conference to announce the new results and offer journalists the opportunity for discussion with the scientists will be held at 16:00 CEST on Tuesday, 19 October 2010. To participate in the teleconference, bona-fide members of the media must get accredited by contacting Douglas Pierce-Price by email (dpiercep@eso.org). Reporters will need access to a computer with a recent version of Adobe Flash Player installed and a broadband internet connection. This research was presented in a paper, Spectroscopic confirmation of a galaxy at redshift z=8.6, Lehnert et al., to appear in Nature on 21 October 2010. The team is composed of M. D. Lehnert (Observatoire de Paris - Laboratoire GEPI / CNRS-INSU / Université Paris Diderot, France), N. P. H. Nesvadba (Institut d'Astrophysique Spatiale / CNRS-INSU / Université Paris-Sud, France), J.-G.Cuby (Laboratoire d'Astrophysique de Marseille / CNRS-INSU / Université de Provence, France), A. M. Swinbank (Durham University, UK), S. Morris (Durham University, UK), B. Clément (Laboratoire d'Astrophysique de Marseille / CNRS-INSU / Université de Provence, France), C. J. Evans (UK Astronomy Technology Centre, Edinburgh, UK), M. N. Bremer (University of Bristol, UK) and S. Basa (Laboratoire d'Astrophysique de Marseille / CNRS-INSU / Université de Provence, France). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe.

PubMed

Zhang, Zhi-Yu; Papadopoulos, Padelis P; Ivison, R J; Galametz, Maud; Smith, M W L; Xilouris, Emmanuel M

2016-06-01

Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H2 gas velocity fields and enclosed H2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh-Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB.

Lacerta I and Cassiopeia III. Two Luminous and Distant Andromeda Satellite Dwarf Galaxies Found in the 3π Pan-STARRS1 Survey

NASA Astrophysics Data System (ADS)

Martin, Nicolas F.; Slater, Colin T.; Schlafly, Edward F.; Morganson, Eric; Rix, Hans-Walter; Bell, Eric F.; Laevens, Benjamin P. M.; Bernard, Edouard J.; Ferguson, Annette M. N.; Finkbeiner, Douglas P.; Burgett, William S.; Chambers, Kenneth C.; Hodapp, Klaus W.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Morgan, Jeffrey S.; Price, Paul A.; Tonry, John L.; Wainscoat, Richard J.

2013-07-01

We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r P1- and i P1-band imaging data. Both are luminous systems (MV ~ -12) located at projected distances of 20.°3 and 10.°5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756^{+44}_{-28}\\,kpc and 772^{+61}_{-56}\\,kpc, respectively, and corresponding M31-centric distances of 275 ± 7 kpc and 144^{+6}_{-4}\\,kpc. The brightest of recent Local Group member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (r_h = 4.2^{+0.4}_{-0.5} arcmin or 912^{+124}_{-93}\\,pc for Lac I r_h = 6.5^{+1.2}_{-1.0} arcmin or 1456 ± 267 pc for Cas III) and consequently low surface brightness (μ0 ~ 26.0 mag arcsec-2), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3π Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.

Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

NASA Technical Reports Server (NTRS)

Aller, Monique C.; Dwek, Eliahu; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim;

Exploring the Structure of the Distant Universe with MUSE Data Cubes

NASA Astrophysics Data System (ADS)

MacDougall, Mason; Christensen, Lise

2018-01-01

The mass distribution in intergalactic and circumgalactic space is not well known since it is difficult to characterize objects in the distant universe. An ideal tool for studying such distant structure is the Multi-Unit Spectroscopic Explorer (MUSE) of the Very Large Telescope array, which employs a wide field-of-view and a large spectral range to produce high spatial resolution datasets. Here we exploit the 2 spatial dimensions and 1 spectral dimension of a particular MUSE “data cube” to identify and characterize emission line sources near the line-of-sight to quasar PKS1937-101, which lies at a redshift of z=3.787. In particular, we search for galaxy companions to a z=3.572 Lyman-limit system measured in the quasar spectrum and find an associated Lyman-alpha emitter at z=3.556 with a projected distance of 30.2 kpc from the quasar line-of-sight. Through a combination of automated source extraction and manual investigation, we also identify 25 emission line galaxies and 1 other Lyman-alpha emitter in our field. The proximity of several of these objects to the quasar line-of-sight allows us to reliably identify absorption lines in the quasar spectrum that can be associated with observed emission lines with resolved fluxes. This will help characterize the metallicities and kinematics of galaxy halos and circumgalactic media in the early universe.

HST Grism Confirmation of 16 Structures at 1.4 < z < 2.8 from the Clusters Around Radio-Loud AGN (CARLA) Survey

NASA Astrophysics Data System (ADS)

Noirot, Gaël; Stern, Daniel; Mei, Simona; Wylezalek, Dominika; Cooke, Elizabeth A.; De Breuck, Carlos; Galametz, Audrey; Hatch, Nina A.; Vernet, Joël; Brodwin, Mark; Eisenhardt, Peter; Gonzalez, Anthony H.; Jarvis, Matt; Rettura, Alessandro; Seymour, Nick; Stanford, S. A.

2018-05-01

We report spectroscopic results from our 40-orbit Hubble Space Telescope slitless grism spectroscopy program observing the 20 densest Clusters Around Radio-Loud AGN (CARLA) candidate galaxy clusters at 1.4 < z < 2.8. These candidate rich structures, among the richest and most distant known, were identified on the basis of [3.6]–[4.5] color from a 408 hr multi-cycle Spitzer program targeting 420 distant radio-loud AGN. We report the spectroscopic confirmation of 16 distant structures at 1.4 < z < 2.8 associated with the targeted powerful high-redshift radio-loud AGN. We also report the serendipitous discovery and spectroscopic confirmation of seven additional structures at 0.87 < z < 2.12 not associated with the targeted radio-loud AGN. We find that 1010–1011 M ⊙ member galaxies of our confirmed CARLA structures form significantly fewer stars than their field counterparts at all redshifts within 1.4 ≤ z ≤ 2. We also observe higher star-forming activity in the structure cores up to z = 2, finding similar trends as cluster surveys at slightly lower redshifts (1.0 < z < 1.5). By design, our efficient strategy of obtaining just two grism orbits per field only obtains spectroscopic confirmation of emission line galaxies. Deeper spectroscopy will be required to study the population of evolved, massive galaxies in these (forming) clusters. Lacking multi-band coverage of the fields, we adopt a very conservative approach of calling all confirmations “structures,” although we note that a number of features are consistent with some of them being bona fide galaxy clusters. Together this survey represents a unique and large homogenous sample of spectroscopically confirmed structures at high redshifts, potentially more than doubling the census of confirmed, massive clusters at z > 1.4.

Missing Black Holes Found!

NASA Image and Video Library

2007-10-25

NASA Spitzer and Chandra space telescopes have uncovered a long-lost population of active supermassive black holes, or quasars located deep in the bellies of distant, massive galaxies circled in blue.

X-Ray Emission from Ultraviolet Luminous Galaxies and Lyman Break Galaxies

NASA Technical Reports Server (NTRS)

Hornschemeier, Ann; Ptak, A. F.; Salim, S.; Heckman, T. P.; Overzier, R.; Mallery, R.; Rich, M.; Strickland, D.; Grimes, J.

2009-01-01

We present results from an XMM mini-survey of GALEX-selected Ultraviolet-Luminous Galaxies (UVLGs) that appear to include an interesting subset that are analogs to the distant (3

The spectral energy distributions of the entire Herschel Reference Survey

NASA Astrophysics Data System (ADS)

Ciesla, Laure

2012-08-01

We present the spectral energy distributions (SED) of the 323 galaxies of the Herschel Reference Survey. In order to provide templates for nearby galaxies calibrated on physical parameters, we computed mean SEDs per bin of morphological types and stellar masses. They will be very useful to study more distant galaxies and their evolution with redshift. This preliminary work aims to study how the most commonly used libraries (Chary & Elbaz 2001, Dale & Helou 2002 and Draine & Li 2007) reproduce the far-infrared emission of galaxies. First results show that they reproduce well the far-infrared part of mean SEDs. For single galaxies the Draine & Li (2007) models seem to reproduce very well the far-infrared emission, as does the Dale & Helou (2002).

Chandra Catches "Piranha" Black Holes

NASA Astrophysics Data System (ADS)

2007-07-01

Supermassive black holes have been discovered to grow more rapidly in young galaxy clusters, according to new results from NASA's Chandra X-ray Observatory. These "fast-track" supermassive black holes can have a big influence on the galaxies and clusters that they live in. Using Chandra, scientists surveyed a sample of clusters and counted the fraction of galaxies with rapidly growing supermassive black holes, known as active galactic nuclei (or AGN). The data show, for the first time, that younger, more distant galaxy clusters contained far more AGN than older, nearby ones. Galaxy clusters are some of the largest structures in the Universe, consisting of many individual galaxies, a few of which contain AGN. Earlier in the history of the universe, these galaxies contained a lot more gas for star formation and black hole growth than galaxies in clusters do today. This fuel allows the young cluster black holes to grow much more rapidly than their counterparts in nearby clusters. Illustration of Active Galactic Nucleus Illustration of Active Galactic Nucleus "The black holes in these early clusters are like piranha in a very well-fed aquarium," said Jason Eastman of Ohio State University (OSU) and first author of this study. "It's not that they beat out each other for food, rather there was so much that all of the piranha were able to really thrive and grow quickly." The team used Chandra to determine the fraction of AGN in four different galaxy clusters at large distances, when the Universe was about 58% of its current age. Then they compared this value to the fraction found in more nearby clusters, those about 82% of the Universe's current age. The result was the more distant clusters contained about 20 times more AGN than the less distant sample. AGN outside clusters are also more common when the Universe is younger, but only by factors of two or three over the same age span. "It's been predicted that there would be fast-track black holes in clusters, but we never had good evidence until now," said co-author Paul Martini, also of OSU. "This can help solve a couple of mysteries about galaxy clusters." One mystery is why there are so many blue, star-forming galaxies in young, distant clusters and fewer in nearby, older clusters. AGN are believed to expel or destroy cool gas in their host galaxy through powerful eruptions from the black hole. This may stifle star formation and the blue, massive stars will then gradually die off, leaving behind only the old, redder stars. This process takes about a billion years or more to take place, so a dearth of star-forming galaxies is only noticeable for older clusters. The process that sets the temperature of the hot gas in clusters when they form is also an open question. These new results suggest that even more AGN may have been present when most clusters were forming about ten billion years ago. Early heating of a cluster by large numbers of AGN can have a significant, long-lasting effect on the structure of a cluster by "puffing up" the gas. "In a few nearby clusters we've seen evidence for huge eruptions generated by supermassive black holes. But this is sedate compared to what might be going on in younger clusters," said Eastman. These results appeared in the July 20th issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

Spectroscopy of Luminous Compact Blue Galaxies in Distant Clusters. I. Spectroscopic Data

NASA Astrophysics Data System (ADS)

Crawford, Steven M.; Wirth, Gregory D.; Bershady, Matthew A.; Hon, Kimo

2011-11-01

We used the DEIMOS spectrograph on the Keck II Telescope to obtain spectra of galaxies in the fields of five distant, rich galaxy clusters over the redshift range 0.5 < z < 0.9 in a search for luminous compact blue galaxies (LCBGs). Unlike traditional studies of galaxy clusters, we preferentially targeted blue cluster members identified via multi-band photometric pre-selection based on imaging data from the WIYN telescope. Of the 1288 sources that we targeted, we determined secure spectroscopic redshifts for 848 sources, yielding a total success rate of 66%. Our redshift measurements are in good agreement with those previously reported in the literature, except for 11 targets which we believe were previously in error. Within our sample, we confirm the presence of 53 LCBGs in the five galaxy clusters. The clusters all stand out as distinct peaks in the redshift distribution of LCBGs with the average number density of LCBGs ranging from 1.65 ± 0.25 Mpc-3 at z = 0.55 to 3.13 ± 0.65 Mpc-3 at z = 0.8. The number density of LCBGs in clusters exceeds the field density by a factor of 749 ± 116 at z = 0.55; at z = 0.8, the corresponding ratio is E = 416 ± 95. At z = 0.55, this enhancement is well above that seen for blue galaxies or the overall cluster population, indicating that LCBGs are preferentially triggered in high-density environments at intermediate redshifts. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

Images From Hubbles's ACS Tell A Tale Of Two Record-Breaking Galaxy Clusters

NASA Astrophysics Data System (ADS)

2004-01-01

Looking back in time nearly 9 billion years, an international team of astronomers found mature galaxies in a young universe. The galaxies are members of a cluster of galaxies that existed when the universe was only 5 billion years old, or about 35 percent of its present age. This compelling evidence that galaxies must have started forming just after the big bang was bolstered by observations made by the same team of astronomers when they peered even farther back in time. The team found embryonic galaxies a mere 1.5 billion years after the birth of the cosmos, or 10 percent of the universe's present age. The "baby galaxies" reside in a still-developing cluster, the most distant proto-cluster ever found. The Advanced Camera for Surveys (ACS) aboard NASA's Hubble Space Telescope was used to make observations of the massive cluster, RDCS 1252.9-2927, and the proto-cluster, TN J1338-1942. Observations by NASA's Chandra X-ray Observatory yielded the mass and heavy element content of RDCS 1252, the most massive known cluster for that epoch. These observations are part of a coordinated effort by the ACS science team to track the formation and evolution of clusters of galaxies over a broad range of cosmic time. The ACS was built especially for studies of such distant objects. These findings further support observations and theories that galaxies formed relatively early in the history of the cosmos. The existence of such massive clusters in the early universe agrees with a cosmological model wherein clusters form from the merger of many sub-clusters in a universe dominated by cold dark matter. The precise nature of cold dark matter, however, is still not known. The first Hubble study estimated that galaxies in RDCS 1252 formed the bulk of their stars more than 11 billion years ago (at redshifts greater than 3). The results were published in the Oct. 20, 2003 issue of the Astrophysical Journal. The paper's lead author is John Blakeslee of the Johns Hopkins University in Baltimore, Md. Optical Image of RDCS 1252.9-2927 HST Optical Image of RDCS 1252.9-2927 The second Hubble study uncovered, for the first time, a proto-cluster of "infant galaxies" that existed more than 12 billion years ago (at redshift 4.1). These galaxies are so young that astronomers can still see a flurry of stars forming within them. The galaxies are grouped around one large galaxy. These results will be published in the Jan. 1, 2004 issue of Nature. The paper's lead author is George Miley of Leiden Observatory in the Netherlands. "Until recently people didn't think that clusters existed when the universe was only about 5 billion years old," Blakeslee explained. "Even if there were such clusters," Miley added, "until recently astronomers thought it was almost impossible to find clusters that existed 8 billion years ago. In fact, no one really knew when clustering began. Now we can witness it." Both studies led the astronomers to conclude that these systems are the progenitors of the galaxy clusters seen today. "The cluster RDCS 1252 looks like a present-day cluster," said Marc Postman of the Space Telescope Science Institute in Baltimore, Md., and co-author of both research papers. "In fact, if you were to put it next to a present-day cluster, you wouldn't know which is which." A Tale of Two Clusters How can galaxies grow so fast after the big bang? "It is a case of the rich getting richer," Blakeslee said. "These clusters grew quickly because they are located in very dense regions, so there is enough material to build up the member galaxies very fast." This idea is strengthened by X-ray observations of the massive cluster RDCS 1252. Chandra and the European Space Agency's XMM-Newton provided astronomers with the most accurate measurements to date of the properties of an enormous cloud of hot gas that pervades the massive cluster. This 160-million-degree Fahrenheit (70-million-degree Celsius) gas is a reservoir of most of the heavy elements in the cluster and an accurate tracer of its total mass. A paper by Piero Rosati of the European Southern Observatory (ESO) and colleagues that presents the X-ray observations of RDCS 1252 will be published in January 2004 in the Astronomical Journal. "Chandra's sharp vision resolved the shape of the hot gas halo and showed that RDCS 1252 is very mature for its age," said Rosati, who discovered the cluster with the ROSAT X-ray telescope. RDCS 1252 may contain many thousands of galaxies. Most of these galaxies, however, are too faint to detect. But the powerful "eyes" of the ACS pinpointed several hundred of them. Observations using ESO's Very Large Telescope (VLT) provided a precise measurement of the distance to the cluster. The ACS enabled the researchers to accurately determine the shapes and colors of the 100 galaxies, providing information on the ages of the stars residing in them. The ACS team estimated that most of the stars in the cluster were already formed when the universe was about 2 billion years old. X-ray observations, furthermore, showed that 5 billion years after the big bang the surrounding hot gas had been enriched with heavy elements from these stars and had been swept away from the galaxies. If most of the galaxies in RDCS 1252 have reached maturity and are settling into a quiet adulthood, the forming galaxies in the distant proto-cluster are in their energetic, unruly youth. The proto-cluster TN J1338 contains a massive embryonic galaxy surrounded by smaller developing galaxies, which look like dots in the Hubble image. The dominant galaxy is producing spectacular radio-emitting jets, fueled by a supermassive black hole deep within the galaxy's nucleus. Interaction between these jets and the gas can stimulate a torrent of star birth. The energetic radio galaxy's discovery by radio telescopes prompted astronomers to hunt for the smaller galaxies that make up the bulk of the cluster. "Massive clusters are the cities of the universe, and the radio galaxies within them are the smokestacks we can use for finding them when they are just beginning to form," Miley said. The two findings underscore the power of combining observations from many different telescopes that provided views of the distant universe in a range of wavelengths. Hubble's advanced camera provided critical information on the structure of both distant galaxy clusters. Chandra's and XMM-Newton's X-ray vision furnished the essential measurements of the primordial gas in which the galaxies in RDCS 1252 are embedded, and accurate estimates of the total mass contained within that cluster. Large ground-based telescopes, like the VLT, provided precise measurements of the distance of both clusters as well as the chemical composition of the galaxies in them. The ACS team is conducting further observations of distant clusters to solidify our understanding of how these young clusters and their galaxies evolve into the shape of things seen today. Their planned observations include using near-infrared observations to analyze the star-formation rates in some of the target clusters, including RDCS 1252, to measure the cosmic history of star formation in these massive structures. The team is also searching the regions around several ultra-distant radio galaxies for additional examples of proto-clusters. The team's ultimate scientific goal is to establish a complete picture of cluster evolution beginning with the formation at the earliest epochs and detailing the evolution up to today. Electronic image files and additional information are available at http://hubblesite.org/newscenter/newsdesk/archive/releases/2004/01/ The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA).

Journey to Elsewhere and Elsewhen

ERIC Educational Resources Information Center

Sagan, Carl

1973-01-01

A Cornell University astronomer discusses teaching astronomy in schools and provides details on concepts such as the theorized black holes that may be apertures to distant galaxies and remote epochs. (Author/JA)

High-redshift galaxies and low-mass stars

NASA Astrophysics Data System (ADS)

Wilkins, Stephen M.; Stanway, Elizabeth R.; Bremer, Malcolm N.

2014-03-01

The sensitivity available to near-infrared surveys has recently allowed us to probe the galaxy population at z ≈ 7 and beyond. The existing Hubble Wide Field Camera 3 (WFC3) and Visible and Infrared Survey Telescope for Astronomy (VISTA) Infrared Camera (VIRCam) instruments allow deep surveys to be undertaken well beyond 1 μm - a capability that will be further extended with the launch and commissioning of the James Webb Space Telescope (JWST). As new regions of parameter space in both colour and depth are probed, new challenges for distant galaxy surveys are identified. In this paper, we present an analysis of the colours of L- and T-dwarf stars in widely used photometric systems. We also consider the implications of the newly identified Y-dwarf population - stars that are still cooler and less massive than T-dwarfs for both the photometric selection and spectroscopic follow-up of faint and distant galaxies. We highlight the dangers of working in the low-signal-to-noise regime, and the potential contamination of existing and future samples. We find that Hubble/WFC3 and VISTA/VIRCam Y-drop selections targeting galaxies at z ˜ 7.5 are vulnerable to contamination from T- and Y-class stars. Future observations using JWST, targeting the z ˜ 7 galaxy population, are also likely to prove difficult without deep medium-band observations. We demonstrate that single emission line detections in typical low-signal-to-noise spectroscopic observations may also be suspect, due to the unusual spectral characteristics of the cool dwarf star population.

Galaxy Protoclusters as Drivers of Cosmic Star Formation History in the First 2 Gyr

NASA Astrophysics Data System (ADS)

Chiang, Yi-Kuan; Overzier, Roderik A.; Gebhardt, Karl; Henriques, Bruno

2017-08-01

Present-day clusters are massive halos containing mostly quiescent galaxies, while distant protoclusters are extended structures containing numerous star-forming galaxies. We investigate the implications of this fundamental change in a cosmological context using a set of N-body simulations and semi-analytic models. We find that the fraction of the cosmic volume occupied by all (proto)clusters increases by nearly three orders of magnitude from z = 0 to z = 7. We show that (proto)cluster galaxies are an important and even dominant population at high redshift, as their expected contribution to the cosmic star formation rate density rises (from 1% at z = 0) to 20% at z = 2 and 50% at z = 10. Protoclusters thus provide a significant fraction of the cosmic ionizing photons, and may have been crucial in driving the timing and topology of cosmic reionization. Internally, the average history of cluster formation can be described by three distinct phases: at z ˜ 10-5, galaxy growth in protoclusters proceeded in an inside-out manner, with centrally dominant halos that are among the most active regions in the universe; at z ˜ 5-1.5, rapid star formation occurred within the entire 10-20 Mpc structures, forming most of their present-day stellar mass; at z ≲ 1.5, violent gravitational collapse drove these stellar contents into single cluster halos, largely erasing the details of cluster galaxy formation due to relaxation and virialization. Our results motivate observations of distant protoclusters in order to understand the rapid, extended stellar growth during cosmic noon, and their connection to reionization during cosmic dawn.

Radio Astronomers Develop New Technique for Studying Dark Energy

NASA Astrophysics Data System (ADS)

2010-07-01

Pioneering observations with the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT) have given astronomers a new tool for mapping large cosmic structures. The new tool promises to provide valuable clues about the nature of the mysterious "dark energy" believed to constitute nearly three-fourths of the mass and energy of the Universe. Dark energy is the label scientists have given to what is causing the Universe to expand at an accelerating rate. While the acceleration was discovered in 1998, its cause remains unknown. Physicists have advanced competing theories to explain the acceleration, and believe the best way to test those theories is to precisely measure large-scale cosmic structures. Sound waves in the matter-energy soup of the extremely early Universe are thought to have left detectable imprints on the large-scale distribution of galaxies in the Universe. The researchers developed a way to measure such imprints by observing the radio emission of hydrogen gas. Their technique, called intensity mapping, when applied to greater areas of the Universe, could reveal how such large-scale structure has changed over the last few billion years, giving insight into which theory of dark energy is the most accurate. "Our project mapped hydrogen gas to greater cosmic distances than ever before, and shows that the techniques we developed can be used to map huge volumes of the Universe in three dimensions and to test the competing theories of dark energy," said Tzu-Ching Chang, of the Academia Sinica in Taiwan and the University of Toronto. To get their results, the researchers used the GBT to study a region of sky that previously had been surveyed in detail in visible light by the Keck II telescope in Hawaii. This optical survey used spectroscopy to map the locations of thousands of galaxies in three dimensions. With the GBT, instead of looking for hydrogen gas in these individual, distant galaxies -- a daunting challenge beyond the technical capabilities of current instruments -- the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies. "Since the early part of the 20th Century, astronomers have traced the expansion of the Universe by observing galaxies. Our new technique allows us to skip the galaxy-detection step and gather radio emissions from a thousand galaxies at a time, as well as all the dimly-glowing material between them," said Jeffrey Peterson, of Carnegie Mellon University. The astronomers also developed new techniques that removed both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the "cosmic web" that correlated neatly with the structure shown by the earlier optical study. The team first proposed their intensity-mapping technique in 2008, and their GBT observations were the first test of the idea. "These observations detected more hydrogen gas than all the previously-detected hydrogen in the Universe, and at distances ten times farther than any radio wave-emitting hydrogen seen before," said Ue-Li Pen of the University of Toronto. "This is a demonstration of an important technique that has great promise for future studies of the evolution of large-scale structure in the Universe," said National Radio Astronomy Observatory Chief Scientist Chris Carilli, who was not part of the research team. In addition to Chang, Peterson, and Pen, the research team included Kevin Bandura of Carnegie Mellon University. The scientists reported their work in the July 22 issue of the scientific journal Nature.

The Growth of Early Galaxies and Reionization of Hydrogen

NASA Astrophysics Data System (ADS)

Chary, Ranga Ram

2012-07-01

The reionization of the intergalactic medium about a billion years after the Big Bang was an important event which occurred due to the release of ionizing photons from the growth of stellar mass and black holes in the early Universe. By leveraging the benefits of field galaxy surveys, I will present some recent breakthroughs in our understanding of how the earliest galaxies in the Universe evolved. I will present evidence that unlike in the local Universe where galaxy growth occurs through intermittent cannibalism, star-formation in the distant Universe is a more continuous if violent process with an overabundance of massive stars. Implications for the reionization history of the Universe will also be discussed.

Galactic Pairs in the Early Universe

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-02-01

In the spirit of Valentines Day, today well be exploring apparent pairs of galaxies in the distant, early universe. How can we tell whether these duos are actually paired galaxies, as opposed to disguised singles?Real Pair, or Trick of the Light?In the schematic timeline of the universe, the epoch of reionization is when the first galaxies and quasars began to form and evolve. [NASA]The statistics of merging galaxies throughout the universe reveal not only direct information about how galaxies interact, but also cosmological information about the structure of the universe. While weve observed many merging galaxy pairs at low redshift, however, its much more challenging to identify these duos in the early universe.A merging pair of galaxies at high redshift appears to us as a pair of unresolved blobs that lie close to each other in the sky. But spotting such a set of objects doesnt necessarily mean were looking at a merger! There are three possible scenarios to explain an observed apparent duo:Its a pair of galaxies in a stage of merger.Its a projection coincidence; the two galaxies arent truly near each other.Its a single galaxy being gravitationally lensed by a foreground object. This strong lensing produces the appearance of multiple galaxies.Hubble photometry of one of the three galaxy groups identified at z 8, with the galaxies in the image labeled with their corresponding approximate photometric redshifts. [Adapted from Chaikin et al. 2018]Hunting for Distant DuosIn a recent study led by Evgenii Chaikin (Peter the Great St. Petersburg Polytechnic University, Russia), a team of scientists has explored the Hubble Ultra Deep Field in search ofhigh-redshift galaxies merging during the epoch of reionization, when the first galaxies formed and evolved.Using an approach called the dropout technique, which leverages the visibility of the galaxies in different wavelength filters, Chaikin and collaborators obtain approximate redshifts for an initial sample of 7,000 objects. They find that roughly 50 have a redshift of z 7, and 22 have a redshift of z 8. None of the galaxies at z 7 are in pairs, but the sample at z 8 includes three groups for which the distance between galaxies is less than 1 arcsecond.But are these three pairs actual merging galaxies?Conclusions from StatisticsTop: Gas density at z 7.7 in the authors simulation output. Bottom: Mock observations of this output withHubbles WFC3 (left) and JWSTs NIRCam (right). [Adapted from Chaikin et al. 2018]To answer this question, the authors next perform numerical simulations of galaxy formation and produce mock observations showing what the simulatedfield would look like in an equivalent deep Hubble exposure.Based on their simulation statistics, Chaikin and collaborators argue that the three pairs at z 8 do represent an unusually high merger fraction but projection coincidences or lensing are far less likely scenarios to account for all three pairs. If the three pairs are indeed all merging galaxies, it could indicate that this Hubble field corresponds to a local overdensity at a redshift of z 8.Looking AheadThe best way to improve on these measurements is to repeat this study with more advanced telescopes. Chaikin and collaborators demonstrate the superiority of the observations that the upcoming James Webb Space Telescope (JWST) will provide. They also point out the potential power of the Wide Field Infrared Survey Telescope (WFIRST) currently under threat under the proposed 2019 federal budget to extend the observational horizon well into the epoch of reionization.Continued studies backed by the power of these future telescopes are sure to discover a wealth of additional distant galactic duos, helping us to characterize the universe in its early stages.CitationEvgenii A. Chaikin et al 2018 ApJ 853 81. doi:10.3847/1538-4357/aaa196

Possible Very Distant or Optically Dark Cluster of Galaxies

NASA Technical Reports Server (NTRS)

Vikhlinin, Alexey; Mushotzky, Richard (Technical Monitor)

2003-01-01

The goal of this proposal was an XMM followup observation of the extended X-ray source detected in our ROSAT PSPC cluster survey. Approximately 95% of extended X-ray sources found in the ROSAT data were optically identified as clusters of galaxies. However, we failed to find any optical counterparts for C10952-0148. Two possibilities remained prior to the XMM observation: (1) This is was a very distant or optically dark cluster of galaxies, too faint in the optical, in which case XMM would easily detect extended X-ray emission and (2) this was a group of point-like sources, blurred to a single extended source in the ROSAT data, but easily resolvable by XMM due to a better energy resolution. The XMM data have settled the case --- C10952-0148 is a group of 7 relatively bright point sources located within 1 square arcmin. All but one source have no optical counterparts down to I=22. Potentially, this can be an interesting group of quasars at a high redshift. We are planning further optical and infrared followup of this system.

Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales

PubMed

Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein

2000-05-11

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model.

Blue compact dwarfs - Extreme dwarf irregular galaxies

NASA Technical Reports Server (NTRS)

Thuan, Trinh X.

1987-01-01

Observational data on the most extreme members of the irregular dwarf (dI) galaxy class, the blue compact dwarfs (BCDs), are characterized, reviewing the results of recent investigations. The properties of the young stellar population, the ionized gas, the older star population, and the gas and dust of BCDs are contrasted with those of other dIs; BCD morphology is illustrated with sample images; and the value of BCDs (as nearby 'young' chemically unevolved galaxies) for studies of galaxy formation, galactic evolution, and starburst triggering mechanisms is indicated.

Astronomers Set a New Galaxy Distance Record

NASA Image and Video Library

2015-05-06

This is a Hubble Space Telescope image of the farthest spectroscopically confirmed galaxy observed to date (inset). It was identified in this Hubble image of a field of galaxies in the CANDELS survey (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey). NASA’s Spitzer Space Telescope also observed the unique galaxy. The W. M. Keck Observatory was used to obtain a spectroscopic redshift (z=7.7), extending the previous redshift record. Measurements of the stretching of light, or redshift, give the most reliable distances to other galaxies. This source is thus currently the most distant confirmed galaxy known, and it appears to also be one of the brightest and most massive sources at that time. The galaxy existed over 13 billion years ago. The near-infrared light image of the galaxy (inset) has been colored blue as suggestive of its young, and hence very blue, stars. The CANDELS field is a combination of visible-light and near-infrared exposures. Credits: NASA, ESA, P. Oesch (Yale U.)

Galactic Metropolis

NASA Image and Video Library

2013-12-18

The collection of red dots seen here show one of several very distant galaxy clusters discovered by combining ground-based optical data from the NOAO Kitt Peak National Observatory with infrared data from NASA Spitzer Space Telescope.

Mass of the Local Group from Proper Motions of Distant Dwarf Galaxies

NASA Astrophysics Data System (ADS)

van der Marel, Roeland

2010-09-01

The Local Group and its two dominant spirals, the Milky Way and M31, have become the benchmark for testing many aspects of cosmological and galaxy formation theories, due to many exciting new discoveries in the past decade. However, it is difficult to put results in a proper cosmological context, because our knowledge of the mass M of the Local Group remains uncertain by a factor 4. In units of 10^{12} solar masses, a spherical infall model for the zero-velocity surface gives M 1.3; the sum of estimates for the Milky Way and M31 masses gives M 2.6; and the Local Group Timing argument for the M31 orbit gives M 5.6. It is possible to discriminate between the proposed masses by calculating the orbits of galaxies at the edge of the Local Group, which requires knowledge of transverse velocity components. We therefore propose to use ACS/WFC to determine the proper motions of the 4 dwarf galaxies near the edge of the Local Group {Cetus, Leo A, Tucana, Sag DIG} for which deep first epoch data {with 5-7 year time baselines} already exist in the HST Archive. Our team has extensive expertise with HST astrometric science, and our past/ongoing work for, e.g., Omega Cen, LMC/SMC and M31 show that the necessary astrometric accuracy is within the reach of HST's demonstrated capabilities. We have developed, tested, and published a new technique that uses compact background galaxies as astrometric reference sources, and we have already reduced the first epoch data. The final predicted transverse velocity accuracy, 36 km/s when averaged over the sample, will be sufficient to discriminate between each of the proposed Local Group masses at 2-sigma significance {4-sigma between the most extreme values}. Our project will yield the most accurate Local Group mass determination to date, and only HST can achieve the required accuracy.

Galaxy growth in a massive halo in the first billion years of cosmic history

NASA Astrophysics Data System (ADS)

Marrone, D. P.; Spilker, J. S.; Hayward, C. C.; Vieira, J. D.; Aravena, M.; Ashby, M. L. N.; Bayliss, M. B.; Béthermin, M.; Brodwin, M.; Bothwell, M. S.; Carlstrom, J. E.; Chapman, S. C.; Chen, Chian-Chou; Crawford, T. M.; Cunningham, D. J. M.; De Breuck, C.; Fassnacht, C. D.; Gonzalez, A. H.; Greve, T. R.; Hezaveh, Y. D.; Lacaille, K.; Litke, K. C.; Lower, S.; Ma, J.; Malkan, M.; Miller, T. B.; Morningstar, W. R.; Murphy, E. J.; Narayanan, D.; Phadke, K. A.; Rotermund, K. M.; Sreevani, J.; Stalder, B.; Stark, A. A.; Strandet, M. L.; Tang, M.; Weiß, A.

2018-01-01

According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly—the first few hundred million years of the Universe—is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.

Galaxy growth in a massive halo in the first billion years of cosmic history.

PubMed

Marrone, D P; Spilker, J S; Hayward, C C; Vieira, J D; Aravena, M; Ashby, M L N; Bayliss, M B; Béthermin, M; Brodwin, M; Bothwell, M S; Carlstrom, J E; Chapman, S C; Chen, Chian-Chou; Crawford, T M; Cunningham, D J M; De Breuck, C; Fassnacht, C D; Gonzalez, A H; Greve, T R; Hezaveh, Y D; Lacaille, K; Litke, K C; Lower, S; Ma, J; Malkan, M; Miller, T B; Morningstar, W R; Murphy, E J; Narayanan, D; Phadke, K A; Rotermund, K M; Sreevani, J; Stalder, B; Stark, A A; Strandet, M L; Tang, M; Weiß, A

2018-01-04

According to the current understanding of cosmic structure formation, the precursors of the most massive structures in the Universe began to form shortly after the Big Bang, in regions corresponding to the largest fluctuations in the cosmic density field. Observing these structures during their period of active growth and assembly-the first few hundred million years of the Universe-is challenging because it requires surveys that are sensitive enough to detect the distant galaxies that act as signposts for these structures and wide enough to capture the rarest objects. As a result, very few such objects have been detected so far. Here we report observations of a far-infrared-luminous object at redshift 6.900 (less than 800 million years after the Big Bang) that was discovered in a wide-field survey. High-resolution imaging shows it to be a pair of extremely massive star-forming galaxies. The larger is forming stars at a rate of 2,900 solar masses per year, contains 270 billion solar masses of gas and 2.5 billion solar masses of dust, and is more massive than any other known object at a redshift of more than 6. Its rapid star formation is probably triggered by its companion galaxy at a projected separation of 8 kiloparsecs. This merging companion hosts 35 billion solar masses of stars and has a star-formation rate of 540 solar masses per year, but has an order of magnitude less gas and dust than its neighbour and physical conditions akin to those observed in lower-metallicity galaxies in the nearby Universe. These objects suggest the presence of a dark-matter halo with a mass of more than 100 billion solar masses, making it among the rarest dark-matter haloes that should exist in the Universe at this epoch.

Distant clusters of galaxies in the 2XMM/SDSS footprint: follow-up observations with the LBT

NASA Astrophysics Data System (ADS)

Rabitz, A.; Lamer, G.; Schwope, A.; Takey, A.

2017-11-01

Context. Galaxy clusters at high redshift are important to test cosmological models and models for the growth of structure. They are difficult to find in wide-angle optical surveys, however, leaving dedicated follow-up of X-ray selected candidates as one promising identification route. Aims: We aim to increase the number of galaxy clusters beyond the SDSS-limit, z 0.75. Methods: We compiled a list of extended X-ray sources from the 2XMMp catalogue within the footprint of the Sloan Digital Sky Survey. Fields without optical counterpart were selected for further investigation. Deep optical imaging and follow-up spectroscopy were obtained with the Large Binocular Telescope, Arizona (LBT), of those candidates not known to the literature. Results: From initially 19 candidates, selected by visually screening X-ray images of 478 XMM-Newton observations and the corresponding SDSS images, 6 clusters were found in the literature. Imaging data through r,z filters were obtained for the remaining candidates, and 7 were chosen for multi-object (MOS) spectroscopy. Spectroscopic redshifts, optical magnitudes, and X-ray parameters (flux, temperature, and luminosity) are presented for the clusters with spectroscopic redshifts. The distant clusters studied here constitute one additional redshift bin for studies of the LX-T relation, which does not seem to evolve from high to low redshifts. Conclusions: The selection method of distant galaxy clusters presented here was highly successful. It is based solely on archival optical (SDSS) and X-ray (XMM-Newton) data. Out of 19 selected candidates, 6 of the 7 candidates selected for spectroscopic follow-up were verified as distant clusters, a further candidate is most likely a group of galaxies at z 1.21. Out of the remaining 12 candidates, 6 were known previously as galaxy clusters, one object is a likely X-ray emission from an AGN radio jet, and for 5 we see no clear evidence for them to be high-redshift galaxy clusters. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: the University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia - http://www.lbto.org/for-investigators.htmlThe catalogue, similar to Table A.1, is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A56

The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsyu, Tiffany; Prochaska, J. Xavier; Bolte, Michael

We report the discovery of the Little Cub, an extremely metal-poor star-forming galaxy in the local universe, found in the constellation Ursa Major (a.k.a. the Great Bear). We first identified the Little Cub as a candidate metal-poor galaxy based on its Sloan Digital Sky Survey photometric colors, combined with spectroscopy using the Kast spectrograph on the Shane 3 m telescope at Lick Observatory. In this Letter, we present high-quality spectroscopic data taken with the Low Resolution Imaging Spectrometer at Keck Observatory, which confirm the extremely metal-poor nature of this galaxy. Based on the weak [O iii] λ 4363 Å emissionmore » line, we estimate a direct oxygen abundance of 12 + log(O/H) = 7.13 ± 0.08, making the Little Cub one of the lowest-metallicity star-forming galaxies currently known in the local universe. The Little Cub appears to be a companion of the spiral galaxy NGC 3359 and shows evidence of gas stripping. We may therefore be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way–like galaxy.« less

The Little Cub: Discovery of an Extremely Metal-poor Star-forming Galaxy in the Local Universe

NASA Astrophysics Data System (ADS)

Hsyu, Tiffany; Cooke, Ryan J.; Prochaska, J. Xavier; Bolte, Michael

2017-08-01

We report the discovery of the Little Cub, an extremely metal-poor star-forming galaxy in the local universe, found in the constellation Ursa Major (a.k.a. the Great Bear). We first identified the Little Cub as a candidate metal-poor galaxy based on its Sloan Digital Sky Survey photometric colors, combined with spectroscopy using the Kast spectrograph on the Shane 3 m telescope at Lick Observatory. In this Letter, we present high-quality spectroscopic data taken with the Low Resolution Imaging Spectrometer at Keck Observatory, which confirm the extremely metal-poor nature of this galaxy. Based on the weak [O III] λ4363 Å emission line, we estimate a direct oxygen abundance of 12 + log(O/H) = 7.13 ± 0.08, making the Little Cub one of the lowest-metallicity star-forming galaxies currently known in the local universe. The Little Cub appears to be a companion of the spiral galaxy NGC 3359 and shows evidence of gas stripping. We may therefore be witnessing the quenching of a near-pristine galaxy as it makes its first passage about a Milky Way-like galaxy.

RELICS: Strong-lensing Analysis of the Massive Clusters MACS J0308.9+2645 and PLCK G171.9‑40.7

NASA Astrophysics Data System (ADS)

Acebron, Ana; Cibirka, Nathália; Zitrin, Adi; Coe, Dan; Agulli, Irene; Sharon, Keren; Bradač, Maruša; Frye, Brenda; Livermore, Rachael C.; Mahler, Guillaume; Salmon, Brett; Umetsu, Keiichi; Bradley, Larry; Andrade-Santos, Felipe; Avila, Roberto; Carrasco, Daniela; Cerny, Catherine; Czakon, Nicole G.; Dawson, William A.; Hoag, Austin T.; Huang, Kuang-Han; Johnson, Traci L.; Jones, Christine; Kikuchihara, Shotaro; Lam, Daniel; Lovisari, Lorenzo; Mainali, Ramesh; Oesch, Pascal A.; Ogaz, Sara; Ouchi, Masami; Past, Matthew; Paterno-Mahler, Rachel; Peterson, Avery; Ryan, Russell E.; Sendra-Server, Irene; Stark, Daniel P.; Strait, Victoria; Toft, Sune; Trenti, Michele; Vulcani, Benedetta

2018-05-01

Strong gravitational lensing by galaxy clusters has become a powerful tool for probing the high-redshift universe, magnifying distant and faint background galaxies. Reliable strong-lensing (SL) models are crucial for determining the intrinsic properties of distant, magnified sources and for constructing their luminosity function. We present here the first SL analysis of MACS J0308.9+2645 and PLCK G171.9‑40.7, two massive galaxy clusters imaged with the Hubble Space Telescope, in the framework of the Reionization Lensing Cluster Survey (RELICS). We use the light-traces-mass modeling technique to uncover sets of multiply imaged galaxies and constrain the mass distribution of the clusters. Our SL analysis reveals that both clusters have particularly large Einstein radii (θ E > 30″ for a source redshift of z s = 2), providing fairly large areas with high magnifications, useful for high-redshift galaxy searches (∼2 arcmin2 with μ > 5 to ∼1 arcmin2 with μ > 10, similar to a typical Hubble Frontier Fields cluster). We also find that MACS J0308.9+2645 hosts a promising, apparently bright (J ∼ 23.2–24.6 AB), multiply imaged high-redshift candidate at z ∼ 6.4. These images are among the brightest high-redshift candidates found in RELICS. Our mass models, including magnification maps, are made publicly available for the community through the Mikulski Archive for Space Telescopes.

Gone with the heat: a fundamental constraint on the imaging of dust and molecular gas in the early Universe

PubMed Central

Zhang, Zhi-Yu; Smith, M. W. L.; Xilouris, Emmanuel M.

2016-01-01

Images of dust continuum and carbon monoxide (CO) line emission are powerful tools for deducing structural characteristics of galaxies, such as disc sizes, H2 gas velocity fields and enclosed H2 and dynamical masses. We report on a fundamental constraint set by the cosmic microwave background (CMB) on the observed structural and dynamical characteristics of galaxies, as deduced from dust continuum and CO-line imaging at high redshifts. As the CMB temperature rises in the distant Universe, the ensuing thermal equilibrium between the CMB and the cold dust and H2 gas progressively erases all spatial and spectral contrasts between their brightness distributions and the CMB. For high-redshift galaxies, this strongly biases the recoverable H2 gas and dust mass distributions, scale lengths, gas velocity fields and dynamical mass estimates. This limitation is unique to millimetre/submillimetre wavelengths and unlike its known effect on the global dust continuum and molecular line emission of galaxies, it cannot be addressed simply. We nevertheless identify a unique signature of CMB-affected continuum brightness distributions, namely an increasing rather than diminishing contrast between such brightness distributions and the CMB when the cold dust in distant galaxies is imaged at frequencies beyond the Raleigh–Jeans limit. For the molecular gas tracers, the same effect makes the atomic carbon lines maintain a larger contrast than the CO lines against the CMB. PMID:27429763

A Search for H(alpha) Emission in the Far Outer Discs of Extremely Large Spiral Galaxies

NASA Astrophysics Data System (ADS)

Rubin, Vera; Hunter, Deidre

2007-08-01

Little is known about the kinematics of galaxies far beyond the relatively bright regions sampled in radio or optical radial velocity studies. Most often, the velocities are obtained as part of large surveys, where the effort is made to obtain many rotation curves, rather than to extend a rotation curve as far as possible. Because the composition of dark matter remains unknown, it is important to devise observations that will help to constrain its properties. We propose to obtain ultra-deep Hα images (in the rest frame of the galaxy) for UGC 2885 and NGC 801, two extremely large Sc galaxies. We expect to detect Hα regions far beyond their nuclei and into the extreme outer disc, for which we will then obtain radial velocities. Increased knowledge concerning the kinematics of these galaxies will tighten the constraints on mass models, and shed light on the properties of dark matter. Ultimately, we hope to learn more about the outermost galaxy, where disc and halo blend.

Extragalactic Supergiants

NASA Astrophysics Data System (ADS)

Urbaneja, Miguel A.; Kudritzki, Rolf P.

2017-11-01

Blue supergiant stars of B and A spectral types are amongst the visually brightest non-transient astronomical objects. Their intrinsic brightness makes it possible to obtain high quality optical spectra of these objects in distant galaxies, enabling the study not only of these stars in different environments, but also to use them as tools to probe their host galaxies. Quantitative analysis of their optical spectra provide tight constraints on their evolution in a wide range of metallicities, as well as on the present-day chemical composition, extinction laws and distances to their host galaxies. We review in this contribution recent results in this field.

The Evolution of Spiral Disks

NASA Astrophysics Data System (ADS)

Bershady, Matthew A.; Andersen, David R.

We report on aspects of an observational study to probe the mass assembly of large galaxy disks. In this contribution we focus on a new survey of integral-field Hα velocity-maps of nearby, face on disks. Preliminary results yield disk asymmetry amplitudes consistent with estimates based on the scatter in the local Tully-Fisher relation. We also show how the high quality of integral-field echelle spectroscopy enables determinations of kinematic inclinations to i ~20 °. This holds the promise that nearly-face-on galaxies can be included in the Tully-Fisher relation. Finally, we discuss the prospects for measuring dynamical asymmetries of distant galaxies.

A Cosmic Baby-Boom

NASA Astrophysics Data System (ADS)

2005-09-01

Large Population of Galaxies Found in the Young Universe with ESO's VLT The Universe was a more fertile place soon after it was formed than has previously been suspected. A team of French and Italian astronomers [1] made indeed the surprising discovery of a large and unknown population of distant galaxies observed when the Universe was only 10 to 30% its present age. ESO PR Photo 29a/05 ESO PR Photo 29a/05 New Population of Distant Galaxies [Preview - JPEG: 400 x 424 pix - 191k] [Normal - JPEG: 800 x 847 pix - 449k] [HiRes - JPEG: 2269 x 2402 pix - 2.0M] ESO PR Photo 29b/05 ESO PR Photo 29b/05 Average Spectra of Distant Galaxies [Preview - JPEG: 400 x 506 pix - 141k] [Normal - JPEG: 800 x 1012 pix - 320k] This breakthrough is based on observations made with the Visible Multi-Object Spectrograph (VIMOS) as part of the VIMOS VLT Deep Survey (VVDS). The VVDS started early 2002 on Melipal, one of the 8.2-m telescopes of ESO's Very Large Telescope Array [2]. In a total sample of about 8,000 galaxies selected only on the basis of their observed brightness in red light, almost 1,000 bright and vigorously star forming galaxies were discovered that were formed between 9 and 12 billion years ago (i.e. about 1,500 to 4,500 million years after the Big Bang). "To our surprise, says Olivier Le Fèvre, from the Laboratoire d'Astrophysique de Marseille (France) and co-leader of the VVDS project, "this is two to six times higher than had been found previously. These galaxies had been missed because previous surveys had selected objects in a much more restrictive manner than we did. And they did so to accommodate the much lower efficiency of the previous generation of instruments." While observations and models have consistently indicated that the Universe had not yet formed many stars in the first billion years of cosmic time, the discovery announced today by scientists calls for a significant change in this picture. The astronomers indeed find that stars formed two to three times faster than previously estimated. "These observations will demand a profound reassessment of our theories of the formation and evolution of galaxies in a changing Universe", says Gianpaolo Vettolani, the other co-leader of the VVDS project, working at INAF-IRA in Bologna (Italy). These results are reported in the September 22 issue of the journal Nature (Le Fèvre et al., "A large population of galaxies 9 to 12 billion years back in the life of the Universe").

KSC-08pd2451

NASA Image and Video Library

2008-08-16

CAPE CANAVERAL, Fla. – Technicians in the Payload Hazardous Servicing Facility complete removal of the protective cover from the Wide Field Camera 3, or WFC3. The WFC3 is part of the payload on space shuttle Atlantis for the fifth and final Hubble servicing mission, STS-125. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2393

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane is moved above the Wide Field Camera 3, or WFC3, for attachment. The WFC3 will be lifted and transferred to a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2453

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians check the Wide Field Camera 3, or WFC3, after removal of its protective cover. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2454

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians check the Wide Field Camera 3, or WFC3, after removal of its protective cover. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2474

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Wide Field Camera 3, or WFC3, is lowered onto the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2472

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Wide Field Camera 3, or WFC3, is moved toward the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2473

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Wide Field Camera 3, or WFC3, is lowered toward the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2471

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane lifts the Wide Field Camera 3, or WFC3, above the stand holding the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2458

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Wide Field Camera 3, or WFC3, is ready to be transferred to the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2448

NASA Image and Video Library

2008-08-16

CAPE CANAVERAL, Fla. – The Wide Field Camera 3, or WFC3, rests on a work stand in the Payload Hazardous Servicing Facility since its arrival Aug. 12. WFC3 is part of the payload on space shuttle Atlantis for the fifth and final Hubble servicing mission, STS-125. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2394

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane begins to lift the Wide Field Camera 3, or WFC3, from the base of the shipping container. The WFC3 will be transferred to a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2395

NASA Image and Video Library

2008-08-12

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane lifts the Wide Field Camera 3, or WFC3, from the base of the shipping container. The WFC3 will be transferred to a work stand. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. WFC3 is part of the payload on the fifth and final Hubble servicing mission, STS-125, targeted for launch Oct. 8. Photo credit: NASA/Jack Pfaller

KSC-08pd2452

NASA Image and Video Library

2008-08-16

CAPE CANAVERAL, Fla. – Technicians in the Payload Hazardous Servicing Facility complete removal of the protective cover from the Wide Field Camera 3, or WFC3. The WFC3 is part of the payload on space shuttle Atlantis for the fifth and final Hubble servicing mission, STS-125. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Jack Pfaller

Surprise Discovery of Highly Developed Structure in the Young Universe

NASA Astrophysics Data System (ADS)

2005-03-01

ESO-VLT and ESA XMM-Newton Together Discover Earliest Massive Cluster of Galaxies Known Summary Combining observations with ESO's Very Large Telescope and ESA's XMM-Newton X-ray observatory, astronomers have discovered the most distant, very massive structure in the Universe known so far. It is a remote cluster of galaxies that is found to weigh as much as several thousand galaxies like our own Milky Way and is located no less than 9,000 million light-years away. The VLT images reveal that it contains reddish and elliptical, i.e. old, galaxies. Interestingly, the cluster itself appears to be in a very advanced state of development. It must therefore have formed when the Universe was less than one third of its present age. The discovery of such a complex and mature structure so early in the history of the Universe is highly surprising. Indeed, until recently it would even have been deemed impossible. PR Photo 05a/05: Discovery X-Ray Image of the Distant Cluster (ESA XMM-Netwon) PR Photo 05b/05: False Colour Image of XMMU J2235.3-2557 (FORS/VLT and ESA XMM-Newton) Serendipitous discovery ESO PR Photo 05a/05 ESO PR Photo 05a/05 Discovery X-Ray Image of the Distant Cluster (ESA XMM-Newton) [Preview - JPEG: 400 x 421 pix - 106k] [Normal - JPEG: 800 x 842 pix - 843k] [Full Res - JPEG: 2149 x 2262 pix - 2.5M] Caption: ESO PR Photo 05a/05 is a reproduction of the XMM-Newton observations of the nearby active galaxy NGC7314 (bright object in the centre) from which the newly found distant cluster (white box) was serendipitously identified. The circular field-of-view of XMM-Newton is half-a-degree in diameter, or about the same angular size as the Full Moon. The inset shows the diffuse X-ray emission from the distant cluster XMMU J2235.3-2557. Clusters of galaxies are gigantic structures containing hundreds to thousands of galaxies. They are the fundamental building blocks of the Universe and their study thus provides unique information about the underlying architecture of the Universe as a whole. About one-fifth of the optically invisible mass of a cluster is in the form of a diffuse, very hot gas with a temperature of several tens of millions of degrees. This gas emits powerful X-ray radiation and clusters of galaxies are therefore best discovered by means of X-ray satellites (cf. ESO PR 18/03 and 15/04). It is for this reason that a team of astronomers [1] has initiated a search for distant, X-ray luminous clusters "lying dormant" in archive data from ESA's XMM-Newton satellite observatory. Studying XMM-Newton observations targeted at the nearby active galaxy NGC 7314, the astronomers found evidence of a galaxy cluster in the background, far out in space. This source, now named XMMU J2235.3-2557, appeared extended and very faint: no more than 280 X-ray photons were detected over the entire 12 hour-long observations. A Mature Cluster at Redshift 1.4 ESO PR Photo 05b/05 ESO PR Photo 05b/05 False Colour Image of XMMU J2235.3-2557 (FORS/VLT and ESA XMM-Newton) [Preview - JPEG: 400 x 455 pix - 50k] [Normal - JPEG: 800 x 909 pix - 564k] [Full Res - JPEG: 1599 x 1816 pix - 1.5M] Caption: ESO PR Photo 05b/05 is a false colour image of the XMMU J2235.3-2557 cluster of galaxies, overlaid with the X-ray intensity contours derived from the ESA XMM-Newton data. The red channel is a VLT-ISAAC image (exposure time: 1 hour) obtained in the near-infrared Ks-band (at wavelength 2.2 microns); the green channel is a VLT-FORS2 z-band image (910 nm; 480 sec); the blue channel is a VLT-FORS2 R-band image (; 657 nm; 1140 sec). The VLT reveals 12 reddish galaxies, of elliptical types, as members of the cluster. Knowing where to look, the astronomers then used the European Southern Observatory's Very Large Telescope (VLT) at Paranal (Chile) to obtain images in the visible wavelength region. They confirmed the nature of this cluster and it was possible to identify 12 comparatively bright member galaxies on the images (see ESO PR Photo 05b/05). The galaxies appear reddish and are of the elliptical type. They are full of old, red stars. All of this indicates that these galaxies are already several thousand million years old. Moreover, the cluster itself has a largely spherical shape, also a sign that it is already a very mature structure. In order to determine the distance of the cluster - and hence its age - Christopher Mullis, former European Southern Observatory post-doctoral fellow and now at the University of Michigan in the USA, and his colleagues used again the VLT, now in the spectroscopic mode. By means of one of the FORS multi-mode instruments, the astronomers zoomed-in on the individual galaxies in the field, taking spectral measurements that reveal their overall characteristics, in particular their redshift and hence, distance [2]. The FORS instruments are among the most efficient and versatile available anywhere for this delicate work, obtaining on the average quite detailed spectra of 30 or more galaxies at a time. The VLT data measured the redshift of this cluster as 1.4, indicating a distance of 9,000 million light-years, 500 million light years farther out than the previous record holding cluster. This means that the present cluster must have formed when the Universe was less than one third of its present age. The Universe is now believed to be 13,700 million years old. "We are quite surprised to see that a fully-fledged structure like this could exist at such an early epoch," says Christopher Mullis. "We see an entire network of stars and galaxies in place, just a few thousand million years after the Big Bang". "We seem to have underestimated how quickly the early Universe matured into its present-day state," adds Piero Rosati of ESO, another member of the team. "The Universe did grow up fast!" Towards a Larger Sample This discovery was relative easy to make, once the space-based XMM and the ground-based VLT observations were combined. As an impressive result of the present pilot programme that is specifically focused on the identification of very distant galaxy clusters, it makes the astronomers very optimistic about their future searches. The team is now carrying out detailed follow-up observations both from ground- and space-based observatories. They hope to find many more exceedingly distant clusters, which would then allow them to test competing theories of the formation and evolution of such large structures. "This discovery encourages us to search for additional distant clusters by means of this very efficient technique," says Axel Schwope, team leader at the Astrophysical Institute Potsdam (Germany) and responsible for the source detection from the XMM-Newton archival data. Hans Böhringer of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, another member of the team, adds: "Our result also confirms the great promise inherent in other facilities to come, such as APEX (Atacama Pathfinder Experiment) at Chajnantor, the site of the future Atacama Large Millimeter Array. These intense searches will ultimately place strong constraints on some of the most fundamental properties of the Universe." More information This finding is presented today by Christopher Mullis at a scientific meeting in Kona, Hawaii, entitled "The Future of Cosmology with Clusters of Galaxies". It will also soon appear in The Astrophysical Journal ("Discovery of an X-ray Luminous Galaxy Cluster at z=1.4", by C. R. Mullis et al.). More images and information is available on Christopher Mullis' dedicated web page at http://www.astro.lsa.umich.edu/~cmullis/research/xmmuj2235/. A German version of the press release is issued by the Max Planck Society and is available at http://www.mpg.de/bilderBerichteDokumente/dokumentation/pressemitteilungen/2005/pressemitteilung20050228/presselogin/ .

Cosmic strings in the real sky

NASA Technical Reports Server (NTRS)

Hogan, Craig J.

1987-01-01

Observational strategies for finding effects associated with the gravitational lensing of distant objects by strings are discussed. In particular, a proposed search program at Steward Observatory to find chains of Galaxy image pairs is described.

A Deep Chandra Observation of the Distant Galaxy Cluster MS 1137.5+6625

NASA Astrophysics Data System (ADS)

Grego, Laura; Vrtilek, J. M.; Van Speybroeck, Leon; David, Laurence P.; Forman, William; Carlstrom, John E.; Reese, Erik D.; Joy, Marshall K.

2004-06-01

We present results from a deep Chandra observation of MS 1137.5+66, a distant (z=0.783) and massive cluster of galaxies. Only a few similarly massive clusters are currently known at such high redshifts; accordingly, this observation provides much needed information on the dynamical state of these rare systems. The cluster appears both regular and symmetric in the X-ray image. However, our analysis of the spectral and spatial X-ray data in conjunction with interferometric Sunyaev-Zel'dovich effect data and published deep optical imaging suggests that the cluster has a fairly complex structure. The angular diameter distance we calculate from the Chandra and Sunyaev-Zel'dovich effect data assuming an isothermal, spherically symmetric cluster implies a low value for the Hubble constant for which we explore possible explanations.

Clumpy Galaxies in CANDELS. II. Physical Properties of UV-bright Clumps at 0.5 ≤ z < 3

NASA Astrophysics Data System (ADS)

Guo, Yicheng; Rafelski, Marc; Bell, Eric F.; Conselice, Christopher J.; Dekel, Avishai; Faber, S. M.; Giavalisco, Mauro; Koekemoer, Anton M.; Koo, David C.; Lu, Yu; Mandelker, Nir; Primack, Joel R.; Ceverino, Daniel; de Mello, Duilia F.; Ferguson, Henry C.; Hathi, Nimish; Kocevski, Dale; Lucas, Ray A.; Pérez-González, Pablo G.; Ravindranath, Swara; Soto, Emmaris; Straughn, Amber; Wang, Weichen

2018-02-01

Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed “clumps” in distant galaxies are the same phenomenon that is seen in simulations. In this paper, as a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed “clumps” in the literature. This sample contains 3193 clumps detected from 1270 galaxies at 0.5≤slant z< 3.0. The clumps are detected from rest-frame UV images, as described in our previous paper. Their physical properties (e.g., rest-frame color, stellar mass ({M}* ), star formation rate (SFR), age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U ‑ V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and {M}* of the host galaxies: at a fixed {M}* , the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with {M}* . Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B ‑ V) gradient, and a positive specific SFR gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.

Physical Properties of UV-bright Clumps in Star-forming Galaxies at 0.5 ≤ z < 3

NASA Astrophysics Data System (ADS)

Guo, Yicheng; Rafelski, Marc; Bell, Eric F.; Dekel, Avishai; Mandelker, Nir; Primack, Joel R.; CANDELS

2018-06-01

Studying giant star-forming clumps in distant galaxies is important to understand galaxy formation and evolution. At present, however, observers and theorists have not reached a consensus on whether the observed “clumps” in distant galaxies are the same phenomenon that is seen in simulations. As a step to establish a benchmark of direct comparisons between observations and theories, we publish a sample of clumps constructed to represent the commonly observed “clumps” in the literature. This sample contains 3193 clumps detected from the rest-frame images of 1270 galaxies at 0.5≤z<3.0. The physical properties of clumps (e.g., rest-frame color, stellar mass, star formation rate, age, and dust extinction) are measured by fitting the spectral energy distribution (SED) to synthetic stellar population models. We carefully test the procedures of measuring clump properties, especially the method of subtracting background fluxes from the diffuse component of galaxies. With our fiducial background subtraction, we find a radial clump U-V color variation, where clumps close to galactic centers are redder than those in outskirts. The slope of the color gradient (clump color as a function of their galactocentric distance scaled by the semimajor axis of galaxies) changes with redshift and stellar mass of the host galaxies: at a fixed stellar mass, the slope becomes steeper toward low redshift, and at a fixed redshift, it becomes slightly steeper with stellar mass. Based on our SED fitting, this observed color gradient can be explained by a combination of a negative age gradient, a negative E(B-V) gradient, and a positive specific star formation rate gradient of the clumps. We also find that the color gradients of clumps are steeper than those of intra-clump regions. Correspondingly, the radial gradients of the derived physical properties of clumps are different from those of the diffuse component or intra-clump regions.

The Multiwavelength Survey by Yale-Chile (MUSYC): Deep Near-Infrared Imaging and the Selection of Distant Galaxies

NASA Astrophysics Data System (ADS)

Quadri, Ryan; Marchesini, Danilo; van Dokkum, Pieter; Gawiser, Eric; Franx, Marijn; Lira, Paulina; Rudnick, Gregory; Urry, C. Megan; Maza, José; Kriek, Mariska; Barrientos, L. Felipe; Blanc, Guillermo A.; Castander, Francisco J.; Christlein, Daniel; Coppi, Paolo S.; Hall, Patrick B.; Herrera, David; Infante, Leopoldo; Taylor, Edward N.; Treister, Ezequiel; Willis, Jon P.

2007-09-01

We present deep near-infrared JHK imaging of four 10' × 10' fields. The observations were carried out as part of the Multiwavelength Survey by Yale-Chile (MUSYC) with ISPI on the CTIO 4 m telescope. The typical point-source limiting depths are J ~ 22.5, H ~ 21.5, and K ~ 21 (5 σ Vega). The effective seeing in the final images is ~1.0″. We combine these data with MUSYC UBVRIz imaging to create K-selected catalogs that are unique for their uniform size, depth, filter coverage, and image quality. We investigate the rest-frame optical colors and photometric redshifts of galaxies that are selected using common color selection techniques, including distant red galaxies (DRGs), star-forming and passive BzKs, and the rest-frame UV-selected BM, BX, and Lyman break galaxies (LBGs). These techniques are effective at isolating large samples of high-redshift galaxies, but none provide complete or uniform samples across the targeted redshift ranges. The DRG and BM/BX/LBG criteria identify populations of red and blue galaxies, respectively, as they were designed to do. The star-forming BzKs have a very wide redshift distribution, extending down to z ~ 1, a wide range of colors, and may include galaxies with very low specific star formation rates. In comparison, the passive BzKs are fewer in number, have a different distribution of K magnitudes, and have a somewhat different redshift distribution. By combining either the DRG and BM/BX/LBG criteria, or the star-forming and passive BzK criteria, it appears possible to define a reasonably complete sample of galaxies to our flux limit over specific redshift ranges. However, the redshift dependence of both the completeness and sampled range of rest-frame colors poses an ultimate limit to the usefulness of these techniques.

A COMPARISON OF GALAXY COUNTING TECHNIQUES IN SPECTROSCOPICALLY UNDERSAMPLED REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Specian, Mike A.; Szalay, Alex S., E-mail: mspecia1@jhu.edu, E-mail: szalay@jhu.edu

2016-11-01

Accurate measures of galactic overdensities are invaluable for precision cosmology. Obtaining these measurements is complicated when members of one’s galaxy sample lack radial depths, most commonly derived via spectroscopic redshifts. In this paper, we utilize the Sloan Digital Sky Survey’s Main Galaxy Sample to compare seven methods of counting galaxies in cells when many of those galaxies lack redshifts. These methods fall into three categories: assigning galaxies discrete redshifts, scaling the numbers counted using regions’ spectroscopic completeness properties, and employing probabilistic techniques. We split spectroscopically undersampled regions into three types—those inside the spectroscopic footprint, those outside but adjacent to it,more » and those distant from it. Through Monte Carlo simulations, we demonstrate that the preferred counting techniques are a function of region type, cell size, and redshift. We conclude by reporting optimal counting strategies under a variety of conditions.« less

Rotation in [C II]-emitting gas in two galaxies at a redshift of 6.8

NASA Astrophysics Data System (ADS)

Smit, Renske; Bouwens, Rychard J.; Carniani, Stefano; Oesch, Pascal A.; Labbé, Ivo; Illingworth, Garth D.; van der Werf, Paul; Bradley, Larry D.; Gonzalez, Valentino; Hodge, Jacqueline A.; Holwerda, Benne W.; Maiolino, Roberto; Zheng, Wei

2018-01-01

The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this ‘epoch of reionization’ involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C II] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C II] luminosities than would be expected from local scaling relations, and searches for the [C II] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C II] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C II] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C II] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation-dominated disks that have been observed in Hα-emitting galaxies two billion years later, at ‘cosmic noon’.

Rotation in [C ii]-emitting gas in two galaxies at a redshift of 6.8.

PubMed

Smit, Renske; Bouwens, Rychard J; Carniani, Stefano; Oesch, Pascal A; Labbé, Ivo; Illingworth, Garth D; van der Werf, Paul; Bradley, Larry D; Gonzalez, Valentino; Hodge, Jacqueline A; Holwerda, Benne W; Maiolino, Roberto; Zheng, Wei

2018-01-10

The earliest galaxies are thought to have emerged during the first billion years of cosmic history, initiating the ionization of the neutral hydrogen that pervaded the Universe at this time. Studying this 'epoch of reionization' involves looking for the spectral signatures of ancient galaxies that are, owing to the expansion of the Universe, now very distant from Earth and therefore exhibit large redshifts. However, finding these spectral fingerprints is challenging. One spectral characteristic of ancient and distant galaxies is strong hydrogen-emission lines (known as Lyman-α lines), but the neutral intergalactic medium that was present early in the epoch of reionization scatters such Lyman-α photons. Another potential spectral identifier is the line at wavelength 157.4 micrometres of the singly ionized state of carbon (the [C ii] λ = 157.74 μm line), which signifies cooling gas and is expected to have been bright in the early Universe. However, so far Lyman-α-emitting galaxies from the epoch of reionization have demonstrated much fainter [C ii] luminosities than would be expected from local scaling relations, and searches for the [C ii] line in sources without Lyman-α emission but with photometric redshifts greater than 6 (corresponding to the first billion years of the Universe) have been unsuccessful. Here we identify [C ii] λ = 157.74 μm emission from two sources that we selected as high-redshift candidates on the basis of near-infrared photometry; we confirm that these sources are two galaxies at redshifts of z = 6.8540 ± 0.0003 and z = 6.8076 ± 0.0002. Notably, the luminosity of the [C ii] line from these galaxies is higher than that found previously in star-forming galaxies with redshifts greater than 6.5. The luminous and extended [C ii] lines reveal clear velocity gradients that, if interpreted as rotation, would indicate that these galaxies have similar dynamic properties to the turbulent yet rotation-dominated disks that have been observed in Hα-emitting galaxies two billion years later, at 'cosmic noon'.

New Constraints on the Faint End of the UV Luminosity Function at z ~ 7-8 Using the Gravitational Lensing of the Hubble Frontier Fields Cluster A2744

NASA Astrophysics Data System (ADS)

Atek, Hakim; Richard, Johan; Kneib, Jean-Paul; Jauzac, Mathilde; Schaerer, Daniel; Clement, Benjamin; Limousin, Marceau; Jullo, Eric; Natarajan, Priyamvada; Egami, Eiichi; Ebeling, Harald

2015-02-01

Exploiting the power of gravitational lensing, the Hubble Frontier Fields (HFF) program aims at observing six massive galaxy clusters to explore the distant universe far beyond the limits of blank field surveys. Using the complete Hubble Space Telescope observations of the first HFF cluster A2744, we report the detection of 50 galaxy candidates at z ~ 7 and eight candidates at z ~ 8 in a total survey area of 0.96 arcmin2 in the source plane. Three of these galaxies are multiply imaged by the lensing cluster. Using an updated model of the mass distribution in the cluster we were able to calculate the magnification factor and the effective survey volume for each galaxy in order to compute the ultraviolet galaxy luminosity function (LF) at both redshifts 7 and 8. Our new measurements reliably extend the z ~ 7 UV LF down to an absolute magnitude of M UV ~ -15.5. We find a characteristic magnitude of M\\star UV = -20.90+0.90-0.73 mag and a faint-end slope α =-2.01+0.20-0.28, close to previous determinations in blank fields. We show here for the first time that this slope remains steep down to very faint luminosities of 0.01 L sstarf. Although prone to large uncertainties, our results at z ~ 8 also seem to confirm a steep faint-end slope below 0.1 L sstarf. The HFF program is therefore providing an extremely efficient way to study the faintest galaxy populations at z > 7 that would otherwise be inaccessible with current instrumentation. The full sample of six galaxy clusters will provide even better constraints on the buildup of galaxies at early epochs and their contribution to cosmic reionization. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 13495, 11386, 13389, and 11689. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. The Hubble Frontier Fields data were obtained from the Mikulski Archive for Space Telescopes (MAST).

Giant Gas Cloud Made of Atoms Formed in First Stars Revealed in Universe's Most Distant Quasar

NASA Astrophysics Data System (ADS)

2003-07-01

Astronomers studying the most distant quasar yet found in the Universe have discovered a massive reservoir of gas containing atoms made in the cores of some of the first stars ever formed. The carbon-monoxide gas was revealed by the National Science Foundation's Very Large Array (VLA) and the Plateau de Bure radio interferometer in Europe. The gas, along with the young galaxy containing it, is seen as it was when the Universe was only one-sixteenth its current age, just emerging from the primeval "Dark Ages" before light could travel freely through the cosmos. VLA Image of Quasar VLA Image of J1148+5251 CREDIT: NRAO/AUI/NSF (Click on Image for Larger Version) "Our discovery of this much carbon monoxide gas in such an extremely distant and young galaxy is surprising. It means that, even at a very early time in the history of the Universe, galaxies already had huge amounts of molecular gas that would eventually form new generations of stars," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The distant galaxy, dubbed J1148+5251, contains a bright quasar powered by a black hole at least a billion times more massive than the Sun. The galaxy is seen as it was only 870 million years after the Big Bang. The Universe now is 13.7 billion years old. J1148+5251 would have been among the first luminous objects in the Universe. The original atoms formed in the Universe within the first three minutes of the Big Bang were only hydrogen and helium. Carbon and oxygen -- the atoms making up carbon monoxide -- had to be made in the thermonuclear furnaces at the cores of the earliest stars. "The carbon and oxygen atoms in the gas we detected were made by some of the first stars ever formed, only about 650 million years after the Big Bang. In the next 200 million years or so, those stars -- probably very different stars from those we see today -- exploded as supernovae, spreading the carbon and oxygen out into space. Those atoms then cooled and combined into the carbon monoxide molecules we detected with our radio telescopes," said Fabian Walter, a Jansky Postdoctoral Fellow at the NRAO. Walter is lead author of a research paper in the July 24 issue of the scientific journal Nature, and, with Carilli and K.Y. Lo of NRAO, did the VLA observations. Frank Bertoldi of the Max-Planck Institute in Germany and Pierre Cox of the Institute of Space Astrophysics in Orsay, France, led the collaborators using the Plateau de Bure telescope. J1148+5251 Timeline Time Since Big Bang Event <300,000 years Universe Fully Ionized 300,000 years Hot charged particles cool and combine into neutral atoms; Universe becomes opaque; "Dark Ages" begin. ~200 million years First luminous objects form; Reionization begins. ~650 million years Stars forming in galaxy J1148+5251; Make carbon, oxygen atoms and begin to blast these atoms into interstellar space 870 million years J1148+5251 has accumulated massive reservoir of cool molecular gas containing Carbon Monoxide (CO) molecules; Radio waves from these molecules begin their journey to Earth. One billion years Reionization complete; Universe is transparent, ending "Dark Ages." 13.7 billion years Radio waves from J1148+5251's CO molecules arrive at radio telescopes on Earth. The discovery gives scientists a tantalizing direct view of one of the earliest galaxies in the young Universe, and raises questions about the nature of the first stars and how galaxies and quasars formed. "The Universe in which this galaxy existed is a very different Universe from the one we know today," Walter said. For about 300,000 years after the Big Bang, the Universe was filled with very hot gas which eventually became protons and electrons. Then, through expansion, the Universe cooled and the protons and electrons combined into neutral atoms that absorbed light and other forms of electromagnetic radiation. This period, from 300,000 years after the Big Bang, until a few hundred million years later when the first stars and galaxies began forming, is known as the cosmic Dark Ages. As the first stars and galaxies formed, intense radiation from the stars began to break apart -- or ionize -- the neutral atoms, allowing light once again to pass. As each new star's radiation ionized interstellar atoms, it formed a transparent "bubble" in the opaque Universe. The Universe began to resemble a cosmic Swiss cheese, with the holes growing larger until, about a billion years after the Big Bang, the holes all met each other and the Universe became fully transparent once again. This period is known as the Reionization Era of the Universe. In fact, combining the radio observations with data from optical telescopes shows that the transparent "bubble" around J1148+5251 is about 30 million light-years in diameter. "This is direct evidence that we are seeing this object helping reionize the Universe," Walter said. The amount of molecular gas in the galaxy -- a mass more than 10 billion times that of the Sun -- tells the scientists that things were happening quickly in the early Universe. "This is as much mass as we see in big galaxies today, and it had little time, astronomically speaking, to accumulate," said Carilli. Also, the most popular theory for how big galaxies formed is that they were built up over long spans of time by multiple mergers of smaller galaxies. "That's why it's so surprising to see such a massive galaxy so early in the Universe," said Walter. Studies of J1148+5251 and other distant objects yet to be discovered will help scientists find the answers to their questions about the Universe's early stars and galaxies. The radio observations of J1148+5251 gave astronomers a look at the galaxy itself, Walter emphasized, while optical telescopes showed only light coming from the bright quasar "engine" at the galaxy's core. Walter added that more VLA observations now being planned are aimed at producing an image of the young galaxy. Discovery Image of J1148+5251 SDSS Discovery Image of J1148+5251: Quasar is Red Dot Pointed Out by Arrow CREDIT: Sloan Digital Sky Survey At Apache Point Observatory (Click on Image for Larger Version) In addition, Walter also looks forward to studying other objects deeper into the era of reionization, both with the expanded VLA (EVLA) and with the Atacama Large Millimeter Array (ALMA), a joint North America-Europe project to be built in Chile. "With the EVLA and ALMA, we will be able to study the structures and dynamics of similar systems in great detail," Walter said. J1148+5251 was discovered by the Sloan Digital Sky Survey, using a 2.5-meter optical telescope at Apache Point, NM, earlier this year. At a distance of more than 12.8 billion light-years, it is the most distant quasar yet found in the Universe. Followup observations at the W.M. Keck Observatory in Hawaii showed a clear signature of light absorption indicating that the object is seen at the end of the reionization era. This signature, found using a spectroscope to analyze light from the object, is known as the Gunn-Peterson Effect, after James Gunn and Bruce Peterson, who predicted it in 1965. The carbon monoxide gas was found using radio telescopes that detected radio waves emitted by the gas molecules. The wavelength of this radio emission was greatly increased by the Doppler Effect produced by the expansion of the Universe. For example, at the great distance of J1148+5251, waves that left the galaxy with a length of less than one millimeter were received by the VLA at a wavelength of more than six millimeters. In addition to Walter, Carilli and Lo, who used the VLA to observe J1148+5251, other team members led by Bertoldi and Cox used the Institute of Millimeter Radio Astronomy's (IRAM) Plateau de Bure radio interferometer in France. These included Roberto Neri of IRAM; Alain Omont of the Paris Institute of Astrophysics; and Karl Menten of Germany's Max Planck Instutute for Radioastronomy. Xiaohui Fan of the University of Arizona's Steward Observatory and Michael Strauss of Princeton University were the Sloan Digital Sky Survey collaborators on the Nature paper. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

DISTANT CLUSTER OF GALAXIES [left

NASA Technical Reports Server (NTRS)

2002-01-01

One of the deepest images to date of the universe, taken with NASA's Hubble Space Telescope (HST), reveals thousands of faint galaxies at the detection limit of present day telescopes. Peering across a large volume of the observable cosmos, Hubble resolves thousands of galaxies from five to twelve billion light-years away. The light from these remote objects has taken billions of years to cross the expanding universe, making these distant galaxies fossil evidence' of events that happened when the universe was one-third its present age. A fraction of the galaxies in this image belong to a cluster located nine billion light-years away. Though the field of view (at the cluster's distance) is only two million light-years across, it contains a multitude of fragmentary objects. (By comparison, the two million light-years between our Milky Way galaxy and its nearest large companion galaxy, in the constellation Andromeda, is essentially empty space!) Very few of the cluster's members are recognizable as normal spiral galaxies (like our Milky Way), although some elongated members might be edge-on disks. Among this zoo of odd galaxies are ``tadpole-like'' objects, disturbed and apparently merging systems dubbed 'train-wrecks,' and a multitude of faint, tiny shards and fragments, dwarf galaxies or possibly an unknown population of objects. However, the cluster also contains red galaxies that resemble mature examples of today's elliptical galaxies. Their red color comes from older stars that must have formed shortly after the Big Bang. The image is the full field view of the Wide Field and Planetary Camera-2. The picture was taken in intervals between May 11 and June 15, 1994 and required an 18-hour long exposure, over 32 orbits of HST, to reveal objects down to 29th magnitude. [bottom right] A close up view of the peculiar radio galaxy 3C324 used to locate the cluster. The galaxy is nine billion light-years away as measured by its spectral redshift (z=1.2), and located in the constellation Serpens. Based on the colors and the statistical distribution of the galaxies in 3C 324's vicinity, astronomers conclude a remote cluster is at the same distance as a radio galaxy. [center right] This pair of elliptical galaxies, seen together with a few fainter companions, is remarkably similar in shape, light distribution, and color to their present day descendants. This Hubble image provides evidence that ellipticals formed remarkably early in the universe. [top right] Some of the objects in this compact tangled group resemble today's spiral galaxies. However, they have irregular shapes and appear disrupted and asymmetric. This might be due to a high frequency of galaxy collisions and close encounters in the early universe. Credit: Mark Dickinson (STScI) and NASA

UVES Investigates the Environment of a Very Remote Galaxy

NASA Astrophysics Data System (ADS)

2002-03-01

Surplus of Intergalactic Material May Be Young Supercluster Summary Observations with ESO's Very Large Telescope (VLT) have enabled an international group of astronomers [1] to study in unprecedented detail the surroundings of a very remote galaxy, almost 12 billion light-years distant [2]. The corresponding light travel time means that it is seen at a moment only about 3 billion years after the Big Bang. This galaxy is designated MS 1512-cB58 and is the brightest known at such a large distance and such an early time. This is due to a lucky circumstance: a massive cluster of galaxies ( MS 1512+36 ) is located about halfway along the line-of-sight, at a distance of about 7 billion light-years, and acts as a gravitational "magnifying glass". Thanks to this lensing effect, the image of MS1512-cB58 appears 50 times brighter . Nevertheless, the apparent brightness is still as faint as magnitude 20.6 (i.e., nearly 1 million times fainter than what can be perceived with the unaided eye). Moreover, MS 1512-cB58 is located 36° north of the celestial equator and never rises more than 29° above the horizon at Paranal. It was therefore a great challenge to secure the present observational data with the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope . The extremely detailed UVES-spectrum of MS 1512-cB58 displays numerous signatures (absorption lines) of intergalactic gas clouds along the line-of-sight . Some of the clouds are quite close to the galaxy and the astronomers have therefore been able to investigate the distribution of matter in its immediate surroundings. They found an excess of material near MS 1512-cB58, possible evidence of a young supercluster of galaxies , already at this very early epoch. The new observations thus provide an invaluable contribution to current studies of the birth and evolution of structures in the early Universe. This is the first time this kind of observation has ever been done of a galaxy at such a large distance . All previous studies were based on much more luminous quasars (QSOs - extremely active galaxy nuclei). However, any investigation of the intergalactic matter around a quasar is complicated by the strong radiation and consequently, high ionization of the gas by the QSO itself, rendering an unbiased assessment of the gas distribution impossible. PR Photo 08a/02 : HST photo of MS 1512-cB58 . PR Photo 08b/02 : UVES spectrum of MS 1512-cB58. PR Photo 08c/02 : UVES spectrum of MS 1512-cB58 ( detail ). Clustering in the Early Universe ESO PR Photo 08a/02 ESO PR Photo 08a/02 [Preview - JPEG: 400 x 614 pix - 304k] [Normal - JPEG: 1200 x 1843 pix - 1.8M] Caption : PR Photo 08a/02 shows the gravitationally amplified, elongated image of the very distant, 20.6-mag galaxy MS 1512-cB58 (indicated with an arrow), as seen in the field of the distant cluster of galaxies MS 1512+36 . The photo is based on exposures with the NASA/ESA Hubble Space Telescope (HST). Technical information about the photo is available below. With new and powerful astronomical telescopes, the exploration of the young Universe is progressing rapidly . By means of highly efficient instruments, scientists are now probing the objects seen at these early times in ever greater detail, painstakingly gaining precious new knowledge about these crucial evolutionary stages. They form an integral part of the long chain of events that has ultimately led to our own existence - no wonder that we would like to know more about those remote times! One of the key questions now asked by cosmologists is how the matter in the early Universe assembled into larger structures . With plenty of gaseous material available, it appears that contraction set in rather soon after the Big Bang, perhaps only a few hundred million years after this initial explosion. Stars and proto-galaxies formed, a web-like structure emerged (cf. ESO PR 11/01 ) and at some moment, these larger building blocks began to gather into "clusters" and "clusters of clusters" (superclusters) . This process took time and it is not yet known when the first major clusters of galaxies formed. However, recent results from the ESO Very Large Telescope at Paranal are casting new light on those early events and may actually provide evidence of an extensive cluster of clouds, perhaps a real supercluster , as early as only 3 billion years after the Big Bang. The lighthouse and the forest In order to investigate the large-scale structure of the Universe, astronomers have since some time employed the powerful technique of spectral analysis of the light from remote "lighthouses" (or "beacons") . One of the strongest spectral lines seen in astronomical objects is the Lyman-alpha line of atomic hydrogen . It is normally seen as a bright spectral peak (an "emission line") in the "lighthouse" object. The rest wavelength is 121.6 nm in the far-ultraviolet part of the spectrum. That spectral region is not accessible to ground-based telescopes - UV-light does not pass through the Earth's atmosphere. However, in very distant objects, the Lyman-alpha line is redshifted towards longer wavelengths and becomes observable from the ground [2]. On its way to us, the light beam from a bright and distant object traverses a long path , mostly through (nearly) empty space. However, once in a while, it passes through a cloud of matter, for instance in the outskirts of a remote galaxy. Each time, specific signatures from the atoms and molecules in that cloud are imprinted on the passing light in the form of spectral absorption lines at particular wavelengths. Such clouds contain hydrogen and thus produce a specific Lyman-alpha signature in the spectrum of the "lighthouse" object [3] Because of the different distances of the individual clouds, their Lyman-alpha spectral lines have different "redshifts" and are therefore observed at different wavelengths. In practice, the Lyman-alpha absorption lines from the intervening clouds are located on the blueward side (i.e., at shorter wavelengths because of their smaller redshifts) of the main emission peak, giving rise to the concept of a "Lyman-alpha forest" of spectral absorption lines. In some cases, over one thousand absorption lines have been seen, showing the presence of as many individual hydrogen-rich gas clouds along the line-of-sight towards the background "lighthouse", cf. ESO PR 15/99 and ESO PR 08/00. MS 1512-cB58 : a bright and remote galaxy MS 1512-cB58 is a remote, very bright galaxy, located at a distance of approximately 12 billion light-years in the northern constellation of Boötes. Its light has travelled 12 billion years to reach us and we therefore observe it as it was when the Universe was about 3 billion years old. Because of the extremely large distance, this galaxy would normally only be seen as a very faint object in the sky, so faint indeed that it could not be observed in any detail by existing telescopes. However, we are lucky, thanks to the fortuitious effect of gravitational lensing . About halfway on its way to us, the light from MS 1512-cB58 happens to pass through the strong gravitational field of a cluster of galaxies known as MS 1512+36 and this produces an amazingly efficient focussing effect: the light from MS 1512-cB58 that finally reaches us has been amplified no less than some 50 times! This beneficial effect makes all the difference. At the observed magnitude of 20.6 - though still nearly 1 million times fainter than what can be perceived with the unaided eye - MS 1512-cB58 is the best suited remote object of its type for the above mentioned kind of investigation. Thus, a detailed study of its spectrum, in particular the spectral region on the shortward side of the Lyman-alpha line (seen in absorption in this comparatively "normal" galaxy), provides very useful information about the many clouds of hydrogen that are located along the line-of-sight towards this object. The UVES spectrum ESO PR Photo 08b/02 ESO PR Photo 08b/02 [Preview - JPEG: 512 x 400 pix - 184k] [Normal - JPEG: 1023 x 800 pix - 448k] ESO PR Photo 08c/02 ESO PR Photo 08c/02 [Preview - JPEG: 750 x 400 pix - 136k] [Normal - JPEG: 1500 x 800 pix - 288k] Caption : PR Photo 08b/02 shows a section of the UVES spectrum of the very distant, 20.6-mag galaxy MS 1512-cB58 , obtained with the UVES high-dispersion spectrograph at the VLT KUEYEN telescope. The Lyman-alpha absorption line from the galaxy itself is seen as the broad depression at about 4530 Å (453 nm; lower panel). The absorption lines at shorter wavelengths are the signatures of individual intergalactic clouds along the line-of-sight; they are indicated by red vertical lines. Blue arrows point at absorption lines associated with heavy elements present in the gas inside the MS 1512-cB58 galaxy. PR Photo 08c/02 is an enlargement of a small wavelength region that shows the full resolution and extreme wealth of information contained in the spectrum of this faint object. Also here, Lyman-alpha absorption lines arising in intervening intergalactic clouds are indicated by red vertical lines. Technical information about the photos is available below. Using one of the most efficient astronomical spectrographs available, the Ultraviolet-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT) at the Paranal Observatory , an international group of astronomers [1] succeeded in obtaining a very detailed (high-dispersion) spectrum of MS 1512-cB58 . Despite the fact that this object is located some 36° north of the celestial equator and can therefore only be observed for about 90 min each night from Paranal (at geographical latitude 25° south), the superposition of several exposures obtained between March and August 2000 has produced the most detailed and informative spectrum ever obtained of a distant galaxy, cf. PR Photos 08b-c/02 . At the same time, it provides a very comprehensive map of the Universe to such a large distance along a line-of-sight , as this can be read from the numerous Lyman-alpha absorption lines from intervening clouds, seen in this spectrum. The surroundings of MS 1512-cB58 The astronomers were particularly interested in the distribution of clouds in the region of space near MS 1512-cB58 . Thanks to the excellent quality of the UVES data, it was possible to identify and measure a substantial number of Lyman-alpha lines blueward of the broad Lyman-alpha absorption line from the galaxy itself, present in the lower panel of PR Photo 08b/01 . They correspond to intergalactic hydrogen clouds comparatively near the "lighthouse" object MS 1512-cB58 . Most interestingly, it turned out that there are exceptionally many such clouds rather near this remote galaxy (the corresponding absorption lines are seen in the middle panel of PR Photo 08b/01 of which a small part has been enlarged for clarity in PR Photo 08c/01 . Comparing with the mean density along the line-of-sight, a surplus of about 200% was evident. An effect of this dimension has never been seen before near such a remote object, i.e., at such an early epoch, only 3 billion years after the Big Bang. A young supercluster? What does this tell us? The astronomers have two explanations: either we are seeing a very large cluster of clouds (proto-galaxies) at some distance from MS 1512-cB58 , or the clouds are in some way directly connected to the environment of that galaxy. A rich distribution of gas clouds is indeed expected around star-forming galaxies like MS 1512-cB58 at this early epoch. For various reasons, however, including the actual distribution of the observed clouds, the astronomers do not favour the second hypothesis. It appears more likely that these clouds are separate objects not related to MS 1512-cB58 . In that case, this would imply the presence of large-scale structure at this early time , only 3 billion years after the Big Bang. MS 1512-cB58 might then be the largest (heaviest) single object in the neigbourhood, a likely progenitor of the local massive galaxies observed at the present time. More information The results described in this Press Release are presented in a research paper "The Lyman-alpha forest of a Lyman-Break Galaxy: VLT Spectra of MS 1512-cB58 at z = 2.724" by Sandra Savaglio, Nino Panagia and Paolo Padovani, appearing in the research journal "Astrophysical Journal" this month. Notes [1]: The team consists of Sandra Savaglio (Johns Hopkins University, Baltimore, MD, USA, and Rome Observatory, Italy), Nino Panagia and Paolo Padovani (both European Space Agency and Space Telescope Science Institute, Baltimore) [2]: The measured redshift of MS 1512-cB58 is z = 2.724. In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a distant cloud or galaxy gives a direct estimate of the apparent recession velocity as caused by the universal expansion. Since the expansion rate increases with distance, the velocity is itself a function (the Hubble relation) of the distance to the object. The distances indicated in the text are based on an age of the Universe of 15 billion years. At the indicated redshift, the Lyman-alpha line of atomic hydrogen (rest wavelength 121.6 nm) is observed at 452.8 nm, i.e. in the blue spectral region. The Lyman-alpha absorption lines from intergalactic clouds along the line-of-sight (and at lower redshifts) are observed at shorter wavelengths. The lower limit of the UVES spectrum of MS 1512-cB58 (415 nm) corresponds to a Lyman-alpha redshift of 2.41, i.e. a distance of about 7.5 billion light-years. [3]: The importance of the Lyman-alpha line in absorption is that it is exquisitely sensitive to the presence of neutral hydrogen which only constitutes a small fraction of the total amount of hydrogen in the intergalactic medium (about 1/10,000). Still, the observed Ly-alpha forest is extremely rich. What we see is most likely the "tip of the iceberg" only and hydrogen in the intergalactic medium at high redshift is probably the dominant component of baryonic matter in the early Universe. Contact Sandra Savaglio Johns Hopkins University Baltimore, MD, USA Tel.: +1 410 516 8583 email: savaglio@pha.jhu.edu Technical information about the photos PR Photo 08a/02 is a reproduction of a composite image of the field around the distant cluster of galaxies MS 1512+36 (redshift 0.37), obtained with the WFPC2 camera at the NASA/ESA Hubble Space Telescope. It is based on exposures in two filters (F555 + F675). The observations are described in a research paper by Seitz et al. (Monthly Notices of the RAS, August 1998, Vol. 298, p. 945 ff). The lensed image of the galaxy MS 1512-cB58 is seen at an angular distance of about 5 arcsec from the centre of the cluster. The north direction is at about 1 o'clock and east is at 10 o'clock. The field measures approx. 45 x 60 arcsec 2. PR Photo 08b/02 shows the composite spectrum of MS 1512-cB58 in the spectral region of interest (415.0 - 459.5 nm), as obtained with the red and blue arms of UVES. Long and short red vertical lines ("ticks") indicate larger and smaller intergalactic hydrogen clouds, respectively. The overlying, continuous red line is the "best-fit" model to the observed spectrum. Due to the low altitude of the object, the exposures never lasted more than 90 min around the northern meridian. The full spectral coverage is 415 - 500 nm (blue arm) and 524 - 621 nm (red arm). The velocity resolution varies from 29 km/s at the blue end to 19 km/sec at the red limit. The S/N-ratio increases from about 3 (415 nm) to 10 (610 nm). PR Photo 08c/02 reproduces a smaller part of the observed spectral region observed at full resolution (434.8 - 443.0 nm), with two dozen detected clouds indicated.

SACS: Spitzer Archival Cluster Survey

NASA Astrophysics Data System (ADS)

Stern, Daniel

Emerging from the cosmic web, galaxy clusters are the most massive gravitationally bound structures in the universe. Thought to have begun their assembly at z > 2, clusters provide insights into the growth of large-scale structure as well as the physics that drives galaxy evolution. Understanding how and when the most massive galaxies assemble their stellar mass, stop forming stars, and acquire their observed morphologies in these environments remain outstanding questions. The redshift range 1.3 < z < 2 is a key epoch in this respect: elliptical galaxies start to become the dominant population in cluster cores, and star formation in spiral galaxies is being quenched. Until recently, however, this redshift range was essentially unreachable with available instrumentation, with clusters at these redshifts exceedingly challenging to identify from either ground-based optical/nearinfrared imaging or from X-ray surveys. Mid-infrared (MIR) imaging with the IRAC camera on board of the Spitzer Space Telescope has changed the landscape. High-redshift clusters are easily identified in the MIR due to a combination of the unique colors of distant galaxies and a negative k-correction in the 3-5 μm range which makes such galaxies bright. Even 90-sec observations with Spitzer/IRAC, a depth which essentially all extragalactic observations in the archive achieve, is sufficient to robustly detect overdensities of L* galaxies out to z~2. Here we request funding to embark on a ambitious scientific program, the “SACS: Spitzer Archival Cluster Survey”, a comprehensive search for the most distant galaxy clusters in all Spitzer/IRAC extragalactic pointings available in the archive. With the SACS we aim to discover ~2000 of 1.3 < z < 2.5 clusters, thus provide the ultimate catalog for high-redshift MIR selected clusters: a lasting legacy for Spitzer. The study we propose will increase by more than a factor of 10 the number of high-redshift clusters discovered by all previous surveys combined, providing a high-purity, uniform sample. Matching the Spitzer/IRAC-selected clusters with data at similar and longer wavelengths available in the archive (WISE 3- 5μm, Spitzer/MIPS 24μm or Herschel/SPIRE 250μm data) we will be also able to study the dependence on the environment of star formation and AGN activity out to z~2, and to study the effect of star-forming galaxies and AGNs on cosmological results from ongoing Sunyaev-Zel'dovich (SZ) and X-ray cluster surveys. The identified clusters will be valuable for both astrophysics and cosmology. In terms of astrophysics, the redshift probed by the MIR color selection targets a key epoch in cluster development, when star formation is shutting down and the galaxies are becoming passive. Massive clusters also distort space-time around them, creating powerful gravitational telescopes that lens the distant universe. This both allows detailed studies of the lensed objects with otherwise unachievable sensitivity, as well as provides a unique probe of the mass distribution in the lensing cluster. In terms of cosmology, clusters are the most massive structures in the universe, and their space density is sensitive to basic cosmological parameters. Clusters identified by this program will become a lasting legacy of Spitzer, providing exciting targets for Chandra, Hubble, James Webb Space Telescope (JWST), Astro-H, Athena, as well as future 30-m class ground-based telescopes (e.g., GMT, ELT, TMT). The upcoming large-scale, space-based surveys of eROSITA, Euclid, and WFIRST all have distant cluster studies as key scientific goals. Our proposed survey will provide new high redshift targets for those satellites, enabling unique, exciting multi-wavelength studies of the Spitzer-selected sample, as well as a training set to identify additional high-redshift clusters outside of the Spitzer footprint.

Mapping all the mass in the universe (with weak gravitational lensing) - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Spencer

Recent discoveries have shown that most of the universe is made of an exotic dark matter that behaves much differently than the normal matter that we experience in everyday life. As we cannot detect dark matter directly, we must infer its location in the universe by indirect effects, such as the distortion of light from distant galaxies as it travels through large clouds of dark matter. While the degree of distortion should be proportional to the amount of dark matter present, we don't know the original shape of the galaxy so the distortion is difficult to quantify. If we hadmore » a model of how dark matter is linked to galaxies, and thus be able predict the amount of distortion that should occur, we could apply the model to galaxy surveys to map out the dark matter in our universe. In this research, I attach a spherical 'halo' of dark matter to each galaxy in a simulated universe to approximate its known complex dark matter structure. I then predict how the halos distort the light from distant galaxies generated behind the halos. As the data is simulated, the true distortion of the light is known which is compared to the halo-predicted distortion. I find that, on average, the model under-predicts the degree of distortion on all scales and fails to capture distortions from large-scale dark matter structure. These issues are likely due to missing features in the model, as the halo model is a greatly simplified version of the actual distribution of dark matter. Potential improvements to the model for future work are discussed.« less

Direct Measurements of Dust Attenuation in z ~ 1.5 Star-forming Galaxies from 3D-HST: Implications for Dust Geometry and Star Formation Rates

NASA Astrophysics Data System (ADS)

Price, Sedona H.; Kriek, Mariska; Brammer, Gabriel B.; Conroy, Charlie; Förster Schreiber, Natascha M.; Franx, Marijn; Fumagalli, Mattia; Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica J.; Skelton, Rosalind E.; van Dokkum, Pieter G.; Whitaker, Katherine E.; Wuyts, Stijn

2014-06-01

The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A V, H II ) and the integrated dust content (A V, star). We select a sample of 163 galaxies between 1.36 <= z <= 1.5 with Hα signal-to-noise ratio >=5 and measure Balmer decrements from stacked spectra to calculate A V, H II . First, we stack spectra in bins of A V, star, and find that A V, H II = 1.86 A V, star, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M *). We find that on average A V, H II increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.

The distant red galaxy neighbour population of 1 <~ z <~ 2 QSOs and optically obscured sources

NASA Astrophysics Data System (ADS)

Bornancini, Carlos G.; García Lambas, Diego

2007-05-01

We study the distant red galaxy (DRG; J - Ks > 2.3) neighbour population of quasi-stellar objects (QSOs) selected from the Sloan Digital Sky Survey (SDSS) in the redshift range 1 <~ z <~ 2. We perform a similar analysis for optically obscured active galactic nuclei (AGNs; i.e. with a limiting magnitude I > 24) detected in the mid-infrared (24 μm) with the Spitzer Space Telescope and a mean redshift z ~ 2.2 in the Flamingos Extragalactic Survey (FLAMEX). Both QSOs and obscured AGN target samples cover 4.7 deg2 in the same region of the sky. We find a significant difference in the environment of these two target samples. Neighbouring galaxies close to QSOs tend to be bluer than galaxies in optically obscured source environments. We also present results on the cross-correlation function of DRGs around QSOs and optically faint mid-infrared sources. The corresponding correlation length obtained for the QSO sample targets is r0 = 5.4 +/- 1.6 Mpc h-1 and a slope of γ = 1.94 +/- 0.10. For the optically obscured galaxy sample, we find r0 = 8.9 +/- 1.4 Mpc h-1 and a slope of γ = 2.27 +/- 0.20. These results indicate that optically faint obscured sources are located in denser environment of evolved red galaxies compared to QSOs. Based on observations and/or data products by the Flamingos Extragalactic Survey. FLAMINGOS was designed and constructed by the IR instrumentation group (PI: R. Elston) at the University of Florida, Department of Astronomy, with support from NSF grant AST97-31180 and Kitt Peak National Observatory. E-mail: bornancini@oac.uncor.edu

Galaxy Protoclusters as Drivers of Cosmic Star Formation History in the First 2 Gyr

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiang, Yi-Kuan; Overzier, Roderik A.; Gebhardt, Karl

Present-day clusters are massive halos containing mostly quiescent galaxies, while distant protoclusters are extended structures containing numerous star-forming galaxies. We investigate the implications of this fundamental change in a cosmological context using a set of N -body simulations and semi-analytic models. We find that the fraction of the cosmic volume occupied by all (proto)clusters increases by nearly three orders of magnitude from z = 0 to z = 7. We show that (proto)cluster galaxies are an important and even dominant population at high redshift, as their expected contribution to the cosmic star formation rate density rises (from 1% at zmore » = 0) to 20% at z = 2 and 50% at z = 10. Protoclusters thus provide a significant fraction of the cosmic ionizing photons, and may have been crucial in driving the timing and topology of cosmic reionization. Internally, the average history of cluster formation can be described by three distinct phases: at z ∼ 10–5, galaxy growth in protoclusters proceeded in an inside-out manner, with centrally dominant halos that are among the most active regions in the universe; at z ∼ 5–1.5, rapid star formation occurred within the entire 10–20 Mpc structures, forming most of their present-day stellar mass; at z ≲ 1.5, violent gravitational collapse drove these stellar contents into single cluster halos, largely erasing the details of cluster galaxy formation due to relaxation and virialization. Our results motivate observations of distant protoclusters in order to understand the rapid, extended stellar growth during cosmic noon, and their connection to reionization during cosmic dawn.« less

Spectroscopic confirmation of the rich z = 1.80 galaxy cluster JKCS 041 using the WFC3 grism: Environmental trends in the ages and structure of quiescent galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Newman, Andrew B.; Ellis, Richard S.; Andreon, Stefano

2014-06-10

We present Hubble Space Telescope imaging and grism spectroscopy in the field of the distant galaxy cluster JKCS 041 using the Wide Field Camera 3. We confirm that JKCS 041 is a rich cluster and derive a redshift z = 1.80 via the spectroscopic identification of 19 member galaxies, of which 15 are quiescent. These are centered upon diffuse X-ray emission seen by the Chandra observatory. As JKCS 041 is the most distant known cluster with such a large, spectroscopically confirmed quiescent population, it provides a unique opportunity to study the effect of the environment on galaxy properties at earlymore » epochs. We construct high-quality composite spectra of the quiescent cluster members that reveal prominent Balmer and metallic absorption lines. Using these, we measure the mean stellar ages in two bins of stellar mass. The quiescent cluster members' ages agree remarkably closely with that inferred by Whitaker et al. for similarly selected samples in the field, supporting the idea that the cluster environment is more efficient at truncating star formation while not having a strong effect on the mean epoch of quenching. We find some evidence (90% confidence) for a lower fraction of disk-like quiescent systems in JKCS 041 compared to a sample of coeval field galaxies drawn from the CANDELS survey. Taking this into account, we do not detect a significant difference between the mass-radius relations of the quiescent JKCS 041 members and our z ∼ 1.8 field sample. Finally, we demonstrate how differences in the morphological mixture of quenched systems can complicate measures of the environmental dependence of size growth.« less

Resolved spectroscopy of adolescent and infant galaxies (1 < z < 10)

NASA Astrophysics Data System (ADS)

Wright, Shelley; IRIS Science Team

2014-07-01

The combination of integral field spectroscopy (IFS) and adaptive optics (AO) on TMT will be revolutionary in studying the distant universe. The high angular resolution exploited by an AO system with this large aperture will be essential for studying high-redshift (1 < z < 5) galaxies' kinematics and chemical abundance histories. At even greater distances, TMT will be essential for conducting follow-up spectroscopy of Ly-alpha emission from first lights galaxies (6 < z < 10) and determining their kinematics and morphologies. I will present simulations and sensitivity calculations for high-z and first light galaxies using the diffraction-limited instrument IRIS coupled with NFIRAOS. I will put these simulations in context with current IFS+AO high-z observations and future capabilities with JWST.

Hubble Views Two Galaxies Merging

NASA Image and Video Library

2017-12-08

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 6052, located around 230 million light-years away in the constellation of Hercules. It would be reasonable to think of this as a single abnormal galaxy, and it was originally classified as such. However, it is in fact a “new” galaxy in the process of forming. Two separate galaxies have been gradually drawn together, attracted by gravity, and have collided. We now see them merging into a single structure. As the merging process continues, individual stars are thrown out of their original orbits and placed onto entirely new paths, some very distant from the region of the collision itself. Since the stars produce the light we see, the “galaxy” now appears to have a highly chaotic shape. Eventually, this new galaxy will settle down into a stable shape, which may not resemble either of the two original galaxies. Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt

The search for molecular gas in the most distant submillimetre galaxy at z=4.76

NASA Astrophysics Data System (ADS)

Coppin, Kristen; Weiss, Axel; De Breuck, Carlos; Walter, Fabian; Edge, Alastair; Kovacs, Attila; Ivison, Rob; Huynh, Minh; Smail, Ian; Schinnerer, Eva; Greve, Thomas; Wardlow, Julie

2009-07-01

We propose to use ATCA to measure the CO(2-1) and CO(5-4) emission in the highest redshift submm-selected galaxy (SMG) known: LESS J033229 at z=4.76. These observations will measure the gas mass and dynamics of this far-infrared luminous galaxy at a time when the Universe was only 1 Gyr old. In conjunction with similar observations of three z~4-4.5 SMG, these observations will constrain the potential evolution of the star formation and dynamical mass of these high redshift, but relatively typical, young galaxies and their potential role as the precursor population to the red-and-dead galaxies seen at z~3, as well as allowing us to contrast the physical state of the gas reservoirs in these early galaxies with the well-studied and more numerous SMG population at z~2. These observations will provide a sneak-preview of the science which ALMA will provide on the formation of the earliest massive galaxies in the Universe.

Gravitational lensing by clusters of galaxies - Constraining the mass distribution

NASA Technical Reports Server (NTRS)

Miralda-Escude, Jordi

1991-01-01

The possibility of placing constraints on the mass distribution of a cluster of galaxies by analyzing the cluster's gravitational lensing effect on the images of more distant galaxies is investigated theoretically in the limit of weak distortion. The steps in the proposed analysis are examined in detail, and it is concluded that detectable distortion can be produced by clusters with line-of-sight velocity dispersions of over 500 km/sec. Hence it should be possible to determine (1) the cluster center position (with accuracy equal to the mean separation of the background galaxies), (2) the cluster-potential quadrupole moment (to within about 20 percent of the total potential if velocity dispersion is 1000 km/sec), and (3) the power law for the outer-cluster density profile (if enough background galaxies in the surrounding region are observed).

Baby Galaxies in the Adult Universe

NASA Image and Video Library

2004-12-21

This artist's conception illustrates the decline in our universe's "birth-rate" over time. When the universe was young, massive galaxies were forming regularly, like baby bees in a bustling hive. In time, the universe bore fewer and fewer "offspring," and newborn galaxies (white circles) matured into older ones more like our own Milky Way (spirals). Previously, astronomers thought that the universe had ceased to give rise to massive, young galaxies, but findings from NASA's Galaxy Evolution Explorer suggest that may not be the case. Surveying thousands of nearby galaxies with its highly sensitive ultraviolet eyes, the telescope spotted three dozen that greatly resemble youthful galaxies from billions of years ago. In this illustration, those galaxies are represented as white circles on the right, or "today" side of the timeline. The discovery not only suggests that our universe may still be alive with youth, but also offers astronomers their first close-up look at what appear to be baby galaxies. Prior to the new result, astronomers had to peer about 11 billion light-years into the distant universe to see newborn galaxies. The newfound galaxies are only about 2 to 4 billion light-years away. http://photojournal.jpl.nasa.gov/catalog/PIA07142

STarlight Absorption Reduction through a Survey of Multiple Occulting Galaxies (STARSMOG)

NASA Astrophysics Data System (ADS)

Holwerda, Benne

2014-10-01

Dust absorption remains the poorest constrained parameter in both Cosmological distances and multi-wavelength studies of galaxy populations. A galaxy's dust distribution can be measured to great accuracy in the case of an overlapping pair of galaxies, i.e., when a foreground spiral galaxy accidentally overlaps a more distant, preferably elliptical galaxy. We have identified over 300 bona-fide overlapping pairs --well separated in redshift but close on the sky-- in the GAMA spectroscopic survey, taking advantage of its high completeness (98%) on small scales. We propose to map the fine-scale (~50pc) dust structure in these occulting galaxies, using HST/WFC3 SNAP observations. The resulting dust maps will (1) serve as an extinction probability for supernova lightcurve fits in similar type host galaxies, (2) strongly constrain the role of ISM structure in Spectral Energy Distribution models of spiral galaxies, and (3) map the level of ISM turbulence (through the spatial power-spectrum). We ask for SNAP observations with a parent list of 355 targets to ensure a complete and comprehensive coverage of each foreground galaxy mass, radius and inclination. The resulting extinction maps will serve as a library for SNIa measurements, galaxy SED modelling and ISM turbulence measurements.

Baby Galaxies in the Adult Universe

NASA Technical Reports Server (NTRS)

2004-01-01

[figure removed for brevity, see original site] Figure 1

This artist's conception illustrates the decline in our universe's 'birth-rate' over time. When the universe was young, massive galaxies were forming regularly, like baby bees in a bustling hive. In time, the universe bore fewer and fewer 'offspring,' and newborn galaxies (white circles) matured into older ones more like our own Milky Way (spirals).

Previously, astronomers thought that the universe had ceased to give rise to massive, young galaxies, but findings from NASA's Galaxy Evolution Explorer suggest that may not be the case. Surveying thousands of nearby galaxies with its highly sensitive ultraviolet eyes, the telescope spotted three dozen that greatly resemble youthful galaxies from billions of years ago. In this illustration, those galaxies are represented as white circles on the right, or 'today' side of the timeline.

The discovery not only suggests that our universe may still be alive with youth, but also offers astronomers their first close-up look at what appear to be baby galaxies. Prior to the new result, astronomers had to peer about 11 billion light-years into the distant universe to see newborn galaxies. The newfound galaxies are only about 2 to 4 billion light-years away.

New View of Distant Galaxy Reveals Furious Star Formation

NASA Astrophysics Data System (ADS)

2007-12-01

A furious rate of star formation discovered in a distant galaxy shows that galaxies in the early Universe developed either much faster or in a different way from what astronomers have thought. "This galaxy is forming stars at an incredible rate," said Wei-Hao Wang, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. The galaxy, Wang said, is forming the equivalent of 4,000 Suns a year. This is a thousand times more violent than our own Milky Way Galaxy. Location of Distant Galaxy Visible-light, left (from HST) and Infrared, right, (from Spitzer) Images: Circles indicate location of GOODS 850-5. CREDIT: Wang et al., STScI, Spitzer, NASA, NRAO/AUI/NSF Click on image for high-resolution file (1 MB) The galaxy, called GOODS 850-5, is 12 billion light-years from Earth, and thus is seen as it was only about 1.5 billion years after the Big Bang. Wang and his colleagues observed it using the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA) on Mauna Kea in Hawaii. Young stars in the galaxy were enshrouded in dust that was heated by the stars and radiated infrared light strongly. Because of the galaxy's great distance from Earth, the infrared light waves have been stretched out to submillimeter-length radio waves, which are seen by the SMA. The waves were stretched or "redshifted," as astronomers say, by the ongoing expansion of the Universe. "This evidence for prolific star formation is hidden by the dust from visible-light telescopes," Wang explained. The dust, in turn, was formed from heavy elements that had to be built up in the cores of earlier stars. This indicates, Wang said, that significant numbers of stars already had formed, then spewed those heavy elements into interstellar space through supernova explosions and stellar winds. "Seeing the radiation from this heated dust revealed star formation we could have found in no other way," Wang said. Similar dusty galaxies in the early Universe may contain most of the star formation at those times. "This means that future telescopes such as the Atacama Large Millimeter/submillimeter Array (ALMA) can reveal many more such galaxies and give us a much more complete picture of star formation in the early Universe," he added. Lennox Cowie of the University of Hawaii said, "We found out in the last decade that most of the recent star formation in the Universe occurs in large dusty galaxies, but we had always expected that early star formation would be dominated by smaller and less obscured galaxies. Now it seems that even at very early times it may be the same big dusty star formers that are the sites of most of the star formation. That's quite a surprise." Astronomers believe that large galaxies originally formed through mergers of smaller objects. Seeing a large galaxy such as GOODS 850-5 forming stars so rapidly at such an early time in the history of the Universe is a surprise. "Either the mergers that formed the galaxy happened much faster than we thought or some other process altogether produced the galaxy," Wang said. Wang and Cowie worked with Jennifer van Saders of Rutgers University and NRAO, Amy Barger of the University of Wisconsin-Madison, and Jonathan Williams of the University of Hawaii. The scientists published their findings in the December 1 edition of the Astrophysical Journal. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.The Submillimeter Array is an 8-element interferometer located atop Mauna Kea in Hawaii. It is a collaboration between the Smithsonian Astrophysical Observatory and the Institute of Astronomy and Astrophysics of the Academia Sinica of Taiwan.

CONSTRAINING VERY HIGH MASS POPULATION III STARS THROUGH He II EMISSION IN GALAXY BDF-521 AT z = 7.01

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Zheng; Fan, Xiaohui; Davé, Romeel

2015-01-30

Numerous theoretical models have long proposed that a strong He II λ1640 emission line is the most prominent and unique feature of massive Population III (Pop III) stars in high-redshift galaxies. The He II λ1640 line strength can constrain the mass and initial mass function (IMF) of Pop III stars. We use F132N narrowband filter on the Hubble Space Telescope's (HST) Wide Field Camera 3 to look for strong He II λ1640 emission in the galaxy BDF-521 at z = 7.01, one of the most distant spectroscopically confirmed galaxies to date. Using deep F132N narrowband imaging, together with our broadband imaging with F125Wmore » and F160W filters, we do not detect He II emission from this galaxy, but place a 2σ upper limit on the flux of 5.3×10{sup −19} erg s{sup −1} cm{sup −2}. This measurement corresponds to a 2σ upper limit on the Pop III star formation rate (SFR{sub PopIII}) of ∼0.2 M {sub ☉} yr{sup –1}, assuming a Salpeter IMF with 50 ≲ M/M {sub ☉} ≲ 1000. From the high signal-to-noise broadband measurements in F125W and F160W, we fit the UV continuum for BDF-521. The spectral flux density is ∼3.6×10{sup −11}×λ{sup −2.32} erg s{sup −1} cm{sup −2} Å{sup –1}, which corresponds to an overall unobscured SFR of ∼5 M {sub ☉} yr{sup –1}. Our upper limit on SFR{sub PopIII} suggests that massive Pop III stars represent ≲ 4% of the total star formation. Further, the HST high-resolution imaging suggests that BDF-521 is an extremely compact galaxy, with a half-light radius of 0.6 kpc.« less

Selections from 2017: Mapping the Universe with SDSS-IV

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

Editors note:In these last two weeks of 2017, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume in January.Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant UniversePublished June2017Main takeaway:The incredibly prolific Sloan Digital Sky Survey has provided photometric observations of around 500 million objects and spectra for more than 3 million objects. The survey has now entered its fourth iteration, SDSS-IV, with the first public data release made in June 2016. A publication led by Michael Blanton (New York University) describes the facilities used for SDSS-IV, its science goals, and itsthree coreprograms.Why its interesting:Since data collection began in 2000, SDSS has been one of the premier surveysproviding imaging and spectroscopy for objects in both the near and distant universe.SDSS has measured spectra not only for the stars in our own Milky Way, but also for galaxies that lie more than 7 billion light-years distant making itan extremelyuseful and powerful tool for mapping our universe.What SDSS-IV is looking for:SDSS image of an example MaNGA target galaxy (left), with some of the many things we can learn about it shown in the right and bottom panels: stellar velocity dispersion, stellar mean velocity, stellar population age, metallicity, etc. [Blanton et al. 2017]SDSS-IV containsthree core programs:Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2)provides high-resolution near-infrared spectra of hundreds of thousands of Milky-Way stars with the goal ofimproving our understanding of the history of the Milky Way and of stellar astrophysics.Mapping Nearby Galaxies at Apache Point Observatory (MaNGA)obtains spatially resolved spectra for thousands of nearby galaxiesto better understand the evolutionary histories of galaxies and what regulates their star formation.Extended Baryon Oscillation Spectroscopic Survey (eBOSS)mapsthe galaxy, quasar, and neutral gas distributions at redshifts out to z = 3.5to better understand dark matter, dark energy, the properties of neutrinos, and inflation.CitationMichael R. Blanton et al 2017 AJ 154 28. doi:10.3847/1538-3881/aa7567

The VLT Opening Symposium

NASA Astrophysics Data System (ADS)

1999-02-01

Scientists Meet in Antofagasta to Discuss Front-Line Astrophysics To mark the beginning of the VLT era, the European Southern Observatory is organizing a VLT Opening Symposium which will take place in Antofagasta (Chile) on 1-4 March 1999, just before the start of regular observations with the ESO Very Large Telescope on April 1, 1999. The Symposium occupies four full days and is held on the campus of the Universidad Catolica del Norte. It consists of plenary sessions on "Science in the VLT Era and Beyond" and three parallel Workshops on "Clusters of Galaxies at High Redshift" , "Star-way to the Universe" and "From Extrasolar Planets to Brown Dwarfs" . There will be many presentations of recent work at the major astronomical facilities in the world. The meeting provides a very useful forum to discuss the latest developments and, in this sense, contributes to the planning of future research with the VLT and other large telescopes. The symposium will be opened with a talk by the ESO Director General, Prof. Riccardo Giacconi , on "Paranal - an observatory for the 21st century". It will be followed by reports about the first scientific results from the main astronomical instruments on VLT UT1, FORS1 and ISAAC. The Symposium participants will see the VLT in operation during special visits to the Paranal Observatory. Press conferences are being arranged each afternoon to inform about the highlights of the conference. After the Symposium, there will be an Official Inauguration Ceremony at Paranal on 5 March Contributions from ESO ESO scientists will make several presentations at the Symposium. They include general reviews of various research fields as well as important new data and results from the VLT that show the great potential of this new astronomical facility. Some of the recent work is described in this Press Release, together with images and spectra of a large variety of objects. Note that all of these data will soon become publicly available via the VLT Archive. The text below summarizes the individual projects. Comprehensive texts with all photos and diagrammes are available in nine separate web documents ( ESO PR Photos 08/99 to 16/99 ) that may be accessed via the links at the top of each section. The degree of detail and level of complexity of the texts depend on the subject and the available materials. 1. Dwarf Galaxies in the Local Group ESO PR Photo 10a/99 ESO PR Photo 10a/99 The Antlia Galaxy (FORS1 colour composite) . Access full text and PR Photos 10a-d/99 In addition to large spiral galaxies like the Milky Way Galaxy, the Andromeda Galaxy and Messier 33, the Local Group of Galaxies contains many dwarf galaxies. The VLT has observed two of these, Antlia and NGC 6822 . Antlia is a low-surface brightness, spheroidal dwarf galaxy that was only discovered in 1997. While it contains a large amount of atomic hydrogen at its centre, no young stars are found, and it appears that most of its stars are old. This is unlike other dwarf galaxies in the Milky Way neighbourhood, as star formation is expected to occur within dense hydrogen clouds. Further observations will be necessary to understand this unusual characteristics. The VLT also obtained images of an irregular dwarf galaxy in the Local Group, NGC 6822, as well as spectra of some of its stars. This galaxy is of the "irregular" type and is situated at a distance of about 2 million light-years. A comparison of the spectra of supergiant stars in NGC 6822 shows that many spectral lines are much weaker than in stars of similar type in the Milky Way, but of similar strength as in stars in the Small Magellanic Cloud. This confirms an earlier finding that NGC 6822 has chemical composition (a lower "metallicity") that is different from what is observed in our Galaxy. 2. The Double Stellar Cluster NGC 1850 in the LMC ESO PR Photo 15/99 ESO PR Photo 15/99 NGC 1850 (FORS1 colour composite) . Access full text and PR Photo 15/99 NGC 1850 is a double cluster in the Large Magellanic Cloud, a satellite galaxy to the Milky Way Galaxy. This cluster is representative of a class of objects, young, globular-like stellar associations , that has no counterpart in our own Galaxy. The VLT images show faint nebulosity in this area, with filaments and various sharp "shocks". This offers support to the theory of supernova-induced star birth in the younger of the two clusters. It is estimated that about 1000 stars in the older of the clusters have exploded during the past 20 million years. 3. The Barred Galaxy NGC 1365 ESO PR Photo 08a/99 ESO PR Photo 08a/99 The Barred Galaxy NGC 1365 (FORS1 colour composite) . Access full text and PR Photos 08a-e/99 NGC 1365 is one of the most prominent "barred" galaxies in the sky. It is a supergiant galaxy and is a member of the Fornax Cluster of Galaxies, at a distance of about 60 million light-years. This galaxy has an intricate structure with a massive straight bar and two pronounced spiral arms. There are many dust lanes and emission nebulae in these and also a bright nuclear region at the center that may hide a black hole. Several images of NGC 1365 have recently been obtained with all three astronomical instruments, now installed at the VLT UT1. They show the overall structure of this magnificent galaxy, and also the fine details of the innermost region, close to the centre. An infrared ISAAC image penetrates deep into the obscuring dust clouds in this area. 4. The colours of NGC 1232 ESO PR Photo 13a/99 ESO PR Photo 13a/99 Differential (UV-B) image of NGC 1232 (FORS1) . Access full text and PR Photos 13a-b/99 NGC 1232 is a large spiral galaxy in the constellation Eridanus (The River). With a diameter of nearly 200,000 light-years, it is about twice the size of the Milky Way galaxy. The distance is about 100 million light-years, but the excellent optical quality of the VLT and FORS allows us to see an incredible wealth of details. Computer processed "colour-index images" have been prepared that show the "difference" between images of the galaxy, as seen in different wavebands. Since different types of objects have different brightness in different colours, this method is very useful to locate objects of a particular type and to obtain an overview of their distribution in the galaxy. The distribution of star-forming regions and dust lanes in NGC 1232 are shown on two such photos. 5. A Selection of ISAAC Spectra ESO PR Photo 11a/99 ESO PR Photo 11a/99 He I 1038 nm line in SN1987A (ISAAC spectrum) . Access full text and PR Photos 11a-c/99 Various observations were made with the ISAAC multi-mode instrument at the Nasmyth focus of VLT UT1 during the recent commissioning periods for this infrared multi-mode instrument. They impressively demonstrate the unique capabilities of this facility. The new data include several infrared spectra of faint objects with interesting features. A spectrum was obtained in the near-infrared region of the ring nebula around SN 1987A in the Large Magellanic Cloud. It consists of material blown off the progenitor star during its evolution. Of particular interest is a jet like structure in the dispersion direction which reveals the presence of a broad, blueshifted, HeI component which presumably originates in the shock ionized ejecta. Another spectrum shows emission features in two galaxies at redshift z = 0.6 [1] that allow the determination of a rotation curve at this large distance. The 1 - 2.5 µm infrared spectrum of the radio galaxy MRC0406 at z =2.42 is also included. 6. The Cluster of Galaxies MS1008.1-1224 ESO PR Photo 09b/99 ESO PR Photo 09b/99 Centre of the Cluster of Galaxies MS1008.1-122 (FORS1 colour composite) . Access full text and PR Photos 09a-b/99 The study of "Deep Fields" is becoming a common tool in astronomy. Among the various sky fields that have been selected for detailed investigation of the faint and distant objects therein, is the FORS Deep Field that will be observed during FORS1 "guaranteed time", available to astronomers from institutes that built this instrument. In preparation of this work, an imaging programme was carried out during the FORS1 Science Verification programme. Multicolour (UBVRI) deep images were obtained of the galaxy cluster MS1008.1-1224 , to be complemented with infrared (JHK) images with ISAAC of the cluster core. The redshift is z = 0.306 and many arclets from gravitational lensing are seen within the cluster area. Such observations serve many purposes, including the study of the distribution of mass and the associated gravitational field of the cluster, of individual cluster galaxies, and also of background objects whose images are amplified and distorted by gravitational lensing caused by the cluster. 7. Quasar Spectra ESO PR Photo 14a/99 ESO PR Photo 14c/99 Spectrum of Quasar at z = 5 Access full text and PR Photos 14a-c/99 The FORS1 multi-mode instrument is able to record images as well as spectra of even very distant objects. During the past months, data have been obtained that show the properties of some of the remotest known objects in the Universe. Three spectral tracings of very distant quasars are included, for which the redshifts have been determined as z = 3.11, 3.83 and 5.0. They were taken by the FORS Commissioning Team in September and December 1998 in the long-slit spectroscopy mode of FORS1. This instrument is very efficient; even for the most distant and faintest quasar, the exposure time was only 1 hour. All spectra show a wealth of details. 8. Spectrum of a Gravitationally Lensed Galaxy ESO PR Photo 16c/99 ESO PR Photo 16c/99 Spectrum of Gravitationally Lensed Galaxy at z = 3.23 (FORS1) . Access full text and PR Photos 16a-c/99 The galaxy cluster 1ES 0657-55 is located in the southern constellation Carina (The Keel), at redshift z = 0.29. It emits strong and very hot X-ray emission and has an asymmetric galaxy distribution, indicating a large mass and recent formation. Earlier images with the ESO NTT at La Silla have revealed the presence of a gravitational arc, i.e. a background galaxy at larger distance, whose image is strongly distorted by the gravitational field of this cluster. New images of this cluster have been obtained with FORS1 under good seeing conditions. They show that this arc is very thin and long. Other arcs and arclets are also visible. It was possible to obtain a spectrum of the arc. Several absorption lines are well visible and show that the arc is the highly distorted image of a young, background galaxy at redshift z = 3.23. 9. Spectra of Faint Primordial Objects ESO PR Photo 12d/99 ESO PR Photo 12d/99 Spectrum of Distant Galaxy EIS 107 at z = 3.92 (FORS1) . Access full text and PR Photos 12a-f/99 During the recent commissioning and science verification of FORS1, spectra were taken of several objects, thought to be high-redshift galaxies. These objects are extremely faint and their spectra can only be observed with very large telescopes like the VLT and a highly efficient spectrograph. The near-infrared (I) magnitudes of the objects studied during the present test observations ranged between 23.4 and 25.5, or between 10 and 65 million times fainter than what can be seen with the unaided eye. As predicted, a large fraction of the spectra obtained turned out to be those of extremely distant galaxies, in the redshift range between z = 2.8 - 4.0. Outlook These observations provide but a small demonstration of the great capability of the ESO VLT to provide front-line astronomical data. Many others will be discussed during the Symposium and contribute to the future planning of the best possible exploitation of this great new research facility. The first 8.2-m VLT Unit Telescope (UT1) with which the observations reported in this Press Release were made will soon be joined by UT2, for which "First Light" is expected shortly, cf. PR Photos 07/99. The first instrument to be mounted on this telescope will be UVES that will provide the capability of obtaining high-dispersion spectra; the next is FORS2. During the coming years, more instruments of different types and capabilities will become available on the four 8.2-m telescopes, together providing an unrivalled potential for astronomical investigations. Note: [1]: In astronomy, the redshift (z) denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a distant galaxy or quasar gives a direct estimate of the universal expansion (i.e. the `recession velocity'). Since this expansion rate increases with the distance, the velocity (and thus the redshift) is itself a function (the Hubble relation) of the distance to the object. The larger the distance, the longer it has taken the light from the object to reach us, and the larger is the "look-back" time, i.e. the fraction of the age of the Universe that has elapsed since the light we now receive, was emitted from the object. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory . Note also the comprehensive VLT Information site.

The Central Molecular Zone of the Milky Way: Lessons about Star Formation from an extreme Environment

NASA Astrophysics Data System (ADS)

Kauffmann, Jens; Thushara Pillai, G. S.; Zhang, Qizhou; Lu, Xing; Immer, Katharina

2015-08-01

The Central Molecular Zone of the Milky Way (CMZ; innermost ~100pc) hosts a number of remarkably dense and massive clouds. These are subject to extreme environmental conditions, including very high cosmic ray fluxes and strong magnetic fields. Exploring star formation under such exceptional circumstances is essential for several of reasons. First, the CMZ permits to probe an extreme point in the star formation parameter space, which helps to test theoretical models. Second, CMZ clouds might help to understand the star formation under extreme conditions in more distant environments, such as in starbursts and the early universe.One particularly striking aspect is that — compared to the solar neighborhood — CMZ star formation in dense gas is suppressed by more than an order of magnitude (Longmore et al. 2012, Kauffmann et al. 2013). This questions current explanations for relations between the dense gas and the star formation rate (e.g., Gao & Solomon 2004, Lada et al. 2012). In other words, the unusually dense and massive CMZ molecular clouds form only very few stars, if any at all. Why is this so?Based on data from ALMA, CARMA, and SMA interferometers, we present results from the Galactic Center Molecular Cloud Survey (GCMS), the first study of a comprehensive sample of molecular clouds in the CMZ. This research yields a curious result: most of the major CMZ clouds are essentially devoid of significant substructure of the sort usually found in regions of high-mass star formation (Kauffmann et al. 2013). Preliminary analysis indicates that some clouds rather resemble homogeneous balls of gas. This suggests a highly dynamic picture of cloud evolution in the CMZ where clouds form, disperse, and re-assemble constantly. This concept is benchmarked against a new ALMA survey and first results from a legacy survey on the SMA.It is plausible that dense clouds in other galaxies have a similar internal structure. Instruments like ALMA and the JWST will soon permit to resolve such regions in nearby galaxies.

The Burrell Schmidt Deep Virgo Survey: Tidal Debris, Galaxy Halos, and Diffuse Intracluster Light in the Virgo Cluster

NASA Astrophysics Data System (ADS)

Mihos, J. Christopher; Harding, Paul; Feldmeier, John J.; Rudick, Craig; Janowiecki, Steven; Morrison, Heather; Slater, Colin; Watkins, Aaron

2017-01-01

We present the results of a deep imaging survey of the Virgo cluster of galaxies, concentrated around the cores of Virgo subclusters A and B. The goal of this survey was to detect and study very low surface brightness features present in Virgo, including discrete tidal features, the faint halos of luminous galaxies, and the diffuse intracluster light (ICL). Our observations span roughly 16 degrees2 in two filters, reaching a 3σ limiting depth of {μ }B = 29.5 and {μ }V = 28.5 mag arcsec-2. At these depths, our limiting systematic uncertainties are astrophysical: variations in faint background sources as well as scattered light from galactic dust. We show that this dust-scattered light is well traced by deep far-infrared imaging, making it possible to separate it from true diffuse light in Virgo. We use our imaging to trace and measure the color of the diffuse tidal streams and ICL in the Virgo core near M87, in fields adjacent to the core including the M86/M84 region, and to the south of the core around M49 and subcluster B, along with the more distant W{}\\prime cloud around NGC 4365. Overall, the bulk of the projected ICL is found in the Virgo core and within the W{}\\prime cloud; we find little evidence for an extensive ICL component in the field around M49. The bulk of the ICL we detect is fairly red in color (B - V = 0.7-0.9), indicative of old, evolved stellar populations. Based on the luminosity of the observed ICL features in the cluster, we estimate a total Virgo ICL fraction of 7%-15%. This value is somewhat smaller than that expected for massive, evolved clusters, suggesting that Virgo is still in the process of growing its extended ICL component. We also trace the shape of M87's extremely boxy outer halo out to ˜150 kpc, and show that the current tidal stripping rate from low luminosity galaxies is insufficient to have built M87's outer halo over a Hubble time. We identify a number of previously unknown low surface brightness structures around galaxies projected close to M86 and M84. The extensive diffuse light seen in the infalling W{}\\prime cloud around NGC 4365 is likely to be subsumed in the general Virgo ICL component once the group enters the cluster, illustrating the importance of group infall in generating ICL. Finally, we also identify another large and extremely low surface brightness ultradiffuse galaxy, likely in the process of being shredded by the cluster tidal field. With the survey complete, the full imaging data set is now available for public release.

Galactic City at the Edge of the Universe

NASA Image and Video Library

2011-01-12

Astronomers have discovered a massive cluster of young galaxies forming in the distant universe. The growing galactic metropolis is known as COSMOS-AzTEC3. This image was taken Japan Subaru telescope atop Mauna Kea in Hawaii.

Ages of Extragalactic Intermediate-Age Star Clusters

NASA Technical Reports Server (NTRS)

Flower, P. J.

1983-01-01

A dating technique for faint, distant star clusters observable in the local group of galaxies with the space telescope is discussed. Color-magnitude diagrams of Magellanic Cloud clusters are mentioned along with the metallicity of star clusters.

Seeing the invisible

NASA Astrophysics Data System (ADS)

Heymans, Catherine

2014-07-01

Light from distant galaxies is distorted on its journey to us via a vast network of dark matter. By observing this phenomenon, known as gravitational lensing, physicists are able to map the structure of this dark cosmic web, as Catherine Heymans explains.

Distant Galaxies in Goods North

NASA Image and Video Library

2014-01-07

The view is a composite of images taken in visible and near-infrared light by NASA Hubble Space Telescope. Researchers have circled four unusually red objects that appear as they existed just 500 million years after the big bang.

Red Shifts with Obliquely Approaching Light Sources.

ERIC Educational Resources Information Center

Head, C. E.; Moore-Head, M. E.

1988-01-01

Refutes the Doppler effect as the explanation of large red shifts in the spectra of distant galaxies and explains the relativistic effects in which the light sources approach the observer obliquely. Provides several diagrams and graphs. (YP)

Distant Galactic Halo Substructures Observed by the Palomar Transient Factory

NASA Astrophysics Data System (ADS)

Sesar, Branimir

2013-01-01

Characterization of Galactic halo substructures is important as their kinematic and chemical properties help constrain the properties of the Galactic dark matter halo, the formation history of the Milky Way, and the galaxy formation process in general. The best practical choice for finding distant halo substructures are pulsating RR Lyrae stars, due to their intrinsic brightness (M_V = 0.6 mag) and distinct light curves. I will present kinematic and chemical properties of two distant halo substructures that were traced using RR Lyrae stars observed by the Palomar Transient Factory. One of these substructures, located at 90 kpc from the Sun in the Cancer constellation, consists of two groups of RR Lyrae stars moving away from the Galaxy at ~80 and ~20 km/s, respectively. The second substructure is located at ~65 kpc from the Sun in the Hercules constellation. The kinematics of RR Lyrae stars tracing this substructure suggest a presence of 2 or 3 stellar streams extending in the similar direction on the sky. Due to their spatial extent, both of these substructures are clearly disrupted and would be very difficult to detect using tradiitonal techniques such as the color-magnitude diagram filtering.

Galaxy Evolution in the Reddest Possible Filter

NASA Astrophysics Data System (ADS)

Richards, E. A.

We describe an observational programme aimed at understanding the radio emission from distant, rapidly evolving galaxy populations. These observations were carried out at 1.4 and 8.5 GHz with the VLA, centred on the Hubble Deep Field, obtaining limiting flux densities of 40 and 8 μJy respectively. The differential count of the radio sources is marginally sub-Euclidean to the completeness limits (γ = - 2.4 +/- 0.1) and fluctuation analysis suggests nearly 60 sources per arcmin^2 at the 1 μJy level. Using high-resolution 1.4 GHz observations obtained with MERLIN, we resolve all radio sources detected in the VLA complete sample and measure a median angular size for the microjansky radio population of 1-2``. This clue, coupled with the steep spectral index of the 1.4 GHz selected sample, suggests diffuse synchrotron radiation in z ~ 1 galactic discs. The wide-field HST and ground-based optical exposures show that the radio sources are identified primarily with disc systems composed of irregulars, peculiars, interacting/merging galaxies and a few isolated field spirals. Only 20% of the radio sources can be attributed to AGN - the majority are probably associated with starburst activity. The available redshifts range from 0.1 to 3, with a mean of about 0.8. We are plrobably witnessing a major episode of starburst activity in these luminous (L > L_*) systems, occasionally accompanied by an embedded AGN. About 20% of the radio sources remain unidentified to I = 26-28 in the HDF and flanking fields. Several of these objects have extremely red counterparts. We suggest that these are high-redshift dusty protogalaxies.

Implications of directed energy for SETI

NASA Astrophysics Data System (ADS)

Lubin, Philip

2016-09-01

We compute the detectability of directed-energy (DE) sources from distant civilizations that may exist. Recent advances in our own DE technology suggest that our eventual capabilities will radically enhance our capacity to broadcast our presence and hence allow us to ponder the reverse case of detection. We show that DE systems are detectable at vast distances, possibly across the entire horizon, which profoundly alters conceivable search strategies for extra-terrestrial, technologically-advanced civilizations. Even modest searches are extremely effective at detecting or constraining many civilization classes. A single civilization anywhere in our galaxy of comparable technological advancement to our own can be detected with near unity probability with a cluster of 0.1 m telescopes on Earth. A 1 m class telescope can detect a single civilization anywhere in the Andromeda galaxy. A search strategy is proposed using small Earth-based telescopes to observe 1012-1020 stellar and planetary systems. Such observations could address whether there exist other civilizations which are broadcasting with similar or more advanced DE capability. We show that such searches have near-unity probability of detecting comparably advanced civilizations anywhere in our galaxy within a few years, assuming the civilization: (1) adopts a simple "intelligent targeting" beacon strategy; (2) is beaconing at a wavelength we can detect; (3) broadcast the beacon long enough for the light to reach Earth now. In this blind-beacon, blind-search strategy, the civilization need not know where we are nor do we need to know where they are. The same basic strategy can be extended to extragalactic distances.

A Cluster and a Sea of Galaxies

NASA Astrophysics Data System (ADS)

2010-05-01

A new wide-field image released today by ESO displays many thousands of distant galaxies, and more particularly a large group belonging to the massive galaxy cluster known as Abell 315. As crowded as it may appear, this assembly of galaxies is only the proverbial "tip of the iceberg", as Abell 315 - like most galaxy clusters - is dominated by dark matter. The huge mass of this cluster deflects light from background galaxies, distorting their observed shapes slightly. When looking at the sky with the unaided eye, we mostly only see stars within our Milky Way galaxy and some of its closest neighbours. More distant galaxies are just too faint to be perceived by the human eye, but if we could see them, they would literally cover the sky. This new image released by ESO is both a wide-field and long-exposure one, and reveals thousands of galaxies crowding an area on the sky roughly as large as the full Moon. These galaxies span a vast range of distances from us. Some are relatively close, as it is possible to distinguish their spiral arms or elliptical halos, especially in the upper part of the image. The more distant appear just like the faintest of blobs - their light has travelled through the Universe for eight billion years or more before reaching Earth. Beginning in the centre of the image and extending below and to the left, a concentration of about a hundred yellowish galaxies identifies a massive galaxy cluster, designated with the number 315 in the catalogue compiled by the American astronomer George Abell in 1958 [1]. The cluster is located between the faint, red and blue galaxies and the Earth, about two billion light-years away from us. It lies in the constellation of Cetus (the Whale). Galaxy clusters are some of the largest structures in the Universe held together by gravity. But there is more in these structures than the many galaxies we can see. Galaxies in these giants contribute to only ten percent of the mass, with hot gas in between galaxies accounting for another ten percent [2]. The remaining 80 percent is made of an invisible and unknown ingredient called dark matter that lies in between the galaxies. The presence of dark matter is revealed through its gravitational effect: the enormous mass of a galaxy cluster acts on the light from galaxies behind the cluster like a cosmic magnifying glass, bending the trajectory of the light and thus making the galaxies appear slightly distorted [3]. By observing and analysing the twisted shapes of these background galaxies, astronomers can infer the total mass of the cluster responsible for the distortion, even when this mass is mostly invisible. However, this effect is usually tiny, and it is necessary to measure it over a huge number of galaxies to obtain significant results: in the case of Abell 315, the shapes of almost 10 000 faint galaxies in this image were studied in order to estimate the total mass of the cluster, which amounts to over a hundred thousand billion times the mass of our Sun [4]. To complement the enormous range of cosmic distances and sizes surveyed by this image, a handful of objects much smaller than galaxies and galaxy clusters and much closer to Earth are scattered throughout the field: besides several stars belonging to our galaxy, many asteroids are also visible as blue, green or red trails [5]. These objects belong to the main asteroid belt, located between the orbits of Mars and Jupiter, and their dimensions vary from some tens of kilometres, for the brightest ones, to just a few kilometres in the case of the faintest ones. This image has been taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. It is a composite of several exposures acquired using three different broadband filters, for a total of almost one hour in the B filter and about one and a half hours in the V and R filters. The field of view is 34 x 33 arcminutes. Notes [1] The Abell catalogue from 1958 comprised 2712 clusters of galaxies, and was integrated with an additional 1361 clusters in 1989. Abell put together this impressive collection by visual inspection of photographic plates of the sky, seeking those areas where more galaxies than average were found at approximately the same distance from us. [2] Ten percent of a galaxy cluster's mass consists of a very hot mixture of protons and electrons (a plasma), with temperatures as high as ten million degrees or more, which makes it visible to X-ray telescopes. [3] Astronomers refer to these slight distortions as weak gravitational lensing, as opposed to strong gravitational lensing, characterised by more spectacular phenomena such as giant arcs, rings and multiple images. [4] A weak lensing study of the galaxy cluster Abell 315 has been published in a paper that appeared in Astronomy & Astrophysics in 2009 ("Weak lensing observations of potentially X-ray underluminous galaxy clusters", by J. Dietrich et al.). [5] The blue, green or red tracks indicate that each asteroid has been detected through one of the three filters, respectively. Each track is composed of several, smaller sub-tracks, reflecting the sequence of several exposures performed in each of the filters; from the length of these sub-tracks, the distance to the asteroid can be calculated. More information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Stars and gas in high redshift galaxies

NASA Astrophysics Data System (ADS)

Pettini, Max

Recent advances in instrumentation and observing techniques have made it possible to begin to study in detail the stellar populations and the interstellar media of galaxies at redshift z=3, when the universe was still in its "teen years". In keeping with the theme of this conference, I show how our knowledge of local star-forming regions can be applied directly to these distant galaxies to deduce their ages, metallicities, initial mass function, and masses. I also discuss areas where current limitations in stellar astrophysics have a direct bearing on the interpretation of the data being gathered, at an ever increasing rate, on the high redshift universe.

REVIEWS OF TOPICAL PROBLEMS: Sky surveys and deep fields of ground-based and space telescopes

NASA Astrophysics Data System (ADS)

Reshetnikov, Vladimir P.

2005-11-01

Selected results obtained in major observational sky surveys (DSS, 2MASS, 2dF, SDSS) and deep field observations (HDF, GOODS, UHDF, etc.) are reviewed. Modern surveys provide information on the characteristics and space distribution of millions of galaxies. Deep fields allow one to study galaxies at the stage of formation and to trace their evolution over billions of years. The wealth of observational data is altering the face of modern astronomy: the formulation of problems and their solutions are changing and all the previous knowledge, from planetary studies in the solar system to the most distant galaxies and quasars, is being revised.

NTT, Spitzer, and Chandra Spectroscopy of SDSSJ095209.56+214313.3: The Most Luminous Coronal-line Supernova Ever Observed, or a Stellar Tidal Disruption Event?

NASA Astrophysics Data System (ADS)

Komossa, S.; Zhou, H.; Rau, A.; Dopita, M.; Gal-Yam, A.; Greiner, J.; Zuther, J.; Salvato, M.; Xu, D.; Lu, H.; Saxton, R.; Ajello, M.

2009-08-01

The galaxy SDSSJ095209.56+214313.3 (SDSSJ0952+2143 hereafter) showed remarkable emission-line and continuum properties and strong emission-line variability first reported in 2008 (Paper I). The spectral properties and low-energy variability are the consequence of a powerful high-energy flare which was itself not observed directly. Here we report follow-up optical, near-infrared (NIR), mid-infrared (MIR), and X-ray observations of SDSSJ0952+2143. We discuss outburst scenarios in terms of stellar tidal disruption by a supermassive black hole, peculiar variability of an active galactic nucleus (AGN), and a supernova (SN) explosion, and possible links between these scenarios and mechanisms. The optical spectrum of SDSSJ0952+2143 exhibits several peculiarities: an exceptionally high ratio of [Fe VII] transitions over [O III], a dramatic decrease by a factor of 10 of the highest-ionization coronal lines, a very unusual and variable Balmer line profile including a triple-peaked narrow component with two unresolved horns, and a large Balmer decrement. The MIR emission measured with the Spitzer IRS in the narrow 10-20 μm band is extraordinarily luminous and amounts to L 10-20 μm = 3.5 × 1043 erg s-1. The IRS spectrum shows a bump around ~11 μm and an increase toward longer wavelengths, reminiscent of silicate emission. The strong MIR excess over the NIR implies the dominance of relatively cold dust. The pre- and post-flare NIR host galaxy colors indicate a nonactive galaxy. The X-ray luminosity of L x,0.1-10 keV = 1041 erg s-1 measured with Chandra is below that typically observed in AGNs. Similarities of SDSSJ0952+2143 with some extreme SNe suggest the explosion of a SN of Type IIn. However, an extreme accretion event in a low-luminosity AGN or inactive galaxy, especially stellar tidal disruption, remain possibilities, which could potentially produce a very similar emission-line response. If indeed a SN, SDSSJ0952+2143 is one of the most distant X-ray- and MIR-detected SNe known so far, the most MIR luminous, and one of the most X-ray luminous. It is also by far the most luminous (>1040 erg s-1) in high-ionization coronal lines, exceeding previous SNe by at least a factor of 100.

The X-ray luminous galaxy cluster XMMU J1007.4+1237 at z = 1.56. The dawn of starburst activity in cluster cores

NASA Astrophysics Data System (ADS)

Fassbender, R.; Nastasi, A.; Böhringer, H.; Šuhada, R.; Santos, J. S.; Rosati, P.; Pierini, D.; Mühlegger, M.; Quintana, H.; Schwope, A. D.; Lamer, G.; de Hoon, A.; Kohnert, J.; Pratt, G. W.; Mohr, J. J.

2011-03-01

Context. Observational galaxy cluster studies at z > 1.5 probe the formation of the first massive M > 1014 M⊙ dark matter halos, the early thermal history of the hot ICM, and the emergence of the red-sequence population of quenched early-type galaxies. Aims: We present first results for the newly discovered X-ray luminous galaxy cluster XMMU J1007.4+1237 at z = 1.555, detected and confirmed by the XMM-Newton Distant Cluster Project (XDCP) survey. Methods: We selected the system as a serendipitous weak extended X-ray source in XMM-Newton archival data and followed it up with two-band near-infrared imaging and deep optical spectroscopy. Results: We can establish XMMU J1007.4+1237 as a spectroscopically confirmed, massive,bona fide galaxy cluster with a bolometric X-ray luminosity of Lbol_X,500≃(2.1 ± 0.4)× 10^{44} erg/s, a red galaxy population centered on the X-ray emission, and a central radio-loud brightest cluster galaxy. However, we see evidence for the first time that the massive end of the galaxy population and the cluster red-sequence are not yet fully in place. In particular, we find ongoing starburst activity for the third ranked galaxy close to the center and another slightly fainter object. Conclusions: At a lookback time of 9.4 Gyr, the cluster galaxy population appears to be caught in an important evolutionary phase, prior to full star-formation quenching and mass assembly in the core region. X-ray selection techniques are an efficient means of identifying and probing the most distant clusters without any prior assumptions about their galaxy content. Based on observations under programme ID 081.A-0312 collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, and observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Figure 2 and Tables 1 and 2 are only available in electronic form at http://www.aanda.org

Hubble Sees a Slashing Smudge Across the Sky

NASA Image and Video Library

2017-12-08

The galaxy cutting dramatically across the frame of this NASA/ESA Hubble Space Telescope image is a slightly warped dwarf galaxy known as UGC1281. Seen here from an edge-on perspective, this galaxy lies roughly 18 million light-years away in the constellation of Triangulum (The Triangle). The bright companion to the lower left of UGC 1281 is the small galaxy PGC 6700, officially known as 2MASX J01493473+3234464. Other prominent stars belonging to our own galaxy, the Milky Way, and more distant galaxies can be seen scattered throughout the sky. The side-on view we have of UGC 1281 makes it a perfect candidate for studies into how gas is distributed within galactic halos — the roughly spherical regions of diffuse gas extending outwards from a galaxy’s center. Astronomers have studied this galaxy to see how its gas vertically extends out from its central plane, and found it to be a quite typical dwarf galaxy. However, it does have a slightly warped shape to its outer edges, and is forming stars at a particularly low rate. European Space Agency Credit: ESA/NASA, Acknowledgement Luca Limatola

EFFECTS OF HOT HALO GAS ON STAR FORMATION AND MASS TRANSFER DURING DISTANT GALAXY–GALAXY ENCOUNTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, Jeong-Sun; Park, Changbom, E-mail: jshwang@kias.re.kr, E-mail: cbp@kias.re.kr

2015-06-01

We use N-body/smoothed particle hydrodynamics simulations of encounters between an early-type galaxy (ETG) and a late-type galaxy (LTG) to study the effects of hot halo gas on the evolution for a case with the mass ratio of the ETG to LTG of 2:1 and the closest approach distance of ∼100 kpc. We find that the dynamics of the cold disk gas in the tidal bridge and the amount of the newly formed stars depend strongly on the existence of a gas halo. In the run of interacting galaxies not having a hot gas halo, the gas and stars accreted into themore » ETG do not include newly formed stars. However, in the run using the ETG with a gas halo and the LTG without a gas halo, a shock forms along the disk gas tidal bridge and induces star formation near the closest approach. The shock front is parallel to a channel along which the cold gas flows toward the center of the ETG. As a result, the ETG can accrete star-forming cold gas and newly born stars at and near its center. When both galaxies have hot gas halos, a shock is formed between the two gas halos somewhat before the closest approach. The shock hinders the growth of the cold gas bridge to the ETG and also ionizes it. Only some of the disk stars transfer through the stellar bridge. We conclude that the hot halo gas can give significant hydrodynamic effects during distant encounters.« less

LACERTA I AND CASSIOPEIA III. TWO LUMINOUS AND DISTANT ANDROMEDA SATELLITE DWARF GALAXIES FOUND IN THE 3{pi} PAN-STARRS1 SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Nicolas F.; Laevens, Benjamin P. M.; Slater, Colin T.

We report the discovery of two new dwarf galaxies, Lacerta I/Andromeda XXXI (Lac I/And XXXI) and Cassiopeia III/Andromeda XXXII (Cas III/And XXXII), in stacked Pan-STARRS1 r{sub P1}- and i{sub P1}-band imaging data. Both are luminous systems (M{sub V} {approx} -12) located at projected distances of 20. Degree-Sign 3 and 10. Degree-Sign 5 from M31. Lac I and Cas III are likely satellites of the Andromeda galaxy with heliocentric distances of 756{sup +44}{sub -28} kpc and 772{sup +61}{sub -56} kpc, respectively, and corresponding M31-centric distances of 275 {+-} 7 kpc and 144{sup +6}{sub -4} kpc. The brightest of recent Local Groupmore » member discoveries, these two new dwarf galaxies owe their late discovery to their large sizes (r{sub h} = 4.2{sup +0.4}{sub -0.5} arcmin or 912{sup +124}{sub -93} pc for Lac I; r{sub h} = 6.5{sup +1.2}{sub -1.0} arcmin or 1456 {+-} 267 pc for Cas III) and consequently low surface brightness ({mu}{sub 0} {approx} 26.0 mag arcsec{sup -2}), as well as to the lack of a systematic survey of regions at large radii from M31, close to the Galactic plane. This latter limitation is now alleviated by the 3{pi} Pan-STARRS1 survey, which could lead to the discovery of other distant Andromeda satellite dwarf galaxies.« less

Radio Selection of the Most Distant Galaxy Clusters

NASA Astrophysics Data System (ADS)

Daddi, E.; Jin, S.; Strazzullo, V.; Sargent, M. T.; Wang, T.; Ferrari, C.; Schinnerer, E.; Smolčić, V.; Calabró, A.; Coogan, R.; Delhaize, J.; Delvecchio, I.; Elbaz, D.; Gobat, R.; Gu, Q.; Liu, D.; Novak, M.; Valentino, F.

2017-09-01

We show that the most distant X-ray-detected cluster known to date, Cl J1001 at {z}{spec}=2.506, hosts a strong overdensity of radio sources. Six of them are individually detected (within 10\\prime\\prime ) in deep 0\\buildrel{\\prime\\prime}\\over{.} 75 resolution VLA 3 GHz imaging, with {S}3{GHz}> 8 μ {Jy}. Of the six, an active galactic nucleus (AGN) likely affects the radio emission in two galaxies, while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2 deg2 field using radio-detected 3 GHz sources and looking for peaks in {{{Σ }}}5 density maps. Cl J1001 is the strongest overdensity by far with > 10σ , with a simple {z}{phot}> 1.5 preselection. A cruder photometric rejection of z< 1 radio foregrounds leaves Cl J1001 as the second strongest overdensity, while even using all radio sources Cl J1001 remains among the four strongest projected overdensities. We conclude that there are great prospects for future deep and wide-area radio surveys to discover large samples of the first generation of forming galaxy clusters. In these remarkable structures, widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1-1 per square degree at z≳ 2.5. Samples of hundreds such high-redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models.

An Extreme Protocluster of Luminous Dusty Starbursts in the Early Universe

NASA Astrophysics Data System (ADS)

Oteo, I.; Ivison, R. J.; Dunne, L.; Manilla-Robles, A.; Maddox, S.; Lewis, A. J. R.; de Zotti, G.; Bremer, M.; Clements, D. L.; Cooray, A.; Dannerbauer, H.; Eales, S.; Greenslade, J.; Omont, A.; Perez–Fournón, I.; Riechers, D.; Scott, D.; van der Werf, P.; Weiss, A.; Zhang, Z.-Y.

2018-03-01

We report the identification of an extreme protocluster of galaxies in the early universe whose core (nicknamed Distant Red Core, DRC, because of its very red color in Herschel SPIRE bands) is formed by at least 10 dusty star-forming galaxies (DSFGs), spectroscopically confirmed to lie at {z}spec}=4.002 via detection of [C I](1–0), 12CO(6–5), 12CO(4–3), 12CO(2–1), and {{{H}}}2{{O}}({2}11{--}{2}02) emission lines with ALMA and ATCA. These DSFGs are distributed over a 260 {kpc}× 310 {kpc} region and have a collective obscured star formation rate (SFR) of ∼ 6500 {M}ȯ {yr}}-1, considerably higher than those seen before in any protocluster at z≳ 4. Most of the star formation is taking place in luminous DSFGs since no Lyα emitters are detected in the protocluster core, apart from a Lyα blob located next to one of the DRC components, extending over 60 {kpc}. The total obscured SFR of the protocluster could rise to {SFR}∼ {{14,400}} {M}ȯ {yr}}-1 if all the members of an overdensity of bright DSFGs discovered around DRC in a wide-field Large APEX BOlometer CAmera 870 μm image are part of the same structure. [C I](1–0) emission reveals that DRC has a total molecular gas mass of at least {M}{{{H}}2}∼ 6.6× {10}11 {M}ȯ , and its total halo mass could be as high as ∼ 4.4× {10}13 {M}ȯ , indicating that it is the likely progenitor of a cluster at least as massive as Coma at z = 0.

Large Binocular Telescope/LUCIFER spectroscopy: kinematics of a compact early-type galaxy at z ≃ 1.4

NASA Astrophysics Data System (ADS)

Longhetti, M.; Saracco, P.; Gargiulo, A.; Tamburri, S.; Lonoce, I.

2014-04-01

We present a high signal-to-noise ratio (S/N > 10) medium-resolution (R = 2000) Large Binocular Telescope/LUCIFER spectrum of the early-type galaxy (ETG) S2F1-142 at z ≃ 1.4. By means of the CaT line at 8662 Å, we measured its redshift z = 1.386 ± 0.001 and we estimated its velocity dispersion σ v=340^{-60}_{+120} km s-1. Its corresponding virial mass is 3.9 × 1011 M⊙, compatible with the stellar mass estimates obtained assuming initial mass functions (IMFs) less dwarf rich than the Salpeter one. S2F1-142 is a compact galaxy with Re = 3.1 ± 0.2 kpc, i.e. an effective radius more than three times smaller than the average Re of ETGs with the same mass in the local Universe. At the same time, we found local and high-redshift galaxies with a similar mass content and similar effective radius confirming that it is fully consistent with the already available measures of Re and σv both in the local and in the distant Universe. Considering the distribution of Re and σv as a function of the stellar mass content of ETGs, both in the local and in the distant Universe, we noticed that the measured velocity dispersions of the more compact galaxies are on average slightly lower than expected on the basis of their compactness and the virial theorem, suggesting that (i) their dark matter content is lower than in the more diffuse galaxies and/or (ii) their luminosity profiles are steeper than in the more diffuse galaxies and/or (iii) their larger compactness is an apparent effect caused by the overestimate of their stellar mass content (due to bottom lighter IMF and/or systematic affecting the stellar mass estimates).

The Carnegie-Chicago Hubble Program: Discovery of the Most Distant Ultra-faint Dwarf Galaxy in the Local Universe

NASA Astrophysics Data System (ADS)

Lee, Myung Gyoon; Jang, In Sung; Beaton, Rachael; Seibert, Mark; Bono, Giuseppe; Madore, Barry

2017-02-01

Ultra-faint dwarf galaxies (UFDs) are the faintest known galaxies, and due to their incredibly low surface brightness, it is difficult to find them beyond the Local Group. We report a serendipitous discovery of a UFD, Fornax UFD1, in the outskirts of NGC 1316, a giant galaxy in the Fornax cluster. The new galaxy is located at a projected radius of 55 kpc in the south-east of NGC 1316. This UFD is found as a small group of resolved stars in the Hubble Space Telescope images of a halo field of NGC 1316, obtained as part of the Carnegie-Chicago Hubble Program. Resolved stars in this galaxy are consistent with being mostly metal-poor red giant branch (RGB) stars. Applying the tip of the RGB method to the mean magnitude of the two brightest RGB stars, we estimate the distance to this galaxy, 19.0 ± 1.3 Mpc. Fornax UFD1 is probably a member of the Fornax cluster. The color-magnitude diagram of these stars is matched by a 12 Gyr isochrone with low metallicity ([Fe/H] ≈ -2.4). Total magnitude and effective radius of Fornax UFD1 are MV ≈ -7.6 ± 0.2 mag and reff = 146 ± 9 pc, which are similar to those of Virgo UFD1 that was discovered recently in the intracluster field of Virgo by Jang & Lee. Fornax UFD1 is the most distant known UFD that is confirmed by resolved stars. This indicates that UFDs are ubiquitous and that more UFDs remain to be discovered in the Fornax cluster. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #10505 and #13691.

Spectroscopic detections of C III] λ1909 Å at z ≃ 6-7: a new probe of early star-forming galaxies and cosmic reionization

NASA Astrophysics Data System (ADS)

Stark, Daniel P.; Richard, Johan; Charlot, Stéphane; Clément, Benjamin; Ellis, Richard; Siana, Brian; Robertson, Brant; Schenker, Matthew; Gutkin, Julia; Wofford, Aida

2015-06-01

Deep spectroscopic observations of z ≳ 6.5 galaxies have revealed a marked decline with increasing redshift in the detectability of Ly α emission. While this may offer valuable insight into the end of the reionization process, it presents a challenge to the detailed spectroscopic study of bright photometrically-selected distant sources now being found via deep Hubble Space Telescope imaging, and particularly those highly magnified sources viewed through foreground lensing clusters. In this paper, we demonstrate the validity of a new way forward via the detection of an alternative diagnostic line, C III] λ1909 Å, seen in spectroscopic exposures of a star-forming galaxy at zLyα = 6.029. We also report tentative detection of C III] λ1909 Å in a galaxy at zLyα = 7.213. The former 3.3σ detection is based on a 3.5 h XShooter spectrum of a bright (J125 = 25.2) gravitationally-lensed galaxy behind the cluster Abell 383. The latter 2.8σ detection is based on a 4.2 h MOSFIRE spectra of one of the most distant spectroscopically confirmed galaxies, GN-108036, with J140 = 25.2. Both targets were chosen for their continuum brightness and previously-known redshift (based on Ly α), ensuring that any C III] emission would be located in a favourable portion of the near-infrared sky spectrum. Since the availability of secure Ly α redshifts significantly narrows the wavelength range where C III] is sought, this increases confidence in these, otherwise, low-signal-to-noise ratio detections. We compare our C III] and Ly α equivalent widths in the context of those found at z ≃ 2 from earlier work and discuss the motivation for using lines other than Ly α to study galaxies in the reionization era.

GRBs: The Most Distant Signposts in our Universe

NASA Technical Reports Server (NTRS)

Kouveliotou, Chryssa

2007-01-01

Gamma-Ray Bursts (GRBs) are the most powerful photon sources in the Universe, rivaled only by supernovae in the magnitude of their energy release. In 1997 GRB were found to originate in host galaxies at cosmological distances, revealing the total energy of their explosions to be an astounding approx.10(exp 52) - 10(exp 53)ergs. GRB durations span over five orders of magnitude, ranging from milliseconds to thousands of seconds. The underlying sources of the energy release remain, however, unknown. Leading candidates are mergers, either of two neutron stars or of a black hole and a neutron star, and core collapses of very massive stars, called "collapsars". To date the furthest GRB galaxy has been found at a cosmological redshift of 6.29, very close to the most distant quasar (at z=6.4). Since the Swift satellite continues to observe these phenomena at a rate of approx.120 per year, and with the upcoming launch of GLAST with two burst instruments on board, we will be able to use GRBs as beacons to probe very high redshifts. Thus bursts found at 6

Star from the Lizard Constellation Photobombs Hubble Observation

NASA Image and Video Library

2017-12-08

In space, being outshone is an occupational hazard. This NASA/ESA Hubble Space Telescope image captures a galaxy named NGC 7250. Despite being remarkable in its own right — it has bright bursts of star formation and recorded supernova explosions— it blends into the background somewhat thanks to the gloriously bright star hogging the limelight next to it. The bright object seen in this Hubble image is a single and little-studied star named TYC 3203-450-1, located in the constellation of Lacerta (The Lizard). The star is much closer than the much more distant galaxy. Only this way can a normal star outshine an entire galaxy, consisting of billions of stars. Astronomers studying distant objects call these stars “foreground stars” and they are often not very happy about them, as their bright light is contaminating the faint light from the more distant and interesting objects they actually want to study. In this case, TYC 3203-450-1 is million times closer than NGC 7250, which lies more than 45 million light-years away from us. If the star were the same distance from us as NGC 7250, it would hardly be visible in this image. Credit: ESA/Hubble & NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Mg II-Absorbing Galaxies in the UltraVISTA Survey

NASA Astrophysics Data System (ADS)

Stroupe, Darren; Lundgren, Britt

2018-01-01

Light that is emitted from distant quasars can become partially absorbed by intervening gaseous structures, including galaxies, in its path toward Earth, revealing information about the chemical content, degree of ionization, organization and evolution of these structures through time. In this project, quasar spectra are used to probe the halos of foreground galaxies at a mean redshift of z=1.1 in the COSMOS Field. Mg II absorption lines in Sloan Digital Sky Survey quasar spectra are paired with galaxies in the UltraVISTA catalog at an impact parameter less than 200 kpc. A sample of 77 strong Mg II absorbers with a rest-frame equivalent width ≥ 0.3 Å and redshift from 0.34 < z < 2.21 are investigated to find equivalent width ratios of Mg II, C IV and Fe II absorption lines, and their relation to the impact parameter and the star formation rates, stellar masses, environments and redshifts of their host galaxies.

Stray Stars Scattered in Space Artist Concept

NASA Image and Video Library

2014-11-06

This artist concept shows a view of a number of galaxies sitting in huge halos of stars. The stars are too distant to be seen individually and instead are seen as a diffuse glow, colored yellow in this illustration.

A Distant, X-Ray Luminous Cluster of Galaxies at Redshift 0.83

NASA Technical Reports Server (NTRS)

Donahue, Megan

1999-01-01

We have observed the most distant (= 0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3(sup 3.1, sub 2.2) keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members we have obtained at the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing signature. The X-ray temperature of this cluster implies a virial mass approximately 7.4 x 10(exp 14) /h solar mass, if the mean matter density in the universe equals the critical value (OMEGA(sub 0) = 1), or larger if OMEGA(sub 0) < 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an OMEGA(sub 0) = 1 universe. Combining the assumptions that OMEGA(sub 0) = 1 and that the initial perturbations were Gaussian with the observed X-ray temperature function at low redshift, we show that this probability of this cluster occurring in the volume sampled by the EMSS is less than a few times 10(exp -5). Nor is MS1054-0321 the only hot cluster at high redshift; the only two other z > 0.5 EMSS clusters already observed with ASCA also have temperatures exceeding 8 keV. Assuming again that the initial perturbations were Gaussian and OMEGA(sub 0) = 1, we find that each one is improbable at the < 10(exp -2) level. These observations, along with the fact that these luminosities and temperatures of the high-z clusters all agree with the low-z L(sub x) - T(sub x) relation, argue strongly that OMEGA(sub 0) < 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.

Discovery of a large-scale clumpy structure of the Lynx supercluster at z[similar]1.27

NASA Astrophysics Data System (ADS)

Nakata, Fumiaki; Kodama, Tadayuki; Shimasaku, Kazuhiro; Doi, Mamoru; Furusawa, Hisanori; Hamabe, Masaru; Kimura, Masahiko; Komiyama, Yutaka; Miyazaki, Satoshi; Okamura, Sadanori; Ouchi, Masami; Sekiguchi, Maki; Yagi, Masafumi; Yasuda, Naoki

2004-07-01

We report the discovery of a probable large-scale structure composed of many galaxy clumps around the known twin clusters at z=1.26 and z=1.27 in the Lynx region. Our analysis is based on deep, panoramic, and multi-colour imaging with the Suprime-Cam on the 8.2 m Subaru telescope. We apply a photometric redshift technique to extract plausible cluster members at z˜1.27 down to ˜ M*+2.5. From the 2-D distribution of these photometrically selected galaxies, we newly identify seven candidates of galaxy groups or clusters where the surface density of red galaxies is significantly high (>5σ), in addition to the two known clusters, comprising the largest most distant supercluster ever identified.

Gravitational-wave bursts from the nuclei of distant galaxies and quasars: Proposal for detection using Doppler tracking of interplanetary spacecraft

NASA Technical Reports Server (NTRS)

Thorne, K. S.; Braginsky, V. B.

1974-01-01

Supermassive black holes which exist in the nuclei of many quasars and galaxies are examined along with the collapse which forms these holes and subsequent collisions between them which produce strong, broad-band bursts of gravitational waves. Such bursts might arrive at earth as often as 50 times per year--or as rarely as once each 300 years. The detection of such bursts with dual-frequency Doppler tracking of interplanetary spacecraft is considered.

Galaxy pairs in the Sloan Digital Sky Survey - XI. A new method for measuring the influence of the closest companion out to wide separations

NASA Astrophysics Data System (ADS)

Patton, David R.; Qamar, Farid D.; Ellison, Sara L.; Bluck, Asa F. L.; Simard, Luc; Mendel, J. Trevor; Moreno, Jorge; Torrey, Paul

2016-09-01

We describe a statistical approach for measuring the influence that a galaxy's closest companion has on the galaxy's properties out to arbitrarily wide separations. We begin by identifying the closest companion for every galaxy in a large spectroscopic sample of Sloan Digital Sky Survey galaxies. We then characterize the local environment of each galaxy by using the number of galaxies within 2 Mpc and by determining the isolation of the galaxy pair from other neighbouring galaxies. We introduce a sophisticated algorithm for creating a statistical control sample for each galaxy, matching on stellar mass, redshift, local density and isolation. Unlike traditional studies of close galaxy pairs, this approach is effective in a wide range of environments, regardless of how faraway the closest companion is (although a very distant closest companion is unlikely to have a measurable influence on the galaxy in question). We apply this methodology to measurements of galaxy asymmetry, and find that the presence of nearby companions drives a clear enhancement in galaxy asymmetries. The asymmetry excess peaks at the smallest projected separations (<10 kpc), where the mean asymmetry is enhanced by a factor of 2.0 ± 0.2. Enhancements in mean asymmetry decline as pair separation increases, but remain statistically significant (1σ-2σ) out to projected separations of at least 50 kpc.

Star Formation-Driven Winds in the Early Universe

NASA Astrophysics Data System (ADS)

Peek, Matthew; Lundgren, Britt; Brammer, Gabriel

2018-01-01

Measuring the extent of star formation-driven winds from galaxies in the early universe is crucial for understanding of how galaxies evolve over cosmic time. Using WFC3/IR grism data from the Hubble Space Telescope (HST), we have measured the star formation rates and star formation rate surface densities of several hundred galaxies at redshift (z) = 1, when the universe was roughly half its present age. The galaxies we examine are also probed by background quasars, whose spectra provide information about the extent of metal-enriched gas in their halos. We use a computational pipeline to measure the density of the star formation in each galaxy and correlate these measurements with detections of Mg II absorption in nearby quasar spectra from the Sloan Digital Sky Survey. Our preliminary results support a model in which galaxies with high SFR surface densities drive metal-enriched gas out of the disk and into these galaxies’ extended halos, where that gas is detected in the spectra of more distant quasars.

The x-ray luminous galaxy cluster population at 0.9 < z ≲ 1.6 as revealed by the XMM-Newton Distant Cluster Project

NASA Astrophysics Data System (ADS)

Fassbender, R.; Böhringer, H.; Nastasi, A.; Šuhada, R.; Mühlegger, M.; de Hoon, A.; Kohnert, J.; Lamer, G.; Mohr, J. J.; Pierini, D.; Pratt, G. W.; Quintana, H.; Rosati, P.; Santos, J. S.; Schwope, A. D.

2011-12-01

We present the largest sample to date of spectroscopically confirmed x-ray luminous high-redshift galaxy clusters comprising 22 systems in the range 0.9 as part of the XMM-Newton Distant Cluster Project (XDCP). All systems were initially selected as extended x-ray sources over 76.1 deg2 of non-contiguous deep archival XMM-Newton coverage, of which 49.4 deg2 are part of the core survey with a quantifiable selection function and 17.7 deg2 are classified as ‘gold’ coverage as the starting point for upcoming cosmological applications. Distant cluster candidates were followed up with moderately deep optical and near-infrared imaging in at least two bands to photometrically identify the cluster galaxy populations and obtain redshift estimates based on the colors of simple stellar population models. We test and calibrate the most promising redshift estimation techniques based on the R-z and z-H colors for efficient distant cluster identifications and find a good redshift accuracy performance of the z-H color out to at least z ˜ 1.5, while the redshift evolution of the R-z color leads to increasingly large uncertainties at z ≳ 0.9. Photometrically identified high-z systems are spectroscopically confirmed with VLT/FORS 2 with a minimum of three concordant cluster member redshifts. We present first details of two newly identified clusters, XDCP J0338.5+0029 at z = 0.916 and XDCP J0027.2+1714 at z = 0.959, and investigate the x-ray properties of SpARCS J003550-431224 at z = 1.335, which shows evidence for ongoing major merger activity along the line-of-sight. We provide x-ray properties and luminosity-based total mass estimates for the full sample of 22 high-z clusters, of which 17 are at z ⩾ 1.0 and seven populate the highest redshift bin at z > 1.3. The median system mass of the sample is M200 ≃ 2 × 1014 M⊙, while the probed mass range for the distant clusters spans approximately (0.7-7) × 1014 M⊙. The majority (>70%) of the x-ray selected clusters show rather regular x-ray morphologies, albeit in most cases with a discernible elongation along one axis. In contrast to local clusters, the z > 0.9 systems mostly do not harbor central dominant galaxies coincident with the x-ray centroid position, but rather exhibit significant brightest cluster galaxy (BCG) offsets from the x-ray center with a median value of about 50 kpc in projection and a smaller median luminosity gap to the second-ranked galaxy of Δm12 ≃ 0.3 mag. We estimate a fraction of cluster-associated NVSS 1.4 GHz radio sources of about 30%, preferentially located within 1‧ from the x-ray center. This value suggests an increase of the fraction of very luminous cluster-associated radio sources by about a factor of 2.5-5 relative to low-z systems. The galaxy populations in z ≳ 1.5 cluster environments show first evidence for drastic changes on the high-mass end of galaxies and signs of a gradual disappearance of a well-defined cluster red-sequence as strong star formation activity is observed in an increasing fraction of massive galaxies down to the densest core regions. The presented XDCP high-z sample will allow first detailed studies of the cluster population during the critical cosmic epoch at lookback times of 7.3-9.5 Gyr on the aggregation and evolution of baryons in the cold and hot phases as a function of redshift and system mass. Based on observations under program IDs 079.A-0634 and 085.A-0647 collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, and observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).

Eight per cent leakage of Lyman continuum photons from a compact, star-forming dwarf galaxy.

PubMed

Izotov, Y I; Orlitová, I; Schaerer, D; Thuan, T X; Verhamme, A; Guseva, N G; Worseck, G

2016-01-14

One of the key questions in observational cosmology is the identification of the sources responsible for ionization of the Universe after the cosmic 'Dark Ages', when the baryonic matter was neutral. The currently identified distant galaxies are insufficient to fully reionize the Universe by redshift z ≈ 6 (refs 1-3), but low-mass, star-forming galaxies are thought to be responsible for the bulk of the ionizing radiation. As direct observations at high redshift are difficult for a variety of reasons, one solution is to identify local proxies of this galaxy population. Starburst galaxies at low redshifts, however, generally are opaque to Lyman continuum photons. Small escape fractions of about 1 to 3 per cent, insufficient to ionize much surrounding gas, have been detected only in three low-redshift galaxies. Here we report far-ultraviolet observations of the nearby low-mass star-forming galaxy J0925+1403. The galaxy is leaking ionizing radiation with an escape fraction of about 8 per cent. The total number of photons emitted during the starburst phase is sufficient to ionize intergalactic medium material that is about 40 times as massive as the stellar mass of the galaxy.

ON THE OXYGEN AND NITROGEN CHEMICAL ABUNDANCES AND THE EVOLUTION OF THE 'GREEN PEA' GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amorin, Ricardo O.; Perez-Montero, Enrique; Vilchez, J. M., E-mail: amorin@iaa.e, E-mail: epm@iaa.e, E-mail: jvm@iaa.e

2010-06-01

We have investigated the oxygen and nitrogen chemical abundances in extremely compact star-forming galaxies (SFGs) with redshifts between {approx}0.11 and 0.35, popularly referred to as 'green peas'. Direct and strong-line methods sensitive to the N/O ratio applied to their Sloan Digital Sky Survey (SDSS) spectra reveal that these systems are genuine metal-poor galaxies, with mean oxygen abundances {approx}20% solar. At a given metallicity these galaxies display systematically large N/O ratios compared to normal galaxies, which can explain the strong difference between our metallicities measurements and previous ones. While their N/O ratios follow the relation with stellar mass of local SFGsmore » in the SDSS, we find that the mass-metallicity relation of the 'green peas' is offset {approx_gt}0.3 dex to lower metallicities. We argue that recent interaction-induced inflow of gas, possibly coupled with a selective metal-rich gas loss, driven by supernova winds, may explain our findings and the known galaxy properties, namely high specific star formation rates, extreme compactness, and disturbed optical morphologies. The 'green pea' galaxy properties seem to be uncommon in the nearby universe, suggesting a short and extreme stage of their evolution. Therefore, these galaxies may allow us to study in great detail many processes, such as starburst activity and chemical enrichment, under physical conditions approaching those in galaxies at higher redshifts.« less

Into the Epoch of Galaxy Formation

NASA Astrophysics Data System (ADS)

2000-02-01

Infrared VLT Observations Identify Hidden Galaxies in the Early Universe Working with the ESO Very Large Telescope (VLT) at the Paranal Observatory , a group of European astronomers [1] has just obtained one of the deepest looks into the distant Universe ever made by an optical telescope. These observations were carried out in the near-infrared spectral region and are part of an attempt to locate very distant galaxies that have so far escaped detection in the visual bands. The first results are very promising and some concentrations of galaxies at very large distances were uncovered. Some early galaxies may be in hiding Current theories hypothesize that more than 80% of all stars ever formed were assembled in galaxies during the latter half of the elapsed lifetime of the Universe, i.e., during the past 7-8 billion years. However, doubts have arisen about these ideas. There are now observational indications that a significant number of those galaxies that formed during the first 20% of the age of the Universe, i.e. within about 3 billion years after the Big Bang, may not be visible to optical telescopes. In some cases, we do not see them, because their light is obscured by dust. Other distant galaxies may escape detection by optical telescopes because star formation in them has ceased and their light is mainly emitted in the red and infrared spectral bands. This is because, while very young galaxies mostly contain hot and blue stars, older galaxies have substantial numbers of cool and red stars. They are then dominated by an older, "evolved" stellar population that is cooler and redder. The large cosmic velocities of these galaxies further enhance this effect by causing their light to be "redshifted" towards longer wavelengths, i.e. into the near-infrared spectral region. Observations in the infrared needed Within the present programme, long exposures in near-infrared wavebands were made with the Infrared Spectrometer And Array Camera (ISAAC) , mounted on ANTU , the first of the four 8.2-m VLT Unit Telescopes. A first analysis of the new observations indicates that "evolved" galaxies were already present when the Universe was only 4 billion years old. This information is of great importance to our understanding of how the matter in the early Universe condensed and the first galaxies and stars came into being. While in the nearby Universe evolved galaxies are preferentially located in denser environments such as groups and clusters of galaxies, little is currently known about the distribution in space of such objects at early cosmic epochs. In order to be able to see such obscured and/or "evolved" galaxies in the early Universe, and to look for hitherto unknown galaxies beyond the limits of "deep-field" imaging in visible spectral bands, it is necessary to employ other observing techniques. The astronomers must search for such objects on large-field, very long-exposure sky images obtained in the near-infrared (NIR, wavelength 1-2 µm) region of the electromagnetic spectrum and at even longer wavelengths (> 10 µm) in the far-IR and in the sub-mm range. Such observations are beyond the capability of the infrared cameras installed on the world's 4-m class telescopes. However, the advent of the ISAAC instrument at the 8.2-m ANTU telescope has now opened new and exciting research opportunities in this direction for European astronomers. With ISAAC , it is possible to obtain "deep" NIR images in an unprecedentedly wide field of view, covering a sky area about 7 times larger than with the best instruments previously available on very large telescopes. Such observations also benefit greatly from the very good optical quality provided by the active optics control of the VLT, as well as the excellent Paranal site. The ISAAC/ANTU observations ESO PR Photo 06a/00 ESO PR Photo 06a/00 [Preview - JPEG: 400 x 427pix - 69k] [Normal - JPEG: 800 x 853 pix - 195k] [Full-Res - JPEG: 942 x 1004 pix - 635k] Caption : ESO PR Photo 06a/00 displays a 4.5 arcmin 2 area of the "AXAF Deep Field" , as observed with the ISAAC multi-mode instrument at VLT ANTU in the near-IR K band (at wavelength 2.x µm). The total integration time is 8.5 hours and the limiting magnitude is K = 23.5 per arcsec 2 (at S/N-ratio = 3). The pixel size is 0.15 arcsec. North is up and east is left. The "Full-Res" version maintains the original pixels and is of the highest reproduction quality (least file compression). The reproduction is "negative", with dark objects on a light sky, in order to better show the faintest objects. See also the technical note below. ESO PR Photo 06b/00 ESO PR Photo 06b/00 [Preview - JPEG: 400 x 451 pix - 103k] [Normal - JPEG: 800 x 902 pix - 270k] [Full-Res - JPEG: 924 x 1042 pix - 704k] Caption : ESO PR Photo 06b/00 is a composite colour image of the field shown in PR Photo 06a/00 . It is a combination of the K-band image from ANTU/ISAAC shown in PR Photo 06a/00 with two images obtained in the B and R bands with the SUSI-2 optical imager at the New Technology Telescope (NTT) on La Silla in the framework of the ESO-EIS survey. Note the relatively high density of red galaxies, visible in the upper right part of this image. The colours of most of these galaxies are consistent with those of "evolved" galaxies, already present when the Universe was only 4 billions years old. The "Full-Res" version maintains the original pixels and is of the highest reproduction quality (least file compression). The group of European astronomers recently obtained a first "ultra-deep" 4.5 arcmin 2 image in the near-infrared J (wavelength 1.2 µm) and K (2.2 µm) bands, centered in the so-called "AXAF Deep Field", cf. PR Photos 06a-b/00 . This area of the sky is remarkably devoid of bright stars and provides a clear view towards the remote Universe, as there is little obscuring dust in our own Galaxy, the Milky Way, in this direction. It is therefore uniquely suited to probe the depth of the Universe. It is exactly for this reason that it was selected for a deep survey to be conducted with the Chandra X-Ray Observatory (CXO) during the guaranteed observing time of the former ESO Director General, Professor Riccardo Giacconi , and as a deep field of the ESO Imaging Survey (EIS, cf. ESO Press Photos 46a-j/99 ). The sky field observed with ISAAC and shown above is near the centre of the WFI image (ESO PR Photo 46a/99); it is displaced about 3.6 arcmin towards West and 1.0 armin towards North. As seen on the photos, there are great numbers of faint galaxies in this direction. Those of very red colour emit most of their light in the infrared spectral region and are particularly interesting since they may either be highly obscured or contain mostly old stars, as described above. New research possibilities With observations as these, ISAAC is now opening a new window towards the distant Universe. The comparison of the new NIR observations with earlier exposures at other wavelengths provides unique research opportunities. It is possible to measure the average star formation rate and the total stellar mass content in galaxies that are heavily obscured and are therefore not observable in the optical bands and which may constitute a substantial fraction of the primeval galaxy population. Such measurements will also allow to test current theories of galaxy formation that predict stars to be gradually assembled into galaxies, and hence envisage a progressive decline in the galaxy population towards very early cosmic times, in particular within 1-2 billion years after the Big Bang. Moreover, a comparison of NIR, optical and X-ray images will make it possible to gain new insights into the nuclear activity at the center of star-forming galaxies. It will become possible to study the distinct effects due to massive black holes and bursts of star formation. Concentrations of galaxies at large distances The relatively large field-of-view of ISAAC allows to gain information about the distribution in space of the faintest and most distant, evolved galaxies and also about the existence of associations of distant galaxies. A first clear example is the concentration of galaxies that appear uniformly yellow in PR Photo 06b/00 , apparently tracing a group of galaxies that was already assembled when the Universe was only 6 billion years old. A confirmation of the distance of a few of these galaxies has already been obtained by means of spectral observations in the framework of an ESO Large Programme , entitled "A Stringent Test on the Formation of Early Type and Massive Galaxies" and carried out by another group of astronomers [2]. A further clear example of a concentration of distant galaxies is seen in the upper right part of PR Photo 06b/00 . The very red colours of several galaxies in this sky area indicate that they are even more distant, "evolved" galaxies, already present when the Universe was only 1/3 of the current age. Notes [1] The European team consists of Emanuele Giallongo (Principal Investigator), Adriano Fontana , Nicola Menci and Francesco Poli (all at Rome Observatory), Stephane Arnouts and Sandro D'Odorico (European Southern Observatory, Garching), Stefano Cristiani (ST European Coordinating Facility, Garching) and Paolo Saracco (Milan Observatory). The data analysis was performed at the Milan ( P. Saracco ) and Rome ( A. Fontana , F. Poli ) Observatories. [2] This programme is conducted Andrea Cimatti (Principal Investigator) and Emanuele Daddi (both at Arcetri Observatory), Tom Broadhurst , Sandro D'Odorico , Roberto Gilmozzi and Alvio Renzini (European Southern Observatory), Stefano Cristiani (ST European Coordinating Facility, Garching), Adriano Fontana , Emanuele Giallongo , Nicola Menci and Francesco Poli (Rome Observatory), Marco Mignoli , Lucia Pozzetti and Giovanni Zamorani (Bologna Observatory) and Paolo Saracco (Milan Observatory). Technical note : The K-band image ( PR Photo 06a/00 ) is the result of 510 min of integration time with ISAAC at VLT ANTU. The 3-sigma magnitude limit is about K = 23.5 per arcsec 2. A J-band image was also obtained during 200 min of integration, with a 3-sigma limit of J = 25 per arcsec 2. The seeing FWHM (Full Width at Half Maximum) is 0.65 arcsec for both bands. The redshift, estimated on the basis of the measured colours of the mentioned over-density of yellow galaxies (cf. PR Photo 06b/00 ), is between 0.6 and 0.7 and that of the red galaxies is between 1 and 1.4. ESO PR Photos may be reproduced, if credit is given to the European Southern Observatory.

ALFALFA DISCOVERY OF THE MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirschauer, Alec S.; Salzer, John J.; Rhode, Katherine L., E-mail: ash@astro.indiana.edu, E-mail: slaz@astro.indiana.edu, E-mail: krhode@indiana.edu

We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part of the Survey of H i in Extremely Low-Mass Dwarfs project, which is a multi-wavelength study of galaxies with H i masses in the range of 10{sup 6}–10{sup 7.2} M {sub ⊙}, discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We have obtained spectra of the lone H ii region in AGC 198691 with the new high-throughput KPNO Ohio State Multi-Object Spectrograph on the Mayall 4 m, as well as with the Blue Channel spectrograph on the MMT 6.5 m telescope. These observations enablemore » the measurement of the temperature-sensitive [O iii] λ 4363 line and hence the determination of a “direct” oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) system with an oxygen abundance of 12+log(O/H) = 7.02 ± 0.03, making AGC 198691 the lowest-abundance star-forming galaxy known in the local universe. Two of the five lowest-abundance galaxies known have been discovered by the ALFALFA blind H i survey; this high yield of XMD galaxies represents a paradigm shift in the search for extremely metal-poor galaxies.« less

New VLA Images Unlocking Galactic Mysteries

NASA Astrophysics Data System (ADS)

2008-01-01

Astronomers have produced a scientific gold mine of detailed, high-quality images of nearby galaxies that is yielding important new insights into many aspects of galaxies, including their complex structures, how they form stars, the motions of gas in the galaxies, the relationship of "normal" matter to unseen "dark matter," and many others. An international team of scientists used more than 500 hours of observations with the National Science Foundation's Very Large Array (VLA) radio telescope to produce detailed sets of images of 34 galaxies at distances from 6 to 50 million light-years from Earth. Their project, called The HI Nearby Galaxy Survey, or THINGS, required two years to produce nearly one TeraByte of data. HI ("H-one") is an astronomical term for atomic hydrogen gas. The astronomers presented their initial findings to the American Astronomical Society's (AAS) meeting in Austin, Texas. "Studying the radio waves emitted by atomic hydrogen gas in galaxies is an extremely powerful way to learn what's going on in nearby galaxies. The THINGS survey uses that tool to provide sets of images of the highest quality and sensitivity for a substantial sample of galaxies of different types," said Fabian Walter, of the Max-Planck Institute for Astronomy in Heidelberg, Germany. IC2574M74 Dwarf galaxy IC2574, left, and spiral galaxy M74, in THINGS images. Credit: Walter et al., NRAO/AUI/NSF Click images for high-resolution files (33 KB & 25 KB) Spiral Galaxies in THINGS Most of the galaxies studied in the THINGS survey also have been observed at other wavelengths, including Spitzer space telescope infrared images and GALEX ultraviolet images. This combination provides an unprecedented resource for unravelling the mystery of how a galaxy's gaseous material influences its overall evolution. Analysis of THINGS data already has yielded numerous scientific payoffs. For example, one study has shed new light on astronomers' understanding of the gas-density threshold required to start the process of star formation. "Using the data from THINGS in combination with observations from NASA's space telescopes has allowed us to investigate how the processes leading to star formation differ in big spiral galaxies like our own and much smaller, dwarf galaxies," said Adam Leroy and Frank Bigiel of the Max-Planck Insitute for Astronomy at the Austin AAS meeting. Because atomic hydrogen emits radio waves at a specific frequency, astronomers can measure motions of the gas by noting the Doppler shift in frequency caused by those motions. "Because the THINGS images are highly detailed, we have been able to measure both the rotational motion of the galaxies and non-circular random motions within the galaxies," noted Erwin de Blok of the University of Cape Town, South Africa. Galaxy Dynamics in THINGS The motion measurements are providing new information about the mysterious, unseen "dark matter" in the galaxies. "The non-circular motions revealed by the THINGS observations, turn out to be too small to solve a long-standing problem in cosmology, namely the inability of state-of-the-art computer simulations to describe the distribution of dark matter in disk galaxies. It was thought that random motions could explain that inability, but our data show otherwise," de Blok explained. The THINGS images revealed what Elias Brinks of the University of Hertfordshire, UK, called a "stunning complexity of structures in the tenuous interstellar medium of the galaxies." These structures include large shells and "bubbles," presumably caused by multiple supernova explosions of massive stars. Analyzing the detail of these complex structures will help astronomers better understand the differences in star formation processes in the varied types of galaxies. Even such a simple question such as how big are the disks of gas in spiral galaxies had largely eluded astronomers previously. "The quality and sensitivity of the THINGS images has allowed us to see the actual edges of these disks in a large sample of galaxies," said Brinks. Dwarf Galaxies in THINGS The new survey also showed a fundamental difference between the nearby galaxies -- part of the "current" Universe, and far more distant galaxies, seen as they were when the Universe was much younger. "It appears that the gas in the galaxies in the early Universe is much more 'stirred up,' possibly because galaxies were colliding more frequently then and there was more intense star formation causing material outflows and stellar winds," explained Martin Zwaan of the European Southern Observatory. The information about gas in the more distant galaxies came through non-imaging analysis. These discoveries, the scientists predict, are only the tip of the iceberg. "This survey produced a huge amount of data, and we've only analyzed a small part of it so far. Further work is sure to tell us much more about galaxies and how they evolve. We expect to be surprised," Walter said. In addition to the presentations made at the Austin AAS meeting, THINGS team members also have submitted a series of scientific papers to the Astronomical Journal. The THINGS project is a large international collaboration led by Walter and includes research teams led by Brinks, de Blok, Michele Thornley of the Bucknell University in the U.S. and Rob Kennicutt of the Cambridge University in the UK. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

The Extremely Metal-Poor Dwarf Galaxy AGC 198691

NASA Astrophysics Data System (ADS)

Hirschauer, Alec S.; Salzer, John Joseph; Cannon, John M.; Skillman, Evan D.; SHIELD II Team

2016-01-01

We present spectroscopic observations of the nearby dwarf irregular galaxy AGC 198691. This object is part of the Survey of HI in Extremely Low-Mass Dwarfs (SHIELD) sample, which consists of ultra-low HI mass galaxies discovered by the Arecibo Legacy Fast-Acting ALFA (ALFALFA) survey. SHIELD is a multi-configuration Expanded Very Large Array (EVLA) study of the neutral gas content and dynamics of galaxies with HI masses in the range of 106-107 M⊙. Our spectral data were obtained using the new high-throughput KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m telescope as part of a systematic study of the nebular abundances in the SHIELD galaxy sample. These observations enable measurement of the temperature sensitive [OIII]λ4363 line and hence the determination of a "direct" oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) galaxy with an oxygen abundance comparable to such objects as I Zw 18, SBS 0335-052W, Leo P, and DDO 68 - the lowest metallicity star-forming systems known. It is worth noting that two of the five lowest-abundance galaxies currently recognized were discovered via the ALFALFA blind HI survey. These XMD galaxies are potential analogues to the first star-forming systems, which through hierarchical accretion processes built up the large galaxies we observe today in the local Universe. Detailed analysis of such XMD systems offers observational constraint to models of galactic evolution and star formation histories to allow a better understanding of the processes that govern the chemical evolution of low-mass galaxies.

HUBBLE VIEWS DISTANT GALAXIES THROUGH A COSMIC LENS

NASA Technical Reports Server (NTRS)

2002-01-01

This NASA Hubble Space Telescope image of the rich galaxy cluster, Abell 2218, is a spectacular example of gravitational lensing. The arc-like pattern spread across the picture like a spider web is an illusion caused by the gravitational field of the cluster. The cluster is so massive and compact that light rays passing through it are deflected by its enormous gravitational field, much as an optical lens bends light to form an image. The process magnifies, brightens and distorts images of objects that lie far beyond the cluster. This provides a powerful 'zoom lens' for viewing galaxies that are so far away they could not normally be observed with the largest available telescopes. Hubble's high resolution reveals numerous arcs which are difficult to detect with ground-based telescopes because they appear to be so thin. The arcs are the distorted images of a very distant galaxy population extending 5-10 times farther than the lensing cluster. This population existed when the universe was just one quarter of its present age. The arcs provide a direct glimpse of how star forming regions are distributed in remote galaxies, and other clues to the early evoution of galaxies. Hubble also reveals multiple imaging, a rarer lensing event that happens when the distortion is large enough to produce more than one image of the same galaxy. Abell 2218 has an unprecedented total of seven multiple systems. The abundance of lensing features in Abell 2218 has been used to make a detailed map of the distribution of matter in the cluster's center. From this, distances can be calculated for a sample of 120 faint arclets found on the Hubble image. These arclets represent galaxies that are 50 times fainter than objects that can be seen with ground-based telescopes. Studies of remote galaxies viewed through well-studied lenses like Abell 2218 promise to reveal the nature of normal galaxies at much earlier epochs than was previously possible. The technique is a powerful combination of Hubble's superlative capabilities and the 'natural' focusing properties of massive clusters like Abell 2218. The image was taken with the Wide Field Planetary Camera 2. Credits: W.Couch (University of New South Wales), R. Ellis (Cambridge University), and NASA

Inefficient star formation in extremely metal poor galaxies.

PubMed

Shi, Yong; Armus, Lee; Helou, George; Stierwalt, Sabrina; Gao, Yu; Wang, Junzhi; Zhang, Zhi-Yu; Gu, Qiusheng

2014-10-16

The first galaxies contain stars born out of gas with few or no 'metals' (that is, elements heavier than helium). The lack of metals is expected to inhibit efficient gas cooling and star formation, but this effect has yet to be observed in galaxies with an oxygen abundance (relative to hydrogen) below a tenth of that of the Sun. Extremely metal poor nearby galaxies may be our best local laboratories for studying in detail the conditions that prevailed in low metallicity galaxies at early epochs. Carbon monoxide emission is unreliable as a tracer of gas at low metallicities, and while dust has been used to trace gas in low-metallicity galaxies, low spatial resolution in the far-infrared has typically led to large uncertainties. Here we report spatially resolved infrared observations of two galaxies with oxygen abundances below ten per cent of the solar value, and show that stars formed very inefficiently in seven star-forming clumps in these galaxies. The efficiencies are less than a tenth of those found in normal, metal rich galaxies today, suggesting that star formation may have been very inefficient in the early Universe.

A Glimpse of the Milky Way

NASA Image and Video Library

2005-12-13

In visible light, the bulk of our Milky Way galaxy stars are eclipsed behind thick clouds of galactic dust and gas. But to the infrared eyes of NASA Spitzer Space Telescope, distant stars and dust clouds shine with unparalleled clarity and color.

HUBBLE'S TOP TEN GRAVITATIONAL LENSES

NASA Technical Reports Server (NTRS)

2002-01-01

The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368+6212 is a blue arc in the Hubble Deep Field (HDF). [Bottom Right] - HST 18078+4600 is a blue arc caused by the gravitational potential of a small group of 4 galaxies. Credit: Kavan Ratnatunga (Carnegie Mellon Univ.) and NASA

Peering Into an Early Galaxy

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-04-01

Thirteen billion years ago, early galaxies ionized the gas around them, producing some of the first light that brought our universe out of its dark ages. Now the Atacama Large Millimeter/submillimeter Array (ALMA) has provided one of the first detailed looks into the interior of one of these early, distant galaxies.Sources of LightArtists illustration of the reionization of the universe (time progresses left to right), in which ionized bubbles that form around the first sources of light eventually overlap to form the fully ionized universe we observe today. [Avi Loeb/Scientific American]For the first roughly hundred million years of its existence, our universe expanded in relative darkness there were no sources of light at that time besides the cosmic microwave background. But as mass started to condense to form the first objects, these objects eventually shone as the earliest luminous sources, contributing to the reionization of the universe.To learn about the early production of light in the universe, our best bet is to study in detail the earliest luminous sources stars, galaxies, or quasars that we can hunt down. One ideal target is the galaxy COSMOS Redshift 7, known as CR7 for short.Targeting CR7CR7 is one of the oldest, most distant galaxies known, lying at a redshift of z 6.6. Its discovery in 2015 and subsequent observations of bright, ultraviolet-emitting clumps within it have led to broad speculation about the source of its emission. Does this galaxy host an active nucleus? Or could it perhaps contain the long-theorized first generation of stars, metal-free Population III stars?To determine the nature of CR7 and the other early galaxies that contributed to reionization, we need to explore their gas and dust in detail a daunting task for such distant sources! Conveniently, this is a challenge that is now made possible by ALMAs incredible capabilities. In a new publication led by Jorryt Matthee (Leiden University, the Netherlands), a team of scientists now reports on what weve learned peering into CR7s interior with ALMA.ALMA observations of [C II] (white contours) are overlaid on an ultraviolet image of the galaxy CR7 taken with Hubble (background image). The presence of [C II] throughout the galaxy indicate that CR7 does not primarily consist of metal-free gas, as had been previously proposed. [Matthee et al. 2017]Metals yet No Dust?Matthee and collaborators deep spectroscopic observations of CR7 targeted the far-infrared dust continuum emission and a gas emission line, [C II]. The authors detected [C II] emission in a large region in and around the galaxy, including near the ultraviolet clumps. This clearly indicates the presence of metals in these star-forming regions, and it rules out the possibility that CR7s gas is mostly primordial and forming metal-free Pop III stars.The authors do not detect far infrared continuum emission from dust, which sets an unusually low upper limit on the amount of dust that may be present in this galaxy. This limit allows them to better interpret their measurements of star formation rates in CR7, providing more information about the galaxys properties.Lastly, Matthee and collaborators note that the [C II] emission is detected in multiple different components that have different velocities. The authors propose that these components are accreting satellite galaxies. If this is correct, then CR7 is not only a target to learn about early sources of light in the universe its also a rare opportunity to directly witness the build-up of a central galaxy in the early universe.CitationJ. Matthee et al 2017 ApJ 851 145. doi:10.3847/1538-4357/aa9931

CLASH: EXTREME EMISSION-LINE GALAXIES AND THEIR IMPLICATION ON SELECTION OF HIGH-REDSHIFT GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Xingxing; Wang, Junxian; Shu, Xinwen

2015-03-01

We utilize the Cluster Lensing And Supernova survey with Hubble observations of 25 clusters to search for extreme emission-line galaxies (EELGs). The selections are carried out in two central bands: F105W (Y {sub 105}) and F125W (J {sub 125}), as the flux of the central bands could be enhanced by the presence of [O III] λλ4959, 5007 at redshifts of ∼0.93-1.14 and 1.57-1.79, respectively. The multiband observations help to constrain the equivalent widths (EWs) of emission lines. Thanks to cluster lensing, we are able to identify 52 candidates down to an intrinsic limiting magnitude of 28.5 and to a rest-framemore » [O III] λλ4959, 5007 EW of ≅ 3700 Å. Our samples include a number of EELGs at lower luminosities that are missed in other surveys, and the extremely high EW can only be found in such faint galaxies. These EELGs can mimic a dropout feature similar to that of high-redshift galaxies and contaminate the color-color selection of high-redshift galaxies when the signal-to-noise ratio is limited or the band coverage is incomplete.« less

Enhancement of AGN Activity in Distant Galaxy Clusters

NASA Astrophysics Data System (ADS)

Krishnan, Charutha; Hatch, Nina; Almaini, Omar

2017-07-01

I present our recent study of the prevalence of X-ray AGN in the high-redshift protocluster Cl 0218.3-0510 at z=1.62, and review the implications for our understanding of galaxy evolution. There has long been a consensus that X-ray AGN avoid clusters in the local universe, particularly their cores. The high-redshift universe appears to not follow these trends, as there is a reversal in the local anti-correlation between galaxy density and AGN activity. In this z=1.62 protocluster, we find a large overdensity of AGN by a factor of 23, and an enhancement in the AGN fraction among massive galaxies relative to the field by a factor of 2. I will discuss the comparison of the properties of AGN in the protocluster to the field, and explain how our results point towards similar triggering mechanisms in the two environments. I will also describe how our study of the morphologies of these galaxies provide tentative evidence towards galaxy mergers and interactions being responsible for triggering AGN, and explain the reversal of the local anti-correlation between galaxy density and AGN activity.

RELICS: Reionization Lensing Cluster Survey - Discovering Brightly Lensed Distant Galaxies for JWST

NASA Astrophysics Data System (ADS)

Coe, Dan; Bradley, Larry; Salmon, Brett; Avila, Roberto J.; Ogaz, Sara; Bradac, Marusa; Huang, Kuang-Han; Strait, Victoria; Hoag, Austin; Sharon, Keren q.; Cerny, Catherine; Paterno-Mahler, Rachel; Johnson, Traci Lin; Mahler, Guillaume; Zitrin, Adi; Sendra Server, Irene; Acebron, Ana; Cibirka, Nathália; Rodney, Steven; Strolger, Louis; Riess, Adam; Dawson, William; Jones, Christine; Andrade-Santos, Felipe; Lovisari, Lorenzo; Czakon, Nicole; Umetsu, Keiichi; Trenti, Michele; Vulcani, Benedetta; Carrasco, Daniela; Livermore, Rachael; Stark, Daniel P.; Mainali, Ramesh; Frye, Brenda; Oesch, Pascal; Lam, Daniel; Toft, Sune; Ryan, Russell; Peterson, Avery; Past, Matthew; Kikuchihara, Shotaro; Ouchi, Masami; Oguri, Masamune

2018-01-01

The Reionization Lensing Cluster Survey (RELICS) Hubble Treasury Program has completed observations of 41 massive galaxy clusters with 188 orbits of HST ACS and WFC3/IR imaging and 390 hours of Spitzer IRAC imaging. This poster presents an overview of the program and data releases. Reduced images, catalogs, and lens models for all clusters are now available on MAST. RELICS is studying the clusters, supernovae, and lensed high-redshift galaxies. A companion poster presents our high-redshift results: over 300 lensed z ~ 6 - 10 candidates, including some of the brightest known at these redshifts (Salmon et al. 2018). These will be excellent targets for detailed follow-up study in JWST Cycle 1 GO proposals.

UV-to-IR spectral energy distributions of galaxies at z>1: the impact of Herschel data on dust attenuation and star formation determinations

NASA Astrophysics Data System (ADS)

Buat, V.; Heinis, S.; Boquien, M.

2013-11-01

We report on our recent works on the UV-to-IR SED fitting of a sample of distant (z>1) galaxies observed by Herschel in the CDFS as part of the GOODS-Herschel project. Combining stellar and dust emission in galaxies is found powerful to constrain their dust attenuation as well as their star formation activity. We focus on the caracterisation of dust attenuation and on the uncertainties on the derivation of the star formation rates and stellar masses, as a function of the range of wavelengths sampled by the data data and of the assumptions made on the star formation histories

Anatomy of a Triangulum

NASA Technical Reports Server (NTRS)

2005-01-01

M33, the Triangulum Galaxy, is a perennial favorite of amateur and professional astronomers alike, due to its orientation and relative proximity to us. It is the second nearest spiral galaxy to our Milky Way (after M31, the Andromeda Galaxy) and a prominent member of the 'local group' of galaxies. From our Milky Way perspective, M33's stellar disk appears at moderate inclination, allowing us to see its internal structure clearly, whereas M31 is oriented nearly edge-on.

The Galaxy Evolution Explorer imaged M33 as it appears in ultraviolet wavelengths. Ultraviolet imaging primarily traces emission from the atmospheres of hot stars, most of which formed in the past few hundred million years. These data provide a reference point as to the internal composition of a typical star-forming galaxy and will help scientists understand the origin of ultraviolet emission in more distant galaxies.

These observations of M33 allow astronomers to compare the population of young, massive stars with other components of the galaxy, such as interstellar dust and gas, on the scale of individual giant molecular clouds. The clouds contain the raw material from which stars form. This presents direct insight into the star formation process as it occurs throughout an entire spiral galaxy and constitutes a unique resource for broader studies of galaxy evolution.

UV, optical and infrared properties of star forming galaxies

NASA Technical Reports Server (NTRS)

Huchra, John P.

1987-01-01

The UVOIR properties of galaxies with extreme star formation rates are examined. These objects seem to fall into three distinct classes which can be called (1) extragalactic H II regions, (2) clumpy irregulars, and (3) starburst galaxies. Extragalactic H II regions are dominated by recently formed stars and may be considered 'young' galaxies if the definition of young is having the majority of total integrated star formation occurring in the last billion years. Clumpy irregulars are bursts of star formation superposed on an old population and are probably good examples of stochastic star formation. It is possible that star formation in these galaxies is triggered by the infall of gas clouds or dwarf companions. Starburst galaxies are much more luminous, dustier and more metal rich than the other classes. These objects show evidence for shock induced star formation where shocks may be caused by interaction with massive companions or are the result of an extremely strong density wave.

AEGIS: The Diversity of Bright Near-IR-selected Distant Red Galaxies

NASA Astrophysics Data System (ADS)

Conselice, C. J.; Newman, J. A.; Georgakakis, A.; Almaini, O.; Coil, A. L.; Cooper, M. C.; Eisenhardt, P.; Foucaud, S.; Koekemoer, A.; Lotz, J.; Noeske, K.; Weiner, B.; Willmer, C. N. A.

2007-05-01

We use deep and wide near-infrared (NIR) imaging from the Palomar telescope combined with DEEP2 spectroscopy and HST and Chandra imaging to investigate the nature of galaxies that are red in NIR colors. We locate these ``distant red galaxies'' (DRGs) through the color cut (J-K)Vega>2.3 over 0.7 deg2, where we find 1010 DRG candidates down to Ks=20.5. We combine 95 high-quality spectroscopic redshifts with photometric redshifts from BRIJK photometry to determine the redshift and stellar mass distributions for these systems, and the morphological/structural and X-ray properties for 107 DRGs in the Extended Groth Strip. We find that many bright (J-K)Vega>2.3 galaxies with Ks<20.5 are at redshifts z<2, with 64% in the range 12 systems being massive with M*>1011 Msolar. HST imaging shows that the structural properties and morphologies of DRGs are also diverse, with the majority elliptical/compact (57%) and the remainder edge-on spiral (7%) and peculiar (29%). The DRGs at z<1.4 with high-quality spectroscopic redshifts are generally compact, with small half-light radii, and span a range in rest-frame optical properties. The spectral energy distribution for the DRGs at z<1.4 differs from higher redshift DRGs: they are bluer by 1 mag in observed (I-J) color. A pure IR color selection of high-redshift populations is not sufficient to identify unique populations, and other colors or spectroscopic redshifts are needed to produce homogeneous samples.

Rise of the Titans: A Dusty, Hyper-luminous “870 μm Riser” Galaxy at z ˜ 6

NASA Astrophysics Data System (ADS)

Riechers, Dominik A.; Leung, T. K. Daisy; Ivison, Rob J.; Pérez-Fournon, Ismael; Lewis, Alexander J. R.; Marques-Chaves, Rui; Oteo, Iván; Clements, Dave L.; Cooray, Asantha; Greenslade, Josh; Martínez-Navajas, Paloma; Oliver, Seb; Rigopoulou, Dimitra; Scott, Douglas; Weiss, Axel

2017-11-01

We report the detection of ADFS-27, a dusty, starbursting major merger at a redshift of z = 5.655, using the Atacama Large Millimeter/submillimeter Array (ALMA). ADFS-27 was selected from Herschel/Spectral and Photometric Imaging Receiver (SPIRE) and APEX/LABOCA data as an extremely red “870 μm riser” (I.e., {S}250μ {{m}}< {S}350μ {{m}}< {S}500μ {{m}}< {S}870μ {{m}}), demonstrating the utility of this technique to identify some of the highest-redshift dusty galaxies. A scan of the 3 mm atmospheric window with ALMA yields detections of CO(J = 5 → 4) and CO(J = 6 → 5) emission, and a tentative detection of H2O(211 → 202) emission, which provides an unambiguous redshift measurement. The strength of the CO lines implies a large molecular gas reservoir with a mass of M gas = 2.5 × 1011 ({α }{CO}/0.8)(0.39/{r}51) M ⊙, sufficient to maintain its ˜2400 M ⊙ yr-1 starburst for at least ˜100 Myr. The 870 μm dust continuum emission is resolved into two components, 1.8 and 2.1 kpc in diameter, separated by 9.0 kpc, with comparable dust luminosities, suggesting an ongoing major merger. The infrared luminosity of L IR ≃ 2.4 × 1013 L ⊙ implies that this system represents a binary hyper-luminous infrared galaxy, the most distant of its kind presently known. This also implies star formation rate surface densities of {{{Σ }}}{SFR}=730 and 750 M ⊙ yr-1 kpc2, consistent with a binary “maximum starburst.” The discovery of this rare system is consistent with a significantly higher space density than previously thought for the most luminous dusty starbursts within the first billion years of cosmic time, easing tensions regarding the space densities of z ˜ 6 quasars and massive quiescent galaxies at z ≳ 3.

Record-breaking ancient galaxy clusters

NASA Astrophysics Data System (ADS)

2003-12-01

A tale of two record-breaking clusters hi-res Size hi-res: 768 kb Credits: for RDCS1252: NASA, ESA, J.Blakeslee (Johns Hopkins Univ.), M.Postman (Space Telescope Science Inst.) and P.Rosati, Chris Lidman & Ricardo Demarco (European Southern Observ.) for TNJ1338: NASA, ESA, G.Miley (Leiden Observ.) and R.Overzier (Leiden Obs) A tale of two record-breaking clusters Looking back in time to when the universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured these revealing images of two galaxy clusters. The image at left, which is made with an additional infrared exposure taken with the European Southern Observatory’s Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5000 million years old. The cluster, called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic (heic0313d) reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure). In the image at right, astronomers are seeing an embryonic cluster as it was when the universe was 1500 million years old. The young system, called TNJ1338-1942, is the most distant known developing cluster, or proto-cluster. It is dominated by a massive ‘baby galaxy’ - the green object. The cluster RDCS1252.9-2927 hi-res Size hi-res: 2611 kb Credits: NASA, ESA, J. Blakeslee (Johns Hopkins University), M. Postman (Space Telescope Science Institute) and P. Rosati, Chris Lidman & Ricardo Demarco (European Southern Observatory) The cluster RDCS1252.9-2927 Looking back in time to when the Universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured this revealing image of the galaxy cluster RDCS1252.9-2927. The image shows the entire cluster (1/15 of a degree, corresponding to about 7 million light-years, across). The cluster probably contains many thousands of galaxies. Most of the other galaxies in the image, including most of the blue galaxies, are foreground or background galaxies. The image, which is made with an additional infrared exposure taken with the European Southern Observatory’s Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5000 million years old. The cluster, called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure). The embryonic cluster TNJ1338-1942 hi-res Size hi-res: 154 kb Credits: NASA, ESA, G. Miley (Leiden Observatory) and R. Overzier (Leiden Observatory) The embryonic cluster TNJ1338-1942 In this image astronomers are seeing an embryonic cluster as it was when the universe was 1500 million years old. The young system, called TNJ1338-1942, is the most distant known developing cluster, or proto-cluster. It is dominated by a massive ‘baby galaxy’ - the green object in the centre. The galaxy is producing powerful radio emissions, and is the brightest galaxy in the proto-cluster. The green colour indicates that the galaxy is emitting glowing hydrogen gas. Its clumpy appearance suggests that it is still in the process of forming. Smaller developing galaxies are scattered around the massive galaxy. The galaxy on the left of the massive galaxy is a foreground galaxy. The bright object in the upper half of the image is a foreground star. This colour-composite image was assembled from observations taken between July 8 and 12, 2002 by the ACS Wide Field Camera. The cluster RDCS1252.9-2927 hi-res Size hi-res: 259 kb Credits: NASA, ESA, J. Blakeslee (Johns Hopkins University), M. Postman (Space Telescope Science Institute) and P. Rosati, Chris Lidman & Ricardo Demarco (European Southern Observatory) The cluster RDCS1252.9-2927 Looking back in time to when the universe was in its formative youth, the Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope captured this revealing image of the galaxy cluster RDCS1252.9-2927. This image is made with an additional infrared exposure taken with the European Southern Observatory’s Very Large Telescope, shows mature galaxies in a massive cluster that existed when the cosmos was 5000 million years old. The cluster, called RDCS1252.9-2927, is as massive as ‘300 trillion’ suns and is the most massive known cluster for its epoch. The image reveals the core of the cluster and is part of a much larger mosaic of the entire cluster. Dominating the core are a pair of large, reddish elliptical galaxies [near centre of image]. Their red colour indicates an older population of stars. Most of the stars are at least 1 000 million years old. The two galaxies appear to be interacting and may eventually merge to form a larger galaxy that is comparable to the brightest galaxies seen in present-day clusters. The red galaxies surrounding the central pair are also cluster members. The cluster probably contains many thousands of galaxies, but only about 50 can be seen in this image. The full mosaic reveals several hundred cluster members. Many of the other galaxies in the image, including several of the blue galaxies, are foreground or background galaxies. The colour-composite image was assembled from two observations (through i and z filters) taken between May and June 2002 by the ACS Wide Field Camera, and one image with the ISAAC instrument on the VLT taken in 2002 (combined from a J filter exposure and a K filter exposure). Looking back in time nearly 9000 million years, an international team of astronomers found mature galaxies in a young Universe. The galaxies are members of a cluster of galaxies that existed when the Universe was only 5000 million years old, or about 35 percent of its present age. This is compelling evidence that galaxies must have started forming just after the Big Bang and is bolstered by observations made by the same team of astronomers when they peered even farther back in time. The team found embryonic galaxies a mere 1500 million years after the birth of the cosmos, or 10 percent of the Universe's present age. The ‘baby galaxies’ reside in a still developing cluster, the most distant proto-cluster ever found. The Advanced Camera for Surveys (ACS) aboard the NASA/ESA Hubble Space Telescope was used to make the observations of the massive cluster, RDCS1252.9-2927, and the proto-cluster, TNJ1338-1942. Observations by NASA’s Chandra X-ray Observatory yielded the mass and heavy element content of RDCS1252.9-2927, the most massive known cluster for that epoch. These observations are part of a co-ordinated effort by the ACS science team to track the formation and evolution of clusters of galaxies over a broad span of cosmic time. The ACS was specially built for such studies of very distant objects. These findings support the theory that galaxies formed relatively early in the history of the cosmos. The existence of such massive clusters in the early Universe agrees with a cosmological model wherein clusters form by the merger of many sub-clusters in a Universe dominated by cold dark matter. The precise nature of cold dark matter, however, is still not known. The first Hubble study estimated that the galaxies in RCDS1252 formed the bulk of their stars more than 11 000 million years ago (redshifts greater than 3). The results were published in the 20 October 2003, issue of the Astrophysical Journal. The paper's lead author is John Blakeslee of the Johns Hopkins University in Baltimore, USA. The second Hubble study uncovered, for the first time, a proto-cluster of ‘infant galaxies’ that existed more than 12 000 million years ago (redshift 4.1). These galaxies are so young that astronomers can still see a flurry of stars forming within them. The galaxies are grouped around one large galaxy. These results will be published in the January 1, 2004 issue of Nature. The paper's lead author is George Miley of Leiden Observatory in the Netherlands. "Until recently people didn't think that clusters existed when the Universe was only about 5000 million years old," Blakeslee explained. "Even if there were such clusters," Miley added, "until recently astronomers thought it was almost impossible to find clusters that existed 8000 million years ago. In fact, no one really knew when clustering began. Now we can witness it." Both studies led the astronomers to conclude that these systems are the progenitors of the galaxy clusters seen today. "The cluster RDCS1252 looks like a present-day cluster," said Marc Postman of the Space Telescope Science Institute in Baltimore, USA, and co-author of both research papers. "In fact, if you were to put it next to a present-day cluster you wouldn't know which is which." ‘A tale of two clusters’ How can galaxies grow so fast after the Big Bang? "It is a case of the rich getting richer," Blakeslee said. "These clusters grew quickly because they are located in very dense regions, so there is enough material to build up the member galaxies very fast." This idea is bolstered by X-ray observations of the massive cluster RDCS1252. Chandra and the European Space Agency's XMM-Newton provided astronomers with the most accurate measurements to date of the properties of an enormous cloud of hot gas that pervades the massive cluster. This 70 million °C gas is a reservoir of most of the heavy elements in the cluster, and an accurate tracer of its total mass. A paper by Piero Rosati of the European Southern Observatory (ESO) and colleagues that presents the X-ray observations of RDCS1252 will be published in January 2004 in the Astronomical Journal. "Chandra's sharp vision resolved the shape of the hot gas halo and showed that RDCS1252 is very mature for its age," said Rosati, who discovered the cluster with the ROSAT X-ray telescope. RDCS1252 may contain many thousands of galaxies. Most of those galaxies, however, are too faint to detect, although the powerful ‘eyes’ of the ACS pinpointed several hundred of them. Observations using ESO's Very Large Telescope (VLT) provided a precise measurement of the distance to the cluster. The ACS enabled the researchers to determine the shapes and the colours of the 100 galaxies accurately, providing information on the ages of the stars residing in them. The ACS team estimated that most of the stars in the cluster were already formed by the time the Universe was about 2000 million years old. In addition X-ray observations showed that 5 000 million years after the Big Bang the surrounding hot gas had been enriched with heavy elements from these stars and swept away from the galaxies. If most of the galaxies in RDCS1252 have reached maturity and are settling into a quiet adulthood, the galaxies forming in the distant proto-cluster are in their energetic, unruly youth. The proto-cluster TN J1338 contains a massive embryonic galaxy surrounded by smaller developing galaxies, which look like dots in the Hubble image. The dominant galaxy is producing spectacular radio-emitting jets, fuelled by a supermassive black hole deep within the galaxy's nucleus. Interaction between these jets and the gas can stimulate a torrent of star birth. The discovery of the energetic radio galaxy by radio telescopes prompted astronomers to hunt for the smaller galaxies that make up the bulk of the cluster. "Massive clusters are the cities of the Universe, and the radio galaxies within them are the smokestacks we can use for finding them when they are just beginning to form," Miley said. The two findings underscore the power of combining observations from many different telescopes to provide views of the distant Universe over a range of wavelengths. Hubble’s advanced camera provided critical information on the structure of both distant galaxy clusters. Chandra's and XMM-Newton’s X-ray vision furnished the essential measurements of the primordial gas in which the galaxies in RDCS1252 are embedded, and accurate estimates of the total mass contained within that cluster. Large ground-based telescopes, like the VLT, provided precise measurements of the distance of both clusters as well as the chemical composition of the galaxies in them. The ACS team is conducting further observations of distant clusters to solidify our understanding of how these young clusters and their galaxies evolve into the shape of things seen today. Their planned observations include using near-infrared observations to analyse the star-formation rates in some of their clusters, including RDCS1252, in order to measure the cosmic history of star formation in these massive structures. The team is also searching the regions around several ultra-distant radio galaxies for additional examples of proto-clusters. The team's ultimate scientific goal is to establish a complete picture of cluster evolution beginning with their formation at the earliest epochs and detailing their evolution up to the present time.

The Interstellar Medium in External Galaxies: Summaries of contributed papers

NASA Technical Reports Server (NTRS)

Hollenbach, David J. (Editor); Thronson, Harley A., Jr. (Editor)

1990-01-01

The Second Wyoming Conference entitled, The Interstellar Medium in External Galaxies, was held on July 3 to 7, 1989, to discuss the current understanding of the interstellar medium in external galaxies and to analyze the basic physical processes underlying interstellar phenomena. The papers covered a broad range of research on the gas and dust in external galaxies and focused on such topics as the distribution and morphology of the atomic, molecular, and dust components; the dynamics of the gas and the role of the magnetic field in the dynamics; elemental abundances and gas depletions in the atomic and ionized components; cooling flows; star formation; the correlation of the nonthermal radio continuum with the cool component of the interstellar medium; the origin and effect of hot galactic halos; the absorption line systems seen in distant quasars; and the effect of galactic collisions.

Long-Duration Gamma-Ray Burst Host Galaxies in Emission and Absorption

NASA Astrophysics Data System (ADS)

Perley, Daniel A.; Niino, Yuu; Tanvir, Nial R.; Vergani, Susanna D.; Fynbo, Johan P. U.

2016-12-01

The galaxy population hosting long-duration GRBs provides a means to constrain the progenitor and an opportunity to use these violent explosions to characterize the nature of the high-redshift universe. Studies of GRB host galaxies in emission reveal a population of star-forming galaxies with great diversity, spanning a wide range of masses, metallicities, and redshifts. However, as a population GRB hosts are significantly less massive and poorer in metals than the hosts of other core-collapse transients, suggesting that GRB production is only efficient at metallicities significantly below Solar. GRBs may also prefer compact galaxies, and dense and/or central regions of galaxies, more than other types of core-collapse explosion. Meanwhile, studies of hosts in absorption against the luminous GRB optical afterglow provide a unique means of unveiling properties of the ISM in even the faintest and most distant galaxies; these observations are helping to constrain the chemical evolution of galaxies and the properties of interstellar dust out to very high redshifts. New ground- and space-based instrumentation, and the accumulation of larger and more carefully-selected samples, are continually enhancing our view of the GRB host population.

ROSAT Discovers Unique, Distant Cluster of Galaxies

NASA Astrophysics Data System (ADS)

1995-06-01

Brightest X-ray Cluster Acts as Strong Gravitational Lens Based on exciting new data obtained with the ROSAT X-ray satellite and a ground-based telescope at the ESO La Silla Observatory, a team of European astronomers [2] has just discovered a very distant cluster of galaxies with unique properties. It emits the strongest X-ray emission of any cluster ever observed by ROSAT and is accompanied by two extraordinarily luminous arcs that represent the gravitationally deflected images of even more distant objects. The combination of these unusual characteristics makes this cluster, now known as RXJ1347.5-1145, a most interesting object for further cosmological studies. DISCOVERY AND FOLLOW-UP OBSERVATIONS This strange cluster of galaxies was discovered during the All Sky Survey with the ROSAT X-ray satellite as a moderately intense X-ray source in the constellation of Virgo. It could not be identified with any already known object and additional ground-based observations were therefore soon after performed with the Max-Planck-Society/ESO 2.2-metre telescope at the La Silla observatory in Chile. These observations took place within a large--scale redshift survey of X-ray clusters of galaxies detected by the ROSAT All Sky Survey, a so-called ``ESO Key Programme'' led by astronomers from the Max-Planck-Institut fur Extraterrestrische Physik and the Osservatorio Astronomico di Brera. The main aim of this programme is to identify cluster X-ray sources, to determine the distance to the X-ray emitting clusters and to investigate their overall properties. These observations permitted to measure the redshift of the RXJ1347.5-1145 cluster as z = 0.45, i.e. it moves away from us with a velocity (about 106,000 km/sec) equal to about one-third of the velocity of light. This is an effect of the general expansion of the universe and it allows to determine the distance as about 5,000 million light-years (assuming a Hubble constant of 75 km/sec/Mpc). In other words, we see these galaxies as they were 5,000 million years ago. Knowing the intensity of the X-ray emission as measured by ROSAT and also the distance, the astronomers were then able to estimate the total X-ray energy emitted by this cluster. It was found to be extremely high [3], in fact higher than that of any other cluster ever observed by ROSAT. It amounts to no less than 1.5 million million times the total energy emitted by the Sun. It is believed that this strong X-ray emission originates in a hot gas located between the galaxies in the cluster. The high temperature indicates that the components of the gas move very rapidly; this is related to the strong gravitational field within the cluster. THE GRAVITATIONAL ARCS To their great surprise and delight, the astronomers also discovered two bright arcs, 5 - 6 arcseconds long and symmetrically placed about 35 arcseconds to the North-East and South-West of the brightest galaxies in the cluster (see the photo). They were detected on exposures of only 3 minutes duration with the 2.2-metre telescope and are among the brightest such arcs ever found. At the indicated distance, the arcs are situated at a projected distance of about 500,000 light-years from the centre of the cluster. It is an interesting possibility that the two arcs may in fact be two images of the same, very distant galaxy, that is situated far beyond RXJ1347.5-1145 and whose light has been bent and split by this cluster's strong gravitational field. This strange phenomenon was first discovered in the late 1970's and is referred to as gravitational lensing. Quite a few examples are now known, in most cases in the form of double or multiple images of quasars. About three dozen cases involve well visible galaxy clusters and elongated arcs, but few, if any, of these arcs are as bright as those seen in the present cluster. This particular arc configuration enables a very accurate determination of the total mass of the cluster, once the distance of the background galaxy has been measured (by obtaining spectra of the arcs and measuring their redshift). The masses of galaxy clusters are important for the determination, for instance of the mean density and distribution of matter in the universe. This is because these clusters are the most massive, clearly defined objects known and as such trace these parameters in the universe on very large scales. Another possibility to derive the cluster mass is offered by X-ray observations, because the distribution of the hot, X-ray emitting gas traces the gravitational field of the cluster. Recently, in some clusters there has been a discrepancy between the mass determined in this way and that found from gravitational lensing effects. The team of astronomers now hopes that follow-up X-ray observations of RXJ1347.5-1145 will help to solve this puzzle. Moreover, the combination of extremely high X-ray brightness and the possibility to perform a rather accurate mass determination by the gravitational lensing effect makes this particular cluster a truly unique object. In view of the exceptional X-ray brightness, a very high mass is expected. The exact determination will be possible, as soon as spectra have been obtained of the two arcs. Contrary to what is the case in other clusters, this will not be so difficult, due to their unusual brightness and their ideal geometrical configuration. [1] This is a joint Press Release of ESO and the Max-Planck-Society. It is accompanied by a B/W photo. [2] The investigation described in this Press Release is the subject of a Letter to the Editor which will soon appear in the European journal Astronomy & Astrophysics, with the following authors: Sabine Schindler (Max-Planck-Institut fuer Extraterrestrische Physik and Max-Planck-Institut fuer Astrophysik, Garching, Germany), Hans Boehringer, Doris M. Neumann and Ulrich G. Briel (Max-Planck-Institut fuer Extraterrestrische Physik, Garching, Germany), Luigi Guzzo (Osservatorio Astronomico di Brera, Merate, Italy), Guido Chincarini (Osservatorio Astronomico di Brera, Merate, and Dipartimento di Fisica, Universita di Milano, Italy), Harald Ebeling (Institute of Astronomy, Cambridge, U.K.), Chris A. Collins (School of Chemical and Physical Sciences, John-Moores University, Liverpool, U.K.), Sabrina De Grandi (Dipartimento di Fisica, Universita di Milano, Italy), Peter Shaver (ESO, Garching, Germany) and Giampaolo Vettolani (Istituto di Radioastronomia del CNR, Bologna, Italy). [3] The total X-ray energy emitted by RXJ1347.5-1145 is (6.2 +-0.6) 10^45 erg s-1 in the range 0.1--2.4 keV. ESO Press Information is made available on the World-Wide Web (URL: http://www.hq.eso.org/) and on CompuServe (space science and astronomy area, GO SPACE)

Very-high-energy gamma rays from a distant quasar: how transparent is the universe?

PubMed

Albert, J; Aliu, E; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Bigongiari, C; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea Del Pozo, E; de Los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Mendez, C Delgado; Dominguez, A; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; López, R J García; Garczarczyk, M; Gaug, M; Goebel, F; Hayashida, M; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Huber, S; Jogler, T; Kneiske, T M; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Otte, N; Oya, I; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Piccioli, A; Prada, F; Prandini, E; Puchades, N; Raymers, A; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Sartori, P; Satalecka, K; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Tluczykont, M; Torres, D F; Turini, N; Vankov, H; Venturini, A; Vitale, V; Wagner, R M; Wittek, W; Zabalza, V; Zandanel, F; Zanin, R; Zapatero, J

2008-06-27

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.

An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core.

PubMed

Gezari, S; Chornock, R; Rest, A; Huber, M E; Forster, K; Berger, E; Challis, P J; Neill, J D; Martin, D C; Heckman, T; Lawrence, A; Norman, C; Narayan, G; Foley, R J; Marion, G H; Scolnic, D; Chomiuk, L; Soderberg, A; Smith, K; Kirshner, R P; Riess, A G; Smartt, S J; Stubbs, C W; Tonry, J L; Wood-Vasey, W M; Burgett, W S; Chambers, K C; Grav, T; Heasley, J N; Kaiser, N; Kudritzki, R-P; Magnier, E A; Morgan, J S; Price, P A

2012-05-02

The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two 'relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decay of the light curve follow the predicted mass accretion rate and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about two million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.

Post-AGB Stars in Nearby Galaxies as Calibrators for HST

NASA Technical Reports Server (NTRS)

Bond, Howard E.

2003-01-01

This report summarizes activities carried out with support from the NASA Ultraviolet, Visible, and Gravitational Astrophysics Research and Analysis Program under Grant NAG 5-6821. The Principal Investigator is Howard E. Bond (Space Telescope Science Institute). STScI Postdoctoral Associates Laura K. Fullton (1998), David Alves (1998-2001), and Michael Siegel (2001) were partially supported by this grant. The aim of the program is to calibrate the absolute magnitudes of post-asymptotic- giant-branch (post-AGB or PAGB) stars, which we believe will be an excellent new "standard candle" for measuring extragalactic distances. The argument is that, in old populations, the stars that are evolving through the PAGB region of the HR diagram arise from only a single main-sequence turnoff mass. In addition, theoretical PAGB evolutionary tracks show that they evolve through this region at constant luminosity; hence the PAGB stars should have an extremely narrow luminosity function. Moreover, as the PAGB stars evolve through spectral types F and A (en route from the AGB to hot stellar remnants and white dwarfs), they have the highest luminosities attained by old stars (both bolometrically and in the visual band). Finally, PAGB stars of these spectral types are very easily identified. because of their large Balmer jumps, which are due to their very low surface gravities. Our approach is first to identify PAGB stars in Milky Way globular clusters and in other Local Group galaxies, which are at known distances, and thus to measure accurate absolute magnitudes for the PAGB stars. With this Milky Way and Local Group luminosity calibration, we will then be in a position to find PAGB stars in more distant galaxies from the ground, and ultimately from the Hubble Space Telescope. and thus derive distances. These PAGB stars are, as noted above, the visually brightest members of Population II, and hence will allow distance measurements to galaxies that do not contain Cepheids, such as elliptical galaxies, as well as distances to spirals using PAGB stars in their halos. Moreover, the method is entirely independent of Cepheids. and thus provides a direct test of the Cepheid distance scale. The program will also provide information on the evolutionary lifetimes of PAGB stars.

VIMOS Ultra-Deep Survey (VUDS): IGM transmission towards galaxies with 2.5 < z < 5.5 and the colour selection of high-redshift galaxies

NASA Astrophysics Data System (ADS)

Thomas, R.; Le Fèvre, O.; Le Brun, V.; Cassata, P.; Garilli, B.; Lemaux, B. C.; Maccagni, D.; Pentericci, L.; Tasca, L. A. M.; Zamorani, G.; Zucca, E.; Amorin, R.; Bardelli, S.; Cassarà, L.; Castellano, M.; Cimatti, A.; Cucciati, O.; Durkalec, A.; Fontana, A.; Giavalisco, M.; Grazian, A.; Hathi, N. P.; Ilbert, O.; Paltani, S.; Pforr, J.; Ribeiro, B.; Schaerer, D.; Scodeggio, M.; Sommariva, V.; Talia, M.; Tresse, L.; Vanzella, E.; Vergani, D.; Capak, P.; Charlot, S.; Contini, T.; Cuby, J. G.; de la Torre, S.; Dunlop, J.; Fotopoulou, S.; Koekemoer, A.; López-Sanjuan, C.; Mellier, Y.; Salvato, M.; Scoville, N.; Taniguchi, Y.; Wang, P. W.

2017-01-01

The observed UV rest-frame spectra of distant galaxies are the result of their intrinsic emission combined with absorption along the line of sight produced by the inter-galactic medium (IGM). Here we analyse the evolution of the mean IGM transmission Tr(Lyα) and its dispersion along the line of sight for 2127 galaxies with 2.5 < z < 5.5 in the VIMOS Ultra Deep Survey (VUDS). We fitted model spectra combined with a range of IGM transmission to the galaxy spectra using the spectral fitting algorithm GOSSIP+. We used these fits to derive the mean IGM transmission towards each galaxy for several redshift slices from z = 2.5 to z = 5.5. We found that the mean IGM transmission defined as Tr(Lyα) = e- τ (with τ as the HI optical depth) is 79%, 69%, 59%, 55%, and 46% at redshifts 2.75, 3.22, 3.70, 4.23, and 4.77, respectively. We compared these results to measurements obtained from quasar lines of sight and found that the IGM transmission towards galaxies is in excellent agreement with quasar values up to redshift z 4. We found tentative evidence for a higher IGM transmission at z ≥ 4 compared to results from QSOs, but a degeneracy between dust extinction and IGM prevents us from firmly concluding whether the internal dust extinction for star-forming galaxies at z > 4 takes a mean value significantly in excess of E(B-V) > 0.15. Most importantly, we found a large dispersion of IGM transmission along the lines of sight towards distant galaxies with 68% of the distribution within 10 to 17% of the median value in δz = 0.5 bins, similar to what is found on the lines of sight towards QSOs. We demonstrate that taking this broad range of IGM transmission into account is important when selecting high-redshift galaxies based on their colour properties (e.g. LBG or photometric redshiftselection) because failing to do so causes a significant incompleteness in selecting high-redshift galaxy populations. We finally discuss the observed IGM properties and speculate that the broad range of observed transmissions might be the result of cosmic variance and clustering along lines of sight. This clearly shows that the sources that cause this extinction need to be more completely modelled. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Program 185.A-0791.

The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shipley, Heath V.

2016-01-01

For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with those available from Paα. This new SFR indicator will be useful for probing the peak of the SFR density in the universe (1 < z < 3) and for studying the co-evolution of star-formation and supermassive blackhole accretion contemporaneously in a galaxy.

Surface brightness and color distributions in blue compact dwarf galaxies. I - Haro 2, an extreme example of a star-forming young elliptical galaxy

NASA Technical Reports Server (NTRS)

Loose, Hans-Hermann; Thuan, Trinh X.

1986-01-01

The first results of a large-scale program to study the morphology and structure of blue compact dwarf galaxies from CCD observations are presented. The observations and reduction procedures are described, and surface brightness and color profiles are shown. The results are used to discuss the morphological type of Haro 2 and its stellar populations. It is found that Haro 2 appears to be an extreme example of an elliptical galaxy undergoing intense star formation in its central regions, and that the oldest stars it contains were made only about four million yr ago. The 'missing' mass problem of Haro 2 is also discussed.

KSC-08pd2470

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane lifts the Wide Field Camera 3, or WFC3, high above the floor for transfer to the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

Molecular clouds in the extreme outer galaxy

NASA Technical Reports Server (NTRS)

Digel, S.; De Geus, E.; Thaddeus, P.

1994-01-01

We present observation of 11 molecular clouds with kinematic Galactocentric distances of 18-28 kpc. The most distant is approximately 10 kpc farther from the Galactic center than any previously known and apparently lies beyond the edge of the optical disk. All are associated with much larger H I concentrations, with typical offsets of approximately 40 pc from the H I peaks. CO observations with the CfA 1.2 m and National Radio Astronomy Observatory (NRAO) 12 m telescopes indicate typical sizes of 20-40 pc, velocity widths of 1-3 km/s, and kinetic temperatures of 10-25 K. They apparently have lower CO luminosities than clouds near the solar circle with similar properties. Some may have associated infrared sources, but owing to the great distances of the clouds, the only general conclusion that can be made about star formation is that stars earlier than B1 are absent. The apparent scarcity of clouds like these indicates that their contribution to the mass of the ISM beyond R = 18 kpc is not significant.

KSC-08pd2457

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technician checks the pick-off mirror on the Wide Field Camera 3, or WFC3, that will be installed on NASA's Hubble Space Telescope. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to Hubble. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2459

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, technicians check the placement of an overhead crane to the Wide Field Camera 3, or WFC3, that will transfer the WFC3 to the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2469

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, an overhead crane moves the Wide Field Camera 3, or WFC3, from its stand. The WFC3 will be transferred to the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

Hubble 2006: Science Year in Review

NASA Technical Reports Server (NTRS)

Brown, R.

2007-01-01

The 10 science articles selected for this years annual science report exemplify the range of Hubble research from the Solar System, across our Milky Way, and on to distant galaxies. The objects of study include a new feature on Jupiter, binaries in the Kuiper Belt, Cepheid variable stars, the Orion Nebula, distant transiting planets, lensing galaxies, active galactic nuclei, red-and-dead galaxies, and galactic outflows and jets. Each narrative strives to construct the readers understanding of the topics and issues, and to place the latest research in historical, as well as scientific, context. These essays reveal trends in the practice of astronomy. More powerful computers are permitting astronomers to study ever larger data sets, enabling the discovery of subtle effects and rare objects. (Two investigations created mosaic images that are among the largest produced to date.) Multiwavelength data sets from ground-based telescopes, as well as other great observatories Spitzer and Chandraare increasingly important for holistic interpretations of Hubble results. This yearbook also presents profiles of 12 individuals who work with Hubble, or Hubble data, on a daily basis. They are representative of the many students, scientists, engineers, and other professions who are proudly associated with Hubble. Their stories collectively communicate the excitement and reward of careers related to space science and technology.

Measuring Distances to Remote Galaxies and Quasars.

ERIC Educational Resources Information Center

McCarthy, Patrick J.

1988-01-01

Describes the use of spectroscopy and the redshift to measure how far an object is by measuring how fast it is receding from earth. Lists the most distant quasars yet found. Tables include "Redshift vs. Distance" and "Distances to Celestial Objects for Various Cosmologies." (CW)

A geometric measure of dark energy with pairs of galaxies.

PubMed

Marinoni, Christian; Buzzi, Adeline

2010-11-25

Observations indicate that the expansion of the Universe is accelerating, which is attributed to a ‘dark energy’ component that opposes gravity. There is a purely geometric test of the expansion of the Universe (the Alcock–Paczynski test), which would provide an independent way of investigating the abundance (Ω(X)) and equation of state (W(X)) of dark energy. It is based on an analysis of the geometrical distortions expected from comparing the real-space and redshift-space shape of distant cosmic structures, but it has proved difficult to implement. Here we report an analysis of the symmetry properties of distant pairs of galaxies from archival data. This allows us to determine that the Universe is flat. By alternately fixing its spatial geometry at Ω(k)≡0 and the dark energy equation-of-state parameter at W(X)≡-1, and using the results of baryon acoustic oscillations, we can establish at the 68.3% confidence level that and -0.85>W(X)>-1.12 and 0.60<Ω(X)<0.80.

A high-frequency survey of the southern Galactic plane for pulsars

NASA Technical Reports Server (NTRS)

Johnston, Simon; Lyne, A. G.; Manchester, R. N.; Kniffen, D. A.; D'Amico, N.; Lim, J.; Ashworth, M.

1992-01-01

Results of an HF survey designed to detect young, distant, and short-period pulsars are presented. The survey detected a total of 100 pulsars, 46 of which were previously unknown. The periods of the newly discovered pulsars range between 47 ms and 2.5 ms. One of the new discoveries, PSR 1259-63, is a member of a long-period binary system. At least three of the pulsars have ages less than 30,000 yr, bringing the total number of such pulsars to 12. The majority of the new discoveries are distant objects with high dispersion measures, which are difficult to detect at low frequencies. This demonstrates that the survey has reduced the severe selection effects of pulse scattering, high Galactic background temperature, and dispersion broadening, which hamper the detection of such pulsars at low radio frequencies. The pulsar distribution in the southern Galaxy is found to extend much further from the Galactic center than that in the north, probably due to two prominent spiral arms in the southern Galaxy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janowiecki, Steven; Salzer, John J.; Zee, Liese van

We discuss and test possible evolutionary connections between blue compact dwarf galaxies (BCDs) and other types of dwarf galaxies. BCDs provide ideal laboratories to study intense star formation episodes in low-mass dwarf galaxies, and have sometimes been considered a short-lived evolutionary stage between types of dwarf galaxies. To test these connections, we consider a sample of BCDs as well as a comparison sample of nearby galaxies from the Local Volume Legacy (LVL) survey for context. We fit the multi-wavelength spectral energy distributions (SED, far-ultra-violet to far-infrared) of each galaxy with a grid of theoretical models to determine their stellar massesmore » and star formation properties. We compare our results for BCDs with the LVL galaxies to put BCDs in the context of normal galaxy evolution. The SED fits demonstrate that the star formation events currently underway in BCDs are at the extreme of the continuum of normal dwarf galaxies, both in terms of the relative mass involved and in the relative increase over previous star formation rates. Today’s BCDs are distinctive objects in a state of extreme star formation that is rapidly transforming them. This study also suggests ways to identify former BCDs whose star formation episodes have since faded.« less

The H IX galaxy survey - II. H I kinematics of H I eXtreme galaxies

NASA Astrophysics Data System (ADS)

Lutz, K. A.; Kilborn, V. A.; Koribalski, B. S.; Catinella, B.; Józsa, G. I. G.; Wong, O. I.; Stevens, A. R. H.; Obreschkow, D.; Dénes, H.

2018-05-01

By analysing a sample of galaxies selected from the H I Parkes All Sky Survey (HIPASS) to contain more than 2.5 times their expected H I content based on their optical properties, we investigate what drives these H I eXtreme (H IX) galaxies to be so H I-rich. We model the H I kinematics with the Tilted Ring Fitting Code TiRiFiC and compare the observed H IX galaxies to a control sample of galaxies from HIPASS as well as simulated galaxies built with the semi-analytic model DARK SAGE. We find that (1) H I discs in H IX galaxies are more likely to be warped and more likely to host H I arms and tails than in the control galaxies, (2) the average H I and average stellar column density of H IX galaxies is comparable to the control sample, (3) H IX galaxies have higher H I and baryonic specific angular momenta than control galaxies, (4) most H IX galaxies live in higher spin haloes than most control galaxies. These results suggest that H IX galaxies are H I-rich because they can support more H I against gravitational instability due to their high specific angular momentum. The majority of the H IX galaxies inherits their high specific angular momentum from their halo. The H I content of H IX galaxies might be further increased by gas-rich minor mergers. This paper is based on data obtained with the Australia Telescope Compact Array through the large program C 2705.

At the centre of the tuning fork

NASA Image and Video Library

2015-11-02

This galaxy is known as Mrk 820 and is classified as a lenticular galaxy — type S0 on the Hubble Tuning Fork. The Hubble Tuning Fork is used to classify galaxies according to their morphology. Elliptical galaxies look like smooth blobs in the sky and lie on the handle of the fork. They are arranged along the handle based on how elliptical they are, with the more spherical galaxies furthest from the tines of the fork, and the more egg-shaped ones closest to the end of the handle where it divides. The two prongs of the tuning fork represent types of unbarred and barred spiral galaxies. Lenticular galaxies like Mrk 820 are in the transition zone between ellipticals and spirals and lie right where the fork divides. A closer look at the appearance of Mrk 820 reveals hints of a spiral structure embedded in a circular halo of stars. Surrounding Mrk 820 in this image is good sampling of other galaxy types, covering almost every type found on the Hubble Tuning Fork, both elliptical and spiral. Most of the smears and specks are distant galaxies, but the prominent bright object at the bottom is a foreground star called TYC 4386-787-1. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Judy Schmidt.

Stellar Archaeology and Galaxy Genesis: The Need for Large Area Multi-Object Spectrograph on 8 m-Class Telescopes

NASA Astrophysics Data System (ADS)

Irwin, Mike J.; Lewis, Geraint F.

The origin and evolution of galaxies like the Milky Way and M31 remain among the key questions in astrophysics. The galaxies we see today in and around the Local Group are representatives of the general field population of the Universe and have been evolving for the majority of cosmic time. As our nearest neighbour systems they can be studied in far more detail than their distant counterparts and hence provide our best hope for understanding star formation and prototypical galaxy evolution over the lifetime of the Universe [K. Freeman, J. Bland-Hawthorn in Annu. Rev. Astron. Astrophys. 40, 487 (2002)]. Significant observational progress has been made, but we are still a long way from understanding galaxy genesis. To unravel this formative epoch, detailed large area multi-object spectroscopy of spatial, kinematic and chemical structures on 8 m-class telescopes are required, to provide the link between local near-field cosmology and predictions from the high-redshift Universe.

A Hungry Quasar Caught in the Act

NASA Astrophysics Data System (ADS)

2001-05-01

The VLT Secures Spectacular Image of Distant Gravitational Interaction Summary A new image of a distant quasar (the luminous core of an "active" galaxy) shows that it is engaged in a gravitational battle with its neighbouring galaxies . It also provides information on how supermassive black holes present in the center of quasars are fed. Using the FORS2 multi-mode instrument at the ESO 8.2-m VLT KUEYEN telescope on Paranal (Chile), a team of German astronomers [1] obtained a spectacular image of the close and complex environment of the distant quasar "HE 1013-2136", located some 10 billion light-years away [2]. The remarkable structures revealed in this photo lend support to the hypothesis that quasar activity is connected to gravitational interaction between galaxies, already at this early epoch of the Universe (about 5 billion years after the Big Bang). PR Photo 20a/01 : A VLT image of the Quasar HE 1013-2136 . PR Photo 20b/01 : A sharpened version of the same image. Feeding the Black Hole "Quasars" (Quasi-Stellar Objects) were first discovered by Dutch-American astronomer Maarten Schmidt in 1963 as distant, energetic objects of star-like appearance. Since then, more than 15,000 quasars have been found and we now know that they are the luminous cores at the heart of distant galaxies. Such "Active Galactic Nuclei (AGN)" are thought to host Supermassive Black Holes of up to one billion solar masses at their centres. Black Holes represent the densest possible state of matter; if the Earth were to become one, it would measure no more than a few millimetres across. The Black Hole in a galaxy gobbles up the gas and dust of its host, a process that efficiently powers the luminous core that we observe as a point-like "quasar". A Black Hole must be continuously fed to remain active. During an active phase of typically 100 million years, the Black Hole in a quasar swallows material with a total weight of up to 10 solar masses every year. This may be predominantly in the form of gas and dust that happen to come too close to the hole. Our own galaxy, the Milky Way, is also very likely to harbour a Black Hole at its center. However, this hole apparently lacks material to swallow and is somewhat starved - in any case it is much less active than some holes in other galaxies. A key question in connection with the quasar phenomenon is therefore to understand how a large amount of material can be brought towards the center of the host galaxy . Most astronomers believe that disturbances caused by gravitational interaction with neighbouring galaxies constitute a triggering mechanism for fueling the centers of Active Galaxies. The efficiency of such tidal interactions taking place of course depends on how many galaxies are located in the immediate neighbourhood of the quasar as well as on the relative velocities of the quasar host and its companions. Searching for quasar companions ESO PR Photo 20a/01 ESO PR Photo 20a/01 [Preview - JPEG: 400 x 452 pix - 304k] [Normal - JPEG: 800 x 900 pix - 744k] ESO PR Photo 20b/01 ESO PR Photo 20b/01 [Preview - JPEG: 400 x 452 pix - 208k] [Normal - JPEG: 800 x 898 pix - 460k] Caption : PR Photo 20a/01 shows an image of the Quasar HE 1013-2136 (center) and its surroundings, as obtained with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope in February 2001. A spectacular arc-like tidal tail stretches from the quasar towards south-east (lower-left) over a distance of more than 150,000 light-years. Another, shorter tidal tail towards the east-northeast is barely visible. PR Photo 20b/01 shows the same field, but sharpened with a computer algorithm to bring out more details in the immediate neighbourhood of the quasar. Now numerous details can be recognized within the two tidal tails, including various knotty structures. In particular, a very close companion galaxy at 20,000 light-years projected distance to the quasar can now be seen (at the 5 o'clock position) that may be in gravitational interaction with the quasar host galaxy. Quasar activity is believed to be triggered by such dramatic events. Since some time, astronomers have therefore been searching for clear evidence for a connection between gravitational interaction and the quasar phenomenon. However, quasars are very bright objects and their light easily outshines all nearby objects. Any companion galaxies and structural features that may indicate interaction are therefore hard to detect. While observations with the Hubble Space Telescope (HST) have much improved our knowledge of the interaction-activity connection in some relatively nearby quasars, it has been difficult to probe the same phenomenon in more distant quasar environments. Such studies clearly require larger telescopes. The observations of the quasar HE 1013-2136 presented here result from a new programme that addresses this issue at earlier cosmic epochs. This 17-mag object is seen in the southern constellation Hydra (The Water Snake) and is located at a distance of about 10 billion light years (the redshift is z = 0.785) PR Photo 20a/01 shows an image of HE 1013-2136 and its immediate surroundings, obtained with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope under very good seeing conditions. The image resolution is about 0.6 arcsec, or about 10,000 light-years at the distance of the quasar. The image has been further sharpened by means of image processing software (the Lucy algorithm) in PR Photo 20b/01 , now also showing the distribution of objects very close to the bright quasar image. This impressively illustrates the light gathering and resolution power of the VLT. Tidal forces at HE 1013-2136 The quasar is the point-like object at the center of the images. It is embedded within a complex structure that mainly consists of two arc-like and knotty tails extending in different directions. Such tails are well-known from nearby galaxy interactions, cf. NGC 6872/IC4970 and are a consequence of tidal forces in the gravitational field of the galaxies. The astronomers believe that the two tidal tails result from a dramatic interaction between the quasar host galaxy and one or more of the close companion galaxies. The longer, southern tail extends over more than 150,000 light years, one-and-a-half times the diameter of the Milky Way. In many respects this distant interaction resembles the well known Antenna Galaxies (see the Hubble image ), where two nearby galaxies distort each other in a gravitational dance. Galaxy mergers in the young Universe In the case of HE 1013-2136 , a number of knots can be seen along both tidal tails. In particular, the object just below the quasar image, most easily seen in the sharpened image ( PR Photo 20b/01 ), lies at a projected distance of only 20,000 light years. This is about two-thirds of the distance from the Earth to the center of the Milky Way galaxy. This object is most likely a companion that is interacting with the quasar host. Recent observations of nearby quasars have revealed that they mostly reside in elliptical galaxies . Numerical simulations suggest that such galaxies can be formed by successive mergers of spiral galaxies. Klaus Jäger and his colleagues point out that " with the VLT observations of HE 1013-2136 , we may be directly witnessing such a dramatic merger of galaxies. The special significance of this observation is the great distance and hence the comparably early time at which this happens, when the Universe was about one third as old as it is now ". He adds: " This particular galaxy will most probably evolve into the same type of elliptical quasar host galaxy that we observe much nearer to us, that is, at much later times ". Notes [1] The team is composed of Klaus Jäger , Klaus J. Fricke (both Universitäts-Sternwarte Göttingen, Germany), Jochen Heidt and Immo Appenzeller (both Landessternwarte Heidelberg, Germany). [2] 1 billion = 1,000 million Technical information about the photos PR Photo 20a/01 is based on an image that was obtained in the morning of February 26, 2001 with the FORS2 instrument on VLT KUEYEN. It is composed of eight exposures in the I-band filter (effective wavelength 768 nm; FWHM 138 nm), lasting a total of 32 min. The combined image has a FWHM of 0.6 arcsec. In PR Photo 20b/01 this image has been processed by applying the Lucy algorithm with 15 iterations. The field shown measures 33 x 33 arcsec 2 , or 540,000 x 540,000 light-years 2 projected at the distance of the quasar; 1 pixel = 0.2 arcsec. North is up and East is left.

The morphological transformation of red sequence galaxies in clusters since z ˜ 1

NASA Astrophysics Data System (ADS)

Cerulo, P.; Couch, W. J.; Lidman, C.; Demarco, R.; Huertas-Company, M.; Mei, S.; Sánchez-Janssen, R.; Barrientos, L. F.; Muñoz, R.

2017-11-01

The study of galaxy morphology is fundamental to understand the physical processes driving the structural evolution of galaxies. It has long been known that dense environments host high fractions of early-type galaxies and low fractions of late-type galaxies, indicating that the environment affects the structural evolution of galaxies. In this paper, we present an analysis of the morphological composition of red sequence galaxies in a sample of nine galaxy clusters at 0.8 < z < 1.5 drawn from the HAWK-I Cluster Survey (HCS), with the aim of investigating the evolutionary paths of galaxies with different morphologies. We classify galaxies according to their apparent bulge-to-total light ratio and compare with red sequence galaxies from the lower redshift WIde-field Nearby Galaxy-cluster Survey (WINGS) and ESO Distant Cluster Survey (EDisCS). We find that, while the HCS red sequence is dominated by elliptical galaxies at all luminosities and stellar masses, the WINGS red sequence is dominated by elliptical galaxies only at its bright end (MV < -21.0 mag), while S0s become the most frequent class at fainter luminosities. Disc-dominated galaxies comprise 10-14 per cent of the red sequence population in the low (WINGS) and high (HCS) redshift samples, although their fraction increases up to 40 per cent at 0.4 < z < 0.8 (EDisCS). We find a 20 per cent increase in the fraction of S0 galaxies from z ∼ 1.5 to 0.05 on the red sequence. These results suggest that elliptical and S0 galaxies follow different evolutionary histories and, in particular, that S0 galaxies result, at least at intermediate luminosities (-22.0 < MV < -20.0), from the morphological transformation of quiescent spiral galaxies.

Galactic Neighborhood and Laboratory Astrophysics

NASA Astrophysics Data System (ADS)

Wang, Q. D.

2011-05-01

The galactic neighborhood, extending from the Milky Way to redshifts of about 0.1, is our unique local laboratory for detailed study of galaxies and their interplay with the environment. Such study provides a foundation of knowledge for interpreting observations of more distant galaxies and their environment. The Astro 2010 Science Frontier Galactic Neighborhood Panel identified four key sci- entific questions: 1) What are the flows of matter and energy in the circumgalac- tic medium? 2) What controls the mass-energy-chemical cycles within galaxies? 3) What is the fossil record of galaxy assembly from first stars to present? 4) What are the connections between dark and luminous matter? These questions, essential to the understanding of galaxies as interconnected complexes, can be addressed most effectively and/or uniquely in the galactic neighborhood. The panel also highlighted the discovery potential of time-domain astronomy and astrometry with powerful new techniques and facilities to greatly advance our understanding of the precise connections among stars, galaxies, and newly dis- covered transient events. The relevant needs for laboratory astrophysics will be emphasized, especially in the context of supporting NASA missions.

A gravitationally lensed starburst galaxy at z=1.03 detected by SOFIA/HAWC+

NASA Astrophysics Data System (ADS)

Brown, Arianna; Ma, Jingzhe; Cooray, Asantha; Nayyeri, Hooshang; Timmons, Nicholas

2018-01-01

We present a high S/N~20 detection at 89 micron (in 15 mins) of the Herschel-selected gravitationally lensed starburst galaxy HATLASJ1429-0028 with the High-resolution Airborne Wideband Camera-plus (HAWC+) onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The spectacular lensing system consists of an edge-on foreground disk galaxy at z=0.22 and a nearly complete Einstein ring of an intrinsic ultra-luminous infrared galaxy at z=1.03. Is this high luminosity powered by pure star formation (SF) or an active galactic nucleus (AGN)? Previous nebular line diagnostics indicate that it is star-formation dominated. SOFIA/HAWC+ allows the broad-band spectral energy distribution of the galaxy to be studied between 20 - 100 micron, which is an important wavelength range for further constraining the fractional AGN contribution to the total IR luminosity. Multi-wavelength SED modeling constrains the AGN fraction to be < 1%. The detection of a source at z of 1 shows the potential of utilizing SOFIA/HAWC+ for distant galaxy studies and the potential to decompose SF/AGN that cannot be obtained with other current facilities.

A Pool of Distant Galaxies

NASA Astrophysics Data System (ADS)

2008-11-01

Anyone who has wondered what it might be like to dive into a pool of millions of distant galaxies of different shapes and colours, will enjoy the latest image released by ESO. Obtained in part with the Very Large Telescope, the image is the deepest ground-based U-band image of the Universe ever obtained. It contains more than 27 million pixels and is the result of 55 hours of observations with the VIMOS instrument. A Sea of Galaxies ESO PR Photo 39/08 A Pool of Distant Galaxies This uniquely beautiful patchwork image, with its myriad of brightly coloured galaxies, shows the Chandra Deep Field South (CDF-S), arguably the most observed and best studied region in the entire sky. The CDF-S is one of the two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant Universe to assist in their study of the formation and evolution of galaxies. The new image released by ESO combines data obtained with the VIMOS instrument in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2 m MPG/ESO telescope at La Silla, in the framework of the GABODS survey. The newly released U-band image - the result of 40 hours of staring at the same region of the sky and just made ready by the GOODS team - is the deepest image ever taken from the ground in this wavelength domain. At these depths, the sky is almost completely covered by galaxies, each one, like our own galaxy, the Milky Way, home of hundreds of billions of stars. Galaxies were detected that are a billion times fainter than the unaided eye can see and over a range of colours not directly observable by the eye. This deep image has been essential to the discovery of a large number of new galaxies that are so far away that they are seen as they were when the Universe was only 2 billion years old. In this sea of galaxies - or island universes as they are sometimes called - only a very few stars belonging to the Milky Way are seen. One of them is so close that it moves very fast on the sky. This "high proper motion star" is visible to the left of the second brightest star in the image. It appears as a funny elongated rainbow because the star moved while the data were being taken in the different filters over several years. Notes Because the Universe looks the same in all directions, the number, types and distribution of galaxies is the same everywhere. Consequently, very deep observations of the Universe can be performed in any direction. A series of fields were selected where no foreground object could affect the deep space observations (such as a bright star in our galaxy, or the dust from our Solar System). These fields have been observed using a number of telescopes and satellites, so as to collect information at all possible wavelengths, and characterise the full spectrum of the objects in the field. The data acquired from these deep fields are normally made public to the whole community of astronomers, constituting the basis for large collaborations. Observations in the U-band, that is, at the boundary between visible light and ultraviolet are challenging: the Earth's atmosphere becomes more and more opaque out towards the ultraviolet, a useful property that protects people's skin, but limiting to ground-based telescopes. At shorter wavelengths, observations can only be done from space, using, for example, the Hubble Space Telescope. On the ground, only the very best sites, such as ESO's Paranal Observatory in the Atacama Desert, can perform useful observations in the U-band. Even with the best atmospheric conditions, instruments are at their limit at these wavelengths: the glass of normal lenses transmits less UV light, and detectors are less sensitive, so only instruments designed for UV observations, such as VIMOS on ESO's Very Large Telescope, can get enough light. The VIMOS U-band image, which was obtained as part of the ESO/GOODS public programme, is based on 40 hours of observations with the VLT. The VIMOS R-band image was obtained co-adding a large number of archival images totaling 15 hours of exposure. The WFI B-band image is part of the GABODS survey.

The Extreme Hosts of Extreme Supernovae

NASA Astrophysics Data System (ADS)

Neill, James D.

2012-01-01

We present the results from a deeper survey of Luminous Supernova (LSN) hosts with the Galaxy Evolution Explorer (GALEX). We have added new, multiple kilo-second observations to our original observations of seventeen LSN hosts providing better constraints on their physical properties. We place the LSNe hosts on the galaxy NUV-r versus M(r) color magnitude diagram (CMD) with a larger comparison sample ( 26,000) to illustrate the extreme nature of these galaxies. The LSN hosts favor low-density regions of the galaxy CMD falling on the blue edge of the blue cloud toward the low luminosity end. The new observations provide tighter constraints on the star formation rates (SFRs) and stellar masses, M(*), and show that the LSNe result from regions of high specific star formation and yet low total SFR. This regime is of particular interest for exploring the upper end of the stellar IMF and its variation. If our understanding of the progenitors of the LSNe leans toward very massive (> 200 M_sun) progenitors, the potential for a conflict with IMF theory exists because the conditions found in the hosts producing the LSNe should not create such massive stars. If it also required that LSNe can only be produced in primordial or very low metallicity environments, then they will also provide evidence for strong variation in metallicity within a dwarf galaxy, since their masses are consistent with low, but not extreme metallicity.

The Physical Properties of Intracluster Gas at z > 1

NASA Technical Reports Server (NTRS)

Rosati, Piero; Ford, Holland C.

2004-01-01

We have used XMM-Newton, Chandra and HST/ACS data on one of the most distant clusters known to date, RDCS1252-29 at z= 1.24, to measure the mass of its baryonic and dark components for the first time at these large redshifts. By comparing physical properties of cluster galaxies and of the X-ray emitting intra-cluster medium (including the iron abundance) with those in low-redshift clusters, we have found that little evolution has taken place over 60% of the lifetime of the Universe. This suggests that most of the stars formed at z>approx.3 and metal enrichment processes took place early in the evolutionary history of galaxy clusters. These findings have a strong bearing on galaxy and cluster evolution models.

A new method to determine the interstellar reddening towards WN stars

NASA Technical Reports Server (NTRS)

Conti, Peter S.; Morris, Patrick W.

1990-01-01

An empirical approach to determine the redding in WN stars is presented, in which the measured strengths of the emission lines of He II at 1640 and 4686 A are used to estimate the extinction. The He II emission lines at these wavelengths are compared for a number of WN stars in the Galaxy and the LMC. It is shown that the equivalent width ratios are single valued and are independent of the spectral subtypes. The reddening for stars in the Galaxy is derived using a Galactic extinction law and observed line flux ratios, showing good agreement with previous determinations of reddening. The possible application of the method to study the absorption properties of the interstellar medium in more distant galaxies is discussed.

The [CII]/[NII] far-infrared line ratio at z>5: extreme conditions for “normal” galaxies

NASA Astrophysics Data System (ADS)

Pavesi, Riccardo; Riechers, Dominik; Capak, Peter L.; Carilli, Chris Luke; Sharon, Chelsea E.; Stacey, Gordon J.; Karim, Alexander; Scoville, Nicholas; Smolcic, Vernesa

2017-01-01

Thanks to the Atacama Large (sub-)Millimeter Array (ALMA), observations of atomic far-infrared fine structure lines are a very productive way of measuring physical properties of the interstellar medium (ISM) in galaxies at high redshift, because they provide an unobscured view into the physical conditions of star formation. While the bright [CII] line has become a routine probe of the dynamical properties of the gas, its intensity needs to be compared to other lines in order to establish the physical origin of the emission. [NII] selectively traces the emission coming from the ionized fraction of the [CII]-emitting gas, offering insight into the phase structure of the ISM. Here we present ALMA measurements of [NII] 205 μm fine structure line emission from a representative sample of galaxies at z=5-6 spanning two orders of magnitude in star formation rate (SFR). Our results show at least two different regimes of ionized gas properties for galaxies in the first billion years of cosmic time, separated by their L[CII]/L[NII] ratio. First, we find extremely low [NII] emission compared to [CII] from a “typical” Lyman Break Galaxy (LBG-1), likely due to low dust content and reminiscent of local dwarfs. Second, the dusty Lyman Break Galaxy HZ10 and the extreme starburst AzTEC-3 show ionized gas fractions typical of local star-forming galaxies and show hints of spatial variations in their [CII]/[NII] line ratio. These observations of far-infrared lines in “normal” galaxies at z>5 yield some of the first constraints on ISM models for young galaxies in the first billion years of cosmic time and shed light on the observed evolution of the dust and gas properties.

The Emission of Galaxies over the Whole Electromagnetic Spectrum

NASA Astrophysics Data System (ADS)

Burgarella, Denis; Boquien, Médéric; Roehlly, Yannick; Ciesla, Laure; Buat, Véronique

2017-08-01

The emission of galaxies is not limited to the usual optical range but extends to a wider spectral range with, most notably, emission in the X-ray, ultraviolet, infrared and radio ranges. Their detection and study brings a lot of information to the astrophysics because the physical phenomena at the origin of the various emissions are different. Each of them allows analysis of a different facet of the physics of galaxies: gas, stars, dust, Active Galactic Nuclei (AGN). However, gathering this multi-wavelength information is not an easy task as some of them do not reach ground-based telescopes and we have to design and launch space telescopes to catch and collect the relevant photons. This paper will present the tools that are available to the astrophysicist to decipher the message sent by local, distant or even the most remote galaxies observed in the universe.

An intensity map of hydrogen 21-cm emission at redshift z approximately 0.8.

PubMed

Chang, Tzu-Ching; Pen, Ue-Li; Bandura, Kevin; Peterson, Jeffrey B

2010-07-22

Observations of 21-cm radio emission by neutral hydrogen at redshifts z approximately 0.5 to approximately 2.5 are expected to provide a sensitive probe of cosmic dark energy. This is particularly true around the onset of acceleration at z approximately 1, where traditional optical cosmology becomes very difficult because of the infrared opacity of the atmosphere. Hitherto, 21-cm emission has been detected only to z = 0.24. More distant galaxies generally are too faint for individual detections but it is possible to measure the aggregate emission from many unresolved galaxies in the 'cosmic web'. Here we report a three-dimensional 21-cm intensity field at z = 0.53 to 1.12. We then co-add neutral-hydrogen (H i) emission from the volumes surrounding about 10,000 galaxies (from the DEEP2 optical galaxy redshift survey). We detect the aggregate 21-cm glow at a significance of approximately 4sigma.

High-Redshift Astrophysics Using Every Photon

NASA Astrophysics Data System (ADS)

Breysse, Patrick; Kovetz, Ely; Rahman, Mubdi; Kamionkowski, Marc

2017-01-01

Large galaxy surveys have dramatically improved our understanding of the complex processes which govern gas dynamics and star formation in the nearby universe. However, we know far less about the most distant galaxies, as existing high-redshift observations can only detect the very brightest sources. Intensity mapping surveys provide a promising tool to access this poorly-studied population. By observing emission lines with low angular resolution, these surveys can make use of every photon in a target line to study faint emitters which are inaccessible using traditional techniques. With upcoming carbon monoxide experiments in mind, I will demonstrate how an intensity map can be used to measure the luminosity function of a galaxy population, and in turn how these measurements will allow us to place robust constraints on the cosmic star formation history. I will then show how cross-correlating CO isotopologue lines will make it possible to study gas dynamics within the earliest galaxies in unprecedented detail.

The kinematics and morphology of cool galactic winds and halo gas from galaxies at 0.3 < z < 1.4

NASA Astrophysics Data System (ADS)

Rubin, Kate H. R.

Large-scale redshift surveys tracing the evolution of the luminous components of galaxies have revealed both an increase in the number density of "red and dead" galaxies and a concomitant decline in the star formation rates (SFRs) of blue galaxies since z ˜ 1. The latter is predicted to be due to a decreasing cool gas supply over time; whereas the former may be explained by the theory of merger-driven galaxy evolution, which suggests that the merging of blue galaxies expels the interstellar medium (ISM), thereby quenching star formation in the remnant. While these theoretical explanations provide robust predictions for the evolution of the gaseous components of distant galaxies, we have few direct measurements of the location and kinematics of cool gas around galaxies beyond the local universe. This thesis uses three complementary observational techniques to provide new constraints on the kinematics and morphology of cool gas in galaxies at 0.3 < z < 1.4. First, we use spectra of ˜470 galaxies at 0.7 < z < 1.5 drawn from the Team Keck Treasury Redshift Survey to study absorption line profiles for the Mg II lambdalambda2796, 2803 and Fe II lambdalambda2586, 2600 transitions, which probe cool, photoionized gas with temperature T ˜ 10 4 K. By coadding several sub-samples of galaxy spectra, we identify gaseous outflows via the Doppler shift of the absorption lines, and find that outflows are ubiquitous in galaxies having SFR > 10 M⊙ yr-1 and stellar masses ≳1010.5M⊙ . By comparing these results to those of Weiner et al. (2009), who present a similar study of outflows in star-forming galaxies at z ˜ 1.4, we find that these outflows persist in high-mass galaxies as they age between z ˜ 1.4 and z ˜ 1. Using HST/ACS imaging of our galaxy sample, we present evidence for a weak trend of increasing outflow absorption strength with increasing galaxy SFR surface density (SigmaSFR). Theoretical studies suggest that a minimum SigmaSFR must be exceeded in the host galaxy for outflows to be driven by either radiation pressure or thermalized energy from supernovae. To test this directly, we use a similar technique to probe cool gas kinematics in the individual Keck/LRIS spectra of a sample of ˜120 galaxies at 0.3 < z < 1.4. These data permit modeling of Mg II and Fe II absorption lines to obtain, e.g., the cool gas outflow velocity and covering fraction. Using Spitzer/MIPS and GALEX imaging to determine SFRs in concert with HST/ACS imaging which enables measurements of the size of star-forming regions, we compare outflow velocity to SigmaSFR. We find that while we detect outflows over a range 0.005 M⊙ yr-1 kpc-2 < Sigma SFR < 1 M⊙ yr-1 kpc-2, outflows occur more frequently with increasing SigmaSFR. The absorption line studies described above provide strong constraints on, e.g., the cool gas velocities. However, they provide only weak constraints on the radial extent and morphology of the gas. Knowledge of the spatial extent of the outflow is essential for accurately estimating its mass and energy; measurements of these rates are in turn crucial to understanding the role of outflows in driving galaxy evolution. Next, we show that emission in Mg II and Fe II* fine-structure lines can provide novel constraints on the spatial extent of an outflow. We identify a starburst galaxy at z = 0.69 which exhibits emission and absorption in Mg II, yielding a P Cygni-like line profile. We demonstrate that this emission is spatially broader than the continuum emission and the emission from H II regions, and associate the Mg II and Fe II* emission with resonance-line scattering and fluorescence in the outflow. These features are common at z ˜ 1, and in principle yield the first direct constraint on the radial extent of the outflow in many distant galaxies. Finally, we present a study of the cool gas around a single galaxy at z = 0.47 using spectroscopy of a bright background galaxy at z = 0.7 at a transverse distance of 16.5 h-170 kpc. While cool halo gas is typically studied along sightlines to background QSOs, the use of background galaxies offers several advantages over more traditional techniques. Because the background galaxy is spatially extended, we probe absorption over a large (> 4 h-170 kpc) area in the foreground halo, and find that the gas exhibits a large velocity dispersion and high covering fraction over this area. Spectroscopy of the foreground host galaxy reveals that it experienced a burst of star formation ˜1 Gyr ago, and we suggest that the absorbing gas in the halo was most likely ejected or tidally stripped during this past violent event. As such, these results again place a novel constraint on the radial extent of cool gas originating in the ISM of a distant galaxy.

The nature of H α-selected galaxies along the large-scale structure at z = 0.4 revealed by Subaru Hyper Suprime-Cam survey

NASA Astrophysics Data System (ADS)

Koyama, Yusei; Hayashi, Masao; Tanaka, Masayuki; Kodama, Tadayuki; Shimakawa, Rhythm; Yamamoto, Moegi; Nakata, Fumiaki; Tanaka, Ichi; Suzuki, Tomoko L.; Tadaki, Ken-ichi; Nishizawa, Atsushi J.; Yabe, Kiyoto; Toba, Yoshiki; Lin, Lihwai; Jian, Hung-Yu; Komiyama, Yutaka

2018-01-01

We present the environmental dependence of color, stellar mass, and star formation (SF) activity in Hα-selected galaxies along the large-scale structure at z = 0.4 hosting twin clusters in the DEEP2-3 field, discovered by the Subaru Strategic Program of Hyper Suprime-Cam (HSC SSP). By combining photo-z-selected galaxies and Hα emitters selected with broadband and narrowband (NB) data from the recent data release of HSC SSP (DR1), we confirm that galaxies in higher-density environments or galaxies in cluster central regions show redder colors. We find that there still remains a possible color-density and color-radius correlation even if we restrict the sample to Hα-selected galaxies, probably due to the presence of massive Hα emitters in denser regions. We also find a hint of increased star formation rates (SFR) amongst Hα emitters toward the highest-density environment, again primarily driven by the excess of red/massive Hα emitters in high-density environments, while their specific SFRs do not significantly change with environment. This work demonstrates the power of the HSC SSP NB data for studying SF galaxies across environments in the distant universe.

GASP. V. Ram-pressure stripping of a ring Hoag's-like galaxy in a massive cluster

NASA Astrophysics Data System (ADS)

Moretti, A.; Poggianti, B. M.; Gullieuszik, M.; Mapelli, M.; Jaffé, Y. L.; Fritz, J.; Biviano, A.; Fasano, G.; Bettoni, D.; Vulcani, B.; D'Onofrio, M.

2018-04-01

Through an ongoing MUSE program dedicated to study gas removal processes in galaxies (GAs Stripping Phenomena in galaxies with MUSE, GASP), we have obtained deep and wide integral field spectroscopy of the galaxy JO171. This galaxy resembles the Hoag's galaxy, one of the most spectacular examples of ring galaxies, characterized by a completely detached ring of young stars surrounding a central old spheroid. At odds with the isolated Hoag's galaxy, JO171 is part of a dense environment, the cluster Abell 3667, which is causing gas stripping along tentacles. Moreover, its ring counter-rotates with respect to the central spheroid. The joint analysis of the stellar populations and the gas/stellar kinematics shows that the origin of the ring was not due to an internal mechanism, but was related to a gas accretion event that happened in the distant past, prior to accretion on to Abell 3667, most probably within a filament. More recently, since infall in the cluster, the gas in the ring has been stripped by ram pressure, causing the quenching of star formation in the stripped half of the ring. This is the first observed case of ram-pressure stripping in action in a ring galaxy, and MUSE observations are able to reveal both of the events (accretion and stripping) that caused dramatic transformations in this galaxy.

Exploring the extremely low surface brightness sky: distances to 23 newly discovered objects in Dragonfly fields

NASA Astrophysics Data System (ADS)

van Dokkum, Pieter

2016-10-01

We are obtaining deep, wide field images of nearby galaxies with the Dragonfly Telephoto Array. This telescope is optimized for low surface brightness imaging, and we are finding many low surface brightness objects in the Dragonfly fields. In Cycle 22 we obtained ACS imaging for 7 galaxies that we had discovered in a Dragonfly image of the galaxy M101. Unexpectedly, the ACS data show that only 3 of the galaxies are members of the M101 group, and the other 4 are very large Ultra Diffuse Galaxies (UDGs) at much greater distance. Building on our Cycle 22 program, here we request ACS imaging for 23 newly discovered low surface brightness objects in four Dragonfly fields centered on the galaxies NGC 1052, NGC 1084, NGC 3384, and NGC 4258. The immediate goals are to construct the satellite luminosity functions in these four fields and to constrain the number density of UDGs that are not in rich clusters. More generally, this complete sample of extremely low surface brightness objects provides the first systematic insight into galaxies whose brightness peaks at >25 mag/arcsec^2.

Flickering Quasar Helps Chandra Measure the Expansion Rate of the universe

NASA Astrophysics Data System (ADS)

2000-11-01

Astronomers using the Chandra X-ray Observatory have identified a flickering, four-way mirage image of a distant quasar. A carefully planned observation of this mirage may be used to determine the expansion rate of the universe as well as to measure the distances to extragalactic objects, arguably two of the most important pursuits in modern astronomy. quasar RX J0911.4+0551 This figure is a composite of the X-ray image of the gravitational lens RX J0911.4+551 (top panel) and the light curves of the lensed images A2 (left panel) and A1 (right panel). Credit: NASA George Chartas, senior research associate at The Pennsylvania State University (Penn State) and Marshall W. Bautz, principal research scientist at the Massachusetts Institute of Technology (MIT) Center for Space Research, present their findings today at the meeting of the High Energy Astrophysics Division of the American Astronomical Society in Honolulu, Hawaii. "With a carefully planned follow-up, the Chandra observation of quasar RX J0911.4+0551 may lead to a measurement of the Hubble constant, the expansion rate of the universe, in less than a day," said Chartas. The observation would be done not with mirrors but with mirages--four images of a single quasar that capture the quasar's light at different moments of time due to the speed of light and the location of the mirages. Quasars are extremely distant galaxies with cores that glow with the intensity of 10 trillion Suns, a phenomenon likely powered by a supermassive black hole in the heart of the galaxy. This single "point source" image of a quasar may appear as four or five sources when the quasar--from our vantage point on Earth--is behind a massive intervening deflector, such as a dim galaxy. A mirage of images form when the gravity of the intervening deflector forces light rays to bend and take different paths to reach us. The time it takes for light to reach us from the distant object will depend on which path a ray decides to take. "An intervening galaxy can act as a lens," said Bautz. "Now imagine that the distant lensed quasar suddenly became brighter. The mirage images of the quasar will brighten up at different times depending on the difference in the light travel delay." Unlike ordinary galaxies, quasars do vary greatly in their intensity, especially in the X-ray waveband, said Gordon Garmire, Evan Pugh Professor of Astronomy and Astrophysics at Penn State. This is caused by the violent and erratic flow of gas into the black hole that is powering the quasar. In quasar RX J0911.4+0551, the astronomers saw a sudden brightening of X-ray intensity that lasted for about 2,000 seconds. This was observed in one of the four mirage images. Measuring the time-delay of the 2,000-second flare--or any flare-- from mirage to mirage can provide the absolute distance to the deflector (intervening galaxy) and can thus be used to estimate the expansion rate of the universe. Sjur Refsdal first proposed this promising method in 1964. The method avoids many uncertainties associated with the classic distance-ladder technique used to measure objects and the Hubble constant. The main difficulty in measuring time-delays is that the brightness of each image has to be carefully monitored over several periods of the time-delay. Also, the quasar has to show sufficient variability over time scales smaller than the time-delay. Most attempts to measure time-delays until now have been made in the optical and radio bands. The modest variability of quasars in these wavebands, however, has made it extremely difficult to place accurate constraints on time-delays. X-ray observations of gravitationally lensed quasars, on the other hand, show strong variability over time scales of hours to days. For example, it has taken almost 20 years of optical and radio monitoring to obtain a universal accepted time-delay for the lensed quasar Q0957+561 to an accuracy of 3percent. Chandra has the potential, the team has found, to determine the time-delay in one observation. "Based on computer models developed at Penn State and MIT, we have identified about ten gravitational lens systems with time-delays of less than a day," said Chartas. "One long observation of each source with a superior X-ray telescope could provide enough data to nail down the Hubble constant in the blink of an eye." The team is planning to apply the gravitational-lens method in the near future to several of these systems using the Chandra and XMM-Newton X-ray observatories. The Chandra observations of quasar RX J0911.4+0551 were made on November 2, 1999, using the Advanced CCD Imaging Spectrometer (ACIS). The effort involved several scientists from Penn State and MIT. ACIS was conceived and developed for NASA by Penn State and MIT under Garmire's leadership. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. TRW, Inc., in Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Massachusetts. RX J0911.4+551 Handout Constellation Hydra To follow Chandra's progress, visit the Chandra site at: http://chandra.harvard.edu AND http://chandra.nasa.gov

Optical Spectroscopy of Distant Red Galaxies

NASA Astrophysics Data System (ADS)

Wuyts, Stijn; van Dokkum, Pieter G.; Franx, Marijn; Förster Schreiber, Natascha M.; Illingworth, Garth D.; Labbé, Ivo; Rudnick, Gregory

2009-11-01

We present optical spectroscopic follow-up of a sample of distant red galaxies (DRGs) with K tot s,Vega < 22.5, selected by (J - K)Vega>2.3, in the Hubble Deep Field South (HDFS), the MS 1054-03 field, and the Chandra Deep Field South (CDFS). Spectroscopic redshifts were obtained for 15 DRGs. Only two out of 15 DRGs are located at z < 2, suggesting a high efficiency to select high-redshift sources. From other spectroscopic surveys in the CDFS targeting intermediate to high-redshift populations selected with different criteria, we find spectroscopic redshifts for a further 30 DRGs. We use the sample of spectroscopically confirmed DRGs to establish the high quality (scatter in Δz/(1 + z) of ~0.05) of their photometric redshifts in the considered deep fields, as derived with EAZY. Combining the spectroscopic and photometric redshifts, we find that 74% of DRGs with K tot s,Vega < 22.5 lie at z>2. The combined spectroscopic and photometric sample is used to analyze the distinct intrinsic and observed properties of DRGs at z < 2 and z>2. In our photometric sample to K tot s,Vega < 22.5, low-redshift DRGs are brighter in Ks than high-redshift DRGs by 0.7 mag, and more extincted by 1.2 mag in AV . Our analysis shows that the DRG criterion selects galaxies with different properties at different redshifts. Such biases can be largely avoided by selecting galaxies based on their rest-frame properties, which requires very good multi-band photometry and high quality photometric redshifts.

Distant intense starbursts: evidence for self-regulated star formation?

NASA Astrophysics Data System (ADS)

Lehnert, M. D.

From an analysis of the Halpha and [NII]∼λ6583 rest-frame optical emission lines in a large sample of intensely star forming galaxies at z=1.3 to 2.7 observed with SINFONI on the ESO-VLT, we have reached a number of conclusions. The galaxies all have broad optical emission lines (sigma ˜50-250 km s-1) which are a function of the underlying star formation intensity as determined from the Halpha surface brightness. These broad lines are intrinsic to the galaxies and not due to beam smearing. The velocity dispersions appear to be related to the star formation intensity (Sigma SFR, star formation rate per unit area) of the form, sigma ˜ epsilon Sigma SFR1/2. This is a simple and direct relationship between the energy injection rate and the kinetic energy of the emission line gas with a coupling efficiency of epsilon . In this contribution, we outline a simple model whereby the energy output of massive stars, both mechanical and radiative, feeds a mass and energy cycle within the interstellar media of these distant galaxies. The mass and energy cycle pushes the global ISM towards the line of stability, Toomre parameter Q˜1, but only if the molecular gas captures, to some extent, the kinematics of the warm ionized gas as probed by the optical emission lines. In such a picture, the star formation intensity is self-regulating.} This work and many of the ideas presented here were developed in collaboration with L. Le Tiran, W. van Driel, P. Di Matteo (GEPI), N. Nesvadba, and F. Boulanger (IAS, Orsay, France).

THE EXTREMELY RED HOST GALAXY OF GRB 080207

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunt, Leslie; Cresci, Giovanni; Palazzi, Eliana

2011-08-01

We present optical, near-infrared, and Spitzer IRAC and MIPS observations of the host galaxy of the dark Swift gamma-ray burst GRB 080207. The host is faint, with extremely red optical-infrared colors (R - K = 6.3, 24 {mu}m/R-band flux {approx}1000) making it an extremely red object (ERO) and a dust-obscured galaxy (DOG). The spectral energy distribution (SED) shows the clear signature of the 1.6 {mu}m photometric 'bump', typical of evolved stellar populations. We use this bump to establish the photometric redshift z{sub phot} as 2.2{sup +0.2}{sub -0.3}, using a vast library of SED templates, including M 82. The star formationmore » rate (SFR) inferred from the SED fitting is {approx}119 M{sub sun} yr{sup -1}, the stellar mass 3 x 10{sup 11} M{sub sun}, and A{sub V} extinction from 1 to 2 mag. The ERO and DOG nature of the host galaxy of the dark GRB 080207 may be emblematic of a distinct class of dark GRB hosts, with high SFRs, evolved and metal-rich stellar populations, and significant dust extinction within the host galaxy.« less

The Secret Lives Of Galaxies Unveiled In Deep Survey

NASA Astrophysics Data System (ADS)

2003-06-01

Two of NASA's Great Observatories, bolstered by the largest ground-based telescopes around the world, are beginning to harvest new clues to the origin and evolution of galaxies. It's a bit like finding a family scrapbook containing snapshots that capture the lives of family members from infancy through adolescence to adulthood. "This is the first time the cosmic tale of how galaxies build themselves has been traced reliably to such early times in the universe's life," said Mauro Giavalisco, head of the Hubble Space Telescope (HST) portion of the survey, and research astronomer at the Space Telescope Science Institute (STScI) in Baltimore. The HST has joined forces with the Chandra X-ray Observatory to survey a relatively broad swath of sky encompassing tens of thousands of galaxies stretching far back into time. The Space Infrared Telescope Facility (SIRTF), scheduled for launch in August, will soon join this unprecedented survey. Called the Great Observatories Origins Deep Survey (GOODS), astronomers are studying galaxy formation and evolution over a wide range of distances and ages. The project is tracing the assembly history of galaxies, the evolution of their stellar populations, and the gusher of energy from star formation and active nuclei powered by immense black holes. HST astronomers report the sizes of galaxies clearly increase continuously from the time the universe was about 1 billion years old to an age of 6 billion years. This is approximately half the current age of the universe, 13.7 billion years. GOODS astronomers also find the star birth rate rose mildly, by about a factor of three, between the time the universe was about one billion years old and 1.5 billion years old, and remained high until about 7 billion years ago, when it quickly dropped to one-tenth the earlier "baby boomer" rate. This is further evidence major galaxy building trailed off when the universe was about half its current age. GOODS Chandra Deep Fields South Chandra Deep Field South This increase in galaxy size is consistent with "bottom-up" models, where galaxies grow hierarchically, through mergers and accretion of smaller satellite galaxies. This is also consistent with the idea the sizes of galaxies match hand-in-glove to a certain fraction of the sizes of their dark-matter halos. Dark matter is an invisible form of mass that comprises most of the matter in the universe. The theory is dark matter essentially pooled into gravitational "puddles" in the early universe, then collected normal gas that quickly contracted to build star clusters and small galaxies. These dwarf galaxies merged piece-by-piece over billions of years to build the immense spiral and elliptical galaxies we see today. The Chandra observations amounted to a "high-energy core sample" of the early universe, allowing us to "study the history of black holes over almost the entire age of the universe," said Niel Brandt of Penn State University, a co-investigator on the Chandra GOODS team. One of the fascinating findings in this deepest X-ray image ever taken is the discovery of mysterious black holes, which have no optical counterparts. "We found seven mysterious sources that are completely invisible in the optical with Hubble," said Anton Koekemoer of the STScI, a co-investigator on both the Hubble and Chandra GOODS teams. "Either they are the most distant black holes ever detected, or they are less distant black holes that are the most dust enshrouded known, a surprising result as well." When comparing the HST and Chandra fields, astronomers also found active black holes in distant, relatively small galaxies were rarer than expected. This may be due to the effects of early generations of massive stars that exploded as supernovae, evacuating galactic gas and thus reducing the supply of gas needed to feed a super massive black hole. These and other results from the GOODS project will be published in a special issue of the Astrophysical Journal Letters, entirely devoted to the team's results. The Chandra results are found in papers led by Koekemoer and Stefano Cristiani of the Trieste Astronomical Observatory. Hubble's findings came from papers led by Giavalisco, Mark Dickinson, and Harry Ferguson of the STScI. The image and additional information are available at: http://chandra.harvard.edu and http://hubblesite.org/newscenter/archive/2003/18/

Faintest Methane Brown Dwarf Discovered with the NTT and VLT

NASA Astrophysics Data System (ADS)

1999-08-01

A team of European astronomers [1] has found a cold and extremely faint object in interstellar space, high above the galactic plane. It is a Methane Brown Dwarf of which only a few are known. This is by far the most distant one identified to date. Brown Dwarfs are star-like objects which are heavier than planets but not massive enough to trigger the nuclear burning of hydrogen and other elements which powers normal stars. They are, nevertheless, heated during their formation by gravitational contraction but then continuously cool as this energy is radiated away. The so-called Methane Brown Dwarfs are the coolest members of the class detected so far, with temperatures around 700 °C, i.e. around 1000 degrees cooler than the coldest stars. The new object, provisionally known as NTTDF J1205-0744 , was found during a deep survey of a small sky region in the constellation Virgo (The Virgin), just south of the celestial equator. The chances of identifying a rare object like this in such a restricted area are very small and the astronomers readily admit that they must have been very lucky. This is the story of an (unexpected) astronomical discovery that may prove to be very important for galactic studies. It also demonstrates the power of modern observational techniques. The NTT Deep Field A long series of exposures of a small sky field in Virgo were made in 1997 and 1998 with the ESO 3.58-m New Technology Telescope (NTT) at La Silla. They were carried out with the aim of measuring and demonstrating the limiting performance of two astronomical instruments at this telescope, the SUperb-Seeing Imager (SUSI) in the visible part of the spectrum (0.35 - 1.00 µm), and the multi-mode Son of ISAAC (SOFI) in the near-infrared region (1.0 - 2.5 µm). The observed sky area measures only 2.3 x 2.3 arcmin 2 and is referred to as the NTT Deep Field. It has been studied in great detail, in particular to identify very distant galaxies for spectroscopic follow-up observations with the FORS1 and ISAAC instruments at the VLT 8.2-m ANTU telescope during the first period of VLT observations. Such distant objects are quite red (due to their high redshift) and are best detected by a combination of visible and infrared exposures. Discovery of an extremely infrared object ESO PR Photo 35a/99 ESO PR Photo 35a/99 [Preview - JPEG: 400 x 251 pix - 72k] [Normal - JPEG: 800 x 502 pix - 224k] [High-Res - JPEG: 3000 x 1881 pix - 1.7M] Caption to ESO PR Photo 35a/99 : Part of the NTT Deep Field , with the new Methane Brown Dwarf NTTDF J1205-0744 at the centre. The field measures 1.3 x 1.3 arcmin 2. The object is well visible in the SOFI infrared exposure (left) in the J-band at wavelength 1.25 µm, but not in the SUSI one at a shorter wavelength (right) in the i-band at 0.8 µm. North is up and East is left. The astronomers noted a star-like object of extreme colour in this field. While it was well visible and similarly bright in both SOFI infrared images (J = 20.2 and K = 20.3), it could not be seen at all on the SUSI images in the visible spectral region, even at the longest wavelength (i-band) observed with that instrument (i-J > 6 mag), cf. PR Photo 35a/99 . No "normal" object is known to have such extreme colours. The new object now received the designation NTTDF J1205-0744 , indicating that it was discovered in the NTT Deep Field at the given position on the sky. It seemed that there were only two possibilities. Either it was an extremely distant quasar (redshift about 8) at the edge of the observable universe, or it must be a very cold object in the Milky Way Galaxy. Whatever its nature, this was obviously a most interesting object. Spectroscopic observations of NTTDF J1205-0744 ESO PR Photo 35b/99 ESO PR Photo 35b/99 [Preview - JPEG: 400 x 337 pix - 56k] [Normal - JPEG: 800 x 674 pix - 124k] Caption to ESO PR Photo 35b/99 : The infrared spectrum of NTTDF J1205-0744 , as obtained with SOFI at the NTT and ISAAC at VLT ANTU, and compared to the spectrum of the much closer and brighter Methane Brown Dwarf Gliese 229B . This issue was resolved by obtaining infrared spectra of NTTDF J1205-0744 . Despite its faintness, initial observations with SOFI at the NTT covering the infrared J and H-bands already revealed some of the molecular absorptions characteristic of methane brown dwarfs. More recently, complementary longer wavelength observations with ISAAC at the first VLT 8.2-m Unit Telescope (ANTU) at Paranal have now confirmed the nature of this object. The combined SOFI/ISAAC infrared spectrum shown in PR Photo 35b/99 is clearly extremely similar to that of Gliese 229B , the first Methane Brown Dwarf discovered a few years ago and which is a member of a binary system at a distance of about 19 light-years. The features in the spectra result from strong absorption by methane (CH 4 ) and water (H 2 O). There is thus no doubt that NTTDF J1205-0744 is of the same type (stellar class T). Unlike Gliese 229B , however, it does not appear to be a member of a binary system. It is also 5-6 magnitudes (i.e., a factor of about 250) fainter than this and a few similar objects discovered recently in large-area sky surveys, implying that it is considerably more distant. Properties of NTTDF J1205-0744 NTTDF J1205-0744 is located at a distance of about 300 light-years (90 pc) and some 240 light-years (75 pc) above the plane of our Milky Way galaxy. Its mass is probably about 20-50 times that of Jupiter, or less than 2% of that of the Sun. Its temperature is around 700 °C (1000 K), suggesting an age of 500 to 1,000 million years. Lacking a stable source of energy at its centre, it is becoming continuously fainter and cooler and will continue to do so for tens of thousands of millions of years. NTTDF J1205-0744 is a very faint and small object indeed, on the still not well understood border zone between stars and planets [2]. How many Brown Dwarfs? How many T-class objects are there in the Milky Way? What is the space density of these extreme objects? Since only a few have been identified so far, any statistics must be quite uncertain. Until now, the best estimates have been of the order of 1 per 3,500 cubic light-years (0.01/pc 3 ). A surprising aspect of this discovery is that NTTDF J1205-0744 was found within a sky area of only 2.3 x 2.3 arcmin 2 , specially selected to be as "empty" as possible in order to facilitate studies of distant galaxies. Based on the above density estimate, the chance of finding such an object should only have been about 1%. Based on model predictions, the chance would have been even smaller than this. Searches like the one described here, based on the combination of optical and infrared data, therefore appear particularly effective at detecting such objects. It is now of high interest to test if this first discovery was just extremely lucky, or if the space density of these extreme objects is in fact much higher than expected. More information A research article about these new results ( Discovery of a faint Field Methane Brown Dwarf from ES0 NTT and VLT observations), will appear in the European journal Astronomy & Astrophysics . Note [1] The team consists of Jean Gabriel Cuby, Alan Moorwood, Sandro D'Odorico, Chris Lidman, Fernando Comeron, Jason Spyromilio (ESO) and Paolo Saracco (Osservatorio Astronomico di Brera, Merate, Milan, Italy). [2] A more nearby, hotter brown dwarf, KELU-1 , was found at La Silla in 1997 at a distance of 33 light-years, cf. ESO Press Release 07/97. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Merging Galaxies Create a Binary Quasar

NASA Astrophysics Data System (ADS)

2010-02-01

Astronomers have found the first clear evidence of a binary quasar within a pair of actively merging galaxies. Quasars are the extremely bright centers of galaxies surrounding super-massive black holes, and binary quasars are pairs of quasars bound together by gravity. Binary quasars, like other quasars, are thought to be the product of galaxy mergers. Until now, however, binary quasars have not been seen in galaxies that are unambiguously in the act of merging. But images of a new binary quasar from the Carnegie Institution's Magellan telescope in Chile show two distinct galaxies with "tails" produced by tidal forces from their mutual gravitational attraction. "This is really the first case in which you see two separate galaxies, both with quasars, that are clearly interacting," says Carnegie astronomer John Mulchaey who made observations crucial to understanding the galaxy merger. Most, if not all, large galaxies, such as our galaxy the Milky Way, host super-massive black holes at their centers. Because galaxies regularly interact and merge, astronomers have assumed that binary super-massive black holes have been common in the Universe, especially during its early history. Black holes can only be detected as quasars when they are actively accreting matter, a process that releases vast amounts of energy. A leading theory is that galaxy mergers trigger accretion, creating quasars in both galaxies. Because most such mergers would have happened in the distant past, binary quasars and their associated galaxies are very far away and therefore difficult for most telescopes to resolve. The binary quasar, labeled SDSS J1254+0846, was initially detected by the Sloan Digital Sky Survey, a large scale astronomical survey of galaxies and over 120,000 quasars. Further observations by Paul Green of the Harvard-Smithsonian Center for Astrophysics and colleagues* using NASA's Chandra's X-ray Observatory and telescopes at Kitt Peak National Observatory in Arizona and Palomar Observatory in California indicated that the object was likely a binary quasar in the midst of a galaxy merger. Carnegie's Mulchaey then used the 6.5 meter Baade-Magellan telescope at the Las Campanas observatory in Chile to obtain deeper images and more detailed spectroscopy of the merging galaxies. "Just because you see two galaxies that are close to each other in the sky doesn't mean they are merging," says Mulchaey. "But from the Magellan images we can actually see tidal tails, one from each galaxy, which suggests that the galaxies are in fact interacting and are in the process of merging." Thomas Cox, now a fellow at the Carnegie Observatories, corroborated this conclusion using computer simulations of the merging galaxies. When Cox's model galaxies merged, they showed features remarkably similar to what Mulchaey observed in the Magellan images. "The model verifies the merger origin for this binary quasar system," he says. "It also hints that this kind of galaxy interaction is a key component of the growth of black holes and production of quasars throughout our universe." * The authors of the paper published in the Astrophysical Journal are Paul J. Green of the Harvard-Smithsonian Center for Astrophysics, Adam D. Myers of the University of Illinois at Urbana-Champaign, Wayne A. Barkhouse of the University of North Dakota, John S. Mulchaey of the Observatories of the Carnegie Institution for Science, Vardha N. Bennert of the Department of Physics, University of California, Santa Barbara, Thomas J. Cox of the Observatories of the Carnegie Institution for Science, Thomas L. Aldcroft of the Harvard-Smithsonian Center for Astrophysics, and Joan M. Wrobel of National Radio Astronomy Observatory, Socorro, NM. More information, including images and other multimedia, can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov

The enhancement of rapidly quenched galaxies in distant clusters at 0.5 < z < 1.0

NASA Astrophysics Data System (ADS)

Socolovsky, Miguel; Almaini, Omar; Hatch, Nina A.; Wild, Vivienne; Maltby, David T.; Hartley, William G.; Simpson, Chris

2018-05-01

We investigate the relationship between environment and galaxy evolution in the redshift range 0.5 < z < 1.0. Galaxy overdensities are selected using a friends-of-friends algorithm, applied to deep photometric data in the Ultra-Deep Survey field. A study of the resulting stellar mass functions reveals clear differences between cluster and field environments, with a strong excess of low-mass rapidly quenched galaxies in cluster environments compared to the field. Cluster environments also show a corresponding deficit of young, low-mass star-forming galaxies, which show a sharp radial decline towards cluster centres. By comparing mass functions and radial distributions, we conclude that young star-forming galaxies are rapidly quenched as they enter overdense environments, becoming post-starburst galaxies before joining the red sequence. Our results also point to the existence of two environmental quenching pathways operating in galaxy clusters, operating on different time-scales. Fast quenching acts on galaxies with high specific star formation rates, operating on time-scales shorter than the cluster dynamical time (<1 Gyr). In contrast, slow quenching affects galaxies with moderate specific star formation rates, regardless of their stellar mass, and acts on longer time-scales (≳ 1 Gyr). Of the cluster galaxies in the stellar mass range 9.0 < log (M/M⊙) < 10.5 quenched during this epoch, we find that 73 per cent were transformed through fast quenching, while the remaining 27 per cent followed the slow quenching route.

Resolved Star Formation in Galaxies Using Slitless Spectroscopy

NASA Astrophysics Data System (ADS)

Pirzkal, Norbert; Finkelstein, Steven L.; Larson, Rebecca L.; Malhotra, Sangeeta; Rhoads, James E.; Ryan, Russell E.; Tilvi, Vithal; FIGS Team

2018-06-01

The ability to spatially resolve individual star-formation regions in distant galaxies and simultaneously extract their physical properties via emission lines is a critical step forward in studying the evolution of galaxies. While efficient, deep slitless spectroscopic observations offer a blurry view of the summed properties of galaxies. We present our studies of resolved star formation over a wide range of redshifts, including high redshift Ly-a sources. The unique capabilities of the WFC3 IR Grism and our two-dimensional emission line method (EM2D) allows us to accurately identify the specific spatial origin of emission lines in galaxies, thus creating a spatial map of star-formation sites in any given galaxy. This method requires the use of multiple position angles on the sky to accurately derive both the location and the observed wavelengths of these emission lines. This has the added benefit of producing better defined redshifts for these sources. Building on our success in applying the EM2D method towards galaxies with [OII]. [OIII], and Ha emission lines, we have also applied EM2D to high redshift (z>6) Ly-a emitting galaxies. We are also able to produce accurate 2D emission line maps (MAP2D) of the Ly-a emission in WFC3 IR grism observations, looking for evidence that a significant amount of resonant scattering is taking place in high redshift galaxies such as in a newly identified z=7.5 Faint Infrared Galaxy Survey (FIGS) Ly-a galaxy.

Evolution of the early-type galaxy fraction in clusters since z = 0.8

NASA Astrophysics Data System (ADS)

Simard, L.; Clowe, D.; Desai, V.; Dalcanton, J. J.; von der Linden, A.; Poggianti, B. M.; White, S. D. M.; Aragón-Salamanca, A.; De Lucia, G.; Halliday, C.; Jablonka, P.; Milvang-Jensen, B.; Saglia, R. P.; Pelló, R.; Rudnick, G. H.; Zaritsky, D.

2009-12-01

We study the morphological content of a large sample of high-redshift clusters to determine its dependence on cluster mass and redshift. Quantitative morphologies are based on PSF-convolved, 2D bulge+disk decompositions of cluster and field galaxies on deep Very Large Telescope FORS2 images of eighteen, optically-selected galaxy clusters at 0.45 < z < 0.80 observed as part of the ESO Distant Cluster Survey (“EDisCS”). Morphological content is characterized by the early-type galaxy fraction f_et, and early-type galaxies are objectively selected based on their bulge fraction and image smoothness. This quantitative selection is equivalent to selecting galaxies visually classified as E or S0. Changes in early-type fractions as a function of cluster velocity dispersion, redshift and star-formation activity are studied. A set of 158 clusters extracted from the Sloan Digital Sky Survey is analyzed exactly as the distant EDisCS sample to provide a robust local comparison. We also compare our results to a set of clusters from the Millennium Simulation. Our main results are: (1) the early-type fractions of the SDSS and EDisCS clusters exhibit no clear trend as a function of cluster velocity dispersion. (2) Mid-z EDisCS clusters around σ = 500 km s-1 have f_et ≃ 0.5 whereas high-z EDisCS clusters have f_et ≃ 0.4. This represents a ~25% increase over a time interval of 2 Gyr. (3) There is a marked difference in the morphological content of EDisCS and SDSS clusters. None of the EDisCS clusters have early-type galaxy fractions greater than 0.6 whereas half of the SDSS clusters lie above this value. This difference is seen in clusters of all velocity dispersions. (4) There is a strong and clear correlation between morphology and star formation activity in SDSS and EDisCS clusters in the sense that decreasing fractions of [OII] emitters are tracked by increasing early-type fractions. This correlation holds independent of cluster velocity dispersion and redshift even though the fraction of [OII] emitters decreases from z ˜0.8 to z ˜ 0.06 in all environments. Our results pose an interesting challenge to structural transformation and star formation quenching processes that strongly depend on the global cluster environment (e.g., a dense ICM) and suggest that cluster membership may be of lesser importance than other variables in determining galaxy properties. Based on observations obtained in visitor and service modes at the ESO Very Large Telescope (VLT) as part of the Large Programme 166.A-0162 (the ESO Distant Cluster Survey). Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with proposal 9476. Support for this proposal was provided by NASA through a grant from the Space Telescope Science Institute. Table [see full textsee full textsee full textsee full textsee full text] is only available in electronic form at http://www.aanda.org

Astronomers Set a New Galaxy Distance Record

NASA Image and Video Library

2015-05-06

This is a Hubble Space Telescope image of the farthest spectroscopically confirmed galaxy observed to date (inset). It was identified in this Hubble image of a field of galaxies in the CANDELS survey (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey). NASA’s Spitzer Space Telescope also observed the unique galaxy. The W. M. Keck Observatory was used to obtain a spectroscopic redshift (z=7.7), extending the previous redshift record. Measurements of the stretching of light, or redshift, give the most reliable distances to other galaxies. This source is thus currently the most distant confirmed galaxy known, and it appears to also be one of the brightest and most massive sources at that time. The galaxy existed over 13 billion years ago. The near-infrared light image of the galaxy (inset) has been colored blue as suggestive of its young, and hence very blue, stars. The CANDELS field is a combination of visible-light and near-infrared exposures. Read more: www.nasa.gov/feature/goddard/astronomers-set-a-new-galaxy... Credits: NASA, ESA, P. Oesch (Yale U.) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The Most Distant Mature Galaxy Cluster - Young, but surprisingly grown-up

NASA Astrophysics Data System (ADS)

2011-03-01

Astronomers have used an armada of telescopes on the ground and in space, including the Very Large Telescope at ESO's Paranal Observatory in Chile to discover and measure the distance to the most remote mature cluster of galaxies yet found. Although this cluster is seen when the Universe was less than one quarter of its current age it looks surprisingly similar to galaxy clusters in the current Universe. "We have measured the distance to the most distant mature cluster of galaxies ever found", says the lead author of the study in which the observations from ESO's VLT have been used, Raphael Gobat (CEA, Paris). "The surprising thing is that when we look closely at this galaxy cluster it doesn't look young - many of the galaxies have settled down and don't resemble the usual star-forming galaxies seen in the early Universe." Clusters of galaxies are the largest structures in the Universe that are held together by gravity. Astronomers expect these clusters to grow through time and hence that massive clusters would be rare in the early Universe. Although even more distant clusters have been seen, they appear to be young clusters in the process of formation and are not settled mature systems. The international team of astronomers used the powerful VIMOS and FORS2 instruments on ESO's Very Large Telescope (VLT) to measure the distances to some of the blobs in a curious patch of very faint red objects first observed with the Spitzer space telescope. This grouping, named CL J1449+0856 [1], had all the hallmarks of being a very remote cluster of galaxies [2]. The results showed that we are indeed seeing a galaxy cluster as it was when the Universe was about three billion years old - less than one quarter of its current age [3]. Once the team knew the distance to this very rare object they looked carefully at the component galaxies using both the NASA/ESA Hubble Space Telescope and ground-based telescopes, including the VLT. They found evidence suggesting that most of the galaxies in the cluster were not forming stars, but were composed of stars that were already about one billion years old. This makes the cluster a mature object, similar in mass to the Virgo Cluster, the nearest rich galaxy cluster to the Milky Way. Further evidence that this is a mature cluster comes from observations of X-rays coming from CL J1449+0856 made with ESA's XMM-Newton space observatory. The cluster is giving off X-rays that must be coming from a very hot cloud of tenuous gas filling the space between the galaxies and concentrated towards the centre of the cluster. This is another sign of a mature galaxy cluster, held firmly together by its own gravity, as very young clusters have not had time to trap hot gas in this way. As Gobat concludes: "These new results support the idea that mature clusters existed when the Universe was less than one quarter of its current age. Such clusters are expected to be very rare according to current theory, and we have been very lucky to spot one. But if further observations find many more then this may mean that our understanding of the early Universe needs to be revised." Notes [1] The strange name refers to the object's position in the sky. [2] The galaxies appear red in the picture partly because they are thought to be mainly composed of cool, red stars. In addition the expansion of the Universe since the light left these remote systems has increased the wavelength of the light further so that it is mostly seen as infrared radiation when it gets to Earth. [3] The astronomers measured the distance to the cluster by splitting the light up into its component colours in a spectrograph. They then compared this spectrum with one of a similar object in the nearby Universe. This allowed them to measure the redshift of the remote galaxies - how much the Universe has expanded since the light left the galaxies. The redshift was found to be 2.07, which means that the cluster is seen about three billion years after the Big Bang. More information This research was presented in a paper, "A mature cluster with X-ray emission at z = 2.07", by R. Gobat et al., published in the journal Astronomy & Astrophysics. The team is composed of R. Gobat (Laboratoire AIM-Paris-Saclay, France), E. Daddi (AIM-Paris), M. Onodera (ETH Zürich, Switzerland), A. Finoguenov (Max-Planck-Institut für extraterrestrische Physik [MPE], Garching, Germany), A. Renzini (INAF-Osservatorio Astronomico di Padova), N. Arimoto (National Astronomical Observatory of Japan), R. Bouwens (Lick Observatory, Santa Cruz, USA), M. Brusa (MPE), R.-R. Chary (California Institute of Technology, USA), A. Cimatti (Università di Bologna, Italy), M. Dickinson (NOAO, Tucson, USA), X. Kong (University of Science and Technology of China), and M.Mignoli (INAF - Osservatorio Astronomico di Bologna, Italy). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Discovery of an Extremely Luminous Dust-obscured Galaxy Observed with SDSS, WISE, JCMT, and SMA

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Ueda, Junko; Lim, Chen-Fatt; Wang, Wei-Hao; Nagao, Tohru; Chang, Yu-Yen; Saito, Toshiki; Kawabe, Ryohei

2018-04-01

We present the discovery of an extremely luminous dust-obscured galaxy (DOG) at z spec = 3.703, WISE J101326.25+611220.1. This DOG is selected as a candidate of extremely luminous infrared (IR) galaxies based on the photometry from the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer. In order to derive its accurate IR luminosity, we perform follow-up observations at 450 and 850 μm using the Submillimetre Common User Bolometer Array 2 on the James Clerk Maxwell Telescope, and at 870 and 1300 μm using the Submillimeter Array, which enable us to pin down its IR Spectral Energy Distribution (SED). We perform SED fitting using 14 photometric data (0.4–1300 μm) and estimate its IR luminosity, L IR (8–1000 μm), to be {2.2}-1.0+1.5 ×1014 L ⊙, making it one of the most luminous IR galaxies in the universe. The energy contribution from an active galactic nucleus (AGN) to the IR luminosity is {94}-20+6%, which indicates that it is an AGN-dominated DOG. On the other hand, its stellar mass (M *) and star formation rate (SFR) are {log}({M}* /{M}ȯ ) = {11.2}-0.2+0.6 and {log}({SFR}/{M}ȯ {yr}}-1) = {3.1}-0.1+0.2, respectively, which means that this DOG can be considered a starburst galaxy in the M *–SFR plane. This extremely luminous DOG shows significant AGN and star-forming activity that provides us with an important laboratory to probe the maximum phase of the coevolution of galaxies and supermassive black holes.

THE SURVEY OF H I IN EXTREMELY LOW-MASS DWARFS (SHIELD)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cannon, John M.; Engstrom, Eric; Allan, John

We present first results from the Survey of H I in Extremely Low-mass Dwarfs (SHIELD), a multi-configuration Expanded Very Large Array (EVLA) study of the neutral gas contents and dynamics of galaxies with H I masses in the 10{sup 6}-10{sup 7} M{sub sun} range detected by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We describe the survey motivation and concept demonstration using Very Large Array imaging of six low-mass galaxies detected in early ALFALFA data products. We then describe the primary scientific goals of SHIELD and present preliminary EVLA and WIYN 3.5 m imaging of the 12 SHIELD galaxies. Withmore » only a few exceptions, the neutral gas distributions of these extremely low-mass galaxies are centrally concentrated. In only one system have we detected H I column densities higher than 10{sup 21} cm{sup -2}. Despite this, the stellar populations of all of these systems are dominated by blue stars. Further, we find ongoing star formation as traced by H{alpha} emission in 10 of the 11 galaxies with H{alpha} imaging obtained to date. Taken together these results suggest that extremely low-mass galaxies are forming stars in conditions different from those found in more massive systems. While detailed dynamical analysis requires the completion of data acquisition, the most well-resolved system is amenable to meaningful position-velocity analysis. For AGC 749237, we find well-ordered rotation of 30 km s{sup -1} at {approx}40'' distance from the dynamical center. At the adopted distance of 3.2 Mpc, this implies the presence of a {approx}>1 x 10{sup 8} M{sub sun} dark matter halo and a baryon fraction {approx}<0.1.« less

No Place to Hide: Missing Primitive Stars Outside Milky Way Uncovered

NASA Astrophysics Data System (ADS)

2010-02-01

After years of successful concealment, the most primitive stars outside our Milky Way galaxy have finally been unmasked. New observations using ESO's Very Large Telescope have been used to solve an important astrophysical puzzle concerning the oldest stars in our galactic neighbourhood - which is crucial for our understanding of the earliest stars in the Universe. "We have, in effect, found a flaw in the forensic methods used until now," says Else Starkenburg, lead author of the paper reporting the study. "Our improved approach allows us to uncover the primitive stars hidden among all the other, more common stars." Primitive stars are thought to have formed from material forged shortly after the Big Bang, 13.7 billion years ago. They typically have less than one thousandth the amount of chemical elements heavier than hydrogen and helium found in the Sun and are called "extremely metal-poor stars" [1]. They belong to one of the first generations of stars in the nearby Universe. Such stars are extremely rare and mainly observed in the Milky Way. Cosmologists think that larger galaxies like the Milky Way formed from the merger of smaller galaxies. Our Milky Way's population of extremely metal-poor or "primitive" stars should already have been present in the dwarf galaxies from which it formed, and similar populations should be present in other dwarf galaxies. "So far, evidence for them has been scarce," says co-author Giuseppina Battaglia. "Large surveys conducted in the last few years kept showing that the most ancient populations of stars in the Milky Way and dwarf galaxies did not match, which was not at all expected from cosmological models." Element abundances are measured from spectra, which provide the chemical fingerprints of stars [2]. The Dwarf galaxies Abundances and Radial-velocities Team [3] used the FLAMES instrument on ESO's Very Large Telescope to measure the spectra of over 2000 individual giant stars in four of our galactic neighbours, the Fornax, Sculptor, Sextans and Carina dwarf galaxies. Since the dwarf galaxies are typically 300 000 light years away - which is about three times the size of our Milky Way - only strong features in the spectrum could be measured, like a vague, smeared fingerprint. The team found that none of their large collection of spectral fingerprints actually seemed to belong to the class of stars they were after, the rare, extremely metal-poor stars found in the Milky Way. The team of astronomers around Starkenburg has now shed new light on the problem through careful comparison of spectra to computer-based models. They found that only subtle differences distinguish the chemical fingerprint of a normal metal-poor star from that of an extremely metal-poor star, explaining why previous methods did not succeed in making the identification. The astronomers also confirmed the almost pristine status of several extremely metal-poor stars thanks to much more detailed spectra obtained with the UVES instrument on ESO's Very Large Telescope. "Compared to the vague fingerprints we had before, this would be as if we looked at the fingerprint through a microscope," explains team member Vanessa Hill. "Unfortunately, just a small number of stars can be observed this way because it is very time consuming." "Among the new extremely metal-poor stars discovered in these dwarf galaxies, three have a relative amount of heavy chemical elements between only 1/3000 and 1/10 000 of what is observed in our Sun, including the current record holder of the most primitive star found outside the Milky Way," says team member Martin Tafelmeyer. "Not only has our work revealed some of the very interesting, first stars in these galaxies, but it also provides a new, powerful technique to uncover more such stars," concludes Starkenburg. "From now on there is no place left to hide!" Notes [1] According to the definition used in astronomy, "metals" are all the elements other than hydrogen and helium. Such metals, except for a very few minor light chemical elements, have all been created by the various generations of stars. [2] As every rainbow demonstrates, white light can be split up into different colours. Astronomers artificially split up the light they receive from distant objects into its different colours (or wavelengths). However, where we distinguish seven rainbow colours, astronomers map hundreds of finely nuanced colours, producing a spectrum - a record of the different amounts of light the object emits in each narrow colour band. The details of the spectrum - more light emitted at some colours, less light at others - provide tell-tale signs about the chemical composition of the matter producing the light. [3] The Dwarf galaxies Abundances and Radial-velocities Team (DART) has members from institutes in nine different countries. More information This research was presented in a paper to appear in Astronomy and Astrophysics ("The NIR Ca II triplet at low metallicity", E. Starkenburg et al.). Another paper is also in preparation (Tafelmeyer et al.) that presents the UVES measurements of several primitive stars. The team is composed of Else Starkenburg, Eline Tolstoy, Amina Helmi, and Thomas de Boer (Kapteyn Astronomical Institute, University of Groningen, the Netherlands), Vanessa Hill (Laboratoire Cassiopée, Université de Nice Sophia Antipolis, Observatoire de la Côte d'Azur, CNRS, France), Jonay I. González Hernández (Observatoire de Paris, CNRS, Meudon, France and Universidad Complutense de Madrid, Spain), Mike Irwin (University of Cambridge, UK), Giuseppina Battaglia (ESO), Pascale Jablonka and Martin Tafelmeyer (Université de Genève, Ecole Polytechnique Fédérale de Lausanne, Switzerland), Matthew Shetrone (University of Texas, McDonald Observatory, USA), and Kim Venn (University of Victoria, Canada). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

SZ observations to study the physics of the intra-cluster medium

NASA Astrophysics Data System (ADS)

Pointecouteau, E.

2017-10-01

Recent Sunyaev-Zeldovich surveys have delivered new catalogues of galaxy clusters over the whole sky and out to distant redshifts. The new generation of SZ facilities (NIKA, MUSTANG, ALMA) now focuses on high angular resolution and high sensitivity. I will discuss the current status of SZ observations and the perspective with the future instruments for the measurement of physical properties of galaxy clusters, and their relevance to the study of the ICM physics. I will also discuss the natural synergy between the SZ signal and the X-ray emission from the hot intra-cluster medium.

The Swift satellite lives up to its name, revealing cosmic explosions as they happen.

PubMed

Starling, Rhaana L C

2008-12-13

Gamma-ray bursts are the most powerful objects in the Universe. Discovered in the 1960s as brief flashes of gamma radiation, we now know that they emit across the entire electromagnetic spectrum, are located in distant galaxies and comprise two distinct populations, one of which may originate in the deaths of massive stars. The launch of the Swift satellite in 2004 brought a flurry of new discoveries, advancing our understanding of these sources and the galaxies that host them. I highlight a number of important results from the Swift era thus far.

A QUANTITATIVE ANALYSIS OF DISTANT OPEN CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janes, Kenneth A.; Hoq, Sadia

2011-03-15

The oldest open star clusters are important for tracing the history of the Galactic disk, but many of the more distant clusters are heavily reddened and projected against the rich stellar background of the Galaxy. We have undertaken an investigation of several distant clusters (Berkeley 19, Berkeley 44, King 25, NGC 6802, NGC 6827, Berkeley 52, Berkeley 56, NGC 7142, NGC 7245, and King 9) to develop procedures for separating probable cluster members from the background field. We next created a simple quantitative approach for finding approximate cluster distances, reddenings, and ages. We first conclude that with the possible exceptionmore » of King 25 they are probably all physical clusters. We also find that for these distant clusters our typical errors are about {+-}0.07 in E(B - V), {+-}0.15 in log(age), and {+-}0.25 in (m - M){sub o}. The clusters range in age from 470 Myr to 7 Gyr and range from 7.1 to 16.4 kpc from the Galactic center.« less

Searching for intermediate-mass black holes in extremely-metal poor galaxies

NASA Astrophysics Data System (ADS)

Mezcua, Mar

2016-09-01

Extremely metal-poor dwarf galaxies (XMPs) are star-forming, low-mass galaxies with metallicites highly sub-solar. Their regions of star formation could be triggered by the accretion of pristine gas from the cosmic web and harbour Population III stars. XMPs are thus ideal laboratories for searching for the seed black holes or intermediate-mass black holes (IMBHs) that populated the early Universe. The combination of X-ray, radio and optical observations offer the best tool for detecting such IMBHs in the local Universe. We propose Chandra observations of a sample of XMPs whose optical spectra indicate the possible presence of an active black hole of 1e4 - 1e6 Msun. The Chandra data could confirm this and yield the first detection of an IMBH in these type of galaxies.

Finding our Origins with the Hubble and James Webb Space Telescopes

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.

2009-01-01

NASA is planning a successor to the Hubble Space Telescope designed to study the origins of galaxies, stars, planets and life in the universe. In this talk, Dr. Gardner will discuss the origin and evolution of galaxies, beginning with the Big Bang and tracing what we have learned with Hubble through to the present day. He will show that results from studies with Hubble have led to plans for its successor, the James Webb Space Telescope. Webb is scheduled to launch in 2014, and is designed to find the first galaxies that formed in the distant past and to penetrate the dusty clouds of gas where stars are still forming today. He will compare Webb to Hubble, and discuss recent progress in the construction of the observatory.

Detection of H I, OH, CO, and optical imaging of the distant galaxy IRAS 12112 + 0305

NASA Technical Reports Server (NTRS)

Mirabel, I. F.; Kazes, I.; Sanders, D. B.

1988-01-01

The detection of H I absorption and OH and CO emission from the galaxy IRAS 12112 + 0305, which is receding from the sun at about 7 percent of the speed of light is reported. This galaxy, which appears to be an ongoing merger, radiates about 2 x 10 to the 12th solar luminosities in the infrared. The H I, OH, and CO spectra are indicative of large turbulent motions. From the millimeter wave CO observations, a total mass of molecular gas of 4 x 10 to the 10th solar masses is inferred. The OH emission in the 1667 MHz line is the most luminous extragalactic OH maser reported so far, with an isotropic luminosity of 1800 solar luminosities.

Finding our Origins with the Hubble and James Webb Space Telescopes

NASA Technical Reports Server (NTRS)

Gardner, Jonathan

2008-01-01

NASA is planning a successor to the Hubble Space Telescope designed to study the origins of galaxies, stars, planets and life in the universe. In this talk, Dr. Gardner will discuss the origin and evolution of galaxies, beginning with the Big Bang and tracing what we have learned with Hubble through to the present day. He will show that results from studies with Hubble have led to plans for its successor, the James Webb Space Telescope. Webb is scheduled to launch in 2013, and is designed to find the first galaxies that formed in the distant past and to penetrate the dusty clouds of gas where stars are still forming today. He will compare Webb to Hubble, and discuss recent progress in the construction of the observatory.

Finding our Origins with the Hubble and James Webb Space Telescopes

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.

2007-01-01

NASA is planning a successor to the Hubble Space Telescope designed to study the origins of galaxies, stars, planets and life in the universe. In this talk, Dr. Gardner will discuss the origin and evolution of galaxies, beginning with the Big Bang and tracing what we have learned with Hubble through to the present day. He will show that results from studies with Hubble have led to plans for its successor, the James Webb Space Telescope. Webb is scheduled to launch in 201 3, and is designed to find the first galaxies that formed in the distant past and to penetrate the dusty clouds of gas where stars are still forming today. He will compare Webb to Hubble, and discuss recent progress in the construction of the observatory.

Finding Our Origins with the Hubble and James Webb Space Telescopes

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.

2003-01-01

NASA's Origins program is a series of space telescopes designed to study the origins of galaxies, stars, planets and life in the universe. In this talk, I will concentrate on the origin and evolution of galaxies, beginning with the Big Bang and tracing what we have learned with the Hubble Space Telescope through to the present day. I will introduce several of the tools that astronomers use to measure distances, measure velocities, and look backwards in time. I will show that results from studies with Hubble have led to plans for its successor, the James Webb Space Telescope, which is designed to find the first galaxies that formed in the distant past. I will finish with a short discussion of other missions in the Origins theme, including the Terrestrial Planet Finder.

Finding our Origins with the Hubble and James Webb Space Telescopes

NASA Technical Reports Server (NTRS)

Gardner, Jonathan P.

2004-01-01

NASA s Origins program is a series of space telescopes designed to study the origins of galaxies, stars, planets and life in the universe. In this talk, I will concentrate on the origin and evolution of galaxies, beginning with the Big Bang and tracing what we have learned with the Hubble Space Telescope through to the present day. I will introduce several of the tools that astronomers use to measure distances, measure velocities, and look backwards in time. I will show that results from studies with Hubble have led to plans for its successor, the James Webb Space Telescope, which is designed to find the first galaxies that formed in the distant past. I will finish with a short discussion of other missions in the Origins theme, including the Terrestrial Planet Finder.

From Galaxies to the Intergalactic Medium

NASA Astrophysics Data System (ADS)

Peeples, Molly S.

2010-07-01

Deep in dark matter halos, galaxies are large factories that convert gas into stars. Gas is accreted from the expansive intergalactic medium (IGM); stars process this gas by fusing lighter elements into heavier ones. In this Dissertation, I combine both observations and theories from a variety of subfields of astrophysics with analytic and numerical models in an aim for a comprehensive understanding of the underlying physics of star formation feedback, galaxy chemical evolution, and the IGM. The mass-metallicity relation is an observed tight correlation between the stellar masses and gas-phase oxygen abundances of star-forming galaxies. I show that while the intrinsic scatter in this relation is small, extreme outliers do exist; I argue that these outliers have unusual metallicities for their masses because they have unusual gas fractions for their masses. The low-mass high-metallicity galaxies appear to be nearing the end of their star formation, and thus should have abnormally small gas reservoirs with which to dilute their metals. On the other hand, the high-mass low-metallicity galaxies appear to be undergoing gas-rich galaxy mergers, implying that they have larger-than-normal amounts of gas diluting their metals. I then show through analytic arguments that while gas fractions can have a large impact on observed metallicities, the low-redshift mass-metallicity relation is dominated by outflow properties because typical galaxies have relatively small gas fractions. Specifically, the mass-metallicity relation implies that the efficiency with which galaxies expel metals should scale steeply with galaxy mass. Combining this model with reasonable models for star formation feedback, I show that the outflow metallicity should likewise vary with galaxy mass; future measurements of wind metallicity can therefore inform models of the physics underlying galaxy winds. The high-redshift IGM is primarily observed through the Lyman-alpha absorption of neutral hydrogen along the line of sight to a distant quasar. As samples of close quasar pairs increase, so does the amount of potential information in the Lya forest transverse to the line-of-sight. Using two cosmological hydrodynamic simulations with different photoionization heating rates and thus different IGM temperature-density relations, I show that the small-scale structure in the Lya forest along the line of sight is dominated by the current thermal state of the gas. On the other hand, the transverse signal is sensitive to - and thus could be used to place unique constraints on - the thermal history of the gas. Finally, I investigate how a two-phase medium is treated in a suite of idealized smoothed particle hydrodynamic (SPH) simulations. I show that cold, dense spherical blobs become over-pressured relative to their hot, tenuous surroundings, arguing that this is because of an effective numerical surface tension owing to the un-resolveable density discontinuity. I then test one proposed modification to how pressure gradients are calculated in SPH, the so-called "relative pressure SPH" (rpSPH); while rpSPH leads to a more uniform pressure across the simulation, I show that it is ultimately unstable because of its lack of momentum conservation.

Discovery of Distant RR Lyrae Stars in the Milky Way Using DECam

NASA Astrophysics Data System (ADS)

Medina, Gustavo E.; Muñoz, Ricardo R.; Vivas, A. Katherina; Carlin, Jeffrey L.; Förster, Francisco; Martínez, Jorge; Galbany, Lluís; González-Gaitán, Santiago; Hamuy, Mario; de Jaeger, Thomas; Maureira, Juan Carlos; San Martín, Jaime

2018-03-01

We report the discovery of distant RR Lyrae stars, including the most distant known in the Milky Way, using data taken in the g-band with the Dark Energy Camera as part of the High cadence Transient Survey (HiTS; 2014 campaign). We detect a total of 173 RR Lyrae stars over a ∼120 deg2 area, including both known RR Lyrae and new detections. The heliocentric distances d H of the full sample range from 9 to >200 kpc, with 18 of them beyond 90 kpc. We identify three sub-groups of RR Lyrae as members of known systems: the Sextans dwarf spheroidal galaxy, for which we report 46 new discoveries, and the ultra-faint dwarf galaxies Leo IV and Leo V. Following an MCMC methodology, we fit spherical and ellipsoidal profiles of the form ρ(R) ∼ R n to the radial density distribution of RR Lyrae in the Galactic halo. The best fit corresponds to the spherical case, for which we obtain a simple power-law index of n=-{4.17}-0.20+0.18, consistent with recent studies made with samples covering shorter distances. The pulsational properties of the outermost RR Lyrae in the sample (d H > 90 kpc) differ from the ones in the halo population at closer distances. The distribution of the stars in a period-amplitude diagram suggest they belong to Oosterhoff-intermediate or Oosterhoff II groups, similar to what is found in the ultra-faint dwarf satellites around the Milky Way. The new distant stars discovered represent an important addition to the few existing tracers of the Milky Way potential in the outer halo.

EVIDENCE FOR ELEVATED X-RAY EMISSION IN LOCAL LYMAN BREAK GALAXY ANALOGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basu-Zych, Antara R.; Lehmer, Bret D.; Hornschemeier, Ann E.

2013-09-10

Our knowledge of how X-ray emission scales with star formation at the earliest times in the universe relies on studies of very distant Lyman break galaxies (LBGs). In this paper, we study the relationship between the 2-10 keV X-ray luminosity (L{sub X}), assumed to originate from X-ray binaries (XRBs), and star formation rate (SFR) in ultraviolet (UV) selected z < 0.1 Lyman break analogs (LBAs). We present Chandra observations for four new Galaxy Evolution Explorer selected LBAs. Including previously studied LBAs, Haro 11 and VV 114, we find that LBAs demonstrate L{sub X}/SFR ratios that are elevated by {approx}1.5{sigma} comparedmore » to local galaxies, similar to the ratios found for stacked LBGs in the early universe (z > 2). Unlike some of the composite LBAs studied previously, we show that these LBAs are unlikely to harbor active galactic nuclei, based on their optical and X-ray spectra and the spatial distribution of the X-rays in three spatially extended cases. Instead, we expect that high-mass X-ray binaries (HMXBs) dominate the X-ray emission in these galaxies, based on their high specific SFRs (sSFRs {identical_to} SFR/M{sub *} {>=} 10{sup -9} yr{sup -1}), which suggest the prevalence of young stellar populations. Since both UV-selected populations (LBGs and LBAs) have lower dust attenuations and metallicities compared to similar samples of more typical local galaxies, we investigate the effects of dust extinction and metallicity on the L{sub X}/SFR for the broader population of galaxies with high sSFRs (>10{sup -10} yr{sup -1}). The estimated dust extinctions (corresponding to column densities of N{sub H} < 10{sup 22} cm{sup -2}) are expected to have insignificant effects on observed L{sub X}/SFR ratio for the majority of galaxy samples. We find that the observed relationship between L{sub X}/SFR and metallicity appears consistent with theoretical expectations from XRB population synthesis models. Therefore, we conclude that lower metallicities, related to more luminous HMXBs such as ultraluminous X-ray sources, drive the elevated L{sub X}/SFR observed in our sample of z < 0.1 LBAs. The relatively metal-poor, active mode of star formation in LBAs and distant z > 2 LBGs may yield higher total HMXB luminosity than found in typical galaxies in the local universe.« less

Important Nearby Galaxies without Accurate Distances

NASA Astrophysics Data System (ADS)

McQuinn, Kristen

2014-10-01

The Spitzer Infrared Nearby Galaxies Survey (SINGS) and its offspring programs (e.g., THINGS, HERACLES, KINGFISH) have resulted in a fundamental change in our view of star formation and the ISM in galaxies, and together they represent the most complete multi-wavelength data set yet assembled for a large sample of nearby galaxies. These great investments of observing time have been dedicated to the goal of understanding the interstellar medium, the star formation process, and, more generally, galactic evolution at the present epoch. Nearby galaxies provide the basis for which we interpret the distant universe, and the SINGS sample represents the best studied nearby galaxies.Accurate distances are fundamental to interpreting observations of galaxies. Surprisingly, many of the SINGS spiral galaxies have numerous distance estimates resulting in confusion. We can rectify this situation for 8 of the SINGS spiral galaxies within 10 Mpc at a very low cost through measurements of the tip of the red giant branch. The proposed observations will provide an accuracy of better than 0.1 in distance modulus. Our sample includes such well known galaxies as M51 (the Whirlpool), M63 (the Sunflower), M104 (the Sombrero), and M74 (the archetypal grand design spiral).We are also proposing coordinated parallel WFC3 UV observations of the central regions of the galaxies, rich with high-mass UV-bright stars. As a secondary science goal we will compare the resolved UV stellar populations with integrated UV emission measurements used in calibrating star formation rates. Our observations will complement the growing HST UV atlas of high resolution images of nearby galaxies.

Jellyfish: the origin and distribution of extreme ram-pressure stripping events in massive galaxy clusters

NASA Astrophysics Data System (ADS)

McPartland, Conor; Ebeling, Harald; Roediger, Elke; Blumenthal, Kelly

2016-01-01

We investigate the observational signatures and physical origin of ram-pressure stripping (RPS) in 63 massive galaxy clusters at z = 0.3-0.7, based on images obtained with the Hubble Space Telescope. Using a training set of a dozen `jellyfish' galaxies identified earlier in the same imaging data, we define morphological criteria to select 211 additional, less obvious cases of RPS. Spectroscopic follow-up observations of 124 candidates so far confirmed 53 as cluster members. For the brightest and most favourably aligned systems, we visually derive estimates of the projected direction of motion based on the orientation of apparent compression shocks and debris trails. Our findings suggest that the onset of these events occurs primarily at large distances from the cluster core (>400 kpc), and that the trajectories of the affected galaxies feature high-impact parameters. Simple models show that such trajectories are highly improbable for galaxy infall along filaments but common for infall at high velocities, even after observational biases are accounted for, provided the duration of the resulting RPS events is ≲500 Myr. We thus tentatively conclude that extreme RPS events are preferentially triggered by cluster mergers, an interpretation that is supported by the disturbed dynamical state of many of the host clusters. This hypothesis implies that extreme RPS might occur also near the cores of merging poor clusters or even merging groups of galaxies. Finally, we present nine additional `jellyfish" galaxies at z > 0.3 discovered by us, thereby doubling the number of such systems known at intermediate redshift.

Satellite dwarf galaxies in a hierarchical universe: the prevalence of dwarf-dwarf major mergers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deason, Alis; Wetzel, Andrew; Garrison-Kimmel, Shea, E-mail: alis@ucolick.org

Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ∼10% of satellite dwarf galaxies with M {sub star} > 10{sup 6} M {sub ☉} that are within the host virial radius experienced a major merger of stellar mass ratio closer than 0.1 since z = 1, with amore » lower fraction for lower mass dwarf galaxies. Recent merger remnants are biased toward larger radial distance and more recent virial infall times, because most recent mergers occurred shortly before crossing within the virial radius of the host halo. Satellite-satellite mergers also occur within the host halo after virial infall, catalyzed by the large fraction of dwarf galaxies that fell in as part of a group. The merger fraction doubles for dwarf galaxies outside of the host virial radius, so the most distant dwarf galaxies in the Local Group are the most likely to have experienced a recent major merger. We discuss the implications of these results on observable dwarf merger remnants, their star formation histories, the gas content of mergers, and massive black holes in dwarf galaxies.« less

Resolving the host galaxy of a distant blazar with LBT/LUCI 1 + ARGOS

NASA Astrophysics Data System (ADS)

Farina, E. P.; Georgiev, I. Y.; Decarli, R.; Terzić, T.; Busoni, L.; Gässler, W.; Mazzoni, T.; Borelli, J.; Rosensteiner, M.; Ziegleder, J.; Bonaglia, M.; Rabien, S.; Buschkamp, P.; Orban de Xivry, G.; Rahmer, G.; Kulas, M.; Peter, D.

2018-05-01

BL Lac objects emitting in the very high energy (VHE) regime are unique tools to peer into the properties of the extragalactic background light (EBL). However, due to the typical absence of features in their spectra, the determination of their redshifts has proven challenging. In this work, we exploit the superb spatial resolution delivered by the new Advanced Rayleigh guided Ground layer adaptive Optics System (ARGOS) at the Large Binocular Telescope to detect the host galaxy of HESS J1943+213, a VHE emitting BL Lac shining through the Galaxy. Deep H-band imaging collected during the ARGOS commissioning allowed us to separate the contribution of the nuclear emission and to unveil the properties of the host galaxy with unprecedented detail. The host galaxy is well fitted by a Sérsic profile with index of n ˜ 2 and total magnitude of HHost ˜ 16.15 mag. Under the assumption that BL Lac host galaxies are standard candles, we infer a redshift of z ˜ 0.21. In the framework of the current model for the EBL, this value is in agreement with the observed dimming of the VHE spectrum due to the annihilation of energetic photons on the EBL

Watching the Birth of a Galaxy Cluster?

NASA Astrophysics Data System (ADS)

1999-07-01

First Visiting Astronomers to VLT ANTU Observe the Early Universe When the first 8.2-m VLT Unit Telescope (ANTU) was "handed over" to the scientists on April 1, 1999, the first "visiting astronomers" at Paranal were George Miley and Huub Rottgering from the Leiden Observatory (The Netherlands) [1]. They obtained unique pictures of a distant exploding galaxy known as 1138 - 262 . These images provide new information about how massive galaxies and clusters of galaxies may have formed in the early Universe. Formation of clusters of galaxies An intriguing question in modern astronomy is how the first galaxies and groupings or clusters of galaxies emerged from the primeval gas produced in the Big Bang. Some theories predict that giant galaxies, often found at the centres of rich galaxy clusters, are built up through a step-wise process. Clumps develop in this gas and stars condense out of those clumps to form small galaxies. Finally these small galaxies merge together to form larger units. An enigmatic class of objects important for investigating such scenarios are galaxies which emit intense radio emission from explosions that occur deep in their nuclei. The explosions are believed to be triggered when material from the merging swarm of smaller galaxies is fed into a rotating black hole located in the central regions. There is strong evidence that these distant radio galaxies are amongst the oldest and most massive galaxies in the early Universe and are often located at the heart of rich clusters of galaxies. They can therefore help pinpoint regions of the Universe in which large galaxies and clusters of galaxies are being formed. The radio galaxy 1138-262 The first visiting astronomers pointed ANTU towards a particularly important radio galaxy named 1138-262 . It is located in the southern constellation Hydra (The Water Snake). This galaxy was discovered some years ago using ESO's 3.5-m New Technology Telescope (NTT) at La Silla. Because 1138-262 is at a distance of about 10,000 million light-years from the Earth (the redshift is 2.2), the VLT sees it as it was when the Universe was only about 20% of its present age. Previous observations of this galaxy by the same team of astronomers showed that its radio, X-ray and optical emission had many extreme characteristics that would be expected from a giant galaxy, forming at the centre of a rich cluster. However, because the galaxy is so distant, the cluster could not be seen directly. Radio data obtained by the Very Large Array (VLA) in the USA and X-ray data with the ROSAT satellite both indicated that the galaxy is surrounded by a hot gas similar to that observed at the centres of nearby rich clusters of galaxies. Most telling was a picture taken by the Hubble Space Telescope that revealed that the galaxy comprises a large number of clumps, and which bore a remarkable resemblance to computer models of the birth of giant galaxies in clusters. From these observations, it was concluded that 1138-262 is likely to be a massive galaxy in the final stage of assemblage through merging with many smaller galaxies in an infant rich cluster and the most distant known X-ray cluster. VLT obtains Lyman-alpha images ESO PR Photo 33a/99 ESO PR Photo 33a/99 [Preview - JPEG: 483 x 400 pix - 86k] [Normal - JPEG: 966 x 800 pix - 230k] [High-Res - JPEG: 2894 x 2396 pix - 1.1M] Caption to ESO PR Photo 33a/99 : False-colour picture of the ionized hydrogen gas surrounding 1138-262 (Lyman-alpha). The size of this cloud is about 5 times larger than the optical extent of the Milky Way Galaxy. A contour plot, as observed with VLT ANTU + FORS1 in a narrow-band filter around the wavelength of the redshifted Lyman-alpha line, is superposed on a false-colour representation of the same image. The contour levels are a geometric progression in steps of 2 1/2. The image has not been flux calibrated, so the first contour level is arbitrary. The field measures 35 x 25 arcsec 2 , corresponding to about 910,000 x 650,000 light-years (280 x 200 kpc). The linear scale is indicated at the lower left. North is up and East is left. The Leiden astronomers used the FORS1 instrument on ANTU to take long-exposure pictures of 1138-262 and a surrounding field of 36 square arcmin. Images were obtained through two optical filters, one which tunes in to light produced by hydrogen gas (the redshifted Lyman-alpha line) and the other which is dominated by light from stars (the B-band). The "difference" between the images shows that the hydrogen gas surrounding the galaxy and from which the galaxy is presumably forming is huge ( Photo 33a/99 ). The measured size is about 20 arcsec or, at the distance of the cluster, somewhat more than 500,000 light-years (160 kpc), making it the largest such structure ever seen. It corresponds to about 5 times the size of the optical extent of the Milky Way Galaxy ! ESO PR Photo 33b/99 ESO PR Photo 33b/99 [Preview - JPEG: 400 x 593 pix - 149k] [Normal - JPEG: 800 x 1185 pix - 335k] [High-Res - JPEG: 1982 x 2935 pix - 1.1M] Caption to ESO PR Photo 33b/99 : Three small fields near radio galaxy 1138-262 as observed with VLT ANTU + FORS1 in a narrow-band filter at the redshifted wavelength of Lyman-alpha emission in that galaxy (left) and a broader filter in the surrounding spectral region (right), respectively. Three excellent candidates of Lyman-alpha emitters are seen at the centres of the fields. They are clearly visible in the narrow-band image (that mostly shows the gas), but are not detected in the broad-band image (that mostly shows the stars). Each field measures 24 x 24 arcsec 2 , corresponding to about 620,000 x 620,000 light-years (190 x 190 kpc); North is up and East is left. Even more intriguing is the presence of a number of objects in the gas picture (to the left in PR Photo 33b/99 ), but absent from the stars' picture (right). These are galaxies whose hydrogen gas is emitting the bright Lyman-alpha spectral line within a distance of the order of about 3 million light-years (1 Mpc) from the radio galaxy, and probably in the surrounding cluster. The team has pinpointed a total of 26 objects in the surrounding field that may be companion galaxies with fainter hydrogen emission. The detection by the VLT of the huge gas halo and of the companion galaxies is further evidence that 1138-262 is a massive galaxy, forming in a group or cluster of galaxies. The next step The next step in the project will be to confirm the distances of the candidate companion galaxies and establish that they are indeed members of a cluster of galaxies surrounding 1138-262 . This can be done using one of the spectrographs on the VLT. Note [1] The project on 1138-262 is being carried out by a large international consortium of scientists led by astronomers from the Leiden Observatory. Besides George Miley and Huub Rottgering , the team includes Jaron Kurk , Laura Pentericci , and Bram Venemans (Leiden), Alan Moorwood (ESO), Chris Carilli (US National Radio Astronomy Observatory - NRAO), Wil van Breugel (University of California, USA) Holland Ford and Tim Heckman (Johns Hopkins University, Baltimore, USA) and Pat McCarthy (Carnegie Institute, Pasadena, USA). Technical information about the VLT images of 1138-262 Narrow and broad-band imaging was carried out on April 12 and 13, 1999, with the ESO VLT ANTU (UT1), using the FORS1 multi-mode instrument in imaging mode. A narrow-band filter was used which has a central wavelength of 381.4 nm and a bandpass of 6.5 nm. For 1138-262 (redshift z = 2.2), the emission of Lyman-alpha at 121.6 nm is redshifted to 383.8 nm, which falls in this narrow band. The broad-band filter was a Bessel-B with central wavelength of 429.0 nm. The detector was a Tektronix CCD with 2048 x 2046 pixels and an image scale of 0.20 arcsec/pixel. Eight separate 30-min exposures were taken in the narrow band and six 5-min in the broad band, shifted by about 20 arcsec with respect to each other to minimize problems due to flat-fielding and to facilitate cosmic ray removal. The average seeing was 1.0 arcsec. Image reduction was carried out by means of the IRAF reduction package. The individual images were bias subtracted and flat-fielded using twilight exposures (narrow band) or an average of the unregistered science exposures (broad-band). The images were then registered by shifting them in position by an amount determined from the location of several stars on the CCD. The registered images were co-added and dark pixels from cosmic rays were cleaned. To improve the signal-to-noise ratio, the resulting images were smoothed with a Gaussian function having full-width-at half-maximum (FWHM) = 1 arcsec (5 pixels). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Hubble Spotlights a Celestial Sidekick

NASA Image and Video Library

2017-12-08

This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), a highly efficient wide-field camera covering the optical and near-infrared parts of the spectrum. While this lovely image contains hundreds of distant stars and galaxies, one vital thing is missing — the object Hubble was actually studying at the time! This is not because the target has disappeared. The ACS actually uses two detectors: the first captures the object being studied — in this case an open star cluster known as NGC 299 — while the other detector images the patch of space just ‘beneath’ it. This is what can be seen here. Technically, this picture is merely a sidekick of the actual object of interest — but space is bursting with activity, and this field of bright celestial bodies offers plenty of interest on its own. It may initially seem to show just stars, but a closer look reveals many of these tiny objects to be galaxies. The spiral galaxies have arms curving out from a bright center. The fuzzier, less clearly shaped galaxies might be ellipticals. Some of these galaxies contain millions or even billions of stars, but are so distant that all of their starry residents are contained within just a small pinprick of light that appears to be the same size as a single star! The bright blue dots are very hot stars, sometimes distorted into crosses by the struts supporting Hubble’s secondary mirror. The redder dots are cooler stars, possibly in the red giant phase when a dying star cools and expands. Credit: ESA/Hubble & NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Deep CO(1-0) Observations of z = 1.62 Cluster Galaxies with Substantial Molecular Gas Reservoirs and Normal Star Formation Efficiencies

NASA Astrophysics Data System (ADS)

Rudnick, Gregory; Hodge, Jacqueline; Walter, Fabian; Momcheva, Ivelina; Tran, Kim-Vy; Papovich, Casey; da Cunha, Elisabete; Decarli, Roberto; Saintonge, Amelie; Willmer, Christopher; Lotz, Jennifer; Lentati, Lindley

2017-11-01

We present an extremely deep CO(1-0) observation of a confirmed z = 1.62 galaxy cluster. We detect two spectroscopically confirmed cluster members in CO(1-0) with signal-to-noise ratio > 5. Both galaxies have log({{ M }}\\star /{{ M }}⊙ ) > 11 and are gas rich, with {{ M }}{mol}/({{ M }}\\star +{{ M }}{mol}) ˜ 0.17-0.45. One of these galaxies lies on the star formation rate (SFR)-{{ M }}\\star sequence, while the other lies an order of magnitude below. We compare the cluster galaxies to other SFR-selected galaxies with CO measurements and find that they have CO luminosities consistent with expectations given their infrared luminosities. We also find that they have gas fractions and star formation efficiencies (SFE) comparable to what is expected from published field galaxy scaling relations. The galaxies are compact in their stellar light distribution, at the extreme end for all high-redshift star-forming galaxies. However, their SFE is consistent with other field galaxies at comparable compactness. This is similar to two other sources selected in a blind CO survey of the HDF-N. Despite living in a highly quenched protocluster core, the molecular gas properties of these two galaxies, one of which may be in the process of quenching, appear entirely consistent with field scaling relations between the molecular gas content, stellar mass, star formation rate, and redshift. We speculate that these cluster galaxies cannot have any further substantive gas accretion if they are to become members of the dominant passive population in z< 1 clusters.

The Universe Going Green: Extraordinarily Strong [OIII]5007 in Typical Dwarf Galaxies at z~3

NASA Astrophysics Data System (ADS)

Malkan, Matthew Arnold; Cohen, Daniel

2017-01-01

We constructed the average SEDs of U-dropout galaxies in the Subaru Deep Field. This sample contains more than 5000 Lyman-break galaxies at z~3. Their average near- and mid-IR colors were obtained by stacking JHK and IRAC imaging, in bins of stellar mass. At the lowest mass bins an increasingly strong excess flux is seen in the K filter. This excess can reach 1 magnitude in the broadband filter, and we attribute it to strong \\OIII $\\lambda{5007}$ line emission. The equivalent width is extraordinarily high, reaching almost 1000\\Ang\\ for the average z=3 galaxy at an i magnitude of 27. Such extreme [OIII] emission is very rare in the current epoch, only seen in a handful of metal-deficient dwarf starbursts sometimes referred to as ''Green Peas". In contrast, extreme [OIII]--strong enough to dominate the entire broad-band SED--was evidently the norm for faint galaxies at high redshift. We present evidence that these small but numerous galaxies were primarily responsible for the reionization of the Universe.

Eternity in six hours: Intergalactic spreading of intelligent life and sharpening the Fermi paradox

NASA Astrophysics Data System (ADS)

Armstrong, Stuart; Sandberg, Anders

2013-08-01

The Fermi paradox is the discrepancy between the strong likelihood of alien intelligent life emerging (under a wide variety of assumptions) and the absence of any visible evidence for such emergence. In this paper, we extend the Fermi paradox to not only life in this galaxy, but to other galaxies as well. We do this by demonstrating that travelling between galaxies - indeed even launching a colonisation project for the entire reachable universe - is a relatively simple task for a star-spanning civilisation, requiring modest amounts of energy and resources. We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to. Given certain technological assumptions, such as improved automation, the task of constructing Dyson spheres, designing replicating probes, and launching them at distant galaxies, become quite feasible. We extensively analyse the dynamics of such a project, including issues of deceleration and collision with particles in space. Using similar methods, there are millions of galaxies that could have reached us by now. This results in a considerable sharpening of the Fermi paradox.

Transformations in our Understanding of Galaxy Evolution

NASA Astrophysics Data System (ADS)

Bershady, M. A.

2016-10-01

A new generation of instruments has launched large surveys now mapping galaxy evolution with single- and multi-object integral-field spectrographs (IFS). These surveys form counterpoints to the mapping of the Milky Way with multi-object stellar spectroscopy and the Gaia satellite. Combined, they allow us to better place the Milky Way in context of the galaxy population at z˜0; to understand if the Milky Way is indeed a normal spiral; and to leverage its unique archaeological record against observations of distant galaxies. These studies illustrate opportunities awaiting next-generation instruments and surveys that push to higher spectral resolution, lower surface-brightness, and into the near and even mid-infrared. Here we focus on the advantages of higher spectral resolution IFS, as enabled by WEAVE. Ground-breaking science opportunities include characterizing and kinematically resolving the ionized gas and stars in dynamically cold galaxies. Such studies will benefit from increased sensitivity both in S/N and line-diagnostics, pushing extragalactic observations in integrated light much closer to where our understanding of Milky Way chemo-dynamics is today.

Electrons in a closed galaxy model of cosmic rays

NASA Technical Reports Server (NTRS)

Ramaty, R.; Westergaard, N. J.

1976-01-01

The consistency of positrons and electrons was studied using a propagation model in which the cosmic rays are stopped by nuclear collisions or energy losses before they can escape from the galaxy (the closed-galaxy model). The fact that no inconsistency was found between the predictions and the data implies that the protons which produce the positrons by nuclear reactions could have their origin in a large number of distant sources, as opposed to the heavier nuclei which in this model come from a more limited set of sources. The closed-galaxy model predicts steep electron and positron spectra at high energies. None of these are inconsistent with present measurements; but future measurements of the spectrum of high-energy positrons could provide a definite test for the model. The closed-galaxy model also predicts that the interstellar electron intensity below a few GeV is larger than that implied by other models. The consequence of this result is that electron bremsstrahlung is responsible for about 50% of the galactic gamma-ray emission at photon energies greater than 100 MeV.

Galaxy Mass Assembly with VLT & HST and lessons for E-ELT/MOSAIC

NASA Astrophysics Data System (ADS)

Hammer, François; Flores, Hector; Puech, Mathieu

2015-02-01

The fraction of distant disks and mergers is still debated, while 3D-spectroscopy is revolutionizing the field. However its limited spatial resolution imposes a complimentary HST imagery and a robust analysis procedure. When applied to observations of IMAGES galaxies at z = 0.4-0.8, it reveals that half of the spiral progenitors were in a merger phase, 6 billion year ago. The excellent correspondence between methodologically-based classifications of morphologies and kinematics definitively probes a violent origin of disk galaxies as proposed by Hammer et al. (2005). Examination of nearby galaxy outskirts reveals fossil imprints of such ancient merger events, under the form of well organized stellar streams. Perhaps our neighbor, M31, is the best illustration of an ancient merger, which modeling in 2010 leads to predict the gigantic plane of satellites discovered by Ibata et al. (2013). There are still a lot of discoveries to be done until the ELT era, which will open an avenue for detailed and accurate 3D-spectroscopy of galaxies from the earliest epochs to the present.

Characterizing the Young Galaxies at Cosmic Dawn

NASA Astrophysics Data System (ADS)

Zheng, Wei

2013-10-01

We propose to analyze the data of the Hubble Frontier Fields, in order to discover and study galaxies at the highest redshifts and to an unprecedented depth. The redshift range of z 10-12 marks the beginning of the IGM reionization and remains as HST's last frontier. In the framework of the CLASH and related projects, our team has succeeded in finding the most distant galaxies. We will carry out a systematic search for galaxy candidates at z 10-12 in the proposed deep observations. At this redshift range, most of the spectral features are shifted longward of the WFC3/IR bands, and additional data are therefore needed in order to secure the candidates and study their intrinsic properties. We will {1} obtain deep photometry in complementary ground-based K-band observations; {2} estimate the global star-formation rate density; {3} measure the sources' UV continuum slope and {4} carry out ALMA observations to study the dust content. Finally, we will estimate the effect of these young galaxies in ionizing the IGM. Our study will serve as an ideal bridge between HST and JWST in exploring the cosmic dawn.

The discovery of five new H2O megamasers in active galaxies

NASA Technical Reports Server (NTRS)

Braatz, J. A.; Wilson, A. S.; Henkel, C.

1994-01-01

H2O megamasers with (isotropic) luminosities between 60 and 200 solar luminosity (H(sub 0) = 75 km/s/Mpc) have been detected in the Seyfert 2 galaxies Mrk 1, Mrk 1210, and NGC 5506 and in the LINERs NGC 1052 and NGC 2639. No megamasers have been found in Seyfert 1's. The galaxies have redshifts between 1500 and 4800 km/s and are the most distant H2O sources reported to date. NGC 1052 is also the first elliptical galaxy known to contain an H2O maser. The intensity distribution of an H2O five-point map obtained toward NGC 5506 shows that the H2O emission is pointlike compared to the 40 sec telescope beam. The lack of CO emission in NGC 1052 implies a conservative lower limit to the H2O brightness temperature of 1000 K, thus ruling out a thermal origin for the H2O emission. The success of this survey relative to other recent searches makes it evident that H2O megamasers are preferentially found in galaxies with active nuclei.

A Hubble Diagram of Distant Type IA Supernovae

NASA Astrophysics Data System (ADS)

Hamuy, M.; Phillips, M. M.; Suntzeff, N. B.; Aviles, R.; Maza, J.

1993-12-01

Due to their extreme luminosities at maximum light, type Ia supernovae (SNe Ia) have long been considered among the most attractive cosmological standard candles. Although nearly all work to date has been devoted to attempts to use these objects to determine the local rate of expansion of the universe (Ho), SNe Ia also provide one of the few direct techniques for measuring the deceleration parameter qo. However, in a recent study of nine well-observed events based largely on data obtained at CTIO, Phillips (1993, ApJ, 413, L105) found clear evidence for a significant intrinsic dispersion in SNe Ia absolute magnitudes amounting to ~ 0.8 mag in B, ~ 0.7 mag in V, and ~ 0.5 mag in I. Such a range in peak luminosity could introduce a subtantial Malmquist bias into searches for distant (z <= 0.3) SNe Ia which, if uncorrected, could lead to an erroneous value of qo. In this paper we present the Hubble diagram for 13 SNe Ia discovered and observed in the course of the Calan/Tololo Supernova Survey. This sample, which covers the redshift range 0.01 <= z <= 0.1, provides unequivocal evidence for an intrinsic spread in the peak luminosities of type Ia events. The data also confirm Phillips' conclusion that the maximum-light luminosity is strongly correlated with the initial decline rate of the B light curve. Interestingly, the most luminous SNe in our sample all occurred in spiral galaxies, which is true for Phillips' sample of nearby SNe Ia as well. This is opposite to what one would expect if dust extinction were important. These findings are consistent with recent speculations that the progenitors of SNe Ia are white dwarfs covering a range of masses, and also suggest that the brightest events may be found in galaxies which are still actively forming stars. The implications for the use of SNe Ia to measure qo are briefly discussed. This research has been supported by Grant 92/0312 from Fondo Nacional de Ciencias y Tecnología (FONDECYT-Chile).

Discovering Our Stellar Neighborhood

ERIC Educational Resources Information Center

Black, David V.

2014-01-01

The stars closest to Earth are not particularly remarkable or exciting. They are average stars typical of the spiral arms of our Milky Way galaxy. In fact, until recently, most astronomy and Earth science textbooks ignored all but the largest of them to focus on distant, more exotic objects like red supergiants or black holes. The recent discovery…

ELEVEN NEW HEAVILY REDDENED FIELD WOLF-RAYET STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, J. D. T.; Cushing, Michael; Barletta, Anthony

We report the results of a medium-narrowband 2 {mu}m line survey covering 5.8 deg{sup 2} near the Galactic plane. We confirm 11 new field Wolf-Rayet stars along three lines of sight probing the inner Galaxy, demonstrating the capability to uncover distant and highly reddened populations of Galactic wind-borne emission-line stars suffering extinction as high as A{sub V} {approx} 40 and as distant as 9 kpc down to modest magnitude limits of K{sub s} {approx} 12.5. All stars are of subtype WC7-8, with median distance d = 6 kpc and median extinction A{sub K{sub s}} = 2.5. Over the fields surveyed,more » the density of Wolf-Rayet stars to limiting magnitude K{sub s} {approx} 12.5 was found to be 1.9 deg{sup -2}. We compare this to models which predict their distribution within the Galaxy and find that, even neglecting survey and subtype incompleteness, they consistently underpredict the number of newly discovered stars along the surveyed lines of sight.« less

Mapping the Extinction Curve in 3D: Structure on Kiloparsec Scales

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlafly, E. F.; Peek, J. E. G.; Finkbeiner, D. P.

Near-infrared spectroscopy from APOGEE and wide-field optical photometry from Pan-STARRS1 have recently made precise measurements of the shape of the extinction curve possible for tens of thousands of stars, parameterized by R ( V ). These measurements revealed structures in R ( V ) with large angular scales, which are challenging to explain in existing dust paradigms. In this work, we combine three-dimensional maps of dust column density with R ( V ) measurements to constrain the three-dimensional distribution of R ( V ) in the Milky Way. We find that the variations in R ( V ) are correlatedmore » on kiloparsec scales. In particular, most of the dust within one kiloparsec in the outer Galaxy, including many local molecular clouds (Orion, Taurus, Perseus, California, and Cepheus), has a significantly lower R ( V ) than more distant dust in the Milky Way. These results provide new input to models of dust evolution and processing, and complicate the application of locally derived extinction curves to more distant regions of the Milky Way and to other galaxies.« less

Classification of X-ray sources in the direction of M31

NASA Astrophysics Data System (ADS)

Vasilopoulos, G.; Hatzidimitriou, D.; Pietsch, W.

2012-01-01

M31 is our nearest spiral galaxy, at a distance of 780 kpc. Identification of X-ray sources in nearby galaxies is important for interpreting the properties of more distant ones, mainly because we can classify nearby sources using both X-ray and optical data, while more distant ones via X-rays alone. The XMM-Newton Large Project for M31 has produced an abundant sample of about 1900 X-ray sources in the direction of M31. Most of them remain elusive, giving us little signs of their origin. Our goal is to classify these sources using criteria based on properties of already identified ones. In particular we construct candidate lists of high mass X-ray binaries, low mass X-ray binaries, X-ray binaries correlated with globular clusters and AGN based on their X-ray emission and the properties of their optical counterparts, if any. Our main methodology consists of identifying particular loci of X-ray sources on X-ray hardness ratio diagrams and the color magnitude diagrams of their optical counterparts. Finally, we examined the X-ray luminosity function of the X-ray binaries populations.

Discovery of extreme [O III] λ5007 Å outflows in high-redshift red quasars

NASA Astrophysics Data System (ADS)

Zakamska, Nadia L.; Hamann, Fred; Pâris, Isabelle; Brandt, W. N.; Greene, Jenny E.; Strauss, Michael A.; Villforth, Carolin; Wylezalek, Dominika; Alexandroff, Rachael M.; Ross, Nicholas P.

2016-07-01

Black hole feedback is now a standard component of galaxy formation models. These models predict that the impact of black hole activity on its host galaxy likely peaked at z = 2-3, the epoch of strongest star formation activity and black hole accretion activity in the Universe. We used XSHOOTER on the Very Large Telescope to measure rest-frame optical spectra of four z ˜ 2.5 extremely red quasars with infrared luminosities ˜1047 erg s-1. We present the discovery of very broad (full width at half max = 2600-5000 km s-1), strongly blueshifted (by up to 1500 km s-1) [O III] λ5007 Å emission lines in these objects. In a large sample of type 2 and red quasars, [O III] kinematics are positively correlated with infrared luminosity, and the four objects in our sample are on the extreme end in both [O III] kinematics and infrared luminosity. We estimate that at least 3 per cent of the bolometric luminosity in these objects is being converted into the kinetic power of the observed wind. Photo-ionization estimates suggest that the [O III] emission might be extended on a few kpc scales, which would suggest that the extreme outflow is affecting the entire host galaxy of the quasar. These sources may be the signposts of the most extreme form of quasar feedback at the peak epoch of galaxy formation, and may represent an active `blow-out' phase of quasar evolution.

Pushing the boundaries: probing the halo of the Milky Way beyond 100 kpc with RR Lyrae

NASA Astrophysics Data System (ADS)

Carlin, Jeffrey L.; Medina, Gustavo; Munoz, Ricardo R.; Vivas, Anna Katherina; Willman, Beth

2018-01-01

Stars in the outermost halo of the Milky Way are vital tracers of the mass of our Galaxy. Furthermore, beyond ~100 kpc from the Galactic center, most (or perhaps all) of the stars are likely to be in faint dwarf galaxies or tidal debris from recently accreted dwarfs, making the outer reaches of the Galaxy important for understanding the Milky Way’s accretion history. However, confirmed stars are scarce at these distances because they are difficult to securely identify among the more numerous foreground stars. Pulsating variables such as RR Lyrae are ideal probes of the distant halo because they are readily identified in time-series data, are intrinsically bright and thus can be seen at large distances, and follow well-known period-luminosity relations that enable precise distance measurements. We present results from our program to find RR Lyrae using deep DECam time series data (from the HiTS supernova survey as well as our own observing program) covering ~300 square degrees. Our sample of distant RR Lyrae more than doubles the number of known Milky Way stars beyond distances of ~150 kpc. Among these, we find two distinct groups of two and three stars that are members of the Leo IV and Leo V ultra-faint dwarf galaxies, located at distances of ~145 kpc and ~175 kpc, respectively. We derive the stellar density as a function of Galactocentric radius, extending to more than 250 kpc from the Galactic center. This sample of RR Lyrae provides a set of important probes of the mass of the Milky Way and the accretion origin of the outer Galactic halo.

The stellar masses of ˜ 40 000 UV selected Galaxies from the WiggleZ survey at 0.3

NASA Astrophysics Data System (ADS)

Banerji, Manda; Glazebrook, Karl; Blake, Chris; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croton, Darren J.; Croom, Scott; Davis, Tamara M.; Drinkwater, Michael J.; Forster, Karl; Gilbank, David; Gladders, Mike; Jelliffe, Ben; Jurek, Russell J.; Li, I.-hui; Madore, Barry; Martin, D. Christopher; Pimbblet, Kevin; Poole, Gregory B.; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted K.; Yee, H. K. C.

2013-05-01

We characterize the stellar masses and star formation rates in a sample of ˜40 000 spectroscopically confirmed UV-luminous galaxies at 0.3 < z < 1.0 selected from within the WiggleZ Dark Energy Survey. In particular, we match this UV bright population to wide-field infrared surveys such as the near-infrared (NIR) UKIDSS Large Area Survey (LAS) and the mid-infrared Wide-Field Infrared Survey Explorer (WISE) All-Sky Survey. We find that ˜30 per cent of the UV-luminous WiggleZ galaxies, corresponding to the brightest and reddest subset, are detected at >5σ in the UKIDSS-LAS at all redshifts. An even more luminous subset of 15 per cent are also detected in the WISE 3.4 and 4.6 μm bands. In addition, 22 of the WiggleZ galaxies are extremely luminous at 12 and 22 μm and have colours consistent with being star formation dominated. We compute stellar masses for this very large sample of extremely blue galaxies and quantify the sensitivity of the stellar mass estimates to various assumptions made during the spectral energy distribution (SED) fitting. The median stellar masses are log10(M*/M⊙) = 9.6 ± 0.7, 10.2 ± 0.5 and 10.4 ± 0.4 for the IR undetected, UKIDSS detected and UKIDSS+WISE detected galaxies, respectively. We demonstrate that the inclusion of NIR photometry can lead to tighter constraints on the stellar masses by bringing down the upper bound on the stellar mass estimate. The mass estimates are found to be most sensitive to the inclusion of secondary bursts of star formation as well as changes in the stellar population synthesis models, both of which can lead to median discrepancies of the order of 0.3 dex in the stellar masses. We conclude that even for these extremely blue galaxies, different SED fitting codes therefore produce extremely robust stellar mass estimates. We find, however, that the best-fitting M/LK is significantly lower than that predicted by simple optical colour-based estimators for many of the WiggleZ galaxies. The simple colour-based estimator overpredicts M/LK by ˜0.4 dex on average. The effect is more pronounced for bluer galaxies with younger best-fitting ages. The WiggleZ galaxies have star formation rates of 3-10 M⊙ yr-1 and mostly lie at the upper end of the main sequence of star-forming galaxies at these redshifts. Their rest-frame UV luminosities and stellar masses are comparable to both local compact UV-luminous galaxies as well as Lyman break galaxies at z ˜ 2-3. The stellar masses from this paper will be made publicly available with the next WiggleZ data release.

Light echoes whisper the distance to a star

NASA Astrophysics Data System (ADS)

2008-02-01

Astronomers have used ESO's Very Large Telescope to measure the distribution and motions of thousands of galaxies in the distant Universe. This opens fascinating perspectives to better understand what drives the acceleration of the cosmic expansion and sheds new light on the mysterious dark energy that is thought to permeate the Universe. ESO PR Photo 04a/08 ESO PR Photo 04a/08 Large-scale structures (Computer Simulation) "Explaining why the expansion of the Universe is currently accelerating is certainly the most fascinating question in modern cosmology," says Luigi Guzzo, lead author of a paper in this week's issue of Nature, in which the new results are presented. "We have been able to show that large surveys that measure the positions and velocities of distant galaxies provide us with a new powerful way to solve this mystery." Ten years ago, astronomers made the stunning discovery that the Universe is expanding at a faster pace today than it did in the past. "This implies that one of two very different possibilities must hold true," explains Enzo Branchini, member of the team. "Either the Universe is filled with a mysterious dark energy which produces a repulsive force that fights the gravitational brake from all the matter present in the Universe, or, our current theory of gravitation is not correct and needs to be modified, for example by adding extra dimensions to space." Current observations of the expansion rate of the Universe cannot distinguish between these two options, but the international team of 51 scientists from 24 institutions found a way that could help in tackling this problem. The technique is based on a well-known phenomenon, namely the fact that the apparent motion of distant galaxies results from two effects: the global expansion of the Universe that pushes the galaxies away from each other and the gravitational attraction of matter present in the galaxies' neighbourhood that pulls them together, creating the cosmic web of large-scale structures. ESO PR Photo 04b/08 ESO PR Photo 04b/08 A Cone in the Universe "By measuring the apparent velocities of large samples of galaxies over the last thirty years, astronomers have been able to reconstruct a three-dimensional map of the distribution of galaxies over large volumes of the Universe. This map revealed large-scale structures such as clusters of galaxies and filamentary superclusters," says Olivier Le Fèvre, member of the team. "But the measured velocities also contain information about the local motions of galaxies; these introduce small but significant distortions in the reconstructed maps of the Universe. We have shown that measuring this distortion at different epochs of the Universe's history is a way to test the nature of dark energy." Guzzo and his collaborators have been able to measure this effect by using the VIMOS spectrograph on Melipal, one of the four 8.2-m telescopes that is part of ESO's VLT. As part of the VIMOS-VLT Deep Survey (VVDS), of which Le Fèvre is the Principal Investigator, spectra of several thousands of galaxies in a 4-square-degree field (or 20 times the size of the full Moon) at epochs corresponding to about half the current age of the Universe (about 7 billion years ago) were obtained and analysed. ESO PR Video 04/08 ESO PR Video 04/08 Journey through galaxies "This is the largest field ever covered homogeneously by means of spectroscopy to this depth," declares Le Fèvre. "We have now collected more than 13,000 spectra in this field and the total volume sampled by the survey is more than 25 million cubic light-years." The astronomers compared their result with that of the 2dFGRS survey that probed the local Universe, i.e. measures the distortion at the present time. Within current uncertainties, the measurement of this effect provides an independent indication of the need for an unknown extra energy ingredient in the 'cosmic soup', supporting the simplest form of dark energy, the so-called cosmological constant, introduced originally by Albert Einstein. The large uncertainties do not yet exclude the other scenarios, though. "We have also shown that by extending our measurements over volumes about ten times larger than the VVDS, this technique should be able to tell us whether cosmic acceleration originates from a dark energy component of exotic origin or requires a modification of the laws of gravity," explains Guzzo. "VIMOS on the VLT would certainly be a wonderful tool to perform this future survey and help us answer this fundamental question. This strongly encourages scientists to proceed with even more ambitious surveys of the distant Universe," concludes Le Fèvre.

The identification of post-starburst galaxies at z ˜ 1 using multiwavelength photometry: a spectroscopic verification

NASA Astrophysics Data System (ADS)

Maltby, David T.; Almaini, Omar; Wild, Vivienne; Hatch, Nina A.; Hartley, William G.; Simpson, Chris; McLure, Ross J.; Dunlop, James; Rowlands, Kate; Cirasuolo, Michele

2016-06-01

Despite decades of study, we still do not fully understand why some massive galaxies abruptly switch off their star formation in the early Universe, and what causes their rapid transition to the red sequence. Post-starburst galaxies provide a rare opportunity to study this transition phase, but few have currently been spectroscopically identified at high redshift (z > 1). In this paper, we present the spectroscopic verification of a new photometric technique to identify post-starbursts in high-redshift surveys. The method classifies the broad-band optical-near-infrared spectral energy distributions (SEDs) of galaxies using three spectral shape parameters (supercolours), derived from a principal component analysis of model SEDs. When applied to the multiwavelength photometric data in the UKIDSS Ultra Deep Survey, this technique identified over 900 candidate post-starbursts at redshifts 0.5 < z < 2.0. In this study, we present deep optical spectroscopy for a subset of these galaxies, in order to confirm their post-starburst nature. Where a spectroscopic assessment was possible, we find the majority (19/24 galaxies; ˜80 per cent) exhibit the strong Balmer absorption (H δ equivalent width Wλ > 5 Å) and Balmer break, characteristic of post-starburst galaxies. We conclude that photometric methods can be used to select large samples of recently-quenched galaxies in the distant Universe.

Cluster galaxy population evolution from the Subaru Hyper Suprime-Cam survey: brightest cluster galaxies, stellar mass distribution, and active galaxies

NASA Astrophysics Data System (ADS)

Lin, Yen-Ting; Hsieh, Bau-Ching; Lin, Sheng-Chieh; Oguri, Masamune; Chen, Kai-Feng; Tanaka, Masayuki; Chiu, I.-non; Huang, Song; Kodama, Tadayuki; Leauthaud, Alexie; More, Surhud; Nishizawa, Atsushi J.; Bundy, Kevin; Lin, Lihwai; Miyazaki, Satoshi; HSC Collaboration

2018-01-01

The unprecedented depth and area surveyed by the Subaru Strategic Program with the Hyper Suprime-Cam (HSC-SSP) have enabled us to construct and publish the largest distant cluster sample out to z~1 to date. In this exploratory study of cluster galaxy evolution from z=1 to z=0.3, we investigate the stellar mass assembly history of brightest cluster galaxies (BCGs), and evolution of stellar mass and luminosity distributions, stellar mass surface density profile, as well as the population of radio galaxies. Our analysis is the first high redshift application of the top N richest cluster selection, which is shown to allow us to trace the cluster galaxy evolution faithfully. Our stellar mass is derived from a machine-learning algorithm, which we show to be unbiased and accurate with respect to the COSMOS data. We find very mild stellar mass growth in BCGs, and no evidence for evolution in both the total stellar mass-cluster mass correlation and the shape of the stellar mass surface density profile. The clusters are found to contain more red galaxies compared to the expectations from the field, even after the differences in density between the two environments have been taken into account. We also present the first measurement of the radio luminosity distribution in clusters out to z~1.

Les galaxies

NASA Astrophysics Data System (ADS)

Combes, Francoise

2016-08-01

Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

The Survey of HI in Extremely Low-mass Dwarfs: A Multi-Wavelength Perspective on Low-Mass Galaxy Evolution

NASA Astrophysics Data System (ADS)

Cannon, John M.; McNichols, Andrew; Teich, Yaron; Adams, Elizabeth A.; Giovanelli, Riccardo; Haynes, Martha P.; McQuinn, Kristen B.; Salzer, John Joseph; Skillman, Evan D.; Dolphin, Andrew E.; Elson, Edward C.; Haurberg, Nathalie C.; Huang, Shan; Janowiecki, Steven; Jozsa, Gyula; Leisman, Luke; Ott, Juergen; Papastergis, Emmanouil; Rhode, Katherine L.; Saintonge, Amelie; Van Sistine, Angela; Warren, Steven R.

2017-01-01

The “Survey of HI in Extremely Low-mass Dwarfs” (SHIELD) is a multiwavelength study of local volume low-mass galaxies drawn from the Arecibo Legacy Fast ALFA (ALFALFA) catalog. HST/Spitzer joint program GO-12658 revealed the stellar populations of the first 12 SHIELD galaxies (Cannon et al. 2011), allowing accurate distance measurements (McQuinn et al. 2014) and detailed studies of the patterns of recent star formation in each galaxy (McQuinn et al. 2015). These HST and Spitzer images are a critical interpretive benchmark for ground-based optical imaging and spectroscopy (Haurberg et al. 2015), as well as for sensitive VLA HI spectral line imaging of the SHIELD galaxies (McNichols et al. 2016; Teich et al. 2016). These results have furthered our understanding of the evolution of galaxies in a mass regime that was previously only sparsely populated. With the low-redshift ALFALFA catalog now complete, the scope of the SHIELD program has been expanded to include all 82 galaxies that meet distance, line width, and HI flux criteria for being gas-rich, low-mass galaxies. In HST program 13750, images of 18 more SHIELD galaxies have again set the physical scales for supporting HI spectral line imaging with both the VLA and the WSRT (Gordon et al. 2016). Taken as a whole, the ongoing SHIELD program is one of the most comprehensive multiwavelength studies of the physical properties of low-mass galaxies outside of the Local Group.

JELLYFISH: EVIDENCE OF EXTREME RAM-PRESSURE STRIPPING IN MASSIVE GALAXY CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebeling, H.; Stephenson, L. N.; Edge, A. C.

Ram-pressure stripping by the gaseous intracluster medium has been proposed as the dominant physical mechanism driving the rapid evolution of galaxies in dense environments. Detailed studies of this process have, however, largely been limited to relatively modest examples affecting only the outermost gas layers of galaxies in nearby and/or low-mass galaxy clusters. We here present results from our search for extreme cases of gas-galaxy interactions in much more massive, X-ray selected clusters at z > 0.3. Using Hubble Space Telescope snapshots in the F606W and F814W passbands, we have discovered dramatic evidence of ram-pressure stripping in which copious amounts ofmore » gas are first shock compressed and then removed from galaxies falling into the cluster. Vigorous starbursts triggered by this process across the galaxy-gas interface and in the debris trail cause these galaxies to temporarily become some of the brightest cluster members in the F606W passband, capable of outshining even the Brightest Cluster Galaxy. Based on the spatial distribution and orientation of systems viewed nearly edge-on in our survey, we speculate that infall at large impact parameter gives rise to particularly long-lasting stripping events. Our sample of six spectacular examples identified in clusters from the Massive Cluster Survey, all featuring M {sub F606W} < –21 mag, doubles the number of such systems presently known at z > 0.2 and facilitates detailed quantitative studies of the most violent galaxy evolution in clusters.« less

Induced Star Formation

NASA Astrophysics Data System (ADS)

Kennicutt, Robert C., Jr.

Overview: Induced Star Formation and Interactions Introduction Historical Background: First Hints Systematic Studies: Starbursts Interactions and Nuclear activity IRAS and Ultralumious starburst Galaxies The 1990's: HST, Supercomputers, and the Distant Universe Key Questions and Issues Organization of Lectures Star Formation Properties of Normal Galaxies Observational Techniques Results: Star Formation in Normal Galaxies Interpretation: Star Formation Histories Global Star Formation in interacting Galaxies A Gallery of Interactions and Mergers Star Formation Statistics: Guilt By Association Tests SFRs in Interacting vs Noninteracting Galaxies Kinematic Properties and Regulation of SFRs Induced Nuclear Activity and Star Formation Background: Nuclear Spectra and Classification Nuclear Star Formation and Starbursts Nuclear Star Formation and Interactions Induced AGN Activity: Statistics of Seyfert Galaxies Environments of Quasars Kinematic Clues to the Triggering of AGNs Infrared Luminous Galaxies and Starbursts Background: IR Luminous Galaxies and IRAS Infrared Luminosity Function and Spectra Infrared Structure and Morphology Interstellar Gas X-Ray Emission and Superwinds Optical, UV, and Near-Infrared Spectra Radio Continuum Emission Evidence for Interactions and Mergers The Power Source: Starbursts or Dusty AGNs? Spectral Diagnostics of Starbursts Evolutionary Synthesis Models Applications: Integrated Colors of Interacting Galaxies Applications: Hα Emission, Colors, and SFRs Applications: Spectral Modelling of Evolved Starbursts Infrared Starbursts and the IMF in starbursts Triggering and Regulation of Star Formation: The Problem Introduction: Star Formation as a Nonlinear Process The schmidt Law in Normal Galaxies Star Formation Regimes in Interacting Galaxies Summary Triggering and Regulation of Starbusts: Theoretical Ideas Gravitational Star Formation Thresholds Cloud Collision Models Radial Transport of Gas: Clues from Barred Galaxies Simulations of Starbursts in Merging Galaxies The Cosmological Role of Interactions and Starbursts Interactions in Hierarchical Cosmology Interaction-Induced Star Formation Today Interaction-Induced Star Formation in the Past Disk kinematics and the Merger Rate Global Effects of Starbursts and Superwinds Concluding Remarks References

TWO DISTANT HALO VELOCITY GROUPS DISCOVERED BY THE PALOMAR TRANSIENT FACTORY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sesar, Branimir; Cohen, Judith G.; Levitan, David

2012-08-20

We report the discovery of two new halo velocity groups (Cancer groups A and B) traced by eight distant RR Lyrae stars and observed by the Palomar Transient Factory survey at R.A. {approx} 129 Degree-Sign , decl. {approx} 20 Degree-Sign (l {approx} 205 Degree-Sign , b {approx} 32 Degree-Sign ). Located at 92 kpc from the Galactic center (86 kpc from the Sun), these are some of the most distant substructures in the Galactic halo known to date. Follow-up spectroscopic observations with the Palomar Observatory 5.1 m Hale telescope and W. M. Keck Observatory 10 m Keck I telescope indicatemore » that the two groups are moving away from the Galaxy at v-bar{sub gsr}{sup A} = 78.0{+-}5.6 km s{sup -1} (Cancer group A) and v-bar{sub gsr}{sup B} = 16.3{+-}7.1 km s{sup -1} (Cancer group B). The groups have velocity dispersions of {sigma}{sub v{sub g{sub s{sub r}{sup A}}}} = 12.4{+-}5.0 km s{sup -1} and {sigma}B{sub v{sub g{sub s{sub r}{sup B}}}} =14.9{+-}6.2 km s{sup -1} and are spatially extended (about several kpc), making it very unlikely that they are bound systems, and more likely to be debris of tidally disrupted dwarf galaxies or globular clusters. Both groups are metal-poor (median metallicities of [Fe/H]{sup A} = -1.6 dex and [Fe/H]{sup B} = -2.1 dex) and have a somewhat uncertain (due to small sample size) metallicity dispersion of {approx}0.4 dex, suggesting dwarf galaxies as progenitors. Two additional RR Lyrae stars with velocities consistent with those of the Cancer groups have been observed {approx}25 Degree-Sign east, suggesting possible extension of the groups in that direction.« less

The effect of the environment on the structure, morphology and star formation history of intermediate-redshift galaxies

NASA Astrophysics Data System (ADS)

Kelkar, Kshitija; Gray, Meghan E.; Aragón-Salamanca, Alfonso; Rudnick, Gregory; Milvang-Jensen, Bo; Jablonka, Pascale; Schrabback, Tim

2017-08-01

With the aim of understanding the effect of the environment on the star formation history and morphological transformation of galaxies, we present a detailed analysis of the colour, morphology and internal structure of cluster and field galaxies at 0.4 ≤ z ≤ 0.8. We use the Hubble Space Telescope data for over 500 galaxies from the ESO Distant Cluster Survey to quantify how the galaxies' light distribution deviate from symmetric smooth profiles. We visually inspect the galaxies' images to identify the likely causes for such deviations. We find that the residual flux fraction (RFF), which measures the fractional contribution to the galaxy light of the residuals left after subtracting a symmetric and smooth model, is very sensitive to the degree of structural disturbance but not the causes of such disturbance. On the other hand, the asymmetry of these residuals (Ares) is more sensitive to the causes of the disturbance, with merging galaxies having the highest values of Ares. Using these quantitative parameters, we find that, at a fixed morphology, cluster and field galaxies show statistically similar degrees of disturbance. However, there is a higher fraction of symmetric and passive spirals in the cluster than in the field. These galaxies have smoother light distributions than their star-forming counterparts. We also find that while almost all field and cluster S0s appear undisturbed, there is a relatively small population of star-forming S0s in clusters but not in the field. These findings are consistent with relatively gentle environmental processes acting on galaxies infalling on to clusters.

STScI-PRC02-11a FARAWAY GALAXIES PROVIDE A STUNNING 'WALLPAPER' BACKDROP FOR A RUNAWAY GALAXY

NASA Technical Reports Server (NTRS)

2002-01-01

Against a stunning backdrop of thousands of galaxies, this odd-looking galaxy with the long streamer of stars appears to be racing through space, like a runaway pinwheel firework. This picture of the galaxy UGC 10214 was taken by the Advanced Camera for Surveys (ACS), which was installed aboard NASA's Hubble Space Telescope in March during Servicing Mission 3B. Dubbed the 'Tadpole,' this spiral galaxy is unlike the textbook images of stately galaxies. Its distorted shape was caused by a small interloper, a very blue, compact galaxy visible in the upper left corner of the more massive Tadpole. The Tadpole resides about 420 million light-years away in the constellation Draco. Seen shining through the Tadpole's disk, the tiny intruder is likely a hit-and-run galaxy that is now leaving the scene of the accident. Strong gravitational forces from the interaction created the long tail of debris, consisting of stars and gas that stretch out more than 280,000 light-years. Numerous young blue stars and star clusters, spawned by the galaxy collision, are seen in the spiral arms, as well as in the long 'tidal' tail of stars. Each of these clusters represents the formation of up to about a million stars. Their color is blue because they contain very massive stars, which are 10 times hotter and 1 million times brighter than our Sun. Once formed, the star clusters become redder with age as the most massive and bluest stars exhaust their fuel and burn out. These clusters will eventually become old globular clusters similar to those found in essentially all halos of galaxies, including our own Milky Way. Two prominent clumps of young bright blue stars in the long tail are separated by a 'gap' -- a section that is fainter than the rest of the tail. These clumps of stars will likely become dwarf galaxies that orbit in the Tadpole's halo. The galactic carnage and torrent of star birth are playing out against a spectacular backdrop: a 'wallpaper pattern' of 6,000 galaxies. These galaxies represent twice the number of those discovered in the legendary Hubble Deep Field, the orbiting observatory's 'deepest' view of the heavens, taken in 1995 by the Wide Field and Planetary Camera 2. The ACS picture, however, was taken in one-twelfth the time it took to observe the original Hubble Deep Field. In blue light, ACS sees even fainter objects than were seen in the 'deep field.' The galaxies in the ACS picture, like those in the deep field, stretch back to nearly the beginning of time. They are a myriad of shapes and represent fossil samples of the universe's 13-billion-year evolution. The ACS image is so sharp that astronomers can identify distant colliding galaxies, the 'building blocks' of galaxies, an exquisite 'Whitman's Sampler' of galaxies, and many extremely faraway galaxies. ACS made this observation on April 1 and 9, 2002. The color image is constructed from three separate images taken in near-infrared, orange, and blue filters. Credit: NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA The ACS Science Team: (H. Ford, G. Illingworth, M. Clampin, G. Hartig, T. Allen, K. Anderson, F. Bartko, N. Benitez, J. Blakeslee, R. Bouwens, T. Broadhurst, R. Brown, C. Burrows, D. Campbell, E. Cheng, N. Cross, P. Feldman, M. Franx, D. Golimowski, C. Gronwall, R. Kimble, J. Krist, M. Lesser, D. Magee, A. Martel, W. J. McCann, G. Meurer, G. Miley, M. Postman, P. Rosati, M. Sirianni, W. Sparks, P. Sullivan, H. Tran, Z. Tsvetanov, R. White, and R. Woodruff)

The beautiful side of IC 335

NASA Image and Video Library

2017-12-08

Hubble sees a galaxy 60 million light-years away This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax Galaxy Cluster 60 million light-years away. As seen in this image, the disk of IC 335 appears edge-on from the vantage point of Earth. This makes it harder for astronomers to classify it, as most of the characteristics of a galaxy’s morphology — the arms of a spiral or the bar across the center — are only visible on its face. Still, the 45 000 light-year-long galaxy could be classified as an S0 type. These lenticular galaxies are an intermediate state in galaxy morphological classification schemes between true spiral and elliptical galaxies. They have a thin stellar disk and a bulge, like spiral galaxies, but in contrast to typical spiral galaxies they have used up most of the interstellar medium. Only a few new stars can be created out of the material that is left and the star formation rate is very low. Hence, the population of stars in S0 galaxies consists mainly of aging stars, very similar to the star population in elliptical galaxies. As S0 galaxies have only ill-defined spiral arms they are easily mistaken for elliptical galaxies if they are seen inclined face-on or edge-on as IC 335 here. And indeed, despite the morphological differences between S0 and elliptical class galaxies, they share some common characteristics, like typical sizes and spectral features. Both classes are also deemed "early-type" galaxies, because they are evolving passively. However, while elliptical galaxies may be passively evolving when we observe them, they have usually had violent interactions with other galaxies in their past. In contrast, S0 galaxies are either aging and fading spiral galaxies, which never had any interactions with other galaxies, or they are the aging result of a single merger between two spiral galaxies in the past. The exact nature of these galaxies is still a matter of debate. Credit: ESA/Hubble and NASA

Hubble Finds a Lenticular Galaxy Standing Out in the Crowd

NASA Image and Video Library

2017-12-08

A lone source shines out brightly from the dark expanse of deep space, glowing softly against a picturesque backdrop of distant stars and colorful galaxies. Captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), this scene shows PGC 83677, a lenticular galaxy — a galaxy type that sits between the more familiar elliptical and spiral varieties. It reveals both the relatively calm outskirts and intriguing core of PGC 83677. Here, studies have uncovered signs of a monstrous black hole that is spewing out high-energy X-rays and ultraviolet light. Credit: NASA/ESA/Hubble; acknowledgements: Judy Schmidt (Geckzilla) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Accounting for Cosmic Variance in Studies of Gravitationally Lensed High-redshift Galaxies in the Hubble Frontier Field Clusters

NASA Astrophysics Data System (ADS)

Robertson, Brant E.; Ellis, Richard S.; Dunlop, James S.; McLure, Ross J.; Stark, Dan P.; McLeod, Derek

2014-12-01

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this Letter, we demonstrate that there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high-redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ~35% at redshift z ~ 7 to >~ 65% at z ~ 10. Previous studies of high-redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint-end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.

GAIA: A WINDOW TO LARGE-SCALE MOTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nusser, Adi; Branchini, Enzo; Davis, Marc, E-mail: adi@physics.technion.ac.il, E-mail: branchin@fis.uniroma3.it, E-mail: mdavis@berkeley.edu

2012-08-10

Using redshifts as a proxy for galaxy distances, estimates of the two-dimensional (2D) transverse peculiar velocities of distant galaxies could be obtained from future measurements of proper motions. We provide the mathematical framework for analyzing 2D transverse motions and show that they offer several advantages over traditional probes of large-scale motions. They are completely independent of any intrinsic relations between galaxy properties; hence, they are essentially free of selection biases. They are free from homogeneous and inhomogeneous Malmquist biases that typically plague distance indicator catalogs. They provide additional information to traditional probes that yield line-of-sight peculiar velocities only. Further, becausemore » of their 2D nature, fundamental questions regarding vorticity of large-scale flows can be addressed. Gaia, for example, is expected to provide proper motions of at least bright galaxies with high central surface brightness, making proper motions a likely contender for traditional probes based on current and future distance indicator measurements.« less

The Swift GRB Host Galaxy Legacy Survey

NASA Astrophysics Data System (ADS)

Perley, Daniel

2015-08-01

I will describe the Swift Host Galaxy Legacy Survey (SHOALS), a comprehensive multiwavelength program to characterize the demographics of the GRB host population and its redshift evolution from z=0 to z=7. Using unbiased selection criteria we have designated a subset of 119 Swift gamma-ray bursts which are now being targeted with intensive observational follow-up. Deep Spitzer imaging of every field has already been obtained and analyzed, with major programs ongoing at Keck, GTC, Gemini, VLT, and Magellan to obtain complementary optical/NIR photometry and spectroscopy to enable full SED modeling and derivation of fundamental physical parameters such as mass, extinction, and star-formation rate. Using these data I will present an unbiased measurement of the GRB host-galaxy luminosity and mass distributions and their evolution with redshift, compare GRB hosts to other star-forming galaxy populations, and discuss implications for the nature of the GRB progenitor and the ability of GRBs to serve as tools for measuring and studying cosmic star-formation in the distant universe.

Are some BL Lacs artefacts of gravitational lensing?

PubMed

Ostriker, J P; Vietri, M

1990-03-01

WE suggested in 1985 that a significant fraction of BL Lacertae objects, a kind of lineless quasar, seen in nearby galaxies are in fact images, gravitationally lensed and substantially amplified by stars in the nearby galaxy, of background objects, optically violent variable (OVV) quasars at redshifts z > 1 (ref. 1). This hypothesis was made on the basis of certain general similarities between BL Lacs and O Ws, but for two recently observed BL Lacs(2,3) a strong case can be made that the accompanying elliptical galaxy is a foreground object. In addition, we argue that the distribution of BL Lac redshifts is hard to understand without gravitational lensing, unless we happen to be at a very local maximum of the spatial cosmic distribution of BL Lacs. Our analysis also indicates that the galaxies whose stars are likely to act as microlenses will be found in two peaks, one nearby, with redshift 0.05-0.10, and the other near the distant quasar.

Detection of X-ray emission from distant clusters of galaxies

NASA Technical Reports Server (NTRS)

Henry, J. P.; Branduardi, G.; Fabricant, D.; Feigelson, E.; Murray, S.; Tananbaum, H.; Briel, U.; Soltan, A.

1979-01-01

The paper reports the first extensive detection of X-ray emission from clusters of galaxies at cosmological distances. The properties of these objects are similar to those observed in objects at low redshifts. The 0.5-4.5 keV luminosities are in the range of less than 1 x 10 to the 43rd to 2 x 10 to the 45th ergs/s; the core radii are on the order of 0.5 Mpc; and Bautz-Morgan type I clusters are more luminous than types II or III. The observations are consistent with models assuming an evolving cluster potential and moderately efficient galaxy formation, but do not require them when observational selection is considered. X-ray observations of the 3C 295 cluster indicate that there is sufficient intergalactic medium to cause stripping of the cluster spirals, but the colors of these galaxies imply that they have not been stripped. A possible explanation of this discrepancy is discussed.

Measuring Star-Formation Rates of AGNs and QSOs using a new calibration from Polycyclic Aromatic Hydrocarbon Emission

NASA Astrophysics Data System (ADS)

Papovich, Casey

Understanding the coevolution of star-formation and supermassive black hole accretion is one of the key questions in galaxy formation theory. This relation is important for understanding why at present the mass in galaxy bulges (on scales of kpc) correlates so tightly with the mass of galaxy central supermassive blackholes (on scales of AU). Feedback from supermassive black hole accretion may also be responsible for heating or expelling cold gas from galaxies, shutting off the fuel for star-formation and additional black hole growth. Did bulges proceed the formation of black holes, or vice versa, or are they contemporaneous? Therefore, understanding the exact rates of star-formation and supermassive black hole growth, and how they evolve with time and galaxy mass has deep implications for how galaxies form. It has previously been nearly impossible to study simultaneously both star-formation and accretion onto supermassive black holes in galaxies because the emission from black hole accretion contaminates nearly all diagnostics of star-formation. The "standard" diagnostics for the star-formation rate (the emission from hydrogen, UV emission, midIR emission, far-IR emission, etc) are not suitable for measuring star-formation rates in galaxies with actively accreting supermassive blackholes. In this proposal, the researchers request NASA/ADP funding for an archival study using spectroscopy with the Spitzer Space Telescope to measure simultaneously the star-formation rate (SFR) and bolometric emission from accreting supermassive blackholes to understand the complex relation between both processes. The key to this study is that they will develop a new calibrator for SFRs in galaxies with active supermassive black holes based on the molecular emission from polycyclic aromatic hydrocarbons (PAHs), which emit strongly in the mid-IR (3 - 20 micron) and are very strong in spectra from the Spitzer Space Telescope. The PAH molecules exist near photo-dissociation regions, and they re-emit a large fraction of the ionization radiation from ongoing star formation. Preliminary work using archival spectra from Spitzer show that the PAH luminosity scales linearly with the SFR with smaller scatter than "gold standard" SFR tracers, such as the (dust corrected) hydrogen emission. The PAH emission becomes important because they are destroyed by the hard UV radiation in the vicinity of accreting supermassive blackholes. Therefore, this makes the PAH emission extremely powerful: it has the unique ability to measure SFRs in galaxies with active supermassive black holes, where every other SFR indicator is contaminated by emission from the supermassive black hole. This objectives for this proposal are to (1) provide a robust recalibration of the SFR from the mid-IR PAH emission features using a large sample of star-forming galaxies in the Spitzer archive; (2) demonstrate the utility of the PAHs to derive valid SFRs from JWST observations, using archival Spitzer spectroscopy for distant galaxies strongly lensed gravitationally; finally, using a large sample of galaxies with Spitzer spectroscopy spanning a large range of total luminosity and AGN activity (from pure starbursts to quasars) to (3) measure the distribution function of the luminosity of star-formation, AGN, and test how these vary with total luminosity and redshift. Theoretical models make strong predictions for this distribution function. Comparing the data to these predictions allows us to test these models directly.

Characterization of Extremely Lightweight Intrusion Detection (ELIDe) Power Utilization by Varying N-gram and Hash Length

DTIC Science & Technology

2015-09-01

changing the weight file used without redeploying the application. 2.1 Mobile Device We used the same Sprint-brand Galaxy S3 smart phone. The... Galaxy S3 line of smart phones varied in its technical specifications depending on the carrier. For reference, the Sprint-brand Galaxy S3 has the

Kinematics of luminous blue compact galaxies

NASA Astrophysics Data System (ADS)

Östlin, Göran; Amram, Philippe; Boulesteix, Jaques; Bergvall, Nils; Masegosa, Josefa; Márquez, Isabel

We present results from a Fabry-Perot study of the Hα velocity fields and morphologies of a sample of luminous blue compact galaxies. We estimate masses from photometry and kinematics and show that many of these BCGs are not rotationally supported. Mergers or strong interactions appear to be the triggering mechanism of the extreme starbursts seen in these galaxies.

Matching Supernovae to Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

One of the major challenges for modern supernova surveys is identifying the galaxy that hosted each explosion. Is there an accurate and efficient way to do this that avoids investing significant human resources?Why Identify Hosts?One problem in host galaxy identification. Here, the supernova lies between two galaxies but though the centroid of the galaxy on the right is closer in angular separation, this may be a distant background galaxy that is not actually near the supernova. [Gupta et al. 2016]Supernovae are a critical tool for making cosmological predictions that help us to understand our universe. But supernova cosmology relies on accurately identifying the properties of the supernovae including their redshifts. Since spectroscopic followup of supernova detections often isnt possible, we rely on observations of the supernova host galaxies to obtain redshifts.But how do we identify which galaxy hosted a supernova? This seems like a simple problem, but there are many complicating factors a seemingly nearby galaxy could be a distant background galaxy, for instance, or a supernovas host could be too faint to spot.The authors algorithm takes into account confusion, a measure of how likely the supernova is to be mismatched. In these illustrations of low (left) and high (right) confusion, the supernova is represented by a blue star, and the green circles represent possible host galaxies. [Gupta et al. 2016]Turning to AutomationBefore the era of large supernovae surveys, searching for host galaxies was done primarily by visual inspection. But current projects like the Dark Energy Surveys Supernova Program is finding supernovae by the thousands, and the upcoming Large Synoptic Survey Telescope will likely discover hundreds of thousands. Visual inspection will not be possible in the face of this volume of data so an accurate and efficient automated method is clearly needed!To this end, a team of scientists led by Ravi Gupta (Argonne National Laboratory) has recently developed a new automated algorithm for matching supernovae to their host galaxies. Their work builds on currently existing algorithms and makes use of information about the nearby galaxies, accounts for the uncertainty of the match, and even includes a machine learning component to improve the matching accuracy.Gupta and collaborators test their matching algorithm on catalogs of galaxies and simulated supernova events to quantify how well the algorithm is able to accurately recover the true hosts.Successful MatchingThe matching algorithms accuracy (purity) as a function of the true supernova-host separation, the supernova redshift, the true hosts brightness, and the true hosts size. [Gupta et al. 2016]The authors find that when the basic algorithm is run on catalog data, it matches supernovae to their hosts with 91% accuracy. Including the machine learning component, which is run after the initial matching algorithm, improves the accuracy of the matching to 97%.The encouraging results of this work which was intended as a proof of concept suggest that methods similar to this could prove very practical for tackling future survey data. And the method explored here has use beyond matching just supernovae to their host galaxies: it could also be applied to other extragalactic transients, such as gamma-ray bursts, tidal disruption events, or electromagnetic counterparts to gravitational-wave detections.CitationRavi R. Gupta et al 2016 AJ 152 154. doi:10.3847/0004-6256/152/6/154

Panchromatic observations of dwarf starburst galaxies: Infant super star clusters and a low-luminosity AGN

NASA Astrophysics Data System (ADS)

Reines, Amy Ellen

2011-01-01

Globular star clusters and supermassive black holes are fundamental components of today's massive galaxies, with origins dating back to the very early universe. Both globular clusters and the seeds of supermassive black holes are believed to have formed in the progenitors of modern massive galaxies, although the details are poorly understood. Direct observations of these low-mass, distant, and hence faint systems are unobtainable with current capabilities. However, gas-rich dwarf starburst galaxies in the local universe, analogous in many ways to protogalaxies at high-redshift, can provide critical insight into the early stages of galaxy evolution including the formation of globular clusters and massive black holes. This thesis presents a panchromatic study of nearby dwarf starburst galaxies harboring nascent globular clusters still embedded in their birth material. Infant clusters are identified via their production of thermal radio emission at centimeter wavelengths, which comes from dense gas ionized by young massive stars. By combining radio observations with complementary data at ultraviolet, optical and infrared wavelengths, we obtain a comprehensive view of massive clusters emerging from their gaseous and dusty birth cocoons. This thesis also presents the first example of a nearby dwarf starburst galaxy hosting an actively accreting massive central black hole. The black hole in this dwarf galaxy is unusual in that it is not associated with a bulge, a nuclear star cluster, or any other well-defined nucleus, likely reflecting an early phase of black hole and galaxy evolution that has not been previously observed.

Tracing the growth of Milky Way-like galaxies

NASA Image and Video Library

2013-11-15

This composite image shows examples of galaxies similar to our Milky Way at various stages of construction over a time span of 11 billion years. The galaxies are arranged according to time. Those on the left reside nearby; those at far right existed when the cosmos was about 2 billion years old. The bluish glow from young stars dominates the color of the galaxies on the right. The galaxies at left are redder from the glow of older stellar populations. Astronomers found the distant galaxies in two Hubble Space Telescope surveys: 3D-HST and the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, or CANDELS. The observations were made in visible and near-infrared light by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. The nearby galaxies were taken from the Sloan Digital Sky Survey. This image traces Milky Way-like galaxies over most of cosmic history, revealing how they evolve over time. Hubble's sharp vision resolved the galaxies' shapes, showing that their bulges and disks grew simultaneously. Credit: NASA, ESA, P. van Dokkum (Yale University), S. Patel (Leiden University), and the 3D-HST Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

An X-ray Luminous, Distant (z=0.78) Cluster of Galaxies

NASA Technical Reports Server (NTRS)

Donahue, Megan

2001-01-01

This granted funded ASCA studies of the most X-ray luminous clusters of galaxies in the Extended Medium Sensitivity Survey. These studies leveraged further observations with Chandra and sparked a new collaboration between the PI and John Carlstrom's Sunyaev-Zel'dovich team. The major scientific results due largely or in part from these observations: the first z=0.5-0.8 cluster temperature function, constraints on cluster evolution which showed definitively that the density of the universe divided by the critical density, Omega-m, could not be 1.0, constraints on cluster evolution limiting Omega_m to 0.2-0.5, independent of lambda, the first detections of intracluster iron in a z>0.6 cluster of galaxies. These results are independent of the supernova and cosmological microwave background results, and provide independent constraint on cosmological parameters.

Extreme emission-line galaxies out to z ~ 1 in zCOSMOS. I. Sample and characterization of global properties

NASA Astrophysics Data System (ADS)

Amorín, R.; Pérez-Montero, E.; Contini, T.; Vílchez, J. M.; Bolzonella, M.; Tasca, L. A. M.; Lamareille, F.; Zamorani, G.; Maier, C.; Carollo, C. M.; Kneib, J.-P.; Le Fèvre, O.; Lilly, S.; Mainieri, V.; Renzini, A.; Scodeggio, M.; Bardelli, S.; Bongiorno, A.; Caputi, K.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Franzetti, P.; Garilli, B.; Iovino, A.; Kampczyk, P.; Knobel, C.; Kovač, K.; Le Borgne, J.-F.; Le Brun, V.; Mignoli, M.; Pellò, R.; Peng, Y.; Presotto, V.; Ricciardelli, E.; Silverman, J. D.; Tanaka, M.; Tresse, L.; Vergani, D.; Zucca, E.

2015-06-01

Context. The study of large and representative samples of low-metallicity star-forming galaxies at different cosmic epochs is of great interest to the detailed understanding of the assembly history and evolution of low-mass galaxies. Aims: We present a thorough characterization of a large sample of 183 extreme emission-line galaxies (EELGs) at redshift 0.11 ≤ z ≤ 0.93 selected from the 20k zCOSMOS bright survey because of their unusually large emission line equivalent widths. Methods: We use multiwavelength COSMOS photometry, HST-ACS I-band imaging, and optical zCOSMOS spectroscopy to derive the main global properties of star-forming EELGs, such as sizes, stellar masses, star formation rates (SFR), and reliable oxygen abundances using both "direct" and "strong-line" methods. Results: The EELGs are extremely compact (r50 ~ 1.3 kpc), low-mass (M∗ ~ 107-1010 M⊙) galaxies forming stars at unusually high specific star formation rates (sSFR ≡ SFR/M⋆ up to 10-7 yr-1) compared to main sequence star-forming galaxies of the same stellar mass and redshift. At rest-frame UV wavelengths, the EELGs are luminous and show high surface brightness and include strong Lyα emitters, as revealed by GALEX spectroscopy. We show that zCOSMOS EELGs are high-ionization, low-metallicity systems, with median 12+log (O/H) = 8.16 ± 0.21 (0.2 Z⊙) including a handful of extremely metal-deficient (<0.1 Z⊙) EELGs. While ~80% of the EELGs show non-axisymmetric morphologies, including clumpy and cometary or tadpole galaxies, we find that ~29% of them show additional low-surface-brightness features, which strongly suggests recent or ongoing interactions. As star-forming dwarfs in the local Universe, EELGs are most often found in relative isolation. While only very few EELGs belong to compact groups, almost one third of them are found in spectroscopically confirmed loose pairs or triplets. Conclusions: The zCOSMOS EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building up a significant fraction of their present-day stellar mass in an ongoing, galaxy-wide starburst. Therefore, the EELGs constitute an ideal benchmark for comparison studies between low- and high-redshift low-mass star-forming galaxies. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A105

Mid-infrared luminous quasars in the GOODS-Herschel fields: a large population of heavily obscured, Compton-thick quasars at z ≈ 2

NASA Astrophysics Data System (ADS)

Del Moro, A.; Alexander, D. M.; Bauer, F. E.; Daddi, E.; Kocevski, D. D.; McIntosh, D. H.; Stanley, F.; Brandt, W. N.; Elbaz, D.; Harrison, C. M.; Luo, B.; Mullaney, J. R.; Xue, Y. Q.

2016-02-01

We present the infrared (IR) and X-ray properties of a sample of 33 mid-IR luminous quasars (νL6 μm ≥ 6 × 1044 erg s-1) at redshift z ≈ 1-3, identified through detailed spectral energy distribution analyses of distant star-forming galaxies, using the deepest IR data from Spitzer and Herschel in the GOODS-Herschel fields. The aim is to constrain the fraction of obscured, and Compton-thick (CT, NH > 1.5 × 1024 cm-2) quasars at the peak era of nuclear and star formation activities. Despite being very bright in the mid-IR band, ≈30 per cent of these quasars are not detected in the extremely deep 2 and 4 Ms Chandra X-ray data available in these fields. X-ray spectral analysis of the detected sources reveals that the majority (≈67 per cent) are obscured by column densities NH > 1022 cm-2; this fraction reaches ≈80 per cent when including the X-ray-undetected sources (9 out of 33), which are likely to be the most heavily obscured, CT quasars. We constrain the fraction of CT quasars in our sample to be ≈24-48 per cent, and their space density to be Φ = (6.7 ± 2.2) × 10-6 Mpc-3. From the investigation of the quasar host galaxies in terms of star formation rates (SFRs) and morphological distortions, as a sign of galaxy mergers/interactions, we do not find any direct relation between SFRs and quasar luminosity or X-ray obscuration. On the other hand, there is tentative evidence that the most heavily obscured quasars have, on average, more disturbed morphologies than the unobscured/moderately obscured quasar hosts, which preferentially live in undisturbed systems. However, the fraction of quasars with disturbed morphology amongst the whole sample is ≈40 per cent, suggesting that galaxy mergers are not the main fuelling mechanism of quasars at z ≈ 2.

European astronomers' successes with the Hubble Space Telescope*

NASA Astrophysics Data System (ADS)

1997-02-01

[Figure: Laguna Nebula] Their work spans all aspects of astronomy, from the planets to the most distant galaxies and quasars, and the following examples are just a few European highlights from Hubble's second phase, 1994-96. A scarcity of midget stars Stars less massive and fainter than the Sun are much numerous in the Milky Way Galaxy than the big bright stars that catch the eye. Guido De Marchi and Francesco Paresce of the European Southern Observatory as Garching, Germany, have counted them. With the wide-field WFPC2 camera, they have taken sample censuses within six globular clusters, which are large gatherings of stars orbiting independently in the Galaxy. In every case they find that the commonest stars have an output of light that is only one-hundredth of the Sun's. They are ten times more numerous than stars like the Sun. More significant for theories of the Universe is a scarcity of very faint stars. Some astronomers have suggested that vast numbers of such stars could account for the mysterious dark matter, which makes stars and galaxies move about more rapidly than expected from the mass of visible matter. But that would require an ever-growing count of objects at low brightnesses, and De Marchi and Paresce find the opposite to be the case -- the numbers diminish. There may be a minimum size below which Nature finds starmaking difficult. The few examples of very small stars seen so far by astronomers may be, not the heralds of a multitude of dark-matter stars, but rareties. Unchanging habits in starmaking Confirmation that very small stars are scarce comes from Gerry Gilmore of the Institute of Astronomy in Cambridge (UK). He leads a European team that analyses long-exposure images in the WFPC2 camera, obtained as a by-product when another instrument is examining a selected object. The result is an almost random sample of well-observed stars and galaxies. The most remarkable general conclusion is that the make-up of stellar populations never seems to vary. In dense or diffuse regions, in very young or very old agglomerations, in the Milky Way Galaxy or elsewhere, the relative numbers of stars of different masses are always roughly the same. Evidently Nature mass-produces quotas of large and small stars irrespective of circumstances. This discovery will assist astronomers in making sense of very distant and early galaxies. They can assume that the stars are of the most familiar kinds. Another surprise was spotted by Rebecca Elson in Gilmore's team, in long-exposure images of the giant galaxy M87, in the nearby Virgo cluster. It possesses globular clusters of very different ages. In the Milky Way and its similar spiral neighbour, the Andromeda galaxy, globular clusters contain the oldest stars. While M87 has ancient globular clusters too, some are different in colour and much younger. The theory is that they were manufactured during collisions of the galaxies that merged into M87, making it the egg-shaped giant seen today. If so, the absence of young globular clusters in the Milky Way may mean that our Galaxy has never suffered a major collision. Accidents in the galactic traffic Brighter than a million million suns, a quasar is the most powerful lamp in the Universe. Astronomers understand it to be powered by matter falling into a massive black hole in the heart of a galaxy. Mike Disney of the University of Wales, Cardiff, leads a European team that asks why some thousands of galaxies harbour quasars, in contrast to the billions that do not. In almost every case that he and his colleagues have investigated, using Hubble's WFPC2 camera at its highest resolution, they see the quasar's home galaxy involved in a collision with another galaxy. "It's my opinion that almost any galaxy can be a quasar," Disney says, "if only its central black hole gets enough to eat. In the galactic traffic accidents that Hubble reveals, we can visualize fresh supplies of stars and gas being driven into the black hole's clutches. My American opposite number, John Bahcall, prefers to stress those quasar hosts that look like undisturbed galaxies. But the important thing is that we have wonderfully clear pictures to argue about. Quasar theories were mostly pure speculation before we had Hubble." The history of the elements Astronomers at the Hamburger Sternwarte use the Faint Object Spectrograph to analyse ultraviolet light from distant quasars, which they also examine by visible light from the ground. They trace the origin, through cosmic time, of elements like carbon, silicon and iron, from which planets and living things can be built. On its way to Hubble, the quasar light passes through various intervening galaxies and gas clouds, like the skewer of a kebab. Each object visited absorbs some of the quasar light, depending on the local abundances of the elements. As they detect more and more objects, Dieter Reimers and his colleagues form an impression of galaxies building up their stocks of elements progressively through time, by the alchemy of successive generations of stars. Apart from primordial hydrogen the second lightest element, helium, has also been abundant since the origin of the Universe. The first major discovery after Hubble's last refurbishment came from Peter Jakobsen of ESA's Space Science Department at Noordwijk, who detected ionized helium in the remote Universe, by the light of a very distant quasar, 0302-003. That was in January 1994, and since then Jakobsen has looked for the ionized helium using other quasars. He now suspects that this helium is nearly all gathered in clumps, rather than scattered freely through intergalactic space. If so, it greatly increases the estimates of the total mass of ordinary matter in the Universe. Through a lens to the early Universe Natural lenses scattered through the cosmos reveal distant galaxies, and make an astronomical tool for Richard Ellis of the Institute of Astronomy, Cambridge (UK). The strong gravity of an intervening cluster of galaxies can bend the light from more distant objects, so magnifying and intensifying their images. In one spectacular case, cluster Abell 2218 creates in Hubble's WFPC2 camera more than a hundred images of galaxies lying beyond it. Without the magnifying effect of the cluster, many of these remote objects would be too faint to study in detail. Compared with man-made optics, the gravitational lenses are complex. They produce multiple images (as many as seven or more views of the same object) and they also smear the images into arcs. Team-member Jean-Paul Kneib, who is now at Toulouse, uses the distortions as a guide to distance. The more distorted the image, the farther off a galaxy is. The galaxies imaged by Abell 2218 are 5 to 8 billion light-years away, and Kneib's estimates have been confirmed by Tim Ebbels of Cambridge using the William Herschel Telescope located on the Spanish island of La Palma. Seen as they were early in the history of the Universe, the objects seem surprisingly similar to nearer and more mature galaxies. The cosmic scale Gustav Tammann of Basel and his collaborators use the Hubble Space Telescope to measure the Hubble Constant. Both are named after Edwin Hubble who discovered, almost 70 years ago, that the galaxies are spreading apart. The Hubble Constant is the rate of expansion -- and the most important number in cosmology, because it fixes the size and the maximum age of the observable Universe. Since the launch of the space telescope in 1990, two independent teams have tried to fix the constant but their answers disagree. A high expansion rate, which makes the Universe relatively young, is preferred by Wendy Freedman's team consisting largely of American astronomers. A lower value for Hubble's Constant, implying an older Universe, comes from a mainly European team led by the American astronomer Allan Sandage. Tammann belongs to the latter, "old Universe" camp and he is philosophical about the delay in reaching a consensus. "I've been waiting nearly 20 years for this result, and I expect the arguments will go on for a while longer," Gustav Tammann says. "In 1979 I asserted that a key task for the space telescope should be to use variable stars to fix the distances to nearby galaxies in which standard supernovae have been seen. Then the supernovae become candles lighting our way far out into the Universe. Well we've done it now, with stars in seven galaxies, and their supernovae give us wonderfully consistent answers. So we're in no mood to compromise, or to split the difference with Wendy Freedman's Hubble Constant. Time will tell us who is closer to the right answer." * Note to TV editors : A betacam tape on this subject is available from ESA Public Relations Office (Tel: 33(0)01.53.69.7155 Fax : 33(0)01.53.69.7690)

KSC-08pd2456

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, a technicians clean the radiator on the Wide Field Camera 3, or WFC3,that will be installed on NASA's Hubble Space Telescope. The radiator is the "outside" of WFC3 that will be exposed to space. It will expel heat out of Hubble and into space through black body radiation. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

KSC-08pd2460

NASA Image and Video Library

2008-08-18

CAPE CANAVERAL, Fla. – In the Payload Hazardous Servicing Facility at NASA's Kennedy Space Center, the Wide Field Camera 3, or WFC3, waits to be transferred to the Super Lightweight Interchangeable Carrier. WFC3 is part of the payload on space shuttle Atlantis' STS-125 mission for the fifth and final Hubble servicing flight to NASA's Hubble Space Telescope. The part shown here is the radiator, the "outside" of WFC3 that will be exposed to space and will expel heat out of Hubble and into space through black body radiation. As Hubble enters the last stage of its life, WFC3 will be Hubble's next evolutionary step, allowing Hubble to peer ever further into the mysteries of the cosmos. WFC3 will study a diverse range of objects and phenomena, from young and extremely distant galaxies, to much more nearby stellar systems, to objects within our very own solar system. WFC3 will take the place of Wide Field Planetary Camera 2, which astronauts will bring back to Earth aboard the shuttle. Launch of Atlantis is targeted at 1:34 a.m. EDT Oct. 8. Photo credit: NASA/Amanda Diller

Dynamical Models of Elliptical Galaxies in z = 0.5 Clusters. I. Data-Model Comparison and Evolution of Galaxy Rotation

NASA Astrophysics Data System (ADS)

van der Marel, Roeland P.; van Dokkum, Pieter G.

2007-10-01

We present spatially resolved stellar rotation velocity and velocity dispersion profiles from Keck/LRIS absorption-line spectra for 25 galaxies, mostly visually classified ellipticals, in three clusters at z~0.5. We interpret the kinematical data and HST photometry using oblate axisymmetric two-integral f(E,Lz) dynamical models based on the Jeans equations. This yields good fits, provided that the seeing and observational characteristics are carefully modeled. The fits yield for each galaxy the dynamical mass-to-light ratio (M/L) and a measure of the galaxy rotation rate. Paper II addresses the implied M/L evolution. Here we study the rotation-rate evolution by comparison to a sample of local elliptical galaxies of similar present-day luminosity. The brightest galaxies in the sample all rotate too slowly to account for their flattening, as is also observed at z=0. But the average rotation rate is higher at z~0.5 than locally. This may be due to a higher fraction of misclassified S0 galaxies (although this effect is insufficient to explain the observed strong evolution of the cluster S0 fraction with redshift). Alternatively, dry mergers between early-type galaxies may have decreased the average rotation rate over time. It is unclear whether such mergers are numerous enough in clusters to explain the observed trend quantitatively. Disk-disk mergers may affect the comparison through the so-called ``progenitor bias,'' but this cannot explain the direction of the observed rotation-rate evolution. Additional samples are needed to constrain possible environmental dependencies and cosmic variance in galaxy rotation rates. Either way, studies of the internal stellar dynamics of distant galaxies provide a valuable new approach for exploring galaxy evolution.

Obituary: Michael James Ledlow, 1964-2004

NASA Astrophysics Data System (ADS)

Puxley, Philip John; Grashuis, Randon M.

2004-12-01

Michael James Ledlow died on 5 June 2004 from a large, unsuspected brain tumor. Since 2000 he had been on the scientific staff of the Gemini Observatory in La Serena, Chile, initially as a Science Fellow and then as a tenure-track astronomer. Michael was born in Bartlesville, Oklahoma on 1 October 1964 to Jerry and Sharon Ledlow. He obtained his Bachelor Degree in astrophysics at the University of Oklahoma in 1987 and attended the University of New Mexico for his graduate work, obtaining his PhD while studying Galaxy Clusters under Frazer Owen in 1994. From 1995-1997 Michael held a postdoctoral position with Jack Burns at New Mexico State University where he used various astronomical facilities including the VLA and Apache Point Observatory to study distant galaxies. From 1998-2000 Michael rejoined the Physics and Astronomy Department at the University of New Mexico where he was a visiting professor until he moved on to Gemini. At the Gemini Observatory, Mike shared in the excitement, hard work and many long days and nights associated with bringing on-line a major new astronomical facility and its instrumentation. Following its commissioning he assisted visiting observers, supported and took data for many more remote users via the queue system, and for each he showed the same care and attention to detail evident in his own research to ensure that all got the best possible data. His research concentrated on the radio and optical properties of galaxy clusters, especially rich Abell clusters such as A2125, on luminous radio galaxies, including the detection of a powerful double radio source in the "wrong sort of galaxy," the spiral system 0313-192, and on EROs (extremely red objects), dusty galaxies barely detectable at optical wavelengths. Michael thoroughly enjoyed living in Chile and enthusiastically immersed himself in the culture of his surroundings. He and his family were actively involved with the International English Spanish Association in La Serena. He had a wide variety of interests including a wonderfully diverse taste in music and an exceptional talent for home brewing beer. Mike was one of those rare individuals, enthusiastic and driven by his work at the Observatory as well as by his personal research, and with the skills to deliver in both aspects. His devotion to the Observatory and to research was surpassed only by that for his family. He is survived by his wife Cheryl, their two children Alexandria ("Andrea") and Abigail ("Abi"), three stepdaughters Mandy, Memoree and Misty and his sister Lisa Gay Gilmore.

Berkeley Lab Scientists to Play Role in New Space Telescope

Science.gov Websites

circling distant suns, among other science aims. The Wide Field Infrared Survey Telescope (WFIRST) will Hubble Space Telescope's Wide Field Camera 3 infrared imager. A Hubble large-scale mapping survey of the survey of the M31 galaxy (shown here) required 432 "pointings" of its imager, while only two

Study of the Lynx-Cancer void galaxies. - V. The extremely isolated galaxy UGC 4722

NASA Astrophysics Data System (ADS)

Chengalur, J. N.; Pustilnik, S. A.; Makarov, D. I.; Perepelitsyna, Y. A.; Safonova, E. S.; Karachentsev, I. D.

2015-04-01

We present a detailed study of the extremely isolated Sdm galaxy UGC 4722 (MB = -17.4) located in the nearby Lynx-Cancer void. UGC 4722 is a member of the Catalogue of Isolated Galaxies, and has also been identified as one of the most isolated galaxies in the Local Supercluster. Optical images of the galaxy however show that it has a peculiar morphology with an elongated ˜14 kpc-long plume. New observations with the Russian 6-m telescope (BTA) and the Giant Metrewave Radio Telescope (GMRT) of the ionized and neutral gas in UGC 4722 reveal the second component responsible for the disturbed morphology of the system. This is a small, almost completely destroyed, very gas-rich dwarf (MB = -15.2, M(H I)/LB ˜ 4.3) We estimate the oxygen abundance for both galaxies to be 12 + log (O/H) ˜ 7.5-7.6 which is two to three times lower than what is expected from the luminosity-metallicity relation for similar galaxies in denser environments. The ugr colours of the plume derived from Sloan Digital Sky Survey (SDSS) images are consistent with a simple stellar population with a post starburst age of 0.45-0.5 Gyr. This system hence appears to be the first known case of a minor merger with a prominent tidal feature consisting of a young stellar population.

The Taxonomy of Blue Amorphous Galaxies. II. Structure and Evolution

NASA Astrophysics Data System (ADS)

Marlowe, Amanda T.; Meurer, Gerhardt R.; Heckman, Timothy M.

1999-09-01

Dwarf galaxies play an important role in our understanding of galaxy formation and evolution, and starbursts are believed to affect the structure and evolution of dwarf galaxies strongly. We have therefore embarked on a systematic study of 12 of the nearest dwarf galaxies thought to be undergoing bursts of star formation. These were selected primarily by their morphological type (blue ``amorphous'' galaxies). We show that these blue amorphous galaxies are not physically distinguishable from dwarfs selected as starbursting by other methods, such as blue compact dwarfs (BCDs) and H II galaxies. All these classes exhibit surface brightness profiles that are exponential in the outer regions (r>~1.5re) but often have a predominantly central blue excess, suggesting a young burst in an older, redder galaxy. Typically, the starbursting ``cores'' are young (~107-108 yr) events compared to the older (~109-1010 yr) underlying galaxy (the ``envelope''). The ratio of the core to envelope in blue light ranges from essentially zero to about 2. These starbursts are therefore modest events involving only a few percent of the stellar mass. The envelopes have surface brightnesses that are much higher than typical dwarf irregular (dI) galaxies, so it is unlikely that there is a straightforward evolutionary relation between typical dIs and dwarf starburst galaxies. Instead we suggest that amorphous galaxies may repeatedly cycle through starburst and quiescent phases, corresponding to the galaxies with strong and weak/absent cores, respectively. Once amorphous galaxies use up the available gas (either through star formation or galactic winds) so that star formation is shut off, the faded remnants would strongly resemble dwarf elliptical galaxies. However, in the current cosmological epoch, this is evidently a slow process that is the aftermath of a series of many weak, recurring bursts. Present-day dE's must have experienced more rapid and intense evolution than this in the distant past.

VEGAS: A VST Early-type GAlaxy Survey. II. Photometric study of giant ellipticals and their stellar halos

NASA Astrophysics Data System (ADS)

Spavone, Marilena; Capaccioli, Massimo; Napolitano, Nicola R.; Iodice, Enrichetta; Grado, Aniello; Limatola, Luca; Cooper, Andrew P.; Cantiello, Michele; Forbes, Duncan A.; Paolillo, Maurizio; Schipani, Pietro

2017-07-01

Observations of diffuse starlight in the outskirts of galaxies are thought to be a fundamental source of constraint on the cosmological context of galaxy assembly in the ΛCDM model. Such observations are not trivial because of the extreme faintness of such regions. In this work, we investigated the photometric properties of six massive early-type galaxies (ETGs) in the VEGAS sample (NGC 1399, NGC 3923, NGC 4365, NGC 4472, NGC 5044, and NGC 5846) out to extremely low surface brightness levels with the goal of characterizing the global structure of their light profiles for comparison to state-of-the-art galaxy formation models. We carried out deep and detailed photometric mapping of our ETG sample taking advantage of deep imaging with VST/OmegaCAM in the g and I bands. By fitting the light profiles, and comparing the results to simulations of elliptical galaxy assembly, we have identified signatures of a transition between relaxed and unrelaxed accreted components and can constrain the balance between in situ and accreted stars. The very good agreement of our results with predictions from theoretical simulations demonstrates that the full VEGAS sample of 100 ETGs will allow us to use the distribution of diffuse light as a robust statistical probe of the hierarchical assembly of massive galaxies.

An extremely young massive clump forming by gravitational collapse in a primordial galaxy.

PubMed

Zanella, A; Daddi, E; Le Floc'h, E; Bournaud, F; Gobat, R; Valentino, F; Strazzullo, V; Cibinel, A; Onodera, M; Perret, V; Renaud, F; Vignali, C

2015-05-07

When cosmic star formation history reaches a peak (at about redshift z ≈ 2), galaxies vigorously fed by cosmic reservoirs are dominated by gas and contain massive star-forming clumps, which are thought to form by violent gravitational instabilities in highly turbulent gas-rich disks. However, a clump formation event has not yet been observed, and it is debated whether clumps can survive energetic feedback from young stars, and afterwards migrate inwards to form galaxy bulges. Here we report the spatially resolved spectroscopy of a bright off-nuclear emission line region in a galaxy at z = 1.987. Although this region dominates star formation in the galaxy disk, its stellar continuum remains undetected in deep imaging, revealing an extremely young (less than ten million years old) massive clump, forming through the gravitational collapse of more than one billion solar masses of gas. Gas consumption in this young clump is more than tenfold faster than in the host galaxy, displaying high star-formation efficiency during this phase, in agreement with our hydrodynamic simulations. The frequency of older clumps with similar masses, coupled with our initial estimate of their formation rate (about 2.5 per billion years), supports long lifetimes (about 500 million years), favouring models in which clumps survive feedback and grow the bulges of present-day galaxies.

A class of compact dwarf galaxies from disruptive processes in galaxy clusters.

PubMed

Drinkwater, M J; Gregg, M D; Hilker, M; Bekki, K; Couch, W J; Ferguson, H C; Jones, J B; Phillipps, S

2003-05-29

Dwarf galaxies have attracted increased attention in recent years, because of their susceptibility to galaxy transformation processes within rich galaxy clusters. Direct evidence for these processes, however, has been difficult to obtain, with a small number of diffuse light trails and intra-cluster stars being the only signs of galaxy disruption. Furthermore, our current knowledge of dwarf galaxy populations may be very incomplete, because traditional galaxy surveys are insensitive to extremely diffuse or compact galaxies. Aware of these concerns, we recently undertook an all-object survey of the Fornax galaxy cluster. This revealed a new population of compact members, overlooked in previous conventional surveys. Here we demonstrate that these 'ultra-compact' dwarf galaxies are structurally and dynamically distinct from both globular star clusters and known types of dwarf galaxy, and thus represent a new class of dwarf galaxy. Our data are consistent with the interpretation that these are the remnant nuclei of disrupted dwarf galaxies, making them an easily observed tracer of galaxy disruption.

Galaxies Burn Bright Like High-Wattage Light Bulbs

NASA Image and Video Library

2012-08-29

NASA WISE has identified about 1,000 extremely obscured objects over the sky, as marked by the magenta symbols. These hot dust-obscured galaxies, or hot DOGs, are turning out to be among the most luminous.

Percolation technique for galaxy clustering

NASA Technical Reports Server (NTRS)

Klypin, Anatoly; Shandarin, Sergei F.

1993-01-01

We study percolation in mass and galaxy distributions obtained in 3D simulations of the CDM, C + HDM, and the power law (n = -1) models in the Omega = 1 universe. Percolation statistics is used here as a quantitative measure of the degree to which a mass or galaxy distribution is of a filamentary or cellular type. The very fast code used calculates the statistics of clusters along with the direct detection of percolation. We found that the two parameters mu(infinity), characterizing the size of the largest cluster, and mu-squared, characterizing the weighted mean size of all clusters excluding the largest one, are extremely useful for evaluating the percolation threshold. An advantage of using these parameters is their low sensitivity to boundary effects. We show that both the CDM and the C + HDM models are extremely filamentary both in mass and galaxy distribution. The percolation thresholds for the mass distributions are determined.

Rest-Frame Mid-Infrared Detection of an Extremely Luminous Lyman Break Galaxy with the Spitzer Infrared Spectrograph (IRS)

NASA Technical Reports Server (NTRS)

Teplitz, H. I.; Charmandaris, V.; Armus, L.; Appleton, P. N.; Houck, J. R.; Soifer, B. T.; Weedman, D.; Brandl, B. R.; vanCleve, J.; Grillmair, C.;

Two new confirmed massive relic galaxies: red nuggets in the present-day Universe

NASA Astrophysics Data System (ADS)

Ferré-Mateu, Anna; Trujillo, Ignacio; Martín-Navarro, Ignacio; Vazdekis, Alexandre; Mezcua, Mar; Balcells, Marc; Domínguez, Lilian

2017-05-01

We confirm two new local massive relic galaxies, I.e. untouched survivors of the early Universe massive population: Mrk 1216 and PGC 032873. Both show early and peaked formation events within very short time-scales (<1 Gyr) and thus old mean mass-weighted ages (˜13 Gyr). Their star formation histories remain virtually unchanged out to several effective radii, even when considering the steeper initial-mass-function values inferred out to ˜3 effective radii. Their morphologies, kinematics and density profiles are like those found in the z > 2 massive population, setting them apart from the typical z ˜ 0 massive early-type galaxies. We find that there seems to exist a degree of relic that is related to how far into the path, to become one of these typical z ˜ 0 massive galaxies, the compact relic has moved. This path is partly dictated by the environment the galaxy lives in. For galaxies in rich environments, such as the previously reported relic galaxy NGC 1277, the most extreme properties (e.g. sizes, short formation time-scales, larger supermassive black holes) are expected, while lower density environments will have galaxies with delayed and/or extended star formations, slightly larger sizes and not that extreme black hole masses. The confirmation of three relic galaxies up to a distance of 106 Mpc, implies a lower limit in the number density of these red nuggets in the local Universe of 6 × 10-7 Mpc3, which is within the theoretical expectations.

A DISTANT RADIO MINI-HALO IN THE PHOENIX GALAXY CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Weeren, R. J.; Andrade-Santos, F.; Forman, W. R.

We report the discovery of extended radio emission in the Phoenix cluster (SPT-CL J2344-4243, z = 0.596) with the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. The diffuse emission extends over a region of at least 400-500 kpc and surrounds the central radio source of the Brightest Cluster Galaxy, but does not appear to be directly associated with it. We classify the diffuse emission as a radio mini-halo, making it the currently most distant mini-halo known. Radio mini-halos have been explained by synchrotron emitting particles re-accelerated via turbulence, possibly induced by gas sloshing generated from a minor merger event. Chandra observationsmore » show a non-concentric X-ray surface brightness distribution, which is consistent with this sloshing interpretation. The mini-halo has a flux density of 17 ± 5 mJy, resulting in a 1.4 GHz radio power of (10.4 ± 3.5) × 10{sup 24} W Hz{sup –1}. The combined cluster emission, which includes the central compact radio source, is also detected in a shallow GMRT 156 MHz observation and together with the 610 MHz data we compute a spectral index of –0.84 ± 0.12 for the overall cluster radio emission. Given that mini-halos typically have steeper radio spectra than cluster radio galaxies, this spectral index should be taken as an upper limit for the mini-halo.« less

A Survey of Distant Clusters of Galaxies Selected by X-Rays

NASA Technical Reports Server (NTRS)

McNamara, Brian

1997-01-01

I will discuss the results of a new survey of X-ray selected, distant clusters of galaxies that has been undertaken by our group at.CfA (Vikhlinin, McNamara, Forman, Jones). We have analyzed the inner 17.5 arcminute region of roughly 650 ROSAT PSPC images of high latitude fields to compile a complete, flux-limited sample of clusters with a mean flux limit roughly 20 times more sensitive than the Einstein Medium Sensitivity Survey. The goal of our survey, which presently contains 233 extended X-ray sources, is to study cluster evolution over cosmological timescales. We have obtained optical images for nearly all of the faintest sources using the 1.2 m telescope of the Fred L. Whipple Observatory, and when including POSS images of the brighter sources, we have nearly completed the identification of all of the extended sources. Roughly 80% of the sources were identified as clusters of galaxies. We have measured redshifts for 42 clusters using the MMT, and including additional measurements from the literature, roughly 70 clusters in our catalog have spectroscopic redshifts. Using CCD photometry and spectroscopic redshifts, we have determined a magnitude-redshift relation which will allow redshifts of the remaining clusters in our sample to be determined photometrically to within a delta z over z of roughly ten percent. I will discuss the Log(N)-Log(S) relation for our sample and compare it to other determinations. In addition, I will discuss the evolution of core radii of clusters.

HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: LEO IV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, Joshua D.; McWilliam, Andrew; Thompson, Ian B.

2010-06-10

We present high-resolution Magellan/MIKE spectroscopy of the brightest star in the ultra-faint dwarf galaxy Leo IV. We measure an iron abundance of [Fe/H] = -3.2, adding to the rapidly growing sample of extremely metal-poor (EMP) stars being identified in Milky Way satellite galaxies. The star is enhanced in the {alpha} elements Mg, Ca, and Ti by {approx}0.3 dex, very similar to the typical Milky Way halo abundance pattern. All of the light and iron-peak elements follow the trends established by EMP halo stars, but the neutron-capture elements Ba and Sr are significantly underabundant. These results are quite similar to thosemore » found for stars in the ultra-faint dwarfs Ursa Major II, Coma Berenices, Booetes I, and Hercules, suggesting that the chemical evolution of the lowest-luminosity galaxies may be universal. The abundance pattern we observe is consistent with predictions for nucleosynthesis from a Population III supernova explosion. The extremely low metallicity of this star also supports the idea that a significant fraction ({approx}>10%) of the stars in the faintest dwarfs have metallicities below [Fe/H] = -3.0.« less

Discovery of a population of bulgeless galaxies with extremely red MID-IR colors: Obscured AGN activity in the low-mass regime?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satyapal, S.; Secrest, N. J.; McAlpine, W.

2014-04-01

In contrast to massive, bulge hosting galaxies, very few supermassive black holes (SMBHs) are known in either low-mass or bulgeless galaxies. Such a population could provide clues to the origins of SMBHs and to secular pathways for their growth. Using the all-sky Wide-field Infrared Survey Explorer (WISE ) survey, and bulge-to-disk decompositions from the Sloan Digital Sky Survey (SDSS) Data Release 7, we report the discovery of a population of local (z < 0.3) bulgeless disk galaxies with extremely red mid-infrared colors which are highly suggestive of a dominant active galactic nucleus (AGN), despite having no optical AGN signatures inmore » their SDSS spectra. Using various mid-infrared selection criteria from the literature, there are between 30 and over 300 bulgeless galaxies with possible AGNs. Other known scenarios that can heat the dust to high temperatures do not appear to explain the observed colors of this sample. If these galaxies are confirmed to host AGNs, this study will provide a breakthrough in characterizing the properties of SMBHs in the low bulge mass regime and in understanding their relation with their host galaxies. Mid-infrared selection identifies AGNs that dominate their host galaxy's emission and therefore reveal a different AGN population than that uncovered by optical studies. We find that the fraction of all galaxies identified as candidate AGNs by WISE is highest at lower stellar masses and drops dramatically in higher mass galaxies, in striking contrast to the findings from optical studies.« less

A low Lyman Continuum escape fraction of <10 per cent for extreme [O III] emitters in an overdensity at z ˜ 3.5

NASA Astrophysics Data System (ADS)

Naidu, Rohan P.; Forrest, Ben; Oesch, Pascal A.; Tran, Kim-Vy H.; Holden, Bradford P.

2018-07-01

Recent work has suggested that extreme [O III] emitting star-forming galaxies are important to reionization. Relatedly, [O III]/[O II] has been put forward as an indirect estimator of the Lyman Continuum (LyC) escape fraction (fesc) at z ≳ 4.5 when the opaque IGM renders LyC photons unobservable. Using deep archival U-band (VLT/VIMOS) imaging of a recently confirmed overdensity at z˜ 3.5, we calculate tight constraints on fesc for a sample (N = 73) dominated by extreme [O III] emitters. We find no LyC signal (f_esc^rel < 6.3^{+0.7}_{-0.7} per cent at 1σ) in a deep U-band stack of our sample (31.98 mag at 1σ). This constraint is in agreement with recent studies of star-forming galaxies spanning z ˜ 1-4 that have found very low average fesc. Despite the galaxies in our study having an estimated average rest-frame EW([O III]λ5007) ˜ 400 Å and [O III]/[O II] ˜ 4 from composite SED fitting, we find no LyC detection, which brings into question the potential of [O III]/[O II] as an effective probe of the LyC - a majority of LyC emitters have [O III]/[O II] > 3, but we establish here that [O III]/[O II] > 3 does not guarantee significant LyC leakage for a population. Since even extreme star-forming galaxies are unable to produce the f_esc˜ 10-15 per cent required by most theoretical calculations for star-forming galaxies to drive reionization, there must either be a rapid evolution of fesc between z˜ 3.5 and the epoch of reionization, or hitherto observationally unstudied sources [e.g. ultrafaint low-mass galaxies with log (M/M⊙) ˜ 7-8.5] must make an outsized contribution to reionization.

A Low Lyman Continuum Escape Fraction of <10% for Extreme [O III] Emitters in an Overdensity at z˜3.5

NASA Astrophysics Data System (ADS)

Naidu, Rohan P.; Forrest, Ben; Oesch, Pascal A.; Tran, Kim-Vy H.; Holden, Bradford P.

2018-04-01

Recent work has suggested extreme [O III] emitting star-forming galaxies are important to reionization. Relatedly, [O III]/[O II] has been put forward as an indirect estimator of the Lyman Continuum (LyC) escape fraction (fesc) at z ≳ 4.5 when the opaque IGM renders LyC photons unobservable. Using deep archival U-band (VLT/VIMOS) imaging of a recently confirmed overdensity at z ˜ 3.5 we calculate tight constraints on fesc for a sample (N=73) dominated by extreme [O III] emitters. We find no Lyman Continuum signal (f_{esc}^{rel} < 6.3^{+0.7}_{-0.7} % at 1σ) in a deep U-band stack of our sample (31.98 mag at 1σ). This constraint is in agreement with recent studies of star-forming galaxies spanning z ˜ 1 - 4 that have found very low average fesc. Despite the galaxies in our study having an estimated average rest-frame EW([O III]λ5007) ˜ 400Å and [O III]/[O II]˜4 from composite SED-fitting, we find no LyC detection, which brings into question the potential of [O III]/[O II] as an effective probe of the LyC-a majority of LyC emitters have [O III]/[O II]>3, but we establish here that [O III]/[O II]>3 does not guarantee significant LyC leakage for a population. Since even extreme star-forming galaxies are unable to produce the fesc ˜ 10 - 15% required by most theoretical calculations for star-forming galaxies to drive reionization, there must either be a rapid evolution of fesc between z ˜ 3.5 and the Epoch of Reionization, or hitherto observationally unstudied sources (e.g. ultra-faint low-mass galaxies with log (M/M⊙) ˜ 7 - 8.5) must make an outsized contribution to reionization.

THE ANATOMY OF AN EXTREME STARBURST WITHIN 1.3 Gyr OF THE BIG BANG REVEALED BY ALMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carilli, C. L.; Riechers, D.; Walter, F.

We present further analysis of the [C II] 158 {mu}m fine structure line and thermal dust continuum emission from the archetype extreme starburst/active galactic nucleus (AGN) group of galaxies in the early universe, BRI 1202-0725 at z = 4.7, using the Atacama Large Millimeter Array. The group has long been noted for having a closely separated (26 kpc in projection) FIR-hyperluminous quasar host galaxy and an optically obscured submillimeter galaxy (SMG). A short ALMA test observation reveals a rich laboratory for the study of the myriad processes involved in clustered massive galaxy formation in the early universe. Strong [C II]more » emission from the SMG and the quasar have been reported earlier by Wagg et al. based on these observations. In this paper, we examine in more detail the imaging results from the ALMA observations, including velocity channel images, position-velocity plots, and line moment images. We present detections of [C II] emission from two Ly{alpha}-selected galaxies in the group, demonstrating the relative ease with which ALMA can detect the [C II] emission from lower star formation rate galaxies at high redshift. Imaging of the [C II] emission shows a clear velocity gradient across the SMG, possibly indicating rotation or a more complex dynamical system on a scale {approx}10 kpc. There is evidence in the quasar spectrum and images for a possible outflow toward the southwest, as well as more extended emission (a {sup b}ridge{sup )}, between the quasar and the SMG, although the latter could simply be emission from Ly{alpha}-1 blending with that of the quasar at the limited spatial resolution of the current observations. These results provide an unprecedented view of a major merger of gas-rich galaxies driving extreme starbursts and AGN accretion during the formation of massive galaxies and supermassive black holes within 1.3 Gyr of the big bang.« less

THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE 'GREEN PEA' GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaskot, A. E.; Oey, M. S.

2013-04-01

Although Lyman-continuum (LyC) radiation from star-forming galaxies likely drove the reionization of the universe, observations of star-forming galaxies at low redshift generally indicate low LyC escape fractions. However, the extreme [O III]/[O II] ratios of the z = 0.1-0.3 Green Pea galaxies may be due to high escape fractions of ionizing radiation. To analyze the LyC optical depths and ionizing sources of these rare, compact starbursts, we compare nebular photoionization and stellar population models with observed emission lines in the Peas' Sloan Digital Sky Survey (SDSS) spectra. We focus on the six most extreme Green Peas, the galaxies with themore » highest [O III]/[O II] ratios and the best candidates for escaping ionizing radiation. The Balmer line equivalent widths and He I {lambda}3819 emission in the extreme Peas support young ages of 3-5 Myr, and He II {lambda}4686 emission in five extreme Peas signals the presence of hard ionizing sources. Ionization by active galactic nuclei or high-mass X-ray binaries is inconsistent with the Peas' line ratios and ages. Although stacked spectra reveal no Wolf-Rayet (WR) features, we tentatively detect WR features in the SDSS spectra of three extreme Peas. Based on the Peas' ages and line ratios, we find that WR stars, chemically homogeneous O stars, or shocks could produce the observed He II emission. If hot stars are responsible, then the Peas' optical depths are ambiguous. However, accounting for emission from shocks lowers the inferred optical depth and suggests that the Peas may be optically thin. The Peas' ages likely optimize the escape of LyC radiation; they are old enough for supernovae and stellar winds to reshape the interstellar medium, but young enough to possess large numbers of UV-luminous O or WR stars.« less

Nebular Line Emission and Stellar Mass of Bright z 8 Galaxies "Super-Eights"

NASA Astrophysics Data System (ADS)

Holwerda, Benne; Bouwens, Rychard; Trenti, Michele; Oesch, Pascal; Labbe, Ivo; Smit, Renske; Roberts-Borsani, Guido; Bernard, Stephanie; Bridge, Joanna

2018-05-01

Searches for the Lyman-alpha emission from the very first galaxies ionizing the Universe have proved to be extremely difficult with limited success beyond z 7 (<3% detections). However, a search of all CANDELS yielded four bright z 8 sources with associated strong Lyman-alpha lines, despite the Universe expected to be 70% neutral at this time. The key to their selection is an extremely red IRAC color ([3.6]-[4.5]> 0.5, Roberts-Borsani+ 2016), indicative of very strong nebular line emission. Do such extreme line emitting galaxies produce most of the photons to reionize the Universe? We propose to expand the sample of bright z 8 galaxies with reliable IRAC colors with seven more Y-band dropouts found with HST and confirmed through HST/Spitzer. The Spitzer observations will test how many of bright z 8 galaxies are IRAC-red and measure both their stellar mass and [OIII]+Hbeta line strength. Together with Keck/VLT spectroscopy, they will address these questions: I) Do all luminous z 8 galaxies show such red IRAC colors ([OIII] emission / hard spectra)? II) Is luminosity or a red IRAC color the dominant predictor for Lyman-alpha emission? III) Or are these sources found along exceptionally transparent sightlines into the early Universe? With 11 bright z 8 sources along different lines-of-sight, all prime targets for JWST, we will aim to determine which of the considered factors (luminosity, color, sight-line) drives the high Lyman-alpha prevalence (100%) and insight into the sources reionizing the Universe.

Molecular Gas in Obscured and Extremely Red Quasars at z ˜ 2.5

NASA Astrophysics Data System (ADS)

Alexandroff, Rachael; Zakamska, Nadia; Hamann, Fred; Greene, Jenny; Rahman, Mubdi

2018-01-01

Quasar feedback is a key element of modern galaxy evolution theory. During powerful episodes of feedback, quasar-driven winds are suspected of removing large amounts of molecular gas from the host galaxy, thus limiting supplies for star formation and ultimately curtailing the maximum mass of galaxies. Here we present Karl A. Jansky Very Large Array (VLA) observations of the CO(1-0) transition in 11 powerful obscured and extremely red quasars (ERQs) at z~2.5. Previous observations have shown that several of these targets display signatures of powerful quasar-driven winds in their ionized gas. Molecular emission is not detected in a single object, whether kinematically disturbed due to a quasar wind or in equilibrium with the host galaxy and neither is molecular gas detected in a combined stack of all objects (equivalent to an exposure time of over 10 hours with the VLA). This observation is in contrast with the previous suggestions that such objects should occupy gas-rich, extremely star-forming galaxies. Possible explanations include a paucity of molecular gas or an excess of high- excitation molecular gas, both of which could be the results of quasar feedback. In the radio continuum, we detect an average point-like (< 5 kpc) emission with luminosity νLν[33 GHz]=2.2 x 1042 erg s-1, consistent with optically-thin (α ≈ -1.0) synchrotron with some possible contribution from thermal free-free emission. The continuum radio emission of these radio-intermediate objects may be a bi-product of radiatively driven winds or may be due to weak jets confined to the host galaxy.

First Results from the UT1 Science Verification Programme

NASA Astrophysics Data System (ADS)

1998-11-01

Performance verification is a step which has regularly been employed in space missions to assess and qualify the scientific capabilities of an instrument. Within this framework, it was the goal of the Science Verification program to submit the VLT Unit Telescope No. 1 (UT1) to the scrutiny that can only be achieved in an actual attempt to produce scientifically valuable results. To this end, an attractive and diversified set of observations were planned in advance to be executed at the VLT. These Science Verification observations at VLT UT1 took place as planned in the period from August 17 to September 1, 1998, cf. the September issue of the ESO Messenger ( No. 93, p. 1 ) and ESO PR 12/98 for all details. Although the meteorological conditions on Paranal were definitely below average, the telescope worked with spectacular efficiency and performance throughout the entire period, and very valuable data were gathered. After completion of all observations, the Science Verification Team started to prepare all of the datasets for the public release that took place on October 2, 1998. The data related to the Hubble Deep Field South (now extensively observed by the Hubble Space Telescope) were made public world-wide, while the release of other data was restricted to ESO member states. With this public release ESO intended to achieve two specific goals: offer to the scientific community an early opportunity to work on valuable VLT data, and in the meantime submit the VLT to the widest possible scrutiny. With the public release, many scientists started to analyse scientifically the VLT data, and the following few examples of research programmes are meant to give a sample of the work that has been carried out on the Science Verification data during the past two months. They represent typical investigations that will be carried out in the future with the VLT. Many of these will be directed towards the distant universe, in order to gather insight on the formation and evolution of galaxies, galaxy clusters, and large scale structure. Others will concentrate on more nearby objects, including stars and nebulae in the Milky Way galaxy, and some will attempt to study our own solar system. The following six research programmes were presented at the Press Conference that took place at the ESO Headquarters in Garching (Germany) today. Deep Galaxy Counts and Photometric Redshifts in the HDF-S NIC3 Field The goal of this programme was to verify the capability of the VLT by obtaining the deepest possible ground-based images and using multicolour information to derive the redshifts (and hence the distances) of the faintest galaxies. The space distribution, luminosity and colour of these extreme objects may provide crucial information on the initial phases of the evolution of the universe. The method is known as photometric redshift determination . The VLT Test Camera was used to collect CCD images for a total of 16.6 hours in five spectral filters (U, B, V, R and I) in the so-called HDF-S NIC3 field. This is a small area (about 1 arcmin square) of the southern sky where very deep observations in the infrared bands J, H and K (1.1, 1.6 and 2.2µm, respectively) have been obtained by the Hubble Space Telescope (HST). The observations were combined and analyzed by a team of astronomers at ESO and the Observatory of Rome (Italy). Galaxies were detected in the field down to magnitude ~ 27-28. In most colours, the planned limiting values of the fluxes were successfully reached. ESO PR Photo 48a/98 ESO PR Photo 48a/98 [Preview - JPEG: 800 x 856 pix - 144k] [High-Res - JPEG: 3000 x 3210 pix - 728k] PR Photo 48a/98 shows some examples of photometric redshift determination for faint galaxies in the HDF-S NIC3 field. The filled points are the fluxes measured in the five colors observed with the VLT Test Camera (U, B, V, R and I) and in the infrared H spectral band with the NICMOS instrument on the Hubble Space Telescope. The curves constitute the best fit to the points obtained from a library of more than 400,000 synthetic spectra of galaxies at various redshifts (Fontana et al., in preparation). For most of these very faint sources, it is not possible to collect enough photons to measure the recession velocity (the redshift) by spectroscopy, even with an 8-m telescope. The redshifts and the main galaxy properties are then determined by comparing the colour observations with synthetic spectra (see PR Photo 48a/98 ). This has been done for more than one hundred galaxies in the field brighter than magnitude 26.5. Around 20 are found to be at redshifts larger than 2. The brighter ones are excellent candidates for future detailed studies with the UT1 instruments FORS1 and ISAAC. The scientists involved in this study are: Sandro D'Odorico, Richard Hook, Alvio Renzini, Piero Rosati, Rodolfo Viezzer (ESO) and Adriano Fontana, Emanuele Giallongo, Francesco Poli (Rome Observatory, Italy). A Gravitational Einstein Ring Because the gravitational pull of matter bends the path of light rays, astronomical objects - stars, galaxies and galaxy clusters - can act like lenses, which magnify and severely distort the images of galaxies behind them, producing weird pictures as in a hall of mirrors. In the most extreme case, where the foreground lensing galaxy and the background galaxy are perfectly lined up, the image of the background galaxy is stretched into a ring. Such an image is known as an Einstein ring , because the correct formula for the bending of light was first described by the famous phycisist Albert Einstein . ESO PR Photo 48b/98 ESO PR Photo 48b/98 [Preview - JPEG: 800 x 1106 pix - 952k] [High-Res - JPEG: 3000 x 4148 pix - 5.4Mb] ESO PR Photo 48c/98 ESO PR Photo 48c/98 [Preview - JPEG: 800 x 977 pix - 272k] [High-Res - JPEG: 3000 x 3664 pix - 1.4Mb] PR Photo 48b/98 (left) shows a new, true colour image of an Einstein ring (upper centre of photo), first discovered at ESO in 1995. The ring, which is the stretched image of a galaxy far out in the Universe, stands out clearly in green, and the red galaxy inside the ring is the lens. The discovery image was very faint, but this new picture, taken with the VLT during the Science Verification Programme allows a much clearer view of the ring because of the great light-gathering capacity of the telescope and, not least, because of the superb image quality. In Photo 48c/98 (right), four images illustrate the deduced model of the lensing effect. In the upper left, the observed ring has been enlarged and the image of the lensing galaxy removed by image processing. Below it is a model of the gravitational field (potential) around this galaxy along with the "true" image of the background galaxy shown. At the lower right is the resulting gravitationally magnified and distorted image of the background galaxy, which to the upper right has been de-sharpened to the same image quality as the observed image. The similarity between the two is most convincing. The picture shows a new, true colour image of an Einstein ring, first discovered at ESO in 1995. The ring, which is the stretched image of a galaxy far out in the Universe, stands out clearly in green, and the red galaxy inside the ring is the lens. The discovery image was very faint, but this new picture, taken with the VLT during the Science Verification Programme allows a much clearer view of the ring because of the great light-gathering capacity the telescope and, not least, because of the superb image quality. Gravitational lensing provides a very useful tool with which to study the Universe. As "weighing scales", it provides a measure of the mass within the lensing body, and as a "magnifying glass", it allows us to see details in objects which would otherwise be beyond the reach of current telescopes. This new detailed picture has allowed a much more accurate measurement of the mass of the lensing galaxy, revealing the presence of vast quantities of "unseen" matter, five times more than if just the light from the galaxy is taken into account. This additional material represents some of the Universe's dark matter . The gravitational lens action is also magnifying the background object by a factor of ten, providing an unparalleled view of this very distant galaxy which is in a stage of active star-formation. The scientists involved in this study are : Palle Møller (ESO), Stephen J. Warren (Blackett Laboratory, Imperial College, UK), Paul C. Hewett (Institute of Astronomy, Cambridge, UK) and Geraint F. Lewis (Dept. of Physics and Astronomy, University of Victoria, Canada). An Extremely Red Galaxy One of the main goals of modern cosmology is to understand when and how the galaxies formed. In the very last years, many high-redshift (i.e. very distant) galaxies have been found, suggesting that some galaxies were already assembled, when the Universe was much younger than now. None of these high-redshift galaxies have ever been found to be a bona-fide red elliptical galaxy . The VLT, however, with its very good capabilities for infrared observations, is an ideal instrument to investigate when and how the red elliptical galaxies formed. The VLT Science Verification images have provided unique multicolour information about an extremely red galaxy that was originally (Treu et al., 1998, A&A Letters, Vol. 340, p. 10) identified on the Hubble Deep Field South (HDF-S) Test Image. This galaxy is shown in PR Photo 48d/98 that is an enlargment from ESO PR Photo 35b/98. It was detected on Near-IR images and also on images obtained in the optical part of the spectrum, at the very faint limit of magnitude B ~ 29 in the blue. However, this galaxy has not been detected in the near-ultraviolet band. ESO PR Photo 48d/98 ESO PR Photo 48d/98 [Preview - JPEG: 800 x 594 pix - 264k] [High-Res - JPEG: 3000 x 2229 pix - 1.8Mb] ESO PR Photo 48e/98 ESO PR Photo 48e/98 [Preview - JPEG: 800 x 942 pix - 96k] [High-Res - JPEG: 3000 x 3533 pix - 576k] PR Photo 48d/98 (left) shows the very red galaxy (at the arrow) in the Hubble Deep Field South , discussed here. Photo 48e/98 (right) is the spectrum of a typical elliptical galaxy, redshifted to z = 1.8 and compared with the brightness of the galaxy in different wavebands (crosses), as measured during the VLT SV programme and the Hubble Deep Field South Test Program (the cross to the right). The arrow indicates the upper limit by the VLT SV in the ultraviolet band. It can be seen that these observations are fully consistent with the object being an old, elliptical galaxy at the high redshift of z=1.8 , i.e. at an epoch, when the Universe was much younger than now. The new ISAAC instrument at VLT UT1 will be able to obtain an infrared spectrum of this galaxy and thus to affirm or refute this provisional conclusion. The colours measured at the VLT and on the HST Test Image are very well matched by those of an old elliptical galaxy at redshift z ~ 1.8 ; see Photo 48e/98 . All the available evidence is thus consistent with this object being an elliptical galaxy with the highest-known redshift for this galaxy type. A preliminary analysis of Hubble Deep Field South data, just released, seems to support this hypothesis. If these conclusions are confirmed by direct measurement of its spectrum, this galaxy must already have been "old" (i.e. significantly evolved) when the Universe had an age of only about one fifth of its present value. A spectroscopic confirmation is still outstanding, but is now possible with the ISAAC instrument at VLT UT1. A positive result would demonstrate that elliptical galaxies can form very early in the history of the Universe. The scientists involved in this study are: Massimo Stiavelli, Tommaso Treu (also Scuola Normale Superiore, Italy), Stefano Casertano, Mark Dickinson, Henry Ferguson, Andrew Fruchter, Crystal Martin (STSci, Baltimore, USA), Piero Rosati and Rodolfo Viezzer (ESO), Marcella Carollo (Johns Hopkins University, Baltimore, USA) and Henry Tieplitz (NASA, Goddard Space Flight Center, Greenbelt, USA). Lyman-alpha Companions and Extended Nebulosity around a Quasar at Redshift z=2.2 In current theories of galaxy formation, luminous galaxies we see to-day were built up through repeated merging of smaller protogalactic clumps. Quasars, prodigious sources pouring out 100 to 1000 times as much light as an entire galaxy, have been used as markers of galaxy formation activity and have guided astronomers in their hunting of primeval galaxies and large-scale structures at high redshift. A supermassive black-hole, swallowing stars, gas and dust, is thought to be the engine powering a quasar and the interaction of the galaxy hosting the black-hole with neighboring galaxies is expected to play a key role in "feeding the monster". At intermediate redshift, a large fraction of radio-loud quasars and radio galaxies inhabit rich clusters of galaxies, whereas radio-quiet quasars are rarely found in very rich environments. Furthermore, tidal interaction between quasars and their nearby companions is also the favoured explanation for the presence of large gaseous nebulosities associated with radio-loud quasars and radio galaxies. At high redshift, searches for Lyman-alpha quasar companions and emission-line nebulosities show strong similarities with those seen at lower redshift, although the detection rate is lower. ESO PR Photo 48f/98 ESO PR Photo 48f/98 [Preview - JPEG: 800 x 977 pix - 184k] [High-Res - JPEG: 3000 x 3662 pix - 1.1Mb] ESO PR Photo 48g/98 ESO PR Photo 48g/98 [Preview - JPEG: 800 x 966 pix - 328k] [High-Res - JPEG: 3000 x 3621 pix - 1.8Mb] PR Photo 48f/98 (left) is a false-colour reproduction of a B-band image of the field around the radio-weak quasar J2233-606 in the Hubble Deep Field South (HDF-S) . Photo 48g/98 (right) represents emission from the same direction at a wavelength that corresponds to Lyman-alpha emission at the redshift ( z = 2.2 ) of the quasar. Three Lyman-alpha candidate companions are indicated with arrows. Note also the extended nebulosity around the quasar. A search for Lyman-alpha companions to the radio-weak quasar J2233-606 in the Hubble Deep Field South (HDF-S) was conducted during the VLT UT1 SV programme in a small field of 1.2 x 1.3 arcmin 2 , centered on the quasar. Candidate Lyman-alpha companions were identified by subtracting a broad-band B (blue) image, that traces the galaxy stellar populations, from a narrow-band image, spectrally centered on the redshifted, narrow Lyman-alpha emission line of the quasar ( z = 2.2 ). Three Lyman-alpha candidate companions were discovered at angular distances of 15 to 23 arcsec, or 200 to 300 kpc (650,000 to 1,000,000 light-years) at the distance corresponding to the quasar redshift. The emission lines are very strong, relative to the continuum emission of the galaxies - this could be a consequence of the strong ionizing radiation field of the quasar. These companions to the quasar may trace a large-scale structure which would extend over larger distances beyond the observed, small field. Even more striking is the presence of a very extended nebulosity whose size (120 kpc x 160 kpc) and Lyman-alpha luminosity (3 x 10 44 erg/cm 2 /s) are among the largest observed around radio galaxies and radio-loud quasars, but rarely seen around a radio-weak quasar. Tidal interaction between the northern, very nearby companion and the quasar is clearly present: the companion is embedded in the quasar nebulosity, most of its gas has been stripped and lies in a tail westwards of the galaxy. The scientists involved in this study are: Jacqueline Bergeron (ESO), Stefano Cristiani, Stephane Arnouts, Gianni Fasano (Padova, Italy) and Patrick Petitjean (Institut d'Astrophysique, Paris, France). Very Distant Galaxy Clusters During the past years, it has become possible to detect and subsequently study progressively more distant clusters of galaxies. For this research programme, UT1 Science Verification data were used, in combination with data obtained with the SOFI instrument at the ESO New Technology Telescope (NTT) at La Silla, to confirm the existence of two very distant galaxy clusters at redshift z ~ 1 , that had originally been detected in the ESO Imaging Survey. This redshift corresponds to an epoch when the age of the Universe was only two-thirds of the present. ESO PR Photo 48h/98 ESO PR Photo 48h/98 [Preview - JPEG: 800 x 917 pix - 896k] [High-Res - JPEG: 3000 x 3438 pix - 6.0Mb] PR Photo 48h/98 (left) is a colour composite that shows the now confirmed cluster EIS0046-2930 . The image has been produced by combining the V (green-yellow), R (red) and I (Near-IR) exposures with the Test Camera obtained during the VLT-UT1 Science Verification. The yellow-orange galaxies are the cluster members and the bluer objects are galaxies belonging to the general field population. The cluster center is at the location of the largest (yellow-orange) cluster galaxy to the left of the center of the image. The field measures 90 x 90 arcsec. This was achieved by the detection of a spatial excess density of galaxies, with measured colour equal to that of elliptical galaxies at this redshift, as established by counts in the respective sky areas. The field of one these clusters is shown in PR Photo 48h/98 . These new data show that the VLT will most certainly play a major role in the studies of the cluster galaxy population in such distant systems. This will contribute to shed important new light on the evolution of galaxies. Furthermore, the VLT clearly has the potential to identify and confirm the reality of many more such clusters and thereby to increase considerably the number of known objects. This will be important in order to determine more accurate values of the basic cosmological constants, and thus for our understanding of the evolution of the Universe as a whole. The presentation was made by Lisbeth Fogh Olsen (Copenhagen Observatory, Denmark, and ESO) on behalf of the scientists involved in this study. Icy Planets in the Outer Solar System Observations with large optical telescopes during the past years have begun to cast more light on the still very little known, distant icy planets in the outer solar system. Until November 1998, about 70 of these have been discovered outside the orbit of Neptune (between 30 and 50 AU, or 4,500 to 7,500 million km, from the Sun). They are accordingly referred to as Trans-Neptunian Objects (TNOs) . Those found so far are believed to represent the "tip of the iceberg" of a large population of such objects belonging to the so-called Kuiper Belt . This is a roughly disk-shaped region between about 50 and 120 AU (about 7,500 to 18,000 million km) from the Sun, in which remnant bodies from the formation of the solar system are thought to be present. From their measured brightness and the distance, it is found that most known TNOs have diameters of the order of a few hundred kilometres. About half of those known move in elongated Pluto-like orbits, the others move somewhat further out in stable, circular orbits. During the two-week Science Verification programme, approximately 200 minutes were spent on a small observing programme aimed at obtaining images of some TNOs in different wavebands (B, V, R and I). Since this programme was primarily designed as a back-up to be executed during less favourable atmospheric conditions, some of the observations could not be used. However, images of three faint TNOs were recorded during an excellent series of 1-10 min exposures. From these data, it was possible to measure quite accurate magnitudes (and thus approximate sizes) and to determine their colours. One of them, 1996 TL66, was among the bluest TNOs ever observed. It is believed that this is because its surface has undergone recent transformation, possibly due to collisions with other objects or the breaking-off of small pieces from the surface, in both cases revealing "fresh" layers below. The combination of all available exposures made it possible to look for faint and tenous atmospheres around these TNOs, but none were found. These results show that it is possible, with little effort and even under quite unfavourable observing conditions, to obtain valuable information with the VLT about icy objects in the outer solar system. Of even greater interest will be future spectroscopic observations with FORS and ISAAC that will allow to study the surface composition in some detail, with the potential of providing direct information about (nearly?) pristine material from the early phases of the solar system. The scientists involved in this study are: Olivier Hainaut, Hermann Boehnhardt, Catherine Delahodde and Richard West (ESO) and Karen Meech (Institute of Astronomy, Hawaii, USA). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Mining the Sloan Digital Sky Survey to trace the M-sigma correlation below 106 solar masses

NASA Astrophysics Data System (ADS)

Barth, A. J.; Greene, J. E.; Ho, L. C.

2004-05-01

Do dwarf galaxies and late-type spirals host central black holes with masses below 106 M⊙? Stellar-dynamical detections of black holes with such low masses are only possible for the very nearest galaxies, but in more distant objects the presence of a black hole can still be inferred if its accretion luminosity can be detected. NGC 4395 and POX 52 are two examples of Seyfert galaxies with black hole masses well below 106 M⊙, but very little is known about the demographics of such objects. We have searched the Sloan DR1 archives to identify Seyfert galaxies that are likely to have black hole masses below 106 M⊙, using the luminosity-radius relation and the broad-line widths to derive virial mass estimates for the black holes (Greene & Ho 2004). To examine the host galaxy properties, we have begun a program to measure their stellar velocity dispersions using the ESI spectrograph at Keck. Here we present preliminary results from this project, including 12 newly identified Seyfert galaxies having stellar velocity dispersions below 70 km s-1. The masses and velocity dispersions of these objects are consistent with an extrapolation of the local M--σ relation to masses below 106 M⊙.