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Sample records for spiral galaxy hubble

  1. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

  2. Hubble Sees Galaxies Spiraling around Leo

    NASA Image and Video Library

    2017-09-27

    Shown here is a spiral galaxy known as NGC 3455, which lies some 65 million light-years away from us in the constellation of Leo (the Lion). Galaxies are classified into different types according to their structure and appearance. This classification system is known as the Hubble Sequence, named after its creator Edwin Hubble. In this image released 14, April, 2014, NGC 3455 is known as a type SB galaxy — a barred spiral. Barred spiral galaxies account for approximately two thirds of all spirals. Galaxies of this type appear to have a bar of stars slicing through the bulge of stars at their center. The SB classification is further sub-divided by the appearance of a galaxy's pinwheeling spiral arms; SBa types have more tightly wound arms, whereas SBc types have looser ones. SBb types, such as NGC 3455, lie in between. NGC 3455 is part of a pair of galaxies — its partner, NGC 3454, lies out of frame. This cosmic duo belong to a group known as the NGC 3370 group, which is in turn one of the Leo II groups, a large collection of galaxies scattered some 30 million light-years to the right of the Virgo cluster. This image is from Hubble's Advanced Camera for Surveys. Credit: ESA/Hubble & NASA, Acknowledgement: Nick Rose 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

  3. Hubble Peers at the Heart of a Spiral Galaxy

    NASA Image and Video Library

    2017-09-27

    This new Hubble image is centered on NGC 5793, a spiral galaxy over 150 million light-years away in the constellation of Libra. This galaxy has two particularly striking features: a beautiful dust lane and an intensely bright center — much brighter than that of our own galaxy, or indeed those of most spiral galaxies we observe. NGC 5793 is a Seyfert galaxy. These galaxies have incredibly luminous centers that are thought to be caused by hungry supermassive black holes — black holes that can be billions of times the size of the sun — that pull in and devour gas and dust from their surroundings. This galaxy is of great interest to astronomers for many reasons. For one, it appears to house objects known as masers. Whereas lasers emit visible light, masers emit microwave radiation. The term "masers" comes from the acronym Microwave Amplification by Stimulated Emission of Radiation. Maser emission is caused by particles that absorb energy from their surroundings and then re-emit this in the microwave part of the spectrum. Naturally occurring masers, like those observed in NGC 5793, can tell us a lot about their environment; we see these kinds of masers in areas where stars are forming. In NGC 5793 there are also intense mega-masers, which are thousands of times more luminous than the sun. Credit: NASA, ESA, and E. Perlman (Florida Institute of Technology) 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

  4. The radio luminosity function of spiral galaxies - Correlations with aggregation and Hubble type

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.; Trinchieri, G.

    1981-04-01

    The Radio Luminosity Function of spiral galaxies is derived from the Arecibo observations of UGC galaxies at 2380 MHz. It is found that the average radio power and the optical luminosity are linearly correlated (αL1) and that, at any given radio power, the probability for a spiral galaxy to become a radio source scales with the optical luminosity as L1.3. Both results confirm the analysis of Hummel (1980, b) who studied with the Westerbork radio telescope (WSRT) the 1415 MHz continuum emission from nearby spiral galaxies. It is also attempted to correlate the radio emission from spiral galaxies with their detailed Hubble type and cluster membership. A weak evidence is found that early type galaxies and cluster members are slightly deficient in radio emission with respect to late type or isolated galaxies, particularly among the optically brightest objects.

  5. THE SPIRAL GALAXY M100 AS SEEN WITH THE HUBBLE'S IMPROVED VISION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the grand design spiral galaxy M100 obtained with the second generation Wide Field and Planetary Camera (WFPC-2), newly installed in the Hubble Space Telescope. Though the galaxy lies several tens of millions of light-years away, modified optics incorporated within the WFPC-2 allow Hubble to view M100 with a level of clarity and sensitivity previously possible only for the very few nearby galaxies that compose our ``Local Group.'' Just as one does not learn about the diversity of mankind by conversing only with your next door neighbor, astronomers must study many galaxies in a host of different environments if they are to come to understand how our own galaxy, our star, and our earth came to be. By expanding the region of the universe that can be studied in such detail a thousand fold, the WFPC-2 will help the Hubble Space Telescope to fulfill this mission. One of the greatest gains of the high resolution provided by Hubble is the ability to resolve individual stars in other galaxies. The new camera not only allows astronomers to separate stars which would have been blurred together at the resolution available from the ground, but also allows astronomers to accurately measure the light from very faint stars. The quantitative study of compositions, ages, temperatures, and other properties of stars and gas in other galaxies will provide important clues about how galaxies form and evolve. In addition, the WFPC-2 will allow the Hubble Space Telescope to be used to attack one of the most fundamental questions in science: the age and scale of the universe. Astronomers have many ``yardsticks'' for measuring the scale of the universe, but lack a good knowledge of how long these yardsticks really are. M100 is a member of the Virgo Cluster of galaxies. By allowing astronomers to resolve and measure individual stars in the Virgo Cluster -- in particular a special type of star called Cepheid variables, which have well known absolute brightnesses -- HST observations

  6. An Atlas of Hubble Space Telescope Spectra and Images of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hughes, M. A.; Alonso-Herrero, A.; Axon, D.; Scarlata, C.; Atkinson, J.; Batcheldor, D.; Binney, J.; Capetti, A.; Carollo, C. M.; Dressel, L.; Gerssen, J.; Macchetto, D.; Maciejewski, W.; Marconi, A.; Merrifield, M.; Ruiz, M.; Sparks, W.; Stiavelli, M.; Tsvetanov, Z.; van der Marel, R.

    2003-08-01

    We have observed 54 nearby spiral galaxies with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to obtain optical long-slit spectra of nuclear gas disks and STIS optical (~R band) images of the central 5''×5'' of the galaxies. These spectra are being used to determine the velocity field of nuclear disks and hence to detect the presence of central massive black holes. Here we present the spectra for the successful observations. Dust obscuration can be significant at optical wavelengths, and so we also combine the STIS images with archival Near-Infrared Camera and Multi-Object Spectrometer H-band images to produce color maps to investigate the morphology of gas and dust in the central regions. We find a great variety in the different morphologies, from smooth distributions to well-defined nuclear spirals and dust lanes. Based on observations 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 NAS5-26555.

  7. Hubble Sees Spiral Bridge of Young Stars Between Two Ancient Galaxies

    NASA Image and Video Library

    2017-09-27

    NASA's Hubble Space Telescope has photographed the dense galaxy cluster SDSS J1531+3414 in the northern constellation Corona Borealis. Made up primarily of giant elliptical galaxies with a few spirals and irregular galaxies thrown in for good measure, the cluster's powerful gravity warps the image of background galaxies into blue streaks and arcs. At the center of the bull's-eye of blue, gravitationally lensed filaments lies a pair of elliptical galaxies that are also exhibiting some interesting features. A 100,000-light-year-long structure that looks like a string of pearls twisted into a corkscrew shape winds around the cores of the two massive galaxies. The "pearls" are superclusters of blazing, blue-white, newly born stars. These super star clusters are evenly spaced along the chain at separations of 3,000 light-years from one another. Read more: 1.usa.gov/1ztQvL9 Credit: NASA/ESA 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

  8. Hubble Space Telescope Imaging of the Circumnuclear Environments of the CfA Seyfert Galaxies: Nuclear Spirals and Fueling

    NASA Technical Reports Server (NTRS)

    Pogge, Richard W.; Martini, Paul

    2002-01-01

    We present archival Hubble Space Telescope (HST) images of the nuclear regions of 43 of the 46 Seyfert galaxies found in the volume limited,spectroscopically complete CfA Redshift Survey sample. Using an improved method of image contrast enhancement, we created detailed high-quality " structure maps " that allow us to study the distributions of dust, star clusters, and emission-line gas in the circumnuclear regions (100-1000 pc scales) and in the associated host galaxy. Essentially all of these Seyfert galaxies have circumnuclear dust structures with morphologies ranging from grand-design two-armed spirals to chaotic dusty disks. In most Seyfert galaxies there is a clear physical connection between the nuclear dust spirals on hundreds of parsec scales and large-scale bars and spiral arms in the host galaxies proper. These connections are particularly striking in the interacting and barred galaxies. Such structures are predicted by numerical simulations of gas flows in barred and interacting galaxies and may be related to the fueling of active galactic nuclei by matter inflow from the host galaxy disks. We see no significant differences in the circumnuclear dust morphologies of Seyfert 1s and 2s, and very few Seyfert 2 nuclei are obscured by large-scale dust structures in the host galaxies. If Sevfert 2s are obscured Sevfert Is, then the obscuration must occur on smaller scales than those probed by HST.

  9. Barred Spiral Galaxy

    NASA Image and Video Library

    2017-09-27

    Barred Spiral Galaxy NGC 1300 Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: P. Knezek (WIYN) The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: www.nasa.gov/mission_pages/hubble/main/index.html

  10. HUBBLE SERVES UP A GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    What may first appear as a sunny side up egg is actually NASA Hubble Space Telescope's face-on snapshot of the small spiral galaxy NGC 7742. But NGC 7742 is not a run-of-the-mill spiral galaxy. In fact, this spiral is known to be a Seyfert 2 active galaxy, a type of galaxy that is probably powered by a black hole residing in its core. The core of NGC 7742 is the large yellow 'yolk' in the center of the image. The lumpy, thick ring around this core is an area of active starbirth. The ring is about 3,000 light-years from the core. Tightly wound spiral arms also are faintly visible. Surrounding the inner ring is a wispy band of material, which is probably the remains of a once very active stellar breeding ground. Credit: Hubble Heritage Team (AURA/STScI/NASA)

  11. Hubble Sees Spiral in Serpens

    NASA Image and Video Library

    2017-09-27

    This new NASA/ESA Hubble Space Telescope image shows a beautiful spiral galaxy known as PGC 54493, located in the constellation of Serpens (The Serpent). This galaxy is part of a galaxy cluster that has been studied by astronomers exploring an intriguing phenomenon known as weak gravitational lensing. This effect, caused by the uneven distribution of matter (including dark matter) throughout the Universe, has been explored via surveys such as the Hubble Medium Deep Survey. Dark matter is one of the great mysteries in cosmology. It behaves very differently from ordinary matter as it does not emit or absorb light or other forms of electromagnetic energy — hence the term "dark." Even though we cannot observe dark matter directly, we know it exists. One prominent piece of evidence for the existence of this mysterious matter is known as the "galaxy rotation problem." Galaxies rotate at such speeds and in such a way that ordinary matter alone — the stuff we see — would not be able to hold them together. The amount of mass that is "missing" visibly is dark matter, which is thought to make up some 27 percent of the total contents of the Universe, with dark energy and normal matter making up the rest. PGC 55493 has been studied in connection with an effect known as cosmic shearing. This is a weak gravitational lensing effect that creates tiny distortions in images of distant galaxies. European Space Agency ESA/Hubble & NASA, Acknowledgement: Judy Schmidt 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

  12. Seeing Galaxies through Thick and Thin. III. Hubble Space Telescope Imaging of the Dust in Backlit Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Keel, William C.; White, Raymond E., III

    2001-03-01

    We present analysis of Wide Field Planetary Camera 2 imaging of two spiral galaxies partially backlit by elliptical or S0 systems in the pairs AM 1316-241 and AM 0500-620, as well as the (probably spiral) foreground system in NGC 1275. Images in B and I are used to determine the reddening curve of dust in these systems. The foreground spiral component of AM 1316-241 shows dust strongly concentrated in discrete arms, with a reddening law very close to the Milky Way mean [R=AV/E(B-V)=3.4+/-0.2]. The dust distribution is scale-free between about 100 pc and the arm dimension, about 8 kpc. The foreground spiral in AM 0500-620 shows dust concentrated in arms and interarm spurs, with measurable interarm extinction as well. In this case, although the dust properties are less well-determined than in AM 1316-241, we find evidence for a steeper extinction law than the Milky Way mean (formally, R~2.5+/-0.4, with substantial variation depending on data quality in each region). The shape of the reddening law suggests that at least in AM 1316-241 we have resolved most of the dust structure. In AM 0500-620 it is less clear that we have resolved most of the dust structure, since the errors are larger. In AM 0500-620, the slope of the perimeter-scale relation (associated with fractal analysis) steepens systematically when going from regions of low to high extinction. A perimeter-smoothing length test for scale-free (fractal) behavior in AM 1316-241 shows a logarithmic slope typically -0.4 on 100-1000 pc scales. However, we cannot determine a unique fractal dimension from the defining area-perimeter relation, so the projected dust distribution is best defined as fractal-like. For scales above 2-4 pixels (120-250 pc), the box-counting estimate yields a fractal dimension close to 1.4, but the perimeter-area relation yields a dimension of 0.7 on large scales and inconsistent results for small scales, so that the distribution shows only some aspects of a fractal nature. In neither galaxy

  13. Backwards Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected.

    A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue.

    Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise.

    NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy.

    Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus.

    The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State

  14. HUBBLE'S INFRARED GALAXY GALLERY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have used the NASA Hubble Space Telescope to produce an infrared 'photo essay' of spiral galaxies. By penetrating the dust clouds swirling around the centers of these galaxies, the telescope's infrared vision is offering fresh views of star birth. These six images, taken with the Near Infrared Camera and Multi-Object Spectrometer, showcase different views of spiral galaxies, from a face-on image of an entire galaxy to a close-up of a core. The top row shows spirals at diverse angles, from face-on, (left); to slightly tilted, (center); to edge-on, (right). The bottom row shows close-ups of the hubs of three galaxies. In these images, red corresponds to glowing hydrogen, the raw material for star birth. The red knots outlining the curving spiral arms in NGC 5653 and NGC 3593, for example, pinpoint rich star-forming regions where the surrounding hydrogen gas is heated by intense ultraviolet radiation from young, massive stars. In visible light, many of these regions can be hidden from view by the clouds of gas and dust in which they were born. The glowing hydrogen found inside the cores of these galaxies, as in NGC 6946, may be due to star birth; radiation from active galactic nuclei (AGN), which are powered by massive black holes; or a combination of both. White is light from middle-age stars. Clusters of stars appear as white dots, as in NGC 2903. The galaxy cores are mostly white because of their dense concentration of stars. The dark material seen in these images is dust. These galaxies are part of a Hubble census of about 100 spiral galaxies. Astronomers at Space Telescope Science Institute took these images to fill gaps in the scheduling of a campaign using the NICMOS-3 camera. The data were non-proprietary, and were made available to the entire astronomical community. Filters: Three filters were used: red, blue, and green. Red represents emission at the Paschen Alpha line (light from glowing hydrogen) at a wavelength of 1.87 microns. Blue shows the

  15. HUBBLE'S INFRARED GALAXY GALLERY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have used the NASA Hubble Space Telescope to produce an infrared 'photo essay' of spiral galaxies. By penetrating the dust clouds swirling around the centers of these galaxies, the telescope's infrared vision is offering fresh views of star birth. These six images, taken with the Near Infrared Camera and Multi-Object Spectrometer, showcase different views of spiral galaxies, from a face-on image of an entire galaxy to a close-up of a core. The top row shows spirals at diverse angles, from face-on, (left); to slightly tilted, (center); to edge-on, (right). The bottom row shows close-ups of the hubs of three galaxies. In these images, red corresponds to glowing hydrogen, the raw material for star birth. The red knots outlining the curving spiral arms in NGC 5653 and NGC 3593, for example, pinpoint rich star-forming regions where the surrounding hydrogen gas is heated by intense ultraviolet radiation from young, massive stars. In visible light, many of these regions can be hidden from view by the clouds of gas and dust in which they were born. The glowing hydrogen found inside the cores of these galaxies, as in NGC 6946, may be due to star birth; radiation from active galactic nuclei (AGN), which are powered by massive black holes; or a combination of both. White is light from middle-age stars. Clusters of stars appear as white dots, as in NGC 2903. The galaxy cores are mostly white because of their dense concentration of stars. The dark material seen in these images is dust. These galaxies are part of a Hubble census of about 100 spiral galaxies. Astronomers at Space Telescope Science Institute took these images to fill gaps in the scheduling of a campaign using the NICMOS-3 camera. The data were non-proprietary, and were made available to the entire astronomical community. Filters: Three filters were used: red, blue, and green. Red represents emission at the Paschen Alpha line (light from glowing hydrogen) at a wavelength of 1.87 microns. Blue shows the

  16. spiral galaxy M83

    NASA Image and Video Library

    2017-09-27

    JANUARY 9, 2014: The vibrant magentas and blues in this Hubble image of the barred spiral galaxy M83 reveal that the galaxy is ablaze with star formation. The galactic panorama unveils a tapestry of the drama of stellar birth and death. The galaxy, also known as the Southern Pinwheel, lies 15 million light-years away in the constellation Hydra. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgement: W. Blair (STScI/Johns Hopkins University) and R. O'Connell (University of Virginia) 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

  17. Collision Between Two Spiral Galaxies

    NASA Image and Video Library

    2008-04-24

    NGC 6050/IC 1179 Arp 272 is a remarkable collision between two spiral galaxies, NGC 6050 and IC 1179, and is part of the Hercules Galaxy Cluster, located in the constellation of Hercules. This image is from NASA Hubble Space Telescope.

  18. NGC 6090 - a Pair of Spiral Galaxies

    NASA Image and Video Library

    2008-04-24

    NGC 6090 is a beautiful pair of spiral galaxies with an overlapping central region and two long tidal tails formed from material ripped out of the galaxies by gravitational interaction. This image is from NASA Hubble Space Telescope.

  19. HUBBLE SPACE TELESCOPE PIXEL ANALYSIS OF THE INTERACTING FACE-ON SPIRAL GALAXY NGC 5194 (M51A)

    SciTech Connect

    Lee, Joon Hyeop; Kim, Sang Chul; Park, Hong Soo; Ree, Chang Hee; Kyeong, Jaemann; Chung, Jiwon E-mail: sckim@kasi.re.kr E-mail: chr@kasi.re.kr E-mail: jiwon@kasi.re.kr

    2011-10-10

    A pixel analysis is carried out on the interacting face-on spiral galaxy NGC 5194 (M51A), using the Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) images in the F435W, F555W, and F814W (BVI) bands. After 4 x 4 binning of the HST/ACS images to secure a sufficient signal-to-noise ratio for each pixel, we derive several quantities describing the pixel color-magnitude diagram (pCMD) of NGC 5194: blue/red color cut, red pixel sequence parameters, blue pixel sequence parameters, and blue-to-red pixel ratio. The red sequence pixels are mostly older than 1 Gyr, while the blue sequence pixels are mostly younger than 1 Gyr, in their luminosity-weighted mean stellar ages. The color variation in the red pixel sequence from V = 20 mag arcsec{sup -2} to V = 17 mag arcsec{sup -2} corresponds to a metallicity variation of {Delta}[Fe/H] {approx}2 or an optical depth variation of {Delta}{tau}{sub V} {approx} 4 by dust, but the actual sequence is thought to originate from the combination of those two effects. At V < 20 mag arcsec{sup -2}, the color variation in the blue pixel sequence corresponds to an age variation from 5 Myr to 300 Myr under the assumption of solar metallicity and {tau}{sub V} = 1. To investigate the spatial distributions of stellar populations, we divide pixel stellar populations using the pixel color-color diagram and population synthesis models. As a result, we find that the pixel population distributions across the spiral arms agree with a compressing process by spiral density waves: dense dust {yields} newly formed stars. The tidal interaction between NGC 5194 and NGC 5195 appears to enhance the star formation at the tidal bridge connecting the two galaxies. We find that the pixels corresponding to the central active galactic nucleus (AGN) area of NGC 5194 show a tight sequence at the bright-end of the pCMD, which are in the region of R {approx} 100 pc and may be a photometric indicator of AGN properties.

  20. Rebuilding Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    2005-01-01

    of distant galaxies at various redshifts taken by the Hubble Space Telescope. The central panel displays the star formation rate as a function of time. The numbers coincide with the numbers shown on the images. The story revealed by these observations is in agreement with the so-called "hierarchical merging of galaxies" scenario, present in the literature since about 20 years. According to this model, small galaxies merge to build larger ones. As François Hammer however points out: "In the current scenario, it was usually assumed that galaxy merging almost ceased 8,000 million years ago. Our complete set of observations show that this is far from being the case. In the following 4,000 million years, galaxies still merged to form the large spirals we observe in the local Universe." To account for all these properties, the astronomers thus devised a new galaxy formation scenario, comprising three major phases: a merger event, a compact galaxy phase and a "growth of the disc" phase (see PR Photo 02b/05). Because of the unique aspects of this scenario, where big galaxies get first disrupted by a major collision to be born again later as a present-day spiral galaxy, the astronomers rather logically dubbed their evolutionary sequence, the "spiral galaxy rebuilding". Although being at odds with standard views which assert that galaxy mergers produce elliptical galaxies instead of spiral ones, the astronomers stress that their scenario is consistent with the observed fractions of the different types of galaxies and can account for all the observations. The new scenario can indeed account for the formation of about three quarters of the present-day spiral galaxies, those with massive central bulge. It would apply for example to the Andromeda Galaxy but not to our own Milky way. It seems that our Galaxy somehow escaped major collisions in the last thousands of million years. Further observations, in particular with the FLAMES instrument on the VLT, will show if spiral

  1. THE SPIRAL GALAXY M100

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the grand design of spiral galaxy M100 obtained with NASA's Hubble Space Telescope resolves individual stars within the majestic spiral arms. (These stars typically appeared blurred together when viewed with ground-based telescopes.) Hubble has the ability to resolve individual stars in other galaxies and measure accurately the light from very faint stars. This makes space telescope invaluable for identifying a rare class of pulsating stars, called Cepheid Variable stars embedded within M100's spiral arms. Cepheids are reliable cosmic distance mileposts. The interval it takes for the Cepheid to complete one pulsation is a direct indication of the stars's intrinsic brightness. This value can be used to make a precise measurement of the galaxy's distance, which turns out to be 56 million light-years. M100 (100th object in the Messier catalog of non-stellar objects) is a majestic face-on spiral galaxy. It is a rotating system of gas and stars, similar to our own galaxy, the Milky Way. Hubble routinely can view M100 with a level of clarity and sensitivity previously possible only for the very few nearby galaxies that compose our 'Local Group.'' M100 is a member of the huge Virgo cluster of an estimated 2,500 galaxies. The galaxy can be seen by amateur astronomers as a faint, pinwheel-shaped object in the spring constellation Coma Berenices. Technical Information: The Hubble Space Telescope image was taken on December 31, 1993 with the Wide Field Planetary Camera 2 (WFPC 2). This color picture is a composite of several images taken in different colors of light. Blue corresponds to regions containing hot newborn stars. The Wide Field and Planetary Camera 2 was developed by the Jet Propulsion Laboratory (JPL) and managed by the Goddard Space Flight Center for NASA's Office of Space Science. Credit: J. Trauger, JPL and NASA

  2. THE SPIRAL GALAXY M100

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the grand design of spiral galaxy M100 obtained with NASA's Hubble Space Telescope resolves individual stars within the majestic spiral arms. (These stars typically appeared blurred together when viewed with ground-based telescopes.) Hubble has the ability to resolve individual stars in other galaxies and measure accurately the light from very faint stars. This makes space telescope invaluable for identifying a rare class of pulsating stars, called Cepheid Variable stars embedded within M100's spiral arms. Cepheids are reliable cosmic distance mileposts. The interval it takes for the Cepheid to complete one pulsation is a direct indication of the stars's intrinsic brightness. This value can be used to make a precise measurement of the galaxy's distance, which turns out to be 56 million light-years. M100 (100th object in the Messier catalog of non-stellar objects) is a majestic face-on spiral galaxy. It is a rotating system of gas and stars, similar to our own galaxy, the Milky Way. Hubble routinely can view M100 with a level of clarity and sensitivity previously possible only for the very few nearby galaxies that compose our 'Local Group.'' M100 is a member of the huge Virgo cluster of an estimated 2,500 galaxies. The galaxy can be seen by amateur astronomers as a faint, pinwheel-shaped object in the spring constellation Coma Berenices. Technical Information: The Hubble Space Telescope image was taken on December 31, 1993 with the Wide Field Planetary Camera 2 (WFPC 2). This color picture is a composite of several images taken in different colors of light. Blue corresponds to regions containing hot newborn stars. The Wide Field and Planetary Camera 2 was developed by the Jet Propulsion Laboratory (JPL) and managed by the Goddard Space Flight Center for NASA's Office of Space Science. Credit: J. Trauger, JPL and NASA

  3. Satellites of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1993-01-01

    We present a survey of satellites around a homogeneous set of late-type spirals with luminosity similar to that of the Milky Way. On average, we find fewer than 1.5 satellites per primary, but we argue that we can treat the survey as an ensemble and so derive the properties of the halo of a 'typical' isolated spiral. The projected density profile of the ensemble falls off approximately as 1/r. Within 50 kpc the azimuthal distribution of satellites shows some evidence for the 'Holmberg effect', an excess near the minor axis of the primary; however, at larger projected distances, the distribution appears isotropic. There is a weak but significant correlation between the size of a satellite and its distance from its primary, as expected if satellites are tidally truncated. Neither Hubble type nor spectral characteristics correlate with apparent separation. The ensemble of satellites appears to be rotating at about 30 km/s in the same direction as the galactic disk. Satellites on prograde orbits tend to be brighter than those on retrograde orbits. The typical velocity difference between a satellite and its primary shows no clear dependence either on apparent separation, or on the rotation speed of the primary. Thus our survey demonstrates that isolated spiral galaxies have massive halos that extend to many optical radii.

  4. Hubble's Megamaser Galaxy

    NASA Image and Video Library

    2017-09-27

    Feast your eyes on Hubble's Megamaser galaxy! Phenomena across the Universe emit radiation spanning the entire electromagnetic spectrum — from high-energy gamma rays, which stream out from the most energetic events in the cosmos, to lower-energy microwaves and radio waves. Microwaves, the very same radiation that can heat up your dinner, are produced by a multitude of astrophysical sources, including strong emitters known as masers (microwave lasers), even stronger emitters with the somewhat villainous name of megamasers and the centers of some galaxies. Especially intense and luminous galactic centers are known as active galactic nuclei. They are in turn thought to be driven by the presence of supermassive black holes, which drag surrounding material inwards and spit out bright jets and radiation as they do so. The two galaxies shown here, imaged by the NASA/ESA Hubble Space Telescope, are named MCG+01-38-004 (the upper, red-tinted one) and MCG+01-38-005 (the lower, blue-tinted one). MCG+01-38-005 (also known as NGC 5765B) is a special kind of megamaser; the galaxy’s active galactic nucleus pumps out huge amounts of energy, which stimulates clouds of surrounding water. Water’s constituent atoms of hydrogen and oxygen are able to absorb some of this energy and re-emit it at specific wavelengths, one of which falls within the microwave regime, invisible to Hubble but detectable by microwave telescopes. MCG+01-38-005 is thus known as a water megamaser! Astronomers can use such objects to probe the fundamental properties of the Universe. The microwave emissions from MCG+01-38-005 were used to calculate a refined value for the Hubble constant, a measure of how fast the Universe is expanding. This constant is named after the astronomer whose observations were responsible for the discovery of the expanding Universe and after whom the Hubble Space Telescope was named, Edwin Hubble.

  5. Superluminous Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity Lr = 8-14L* (4.3-7.5 × 1044 erg s-1). These super spiral galaxies are also giant and massive, with diameter D = 57-134 kpc and stellar mass Mstars = 0.3-3.4 × 1011M⊙. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and Lr > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5-65 M⊙ yr-1 place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  6. HUBBLE SPACE TELESCOPE Imaging of Globular Clusters in the Edge-on Spiral Galaxies NGC 4565 and NGC 5907

    NASA Astrophysics Data System (ADS)

    Kissler-Patig, Markus; Ashman, Keith M.; Zepf, Stephen E.; Freeman, Kenneth C.

    1999-07-01

    We present a study of the globular cluster systems of two edge-on spiral galaxies, NGC 4565 and NGC 5907, from WFPC2 images in the F450W and F814W filters. The globular cluster systems of both galaxies appear to be similar to the Galactic globular cluster system. In particular, we derive total numbers of globular clusters of N_GC(4565)=204+/-38^+87_-53 and N_GC(5907)=170+/-41^+47_-72 (where the first are statistical, the second potential systematic errors) for NGC 4565 and NGC 5907, respectively. This determination is based on a comparison with the Milky Way system, for which we adopt a total number of globular clusters of 180+/-20. The specific frequency of both galaxies is S_N~=0.6, indistinguishable from the value for the Milky Way. The similarity in the globular cluster systems of the two galaxies is noteworthy, since they have significantly different thick disks and bulge-to-disk ratios. This would suggest that these two components do not play a major role in the building up of a globular cluster system around late-type galaxies.

  7. Hubble's Hockey Stick Galaxy

    NASA Image and Video Library

    2017-09-27

    The star of this NASA/ESA Hubble Space Telescope image is a galaxy known as NGC 4656, located in the constellation of Canes Venatici (The Hunting Dogs). However, it also has a somewhat more interesting and intriguing name: the Hockey Stick Galaxy! The reason for this is a little unclear from this partial view, which shows the bright central region, but the galaxy is actually shaped like an elongated, warped stick, stretching out through space until it curls around at one end to form a striking imitation of a celestial hockey stick. This unusual shape is thought to be due to an interaction between NGC 4656 and a couple of near neighbors, NGC 4631 (otherwise known as The Whale Galaxy) and NGC 4627 (a small elliptical). Galactic interactions can completely reshape a celestial object, shifting and warping its constituent gas, stars, and dust into bizarre and beautiful configurations. 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

  8. Outskirts of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Bresolin, Fabio

    2017-03-01

    I present an overview of the recent star formation activity in the outer disks of spiral galaxies, from the observational standpoint, with emphasis on the gas content, the star formation law, the metallicity and the stellar populations.

  9. SUPERLUMINOUS SPIRAL GALAXIES

    SciTech Connect

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M{sub ⊙} yr{sup −1} place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  10. Spiral Galaxies Stripped Bare

    NASA Astrophysics Data System (ADS)

    2010-10-01

    Six spectacular spiral galaxies are seen in a clear new light in images from ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile. The pictures were taken in infrared light, using the impressive power of the HAWK-I camera, and will help astronomers understand how the remarkable spiral patterns in galaxies form and evolve. HAWK-I [1] is one of the newest and most powerful cameras on ESO's Very Large Telescope (VLT). It is sensitive to infrared light, which means that much of the obscuring dust in the galaxies' spiral arms becomes transparent to its detectors. Compared to the earlier, and still much-used, VLT infrared camera ISAAC, HAWK-I has sixteen times as many pixels to cover a much larger area of sky in one shot and, by using newer technology than ISAAC, it has a greater sensitivity to faint infrared radiation [2]. Because HAWK-I can study galaxies stripped bare of the confusing effects of dust and glowing gas it is ideal for studying the vast numbers of stars that make up spiral arms. The six galaxies are part of a study of spiral structure led by Preben Grosbøl at ESO. These data were acquired to help understand the complex and subtle ways in which the stars in these systems form into such perfect spiral patterns. The first image shows NGC 5247, a spiral galaxy dominated by two huge arms, located 60-70 million light-years away. The galaxy lies face-on towards Earth, thus providing an excellent view of its pinwheel structure. It lies in the zodiacal constellation of Virgo (the Maiden). The galaxy in the second image is Messier 100, also known as NGC 4321, which was discovered in the 18th century. It is a fine example of a "grand design" spiral galaxy - a class of galaxies with very prominent and well-defined spiral arms. About 55 million light-years from Earth, Messier 100 is part of the Virgo Cluster of galaxies and lies in the constellation of Coma Berenices (Berenice's Hair, named after the ancient Egyptian queen Berenice II). The third

  11. Stellar Populations in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    MacArthur, L. A.; Courteau, S.; Bell, E. F.; Holtzman, J. A.

    2004-12-01

    We investigate optical and near-IR color gradients in a sample of 172 low-inclination galaxies spanning Hubble types S0--Irr. The colors are compared to stellar population synthesis models from which luminosity-weighted average ages and metallicities are determined. We explore the effects of different underlying star formation histories and additional bursts of star formation. Because the observed gradients show radial structure, we measure ``inner'' and ``outer'' disk age and metallicity gradients. Relative trends in age and metallicity and their gradients are explored as a function of Hubble type, rotational velocity, total near-IR galaxy magnitude, central surface brightness, and scale length. We find strong correlations in age and metallicity with Hubble type, rotational velocity, total magnitude, and central surface brightness in the sense that earlier-type, faster rotating, more luminous, and higher surface brightness galaxies are older and more metal-rich, suggesting an early and more rapid star formation history for these galaxies. The increasing trends level off for T ⪉ 4 (Sbc and earlier), V {rot} ⪆ 120 km s-1, MK ⪉ -23 mag, and μ 0 ⪉ 18.5 mag arcsec-2. Outer disk gradients are weaker than the inner gradients as expected for a slower variation of the potential and surface brightness in the outer parts. We find that stronger age gradients are associated with weaker metallicity gradients. Relative trends in gradients with galaxy parameters do not agree with predictions of semi-analytic models of hierarchical galaxy formation, possibly as a result of bar-induced radial flows. However, the observed trends are in agreement with chemo-spectro photometric models of spiral galaxy evolution based on CDM-motivated scaling laws but including none of the hierarchical merging characteristics. This implies a strong dependence of the star formation history of spiral galaxies on the galaxy potential and halo spin parameter. L.A.M. and S.C acknowledge support

  12. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi

    The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.

  13. The Structure of Nuclear Star Clusters in Nearby Late-type Spiral Galaxies from Hubble Space Telescope Wide Field Camera 3 Imaging

    NASA Astrophysics Data System (ADS)

    Carson, Daniel J.; Barth, Aaron J.; Seth, Anil C.; den Brok, Mark; Cappellari, Michele; Greene, Jenny E.; Ho, Luis C.; Neumayer, Nadine

    2015-05-01

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters (NCs) residing in late-type spiral galaxies, in seven bands that span the near-UV to the near-IR. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties, with F814W absolute magnitudes that range from -11.2 to -15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc. For 6 of the 10 clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population that is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer wavelengths, as well as a correlation between the axis ratios of the NCs and their host galaxies. These observations indicate that blue disks aligned with the host galaxy plane are a common feature of NCs in late-type galaxies, but are difficult to detect in galaxies that are close to face-on. In color-color diagrams spanning the near-UV through the near-IR, most of the clusters lie far from single-burst evolutionary tracks, showing evidence for multi-age populations. Most of the clusters have integrated colors consistent with a mix of an old population (>1 Gyr) and a young population (˜100-300 Myr). The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only. The surface brightness profiles presented in this work will be used for future stellar

  14. Magnificant Details in a Dusty Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In 1995, the majestic spiral galaxy NGC 4414 was imaged by the Hubble Space Telescope as part of the HST Key Project on the Extragalactic Distance Scale. An international team of astronomers, led by Dr. Wendy Freedman of the Observatories of the Carnegie Institution of Washington, observed this galaxy on 13 different occasions over the course of two months. Images were obtained with Hubble's Wide Field Planetary Camera 2 (WFPC2) through three different color filters. Based on their discovery and careful brightness measurements of variable stars in NGC 4414, the Key Project astronomers were able to make an accurate determination of the distance to the galaxy. The resulting distance to NGC 4414, 19.1 megaparsecs or about 60 million light-years, along with similarly determined distances to other nearby galaxies, contributes to astronomers' overall knowledge of the rate of expansion of the universe. In 1999, the Hubble Heritage Team revisited NGC 4414 and completed its portrait by observing the other half with the same filters as were used in 1995. The end result is a stunning full-color look at the entire dusty spiral galaxy. The new Hubble picture shows that the central regions of this galaxy, as is typical of most spirals, contain primarily older, yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust, seen as dark patches and streaks silhouetted against the starlight.

  15. MAGNIFICENT DETAILS IN A DUSTY SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1995, the majestic spiral galaxy NGC 4414 was imaged by the Hubble Space Telescope as part of the HST Key Project on the Extragalactic Distance Scale. An international team of astronomers, led by Dr. Wendy Freedman of the Observatories of the Carnegie Institution of Washington, observed this galaxy on 13 different occasions over the course of two months. Images were obtained with Hubble's Wide Field Planetary Camera 2 (WFPC2) through three different color filters. Based on their discovery and careful brightness measurements of variable stars in NGC 4414, the Key Project astronomers were able to make an accurate determination of the distance to the galaxy. The resulting distance to NGC 4414, 19.1 megaparsecs or about 60 million light-years, along with similarly determined distances to other nearby galaxies, contributes to astronomers' overall knowledge of the rate of expansion of the universe. The Hubble constant (H0) is the ratio of how fast galaxies are moving away from us to their distance from us. This astronomical value is used to determine distances, sizes, and the intrinsic luminosities for many objects in our universe, and the age of the universe itself. Due to the large size of the galaxy compared to the WFPC2 detectors, only half of the galaxy observed was visible in the datasets collected by the Key Project astronomers in 1995. In 1999, the Hubble Heritage Team revisited NGC 4414 and completed its portrait by observing the other half with the same filters as were used in 1995. The end result is a stunning full-color look at the entire dusty spiral galaxy. The new Hubble picture shows that the central regions of this galaxy, as is typical of most spirals, contain primarily older, yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust

  16. MAGNIFICENT DETAILS IN A DUSTY SPIRAL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In 1995, the majestic spiral galaxy NGC 4414 was imaged by the Hubble Space Telescope as part of the HST Key Project on the Extragalactic Distance Scale. An international team of astronomers, led by Dr. Wendy Freedman of the Observatories of the Carnegie Institution of Washington, observed this galaxy on 13 different occasions over the course of two months. Images were obtained with Hubble's Wide Field Planetary Camera 2 (WFPC2) through three different color filters. Based on their discovery and careful brightness measurements of variable stars in NGC 4414, the Key Project astronomers were able to make an accurate determination of the distance to the galaxy. The resulting distance to NGC 4414, 19.1 megaparsecs or about 60 million light-years, along with similarly determined distances to other nearby galaxies, contributes to astronomers' overall knowledge of the rate of expansion of the universe. The Hubble constant (H0) is the ratio of how fast galaxies are moving away from us to their distance from us. This astronomical value is used to determine distances, sizes, and the intrinsic luminosities for many objects in our universe, and the age of the universe itself. Due to the large size of the galaxy compared to the WFPC2 detectors, only half of the galaxy observed was visible in the datasets collected by the Key Project astronomers in 1995. In 1999, the Hubble Heritage Team revisited NGC 4414 and completed its portrait by observing the other half with the same filters as were used in 1995. The end result is a stunning full-color look at the entire dusty spiral galaxy. The new Hubble picture shows that the central regions of this galaxy, as is typical of most spirals, contain primarily older, yellow and red stars. The outer spiral arms are considerably bluer due to ongoing formation of young, blue stars, the brightest of which can be seen individually at the high resolution provided by the Hubble camera. The arms are also very rich in clouds of interstellar dust

  17. THE STRUCTURE OF NUCLEAR STAR CLUSTERS IN NEARBY LATE-TYPE SPIRAL GALAXIES FROM HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 IMAGING

    SciTech Connect

    Carson, Daniel J.; Barth, Aaron J.; Seth, Anil C.; Brok, Mark den; Cappellari, Michele; Greene, Jenny E.; Ho, Luis C.; Neumayer, Nadine

    2015-05-15

    We obtained Hubble Space Telescope/Wide Field Camera 3 imaging of a sample of ten of the nearest and brightest nuclear clusters (NCs) residing in late-type spiral galaxies, in seven bands that span the near-UV to the near-IR. Structural properties of the clusters were measured by fitting two-dimensional surface brightness profiles to the images using GALFIT. The clusters exhibit a wide range of structural properties, with F814W absolute magnitudes that range from −11.2 to −15.1 mag and F814W effective radii that range from 1.4 to 8.3 pc. For 6 of the 10 clusters in our sample, we find changes in the effective radius with wavelength, suggesting radially varying stellar populations. In four of the objects, the effective radius increases with wavelength, indicating the presence of a younger population that is more concentrated than the bulk of the stars in the cluster. However, we find a general decrease in effective radius with wavelength in two of the objects in our sample, which may indicate extended, circumnuclear star formation. We also find a general trend of increasing roundness of the clusters at longer wavelengths, as well as a correlation between the axis ratios of the NCs and their host galaxies. These observations indicate that blue disks aligned with the host galaxy plane are a common feature of NCs in late-type galaxies, but are difficult to detect in galaxies that are close to face-on. In color–color diagrams spanning the near-UV through the near-IR, most of the clusters lie far from single-burst evolutionary tracks, showing evidence for multi-age populations. Most of the clusters have integrated colors consistent with a mix of an old population (>1 Gyr) and a young population (∼100–300 Myr). The wide wavelength coverage of our data provides a sensitivity to populations with a mix of ages that would not be possible to achieve with imaging in optical bands only. The surface brightness profiles presented in this work will be used for future

  18. HUBBLE UNVEILS A GALAXY IN LIVING COLOR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this view of the center of the magnificent barred spiral galaxy NGC 1512, NASA Hubble Space Telescope's broad spectral vision reveals the galaxy at all wavelengths from ultraviolet to infrared. The colors (which indicate differences in light intensity) map where newly born star clusters exist in both 'dusty' and 'clean' regions of the galaxy. This color-composite image was created from seven images taken with three different Hubble cameras: the Faint Object Camera (FOC), the Wide Field and Planetary Camera 2 (WFPC2), and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). NGC 1512 is a barred spiral galaxy in the southern constellation of Horologium. Located 30 million light-years away, relatively 'nearby' as galaxies go, it is bright enough to be seen with amateur telescopes. The galaxy spans 70,000 light-years, nearly as much as our own Milky Way galaxy. The galaxy's core is unique for its stunning 2,400 light-year-wide circle of infant star clusters, called a 'circumnuclear' starburst ring. Starbursts are episodes of vigorous formation of new stars and are found in a variety of galaxy environments. Taking advantage of Hubble's sharp vision, as well as its unique wavelength coverage, a team of Israeli and American astronomers performed one of the broadest and most detailed studies ever of such star-forming regions. The results, which will be published in the June issue of the Astronomical Journal, show that in NGC 1512 newly born star clusters exist in both dusty and clean environments. The clean clusters are readily seen in ultraviolet and visible light, appearing as bright, blue clumps in the image. However, the dusty clusters are revealed only by the glow of the gas clouds in which they are hidden, as detected in red and infrared wavelengths by the Hubble cameras. This glow can be seen as red light permeating the dark, dusty lanes in the ring. 'The dust obscuration of clusters appears to be an on-off phenomenon,' says Dan Maoz, who headed the

  19. HUBBLE UNVEILS A GALAXY IN LIVING COLOR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In this view of the center of the magnificent barred spiral galaxy NGC 1512, NASA Hubble Space Telescope's broad spectral vision reveals the galaxy at all wavelengths from ultraviolet to infrared. The colors (which indicate differences in light intensity) map where newly born star clusters exist in both 'dusty' and 'clean' regions of the galaxy. This color-composite image was created from seven images taken with three different Hubble cameras: the Faint Object Camera (FOC), the Wide Field and Planetary Camera 2 (WFPC2), and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). NGC 1512 is a barred spiral galaxy in the southern constellation of Horologium. Located 30 million light-years away, relatively 'nearby' as galaxies go, it is bright enough to be seen with amateur telescopes. The galaxy spans 70,000 light-years, nearly as much as our own Milky Way galaxy. The galaxy's core is unique for its stunning 2,400 light-year-wide circle of infant star clusters, called a 'circumnuclear' starburst ring. Starbursts are episodes of vigorous formation of new stars and are found in a variety of galaxy environments. Taking advantage of Hubble's sharp vision, as well as its unique wavelength coverage, a team of Israeli and American astronomers performed one of the broadest and most detailed studies ever of such star-forming regions. The results, which will be published in the June issue of the Astronomical Journal, show that in NGC 1512 newly born star clusters exist in both dusty and clean environments. The clean clusters are readily seen in ultraviolet and visible light, appearing as bright, blue clumps in the image. However, the dusty clusters are revealed only by the glow of the gas clouds in which they are hidden, as detected in red and infrared wavelengths by the Hubble cameras. This glow can be seen as red light permeating the dark, dusty lanes in the ring. 'The dust obscuration of clusters appears to be an on-off phenomenon,' says Dan Maoz, who headed the

  20. Pitch Angle Survey of GOODS Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Boe, Benjamin; Kennefick, Daniel; Arkansas Galaxy Evolution Survey, Arkansas CenterSpace; Planetary Sciences

    2015-01-01

    This research looks at how the pitch angles of galaxies change over scales of cosmic time. We measure the pitch angle, or tightness of spiral winding, using a new code, Spirality. We then compare the results to those obtained from established software, 2DFFT (2 Dimensional Fast Fourier Transform). We investigate any correlation between pitch angle and redshift, or distance from Earth. Previous research indicates that the pitch angle of a galaxy correlates with its central bulge mass and the mass of its central black hole. Thus any evolution in the distribution of pitch angles could ultimately prove to be indicative of evolution in the supermassive black hole mass function. Galaxies from the Hubble GOODS (Great Observatories Origins Deep Survey) North and South were measured. We found that there was strong agreement between Spirality and 2DFFT measurements. Spirality measured the pitch angle of the GOODS galaxies with a lower error than 2DFFT on average. With both software a correlation between pitch angle and redshift was found. Spirality observed a 6.150 increase in pitch per unit redshift. The increase in pitch angle with redshift suggests that in the past galaxies had higher pitch angles, which could be indicative of lower central black hole masses (or, more directly, central bulge masses).

  1. Variable Stars in a Distant Spiral Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A NASA Hubble Space Telescope (HST) view of the magnificent spiral galaxy NGC 4603, the most distant galaxy in which a special class of pulsating stars called Cepheid variables have been found. It is associated with the Centaurus cluster, one of the most massive assemblages of galaxies in the nearby universe. The Local Group of galaxies, of which the Milky Way is a member, is moving in the direction of Centaurus at a speed of more than a million miles an hour under the influence of the gravitational pull of the matter in that direction. Clusters of young bright blue stars highlight the galaxy's spiral arms. In contrast, red giant stars in the process of dying are also found. Only the very brightest stars in NGC 4603 can be seen individually, even with the unmatched ability of the Hubble Space Telescope to obtain detailed images of distant objects. Much of the diffuse glow comes from fainter stars that cannot be individually distinguished by Hubble. The reddish filaments are regions where clouds of dust obscure blue light from the stars behind them. This galaxy was observed by a team affiliated with the HST Key Project on the Extragalactic Distance Scale. Because NGC 4603 is much farther away than the other galaxies studied with Hubble by the Key Project team, 108 million light-years, its stars appear very faint from the Earth, and so accurately measuring their brightness, as is required for distinguishing the characteristic variations of Cepheids, is extremely difficult. Determining the distance to the galaxy required an unprecedented statistical analysis based on extensive computer simulations.

  2. HUBBLE REVEALS STELLAR FIREWORKS ACCOMPANYING GALAXY COLLISION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Hubble Space Telescope image provides a detailed look at a brilliant 'fireworks show' at the center of a collision between two galaxies. Hubble has uncovered over 1,000 bright, young star clusters bursting to life as a result of the head-on wreck. [Left] A ground-based telescopic view of the Antennae galaxies (known formally as NGC 4038/4039) - so named because a pair of long tails of luminous matter, formed by the gravitational tidal forces of their encounter, resembles an insect's antennae. The galaxies are located 63 million light-years away in the southern constellation Corvus. [Right] The respective cores of the twin galaxies are the orange blobs, left and right of image center, crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the overlap region, stretches between the cores of the two galaxies. The sweeping spiral- like patterns, traced by bright blue star clusters, shows the result of a firestorm of star birth activity which was triggered by the collision. This natural-color image is a composite of four separately filtered images taken with the Wide Field Planetary Camera 2 (WFPC2), on January 20, 1996. Resolution is 15 light-years per pixel (picture element). Credit: Brad Whitmore (STScI), and NASA

  3. HUBBLE REVEALS STELLAR FIREWORKS ACCOMPANYING GALAXY COLLISION

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Hubble Space Telescope image provides a detailed look at a brilliant 'fireworks show' at the center of a collision between two galaxies. Hubble has uncovered over 1,000 bright, young star clusters bursting to life as a result of the head-on wreck. [Left] A ground-based telescopic view of the Antennae galaxies (known formally as NGC 4038/4039) - so named because a pair of long tails of luminous matter, formed by the gravitational tidal forces of their encounter, resembles an insect's antennae. The galaxies are located 63 million light-years away in the southern constellation Corvus. [Right] The respective cores of the twin galaxies are the orange blobs, left and right of image center, crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the overlap region, stretches between the cores of the two galaxies. The sweeping spiral- like patterns, traced by bright blue star clusters, shows the result of a firestorm of star birth activity which was triggered by the collision. This natural-color image is a composite of four separately filtered images taken with the Wide Field Planetary Camera 2 (WFPC2), on January 20, 1996. Resolution is 15 light-years per pixel (picture element). Credit: Brad Whitmore (STScI), and NASA

  4. Environment Dependence of Disk Morphology of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ann, Hong Bae

    2014-02-01

    We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density (Σ_{n}), project distance (r_{p}), and tidal index (TI) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing Σ_{n}, 1/r_{p}, and TI, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on Σ_{n}, they show a fairly clear dependence on r_{p} with a high frequency of SB galaxies at small r_{p}. The arm class also exhibits a stronger correlation with r_{p} than Σ_{n} and TI, whereas the Hubble type exhibits similar correlations with Σ_{n} and r_{p}. This suggests that the arm class is mostly affected by the nearest neighbor while the Hubble type is affected by the local densities contributed by neighboring galaxies as well as the nearest neighbor.

  5. STAR CLUSTERS IN PSEUDOBULGES OF SPIRAL GALAXIES

    SciTech Connect

    Di Nino, Daiana; Trenti, Michele; Stiavelli, Massimo; Carollo, C. Marcella; Scarlata, Claudia; Wyse, Rosemary F. G.

    2009-11-15

    We present a study of the properties of the star-cluster systems around pseudobulges of late-type spiral galaxies using a sample of 11 galaxies with distances from 17 Mpc to 37 Mpc. Star clusters are identified from multiband Hubble Space Telescope ACS and WFPC2 imaging data by combining detections in three bands (F435W and F814W with ACS and F606W with WFPC2). The photometric data are then compared to population synthesis models to infer the masses and ages of the star clusters. Photometric errors and completeness are estimated by means of artificial source Monte Carlo simulations. Dust extinction is estimated by considering F160W NICMOS observations of the central regions of the galaxies, augmenting our wavelength coverage. In all galaxies we identify star clusters with a wide range of ages, from young (age {approx}< 8 Myr) blue clusters, with typical mass of 10{sup 3} M {sub sun} to older (age >100-250 Myr), more massive, red clusters. Some of the latter might likely evolve into objects similar to the Milky Way's globular clusters. We compute the specific frequencies for the older clusters with respect to the galaxy and bulge luminosities. Specific frequencies relative to the galaxy light appear consistent with the globular cluster specific frequencies of early-type spirals. We compare the specific frequencies relative to the bulge light with the globular cluster specific frequencies of dwarf galaxies, which have a surface brightness profile that is similar to that of the pseudobulges in our sample. The specific frequencies we derive for our sample galaxies are higher than those of the dwarf galaxies, supporting an evolutionary scenario in which some of the dwarf galaxies might be the remnants of harassed late-type spiral galaxies that hosted a pseudobulge.

  6. Hubble Sees Young Galaxies Bursting with Stars

    NASA Image and Video Library

    This video shows a zoom into the Hubble GOODS South Deep (GSD) field. Candidate extreme emission line galaxies are identified. This object was observed as part of the Hubble CANDELS Legacy Project....

  7. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with

  8. Hubble's deepest view ever of the Universe unveils earliest galaxies

    NASA Astrophysics Data System (ADS)

    2004-03-01

    Hubble sees galaxies galore hi-res Size hi-res: 446 kb Credits: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team Hubble sees galaxies galore Galaxies, galaxies everywhere - as far as the NASA/ESA Hubble Space Telescope can see. This view of nearly 10,000 galaxies is the deepest visible-light image of the cosmos. Called the Hubble Ultra Deep Field, this galaxy-studded view represents a ‘deep’ core sample of the universe, cutting across billions of light-years. Hubble reveals galactic drama hi-res Size hi-res: 879 kb Credits: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team Hubble reveals galactic drama A galactic brawl. A close encounter with a spiral galaxy. Blue wisps of galaxies. These close-up snapshots of galaxies in the Hubble Ultra Deep Field reveal the drama of galactic life. Here three galaxies just below centre are enmeshed in battle, their shapes distorted by the brutal encounter. Hubble reveals galactic drama hi-res Size hi-res: 886 kb Credits: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team Hubble reveals galactic drama A galactic brawl. A close encounter with a spiral galaxy. Blue wisps of galaxies. These close-up snapshots of galaxies in the Hubble Ultra Deep Field reveal the drama of galactic life. Here three galaxies just below centre are enmeshed in battle, their shapes distorted by the brutal encounter. Hubble reveals galactic drama hi-res Size hi-res: 892 kb Credits: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team Hubble reveals galactic drama A galactic brawl. A close encounter with a spiral galaxy. Blue wisps of galaxies. These close-up snapshots of galaxies in the Hubble Ultra Deep Field reveal the drama of galactic life. The galaxies in this panel were plucked from a harvest of nearly 10,000 galaxies in the Ultra Deep Field, the deepest visible-light image of the cosmos. This historic new view is actually made up by two separate images taken by Hubble's Advanced Camera for Surveys (ACS) and the Near Infrared Camera and

  9. HUBBLE SPIES GLOBULAR CLUSTER IN NEIGHBORING GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hubble Space Telescope has captured a view of a globular cluster called G1, a large, bright ball of light in the center of the photograph consisting of at least 300,000 old stars. G1, also known as Mayall II, orbits the Andromeda galaxy (M31), the nearest major spiral galaxy to our Milky Way. Located 130,000 light-years from Andromeda's nucleus, G1 is the brightest globular cluster in the Local Group of galaxies. The Local Group consists of about 20 nearby galaxies, including the Milky Way. The crisp image is comparable to ground-based telescope views of similar clusters orbiting the Milky Way. The Andromeda cluster, however, is nearly 100 times farther away. A glimpse into the cluster's finer details allow astronomers to see its fainter helium-burning stars whose temperatures and brightnesses show that this cluster in Andromeda and the oldest Milky Way clusters have approximately the same age. These clusters probably were formed shortly after the beginning of the universe, providing astronomers with a record of the earliest era of galaxy formation. During the next two years, astronomers will use Hubble to study about 20 more globular clusters in Andromeda. The color picture was assembled from separate images taken in visible and near-infrared wavelengths taken in July of 1994. CREDIT: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories), 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.

  10. HUBBLE SPIES GLOBULAR CLUSTER IN NEIGHBORING GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hubble Space Telescope has captured a view of a globular cluster called G1, a large, bright ball of light in the center of the photograph consisting of at least 300,000 old stars. G1, also known as Mayall II, orbits the Andromeda galaxy (M31), the nearest major spiral galaxy to our Milky Way. Located 130,000 light-years from Andromeda's nucleus, G1 is the brightest globular cluster in the Local Group of galaxies. The Local Group consists of about 20 nearby galaxies, including the Milky Way. The crisp image is comparable to ground-based telescope views of similar clusters orbiting the Milky Way. The Andromeda cluster, however, is nearly 100 times farther away. A glimpse into the cluster's finer details allow astronomers to see its fainter helium-burning stars whose temperatures and brightnesses show that this cluster in Andromeda and the oldest Milky Way clusters have approximately the same age. These clusters probably were formed shortly after the beginning of the universe, providing astronomers with a record of the earliest era of galaxy formation. During the next two years, astronomers will use Hubble to study about 20 more globular clusters in Andromeda. The color picture was assembled from separate images taken in visible and near-infrared wavelengths taken in July of 1994. CREDIT: Michael Rich, Kenneth Mighell, and James D. Neill (Columbia University), and Wendy Freedman (Carnegie Observatories), 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.

  11. Quasar Host Galaxies/Neptune Rotation/Galaxy Building Blocks/Hubble Deep Field/Saturn Storm

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Computerized animations simulate a quasar erupting in the core of a normal spiral galaxy, the collision of two interacting galaxies, and the evolution of the universe. Hubble Space Telescope (HST) images show six quasars' host galaxies (including spirals, ellipticals, and colliding galaxies) and six clumps of galaxies approximately 11 billion light years away. A false color time lapse movie of Neptune displays the planet's 16-hour rotation, and the evolution of a storm on Saturn is seen though a video of the planet's rotation. A zoom sequence starts with a ground-based image of the constellation Ursa major and ends with the Hubble Deep Field through progressively narrower and deeper views.

  12. Quasar Host Galaxies/Neptune Rotation/Galaxy Building Blocks/Hubble Deep Field/Saturn Storm

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Computerized animations simulate a quasar erupting in the core of a normal spiral galaxy, the collision of two interacting galaxies, and the evolution of the universe. Hubble Space Telescope (HST) images show six quasars' host galaxies (including spirals, ellipticals, and colliding galaxies) and six clumps of galaxies approximately 11 billion light years away. A false color time lapse movie of Neptune displays the planet's 16-hour rotation, and the evolution of a storm on Saturn is seen though a video of the planet's rotation. A zoom sequence starts with a ground-based image of the constellation Ursa major and ends with the Hubble Deep Field through progressively narrower and deeper views.

  13. Hubble Reveals Sombrero Galaxy (M104)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    In the 19th century, astronomer V. M. Slipher first discovered a hat-like object that appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that it was really another galaxy, and that the universe was expanding in all directions. The trained razor sharp eye of the Hubble Space Telescope (HST) easily resolves this Sombrero galaxy, Messier 104 (M104). The galaxy is 50,000 light-years across and is located 28 million light-years from Earth at the southern edge of the rich Virgo cluster of galaxies. Equivalent to 800 billion suns, Sombrero is one of the most massive objects in that group. The hallmark of Sombrero is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. This rich system of globular clusters are estimated to be nearly 2,000 in number which is 10 times as many as in our Milky Way galaxy. The ages of the clusters are similar to the clusters in the Milky Way, ranging from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides. The Marshall Space Flight Center (MSFC) had responsibility for design, development, and construction of the HST.

  14. Hubble Reveals Sombrero Galaxy (M104)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    In the 19th century, astronomer V. M. Slipher first discovered a hat-like object that appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that it was really another galaxy, and that the universe was expanding in all directions. The trained razor sharp eye of the Hubble Space Telescope (HST) easily resolves this Sombrero galaxy, Messier 104 (M104). The galaxy is 50,000 light-years across and is located 28 million light-years from Earth at the southern edge of the rich Virgo cluster of galaxies. Equivalent to 800 billion suns, Sombrero is one of the most massive objects in that group. The hallmark of Sombrero is a brilliant white, bulbous core encircled by the thick dust lanes comprising the spiral structure of the galaxy. As seen from Earth, the galaxy is tilted nearly edge-on. We view it from just six degrees north of its equatorial plane. At a relatively bright magnitude of +8, M104 is just beyond the limit of naked-eye visibility and is easily seen through small telescopes. This rich system of globular clusters are estimated to be nearly 2,000 in number which is 10 times as many as in our Milky Way galaxy. The ages of the clusters are similar to the clusters in the Milky Way, ranging from 10-13 billion years old. Embedded in the bright core of M104 is a smaller disk, which is tilted relative to the large disk. X-ray emission suggests that there is material falling into the compact core, where a 1-billion-solar-mass black hole resides. The Marshall Space Flight Center (MSFC) had responsibility for design, development, and construction of the HST.

  15. HUBBLE REVEALS THE HEART OF THE WHIRLPOOL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    New images from NASA's Hubble Space Telescope are helping researchers view in unprecedented detail the spiral arms and dust clouds of a nearby galaxy, which are the birth sites of massive and luminous stars. The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms. M51, also known as NGC 5194, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion's gravitational pull is triggering star formation in the main galaxy, as seen in brilliant detail by numerous, luminous clusters of young and energetic stars. The bright clusters are highlighted in red by their associated emission from glowing hydrogen gas. This Wide Field Planetary Camera 2 image enables a research group, led by Nick Scoville (Caltech), to clearly define the structure of both the cold dust clouds and the hot hydrogen and link individual clusters to their parent dust clouds. Team members include M. Polletta (U. Geneva); S. Ewald and S. Stolovy (Caltech); R. Thompson and M. Rieke (U. of Arizona). Intricate structure is also seen for the first time in the dust clouds. Along the spiral arms, dust 'spurs' are seen branching out almost perpendicular to the main spiral arms. The regularity and large number of these features suggests to astronomers that previous models of 'two-arm' spiral galaxies may need to be revisited. The new images also reveal a dust disk in the nucleus, which may provide fuel for a nuclear black hole. The team is also studying this galaxy at near-infrared wavelengths with the NICMOS instrument onboard Hubble. At these

  16. HUBBLE REVEALS THE HEART OF THE WHIRLPOOL GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    New images from NASA's Hubble Space Telescope are helping researchers view in unprecedented detail the spiral arms and dust clouds of a nearby galaxy, which are the birth sites of massive and luminous stars. The Whirlpool galaxy, M51, has been one of the most photogenic galaxies in amateur and professional astronomy. Easily photographed and viewed by smaller telescopes, this celestial beauty is studied extensively in a range of wavelengths by large ground- and space-based observatories. This Hubble composite image shows visible starlight as well as light from the emission of glowing hydrogen, which is associated with the most luminous young stars in the spiral arms. M51, also known as NGC 5194, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion's gravitational pull is triggering star formation in the main galaxy, as seen in brilliant detail by numerous, luminous clusters of young and energetic stars. The bright clusters are highlighted in red by their associated emission from glowing hydrogen gas. This Wide Field Planetary Camera 2 image enables a research group, led by Nick Scoville (Caltech), to clearly define the structure of both the cold dust clouds and the hot hydrogen and link individual clusters to their parent dust clouds. Team members include M. Polletta (U. Geneva); S. Ewald and S. Stolovy (Caltech); R. Thompson and M. Rieke (U. of Arizona). Intricate structure is also seen for the first time in the dust clouds. Along the spiral arms, dust 'spurs' are seen branching out almost perpendicular to the main spiral arms. The regularity and large number of these features suggests to astronomers that previous models of 'two-arm' spiral galaxies may need to be revisited. The new images also reveal a dust disk in the nucleus, which may provide fuel for a nuclear black hole. The team is also studying this galaxy at near-infrared wavelengths with the NICMOS instrument onboard Hubble. At these

  17. Pitch Angle Restriction in late Type Spiral Galaxies.

    NASA Astrophysics Data System (ADS)

    Perez Villegas, Maria de Los Angeles; Pichardo, B.; Moreno, E.; Peimbert, A.; Velazquez, H. M.

    2012-01-01

    With a set of models for low bulge mass spiral galaxies (late type as defined by Hubble classification), that include a novel 3-D self-gravitating potential based on density distribution for spiral arms (PERLAS), instead of the usual 2D approximations (cosine potentials), we have analyzed the galactic orbital dynamics as a function of the pitch angle (going from 10 to 60 degrees). We found, from an extensive orbital study in phase space, that for late spiral galaxies, with angles lager than 50 deg, chaos may become pervasive, having the effects of destroying the order phase space surrounding the main stable periodic orbits that sculpt spiral arms and even destroying them. This result is in good agreement with observations of late spiral galaxies, where the maximum observed pitch angle is about 50 degrees.

  18. A Grazing Encounter Between Two Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The larger and more massive galaxy is cataloged as NGC 2207 (on the left in the Hubble Heritage image), and the smaller one on the right is IC 2163. Strong tidal forces from NGC 2207 have distorted the shape of IC 2163, flinging out stars and gas into long streamers stretching out a hundred thousand light-years toward the right-hand edge of the image. Computer simulations, carried out by a team led by Bruce and Debra Elmegreen, demonstrate the leisurely timescale over which galactic collisions occur. In addition to the Hubble images, measurements made with the National Science Foundation's Very Large Array Radio Telescope in New Mexico reveal the motions of the galaxies and aid the reconstruction of the collision. The calculations indicate that IC 2163 is swinging past NGC 2207 in a counterclockwise direction, having made its closest approach 40 million years ago. However, IC 2163 does not have sufficient energy to escape from the gravitational pull of NGC 2207, and is destined to be pulled back and swing past the larger galaxy again in the future. The high resolution of the Hubble telescope image reveals dust lanes in the spiral arms of NGC 2207, clearly silhouetted against IC 2163, which is in the background. Hubble also reveals a series of parallel dust filaments extending like fine brush strokes along the tidally stretched material on the right-hand side. The large concentrations of gas and dust in both galaxies may well erupt into regions of active star formation in the near future. Trapped in their mutual orbit around each other, these two galaxies will continue to distort and disrupt each other. Eventually, billions of years from now, they will merge into a single, more massive galaxy. It is believed that many present-day galaxies, including the Milky Way, were assembled from a similar process of coalescence of smaller galaxies occurring over billions of years. This image was created from 3 separate pointings of Hubble. The Wide Field Planetary Camera 2 data

  19. How Opaque Are Spiral Galaxies?

    NASA Astrophysics Data System (ADS)

    Allen, Ronald

    1999-07-01

    Using HST Archival images in a previous modest AR program, we have developed a new method to calibrate the effects of crowding and confusion from foreground structure on the counts of background galaxies seen through a foreground system. This new method, the Synthetic Field Method, permits us to establish the area-averaged amount of extinction through the entire thickness of the foreground galaxy. No assumptions about the spatial distribution of the obscuring material in the foreground system or about its reddening law are required. We now propose to exploit this method by applying it to deep Archival images of all 17 nearby spiral galaxies obtained earlier with the HST/WFPC2 in the Cepheid distance scale programs. Applying the method to this large sample of spirals will permit us: {1} to decrease the fundamental uncertainty in our results owing to field-to-field variations in the surface number density of the background galaxies, and {2} to begin quantifying the differences in extinction between arms and inter-arm regions, and between the inner and outer parts of spiral galaxy disks. The results of this project will provide the largest study to date of TOTAL extinction in spiral galaxies using background illuminating objects.

  20. More Satellites of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Zaritsky, Dennis; Smith, Rodney; Frenk, Carlos; White, Simon D. M.

    1997-03-01

    We present a revised and expanded catalog of satellite galaxies of a set of isolated spiral galaxies similar in luminosity to the Milky Way. This sample of 115 satellites, 69 of which were discovered in our multifiber redshift survey, is used to probe the results obtained from the original sample further (Zaritsky et al.). The satellites are, by definition, at projected separations <~500 kpc, have absolute recessional velocity differences with respect to the parent spiral of less than 500 km s-1, and are at least 2.2 mag fainter than their associated primary galaxy. A key characteristic of this survey is the strict isolation of these systems, which simplifies any dynamical analysis. We find no evidence for a decrease in the velocity dispersion of the satellite system as a function of radius out to galactocentric radii of 400 kpc, which suggests that the halo extends well beyond 200 kpc. Furthermore, the new sample affirms our previous conclusions (Zaritsky et al.) that (1) the velocity difference between a satellite and its primary is not strongly correlated with the rotation speed of the primary, (2) the system of satellites has a slight net rotation (34 +/- 14 km s-1) in the same sense as the primary's disk, and (3) that the halo mass of an ~L* spiral galaxy is in excess of 2 × 1012 M⊙. Lick Observatory Bulletin B1346.

  1. HUBBLE PHOTOGRAPHS WARPED GALAXY AS CAMERA PASSES MILESTONE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope has captured an image of an unusual edge-on galaxy, revealing remarkable details of its warped dusty disk and showing how colliding galaxies spawn the formation of new generations of stars. The dust and spiral arms of normal spiral galaxies, like our own Milky Way, appear flat when viewed edge-on. This month's Hubble Heritage image of ESO 510-G13 shows a galaxy that, by contrast, has an unusual twisted disk structure, first seen in ground-based photographs obtained at the European Southern Observatory (ESO) in Chile. ESO 510-G13 lies in the southern constellation Hydra, roughly 150 million light-years from Earth. Details of the structure of ESO 510-G13 are visible because the interstellar dust clouds that trace its disk are silhouetted from behind by light from the galaxy's bright, smooth central bulge. The strong warping of the disk indicates that ESO 510-G13 has recently undergone a collision with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort the structures of the galaxies as their stars, gas, and dust merge together in a process that takes millions of years. Eventually the disturbances will die out, and ESO 510-G13 will become a normal-appearing single galaxy. In the outer regions of ESO 510-G13, especially on the right-hand side of the image, we see that the twisted disk contains not only dark dust, but also bright clouds of blue stars. This shows that hot, young stars are being formed in the disk. Astronomers believe that the formation of new stars may be triggered by collisions between galaxies, as their interstellar clouds smash together and are compressed. The Heritage Team used Hubble's Wide Field Planetary Camera 2 (WFPC2) to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty spiral arms, the bright bulge, and the blue star-forming regions. During the

  2. HUBBLE PHOTOGRAPHS WARPED GALAXY AS CAMERA PASSES MILESTONE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope has captured an image of an unusual edge-on galaxy, revealing remarkable details of its warped dusty disk and showing how colliding galaxies spawn the formation of new generations of stars. The dust and spiral arms of normal spiral galaxies, like our own Milky Way, appear flat when viewed edge-on. This month's Hubble Heritage image of ESO 510-G13 shows a galaxy that, by contrast, has an unusual twisted disk structure, first seen in ground-based photographs obtained at the European Southern Observatory (ESO) in Chile. ESO 510-G13 lies in the southern constellation Hydra, roughly 150 million light-years from Earth. Details of the structure of ESO 510-G13 are visible because the interstellar dust clouds that trace its disk are silhouetted from behind by light from the galaxy's bright, smooth central bulge. The strong warping of the disk indicates that ESO 510-G13 has recently undergone a collision with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort the structures of the galaxies as their stars, gas, and dust merge together in a process that takes millions of years. Eventually the disturbances will die out, and ESO 510-G13 will become a normal-appearing single galaxy. In the outer regions of ESO 510-G13, especially on the right-hand side of the image, we see that the twisted disk contains not only dark dust, but also bright clouds of blue stars. This shows that hot, young stars are being formed in the disk. Astronomers believe that the formation of new stars may be triggered by collisions between galaxies, as their interstellar clouds smash together and are compressed. The Heritage Team used Hubble's Wide Field Planetary Camera 2 (WFPC2) to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty spiral arms, the bright bulge, and the blue star-forming regions. During the

  3. Molecular gas in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Casoli, F.; Sauty, S.; Gerin, M.; Boselli, A.; Fouque, P.; Braine, J.; Gavazzi, G.; Lequeux, J.; Dickey, J.

    1998-03-01

    The molecular hydrogen content of a galaxy is a key parameter for its activity and future evolution. Its variations with basic properties such as size, mass, morphological type, and environment, the ratio of molecular to atomic gas masses, should provide us with a better view of galaxy evolution. Such studies have been done in the past by Sage (1993a) or the FCRAO group (e.g. Young & Knezek 1989), and have led to controversial results, for example about the MHH /MHI ratio. While Sage (1993a), using a distance-limited sample of 65 galaxies and the \\COA line emission as a tracer of the HH mass, finds that most galaxies have MHH /MHI lower than 1, Young & Knezek (1989) and Young et al. (1995), from a different sample of 178 objects, claim equal amounts of gas in the molecular and atomic phase. Here we again tackle this problem, by gathering a much larger sample of 582 objects, not only from the literature but also from several \\COA surveys that we have completed and which are largely unpublished. Our sample is clearly not complete and contains a large number of cluster galaxies as well as many more massive objects than a distance-limited sample. Contrary to previous analyses, we have taken into account the non-detections by using the survival analysis method. Our sample includes 105 isolated galaxies, observed by us, that we use as a reference sample in order to determine whether cluster galaxies are CO-deficient. We find that the ratio of HH and HI masses is on the average lower than 1, with = log(0.20) +/- 0.04 (median = log(0.27) +/- 0.04). For spirals with types Sa to Sc, we have slightly higher values: log(0.28) and log(0.34) respectively. The actual HH masses and MHH /MHI ratios could be lower than given above if, as suggested by recent gamma -ray and 1.3 mm continuum data, the conversion factor between \\COA emissivities and HH masses for large spiral galaxies is lower than the value adopted here (X=2.310(20) cm(-2) /(Kkms(-1) )). The

  4. Globular cluster systems in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Nantais, Julie Beth

    We have performed a comprehensive spectroscopic and photometric analysis of the M81 globular cluster system, using Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) imaging in the B, V, and I bands and 74 globular cluster spectra from Hectospec at the MMT. We have also performed a small spectroscopic study of the NGC 300 globular cluster system using the Boller & Chivens (B&C) Spectrograph on the Baade Telescope in Chile. We confirm 9 probable globular clusters in NGC 300 and 3 possible clusters with very low radial velocities. For our full NGC 300 cluster sample, plus one cluster from the literature, we find a mean [Fe/H] = --0.94 +/- 0.15; without the 3 "possible" clusters we find a mean [Fe/H] = --0.98 +/- 0.12. We identify over 200 globular cluster candidates in HST I-band imaging, and spectroscopically confirm 62 new globular clusters in M81. The M81 globular cluster system shows marginal evidence for a bimodal metallicity distribution. The mean metallicity of 107 confirmed M81 globular clusters is [Fe/H] = 1.06 +/- 0.07. The M81 globular cluster system shows significant rotation, at 108 +/- 22 km s-1. There is evidence for a metallicity gradient among the metal-poor clusters. We perform HST ACS BV I photometry and radial profile fitting on 85 spectroscopically confirmed globular clusters, 136 "good" globular cluster candidates, and 198 other star cluster candidates. The globular cluster luminosity function peaks at V0 ˜20.26. The properties of the M81 globular cluster system are very similar to those of the Milky Way and M31, suggesting a similar origin for all three galaxies. Our understanding of the origins of spiral galaxy globular cluster systems would be vastly improved by comprehensive studies of low-mass and late-type spiral galaxies, including HST I-band imaging to identify globular cluster candidates for spectroscopic confirmation.

  5. Large Face on Spiral Galaxy NGC 3344

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image from NASA Galaxy Evolution Explorer is of the large face on spiral galaxy NGC 3344. The inner spiral arms are wrapped so tightly that they are difficult to distinguish. http://photojournal.jpl.nasa.gov/catalog/PIA07904

  6. 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)

  7. 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)

  8. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  9. HUBBLE CAPTURES AN EXTRAORDINARY AND POWERFUL ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Resembling a swirling witch's cauldron of glowing vapors, the black hole-powered core of a nearby active galaxy appears in this colorful NASA Hubble Space Telescope image. The galaxy lies 13 million light-years away in the southern constellation Circinus. This galaxy is designated a type 2 Seyfert, a class of mostly spiral galaxies that have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGN. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at the center of this galaxy as well. Much of the gas in the disk of the Circinus spiral is concentrated in two specific rings -- a larger one of diameter 1,300 light-years, which has already been observed by ground-based telescopes, and a previously unseen ring of diameter 260 light-years. In the Hubble image, the smaller inner ring is located on the inside of the green disk. The larger outer ring extends off the image and is in the plane of the galaxy's disk. Both rings are home to large amounts of gas and dust as well as areas of major 'starburst' activity, where new stars are rapidly forming on timescales of 40 - 150 million years, much shorter than the age of the entire galaxy. At the center of the starburst rings is the Seyfert nucleus, the believed signature of a supermassive black hole that is accreting surrounding gas and dust. The black hole and its accretion disk are expelling gas out of the galaxy's disk and into its halo (the region above and below the disk). The detailed structure of this gas is seen as magenta-colored streamers extending towards the top of the image. In the center of the galaxy and within the inner starburst ring is a V-shaped structure of gas. The structure appears whitish-pink in this composite image, made up of four filters. Two

  10. HUBBLE CAPTURES AN EXTRAORDINARY AND POWERFUL ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Resembling a swirling witch's cauldron of glowing vapors, the black hole-powered core of a nearby active galaxy appears in this colorful NASA Hubble Space Telescope image. The galaxy lies 13 million light-years away in the southern constellation Circinus. This galaxy is designated a type 2 Seyfert, a class of mostly spiral galaxies that have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGN. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at the center of this galaxy as well. Much of the gas in the disk of the Circinus spiral is concentrated in two specific rings -- a larger one of diameter 1,300 light-years, which has already been observed by ground-based telescopes, and a previously unseen ring of diameter 260 light-years. In the Hubble image, the smaller inner ring is located on the inside of the green disk. The larger outer ring extends off the image and is in the plane of the galaxy's disk. Both rings are home to large amounts of gas and dust as well as areas of major 'starburst' activity, where new stars are rapidly forming on timescales of 40 - 150 million years, much shorter than the age of the entire galaxy. At the center of the starburst rings is the Seyfert nucleus, the believed signature of a supermassive black hole that is accreting surrounding gas and dust. The black hole and its accretion disk are expelling gas out of the galaxy's disk and into its halo (the region above and below the disk). The detailed structure of this gas is seen as magenta-colored streamers extending towards the top of the image. In the center of the galaxy and within the inner starburst ring is a V-shaped structure of gas. The structure appears whitish-pink in this composite image, made up of four filters. Two

  11. Galaxy Zoo Hubble: Crowdsourced Morphologies for 169,944 Galaxies at 0

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Galloway, Melanie; Fortson, Lucy; Bamford, Steven; Masters, Karen; Lintott, Chris; Simmons, Brooke; Cheung, Edmond; Schawinski, Kevin; Scarlata, Claudia; Beck, Melanie; Galaxy Zoo volunteers

    2016-01-01

    The Galaxy Zoo project uses crowdsourced visual classifications to create large and statistically robust catalogs of detailed galaxy morphology. We present initial results for the Galaxy Zoo: Hubble dataset, which includes 169,944 images of galaxies selected from the AEGIS, COSMOS, GEMS, and GOODS surveys. The galaxies span a redshift range of 0galaxies, as well as identifying kpc-scale features including galactic bars, spiral arms, irregular structure, and mergers. In addition, we also measure the geometry and relative positions of clumpy structures that are unique to high-redshift star-forming galaxies. Visual classifications are calibrated using a set of z≈0.05 SDSS images that are processed to appear as they would at a variety of simulated redshifts using Hubble; this measures the morphological bias for galaxies as a function of changing the apparent size and brightness, without overcorrecting for effects such as an evolving Lstar. We present a new technique for debiasing the morphologies based on a simple parametric model of surface brightness and distance, which adjusts the threshold for detecting feature or disk-dominated galaxies in fainter galaxies and at higher redshifts. We demonstrate the effectiveness of this technique for bulge/disk separation, and discuss its applications and limitations for smaller physical sub-structures. We also present preliminary results analyzing the evolution of disk sub-structure as a function of cosmic time. All the above data will be included in the upcoming release of the full Galaxy Zoo: Hubble catalog.

  12. The EFIGI catalogue of 4458 nearby galaxies with morphology. II. Statistical properties along the Hubble sequence

    NASA Astrophysics Data System (ADS)

    de Lapparent, V.; Baillard, A.; Bertin, E.

    2011-08-01

    Aims: The EFIGI catalogue of 4458 galaxies extracted from the PGC and SDSS DR4 was designed to provide a multiwavelength reference database of the morphological properties of nearby galaxies. The sample is limited in apparent diameter and densely samples all RC3 Hubble types. Methods: We examine the statistics of the 16 EFIGI shape attributes, describing the various dynamical components, the texture, and the contamination by the environment of each galaxy. Using the redshifts from SDSS, HyperLeda, or NED for 99.53% of EFIGI galaxies, we derive estimates of absolute major isophotal diameters and the corresponding mean surface brightness in the SDSS g-band. Results: We study the variations of the EFIGI morphological attributes with Hubble type and confirm that the visual Hubble sequence is a decreasing sequence of bulge-to-total ratio and an increasing sequence of disk contribution to the total galaxy flux. There is, nevertheless, a total spread of approximately five types for a given bulge-to-total ratio, because the Hubble sequence is primarily based on the strength and pitch angle of the spiral arms, independently from the bulge-to-total ratio. A steep decrease in the presence of dust from Sb to Sbc-Sc types appears to produce the grand spiral design of the Sc galaxies. In contrast, the scattered and giant HII regions show different strength variation patterns, with peaks for types Scd and Sm; hence, they do not appear to directly participate in the establishment of the visual Hubble sequence. The distortions from a symmetric profile also incidentally increase along the sequence. Bars and inner rings are frequent and occur in 41% and 25% of the disk galaxies respectively. Outer rings are half as frequent than inner rings, and outer pseudo-rings occur in 11% of barred galaxies. Finally, we find a smooth decrease in mean surface brightness and intrinsic size along the Hubble sequence. The largest galaxies are cD, ellipticals and Sab-Sbc intermediate spirals (20

  13. Hubble Sees 'Ghost Light' From Dead Galaxies

    NASA Image and Video Library

    2017-09-28

    NASA’s Hubble Space Telescope has picked up the faint, ghostly glow of stars ejected from ancient galaxies that were gravitationally ripped apart several billion years ago. The mayhem happened 4 billion light-years away, inside an immense collection of nearly 500 galaxies nicknamed “Pandora’s Cluster,” also known as Abell 2744. The scattered stars are no longer bound to any one galaxy, and drift freely between galaxies in the cluster. By observing the light from the orphaned stars, Hubble astronomers have assembled forensic evidence that suggests as many as six galaxies were torn to pieces inside the cluster over a stretch of 6 billion years. Read more: 1.usa.gov/1yK2Ucp Credit: NASA/ESA/IAC/HFF Team, STScI 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

  14. Ultraviolet Spectra of Normal Spiral Galaxies

    NASA Technical Reports Server (NTRS)

    Kinney, Anne

    1997-01-01

    The data related to this grant on the Ultraviolet Spectra of Normal Spiral Galaxies have been entirely reduced and analyzed. It is incorporated into templates of Spiral galaxies used in the calculation of K corrections towards the understanding of high redshift galaxies. The main paper was published in the Astrophysical Journal, August 1996, Volume 467, page 38. The data was also used in another publication, The Spectral Energy Distribution of Normal Starburst and Active Galaxies, June 1997, preprint series No. 1158. Copies of both have been attached.

  15. Outer spiral structure in disk galaxies

    NASA Astrophysics Data System (ADS)

    Patsis, P. A.

    2017-03-01

    In several grand design barred-spiral galaxies it is observed a second, fainter, outer set of spiral arms. Typical examples of objects of this morphology can be considered NGC 1566 and NGC 5248. I suggest that such an overall structure can be the result of two dynamical mechanisms acting in the disc. The bar and both spiral systems rotate with the same pattern speed. The inner spiral is reinforced by regular orbits trapped around the stable, elliptical, periodic orbits of the central family, while the outer system of spiral arms is supported by chaotic orbits. Chaotic orbits are also responsible for a rhomboidal area surrounding the inner barred-spiral region. In general there is a discontinuity between the two spiral structures at the corotation region.

  16. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  17. HUBBLE CAPTURES MERGER BETWEEN QUASAR AND GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope image shows evidence fo r a merger between a quasar and a companion galaxy. This surprising result might require theorists to rethink their explanations for the nature of quasars, the most energetic objects in the universe. The bright central object is the quasar itself, located several billion light-years away. The two wisps on the (left) of the bright central object are remnants of a bright galaxy that have been disrupted by the mutual gravitational attraction between the quasar and the companion galaxy. This provides clear evidence for a merger between the two objects. Since their discovery in 1963, quasars (quasi-stellar objects) have been enigmatic because they emit prodigious amounts of energy from a very compact source. The most widely accepted model is that a quasar is powered by a supermassive black hole in the core of a galaxy. These new observations proved a challenge for theorists as no current models predict the complex quasar interactions unveiled by Hubble. The image was taken with the Wide Field Planetary Camera-2. Credit: John Bahcall, Institute for Advanced Study, NASA.

  18. Nonresonance Spiral Responses in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Polyachenko, V. L.; Polyachenko, E. V.

    2002-01-01

    The behavior of the gravitational potential outside the region where the main spiral arms of galaxies are located is investigated. The characteristic features of this behavior include nearly circular extensions of the main arms, which typically have an angular extent of 90°. It is natural to interpret these quarter-turn spirals as the response of the galactic disk to the gravitational potential of the main spiral arms. The theoretical models are supported by observational data for the brightness distributions in both normal (NGC 3631) and barred (NGC 1365) galaxies.

  19. The Spiral Structure of AGN Host Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, J.; Barrows, R. S.; Hughes, J. A.; Schilling, A.; Davis, B.; Shields, D.; Madey, A.; Kennefick, D.; Lacy, C.; Seigar, M.

    2014-03-01

    Recent work has uncovered a correlation between the black hole mass, M, in the centers of local spiral galaxies and the pitch angles, P, of their spiral arms. We propose to test this M-P correlation at moderate to high redshifts, using a sample of active galaxies selected from the Great Observatories Origins Survey and the Sloan Digital Sky Survey showing evidence for spiral structure in their host galaxies. The mass of the central black holes are estimated using the Hβ or Mg II lines in existing spectra using luminosity-radius scaling relations. Pitch angles are measured using an iterative 2D FFT algorithm. The aim is to establish this M-P relation beyond our local epoch, test for evolution in its form, and eventually to compute a BH mass function for late-type galaxies out to moderate redshifts.

  20. Cinematique et dynamique des galaxies spirales barrees

    NASA Astrophysics Data System (ADS)

    Hernandez, Olivier

    The total mass (luminous and dark) of galaxies is derived from their circular velocities. Spectroscopic Fabry-Perot observations of the ionized gas component of spiral galaxies allow one to derive their kinematics. In the case of purely axisymmetric velocity fields--as in non-active and unbarred spirals galaxies-- the circular velocities can be derived directly. However, the velocity fields of barred galaxies (which constitute two thirds of the spirals) exhibit strong non-circular motions and need a careful analysis to retrieve the circular component. This thesis proposes the necessary steps to recover the axisymmetric component of barred spiral galaxies. The first step was to develop the best instrumentation possible for this work. [Special characters omitted.] , which is the most sensitive photon counting camera ever developed, was coupled to a Fabry-Perot interferometer. The observations of a sample of barred spiral galaxies--the BH a BAR sample--was assembled in order to obtain the most rigourous velocity fields. Then, the Tremaine-Weinberg method, which can determine the bar pattern speed and is usually used with the observations of stellar component, has been tested on the ionised gas and gave satisfactory results. Finally, all the above techniques have been applied to the BH a BAR sample in order to study the key parameters of the galaxies' evolution--bar pattern speeds, multiple stationary waves, resonances etc.--which will allow one to use N-body+SPH simulations to model properly the non-circular motions and determine the true total mass of barred spiral galaxies.

  1. Pitch angle variations in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Savchenko, S. S.; Reshetnikov, V. P.

    2013-12-01

    We present a detailed photometric study and measurements of spiral arm pitch angles for a sample of 50 non-barred or weakly barred grand-design spiral galaxies selected from Sloan Digital Sky Survey. In order to find pitch angles, we used a new method based on the window Fourier analysis of their images. This method allows us not only to infer the average pitch angle, but to obtain its value as a function of galactocentric radius as well. Our main results are as follows: (1) Spiral arms of most galaxies cannot be described by a single value of the pitch angle. About 2/3 of galaxies demonstrate pitch angle variations exceeding 20 per cent. In most galaxies in the sample their pitch angle decreases by increasing the distance from the centre. (2) Pitch angle variations correlate with the properties of galaxies - with the shape of the surface brightness distribution (envelope-type or truncated disc), and with the sign of stellar disc colour gradient. (3) More luminous and bright bulges produce more tightly wound spiral arms, that is in agreement with current models for spiral arms formation.

  2. HUBBLE PROBES THE VIOLENT BIRTH OF STARS IN GALAXY NGC 253 [Left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the spiral galaxy NGC 253, taken with a ground-based telescope. The galaxy is located about 8 million light-years away in the constellation Sculptor. Credit: Jay Gallagher (University of Wisconsin-Madison), Alan Watson (Lowell Observatory, Flagstaff, AZ), and NASA [Right] This NASA Hubble Space Telescope image of the core of the nearest starburst spiral galaxy, NGC 253, reveals violent star formation within a region 1,000 light-years across. A starburst galaxy has an exceptionally high rate of star birth, first identified by its excess of infrared radiation from warm dust. Hubble's high resolution allows astronomers to quantify complex structures in the starburst core of the galaxy for the first time, including luminous star clusters, dust lanes which trace regions of dense gas and filaments of glowing gas. Hubble identifies several regions of intense star formation, which include a bright, super-compact star cluster. These observations confirm that stars are often born in dense clusters within starbursts, and that dense gas coexists with and obscures the starburst core. This image was taken with Hubble's Wide Field Planetary Camera 2 (in PC mode). Credit: Carnegie Institution of Washington

  3. HUBBLE PROBES THE VIOLENT BIRTH OF STARS IN GALAXY NGC 253 [Left

    NASA Technical Reports Server (NTRS)

    2002-01-01

    An image of the spiral galaxy NGC 253, taken with a ground-based telescope. The galaxy is located about 8 million light-years away in the constellation Sculptor. Credit: Jay Gallagher (University of Wisconsin-Madison), Alan Watson (Lowell Observatory, Flagstaff, AZ), and NASA [Right] This NASA Hubble Space Telescope image of the core of the nearest starburst spiral galaxy, NGC 253, reveals violent star formation within a region 1,000 light-years across. A starburst galaxy has an exceptionally high rate of star birth, first identified by its excess of infrared radiation from warm dust. Hubble's high resolution allows astronomers to quantify complex structures in the starburst core of the galaxy for the first time, including luminous star clusters, dust lanes which trace regions of dense gas and filaments of glowing gas. Hubble identifies several regions of intense star formation, which include a bright, super-compact star cluster. These observations confirm that stars are often born in dense clusters within starbursts, and that dense gas coexists with and obscures the starburst core. This image was taken with Hubble's Wide Field Planetary Camera 2 (in PC mode). Credit: Carnegie Institution of Washington

  4. Ring Galaxy AM 0644-741 Captured by Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Released to commemorate the 14th anniversary of NASA's Hubble Space Telescope (HST) is the image of a galaxy cataloged as AM 0644-741. Resembling a diamond encrusted bracelet, the ring of brilliant blue star clusters wraps around a yellowish nucleus of what was once a normal spiral galaxy. Located 300 million light years away in the direction of the southern constellation Dorado, the sparkling blue ring is 150,000 light years in diameter, making it larger than our entire home galaxy, the Milky Way. Ring galaxies are a striking example of how collisions between galaxies can dramatically change their structure, while triggering the formation of new stars. Typically one galaxy plunges directly into the disk of another one. The ring that pierced through this galaxy's ring is out of the image but is visible in larger-field images. The soft galaxy visible to the left of the ring galaxy is a coincidental background galaxy which is not interacting with the ring. Rampant star formation explains why the ring is so blue. It is continuously forming massive, young, hot stars. Another sign of robust star formation is the pink regions along the ring. These are rare clouds of glowing hydrogen gas, fluorescing because of the strong ultraviolet light from the newly formed stars. The Hubble Heritage Team used the Hubble Advanced Camera for Surveys to take this image using a combination of four separate filters that isolate blue, green, red, and near-infrared light to create the color image.

  5. Ring Galaxy AM 0644-741 Captured by Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Released to commemorate the 14th anniversary of NASA's Hubble Space Telescope (HST) is the image of a galaxy cataloged as AM 0644-741. Resembling a diamond encrusted bracelet, the ring of brilliant blue star clusters wraps around a yellowish nucleus of what was once a normal spiral galaxy. Located 300 million light years away in the direction of the southern constellation Dorado, the sparkling blue ring is 150,000 light years in diameter, making it larger than our entire home galaxy, the Milky Way. Ring galaxies are a striking example of how collisions between galaxies can dramatically change their structure, while triggering the formation of new stars. Typically one galaxy plunges directly into the disk of another one. The ring that pierced through this galaxy's ring is out of the image but is visible in larger-field images. The soft galaxy visible to the left of the ring galaxy is a coincidental background galaxy which is not interacting with the ring. Rampant star formation explains why the ring is so blue. It is continuously forming massive, young, hot stars. Another sign of robust star formation is the pink regions along the ring. These are rare clouds of glowing hydrogen gas, fluorescing because of the strong ultraviolet light from the newly formed stars. The Hubble Heritage Team used the Hubble Advanced Camera for Surveys to take this image using a combination of four separate filters that isolate blue, green, red, and near-infrared light to create the color image.

  6. Chandra Observatory Reveals Spiral Galaxy's Boisterous Activity

    NASA Technical Reports Server (NTRS)

    2003-01-01

    This Chandra X-ray observatory image of M83 shows numerous point-like neutron stars and black hole x-ray sources scattered throughout the disk of this spiral galaxy. The bright nuclear region of the galaxy glows prominently due to a burst of star formation that is estimated to have begun about 20 million years ago in the galaxy's time frame. The nuclear region, enveloped by a 7 million degree Celsius gas cloud of carbon, neon, magnesium, silicon, and sulfur atoms, contains a much higher concentration of neutron stars and black holes than the rest of the galaxy. Hot gas with a slightly lower temperature of 4 million degrees observed along the spiral arms of the galaxy suggests that star formation in this region may be occurring at a more sedate rate.

  7. 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

  8. Thickness determination of three-dimensional spiral galaxies.

    NASA Astrophysics Data System (ADS)

    Zhao, Shanghui; Bao, Mengxian; Zhang, Wenyuan; Peng, Qiuhe

    1992-12-01

    CCD images of some spiral galaxies were obtained with the 1-m telescope of Yunnan Observatory. After processing and measuring the images, the authors get the morphological parameters, thickness and their relative errors of seven spiral galaxies (NGC 2608, NGC 2713, NGC 2776, NGC 3631, NGC 5669, NGC 5985 and NGC 7156) by fitting their spiral arms with logarithmic spirals.

  9. Precision distances with spiral galaxy apparent diameters

    NASA Astrophysics Data System (ADS)

    Steer, Ian

    2016-01-01

    Spiral galaxy diameters offer the oldest extragalactic distance indicator known. Although outdated and hitherto imprecise, two spiral diameter-based distance indicators applied in the 1980s can be tested, calibrated, and re-established for precision era use, based on abundant redshift-independent distances data available in NED-D. Indicator one employs the largest Giant Spiral Galaxies, which have an absolute isophotal major diameter of ~70 +/- 10 kpc, offering standard ruler-based distances with <10% precision. Indicator two employs the diameter-magnitude relation for spirals in general, as a secondary indicator, offering ~20% precision. The ruler-based indicator is the only indicator with <10% precision able to independently calibrate type Ia supernovae-based distances at cosmological distances. The secondary-based indicator is the only indicator with 20% precision applicable to more galaxies than in current Tully-Fisher surveys. The primary indicator gives researchers a new tool to confirm or refute if, as currently believed, universal expansion is accelerating. The secondary indicator gives researchers a new path toward acquiring a more complete 3D picture of the local universe and potentially, because the majority of galaxies in the universe are spirals, the distant universe.

  10. Hubble Reveals Stellar Fireworks in ‘Skyrocket’ Galaxy

    NASA Image and Video Library

    2017-09-28

    Fireworks shows are not just confined to Earth’s skies. NASA’s Hubble Space Telescope has captured a spectacular fireworks display in a small, nearby galaxy, which resembles a July 4th skyrocket. A firestorm of star birth is lighting up one end of the diminutive galaxy Kiso 5639. The dwarf galaxy is shaped like a flattened pancake, but because it is tilted edge-on, it resembles a skyrocket, with a brilliant blazing head and a long, star-studded tail. Kiso 5639 is a rare, nearby example of elongated galaxies that occur in abundance at larger distances, where we observe the universe during earlier epochs. Astronomers suggest that the frenzied star birth is sparked by intergalactic gas raining on one end of the galaxy as it drifts through space. “I think Kiso 5639 is a beautiful, up-close example of what must have been common long ago,” said lead researcher Debra Elmegreen of Vassar College, in Poughkeepsie, New York. “The current thinking is that galaxies in the early universe grow from accreting gas from the surrounding neighborhood. It’s a stage that galaxies, including our Milky Way, must go through as they are growing up.” Observations of the early universe, such as Hubble’s Ultra-Deep Field, reveal that about 10 percent of all galaxies have these elongated shapes, and are collectively called “tadpoles.” But studies of the nearby universe have turned up only a few of these unusual galaxies, including Kiso 5639. The development of the nearby star-making tadpole galaxies, however, has lagged behind that of their peers, which have spent billions of years building themselves up into many of the spiral galaxies seen today. Elmegreen used Hubble’s Wide Field Camera 3 to conduct a detailed imaging study of Kiso 5639. The images in different filters reveal information about an object by dissecting its light into its component colors. Hubble’s crisp resolution helped Elmegreen and her team analyze the giant star-forming clumps in Kiso 5639 and

  11. Energetic constraints to chemo-photometric evolution of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Buzzoni, Alberto

    2011-08-01

    galaxies; (iii) although lower-mass galaxies tend more likely to take the look of later-type spirals, it is mass, not morphology, that drives galaxy chemical properties. Facing the relatively flat trend of ? versus galaxy type, the increasingly poorer gas metallicity, as traced by the [O/H] abundance of H II regions along the Sa → Im Hubble sequence, seems to be mainly the result of the softening process, that dilute enriched stellar mass within a larger fraction of residual gas. The problem of the residual lifetime for spiral galaxies as active star-forming systems has been investigated. If returned mass is left as the main (or unique) gas supplier to the ISM, as implied by the Roberts time-scale, then star formation might continue only at a maximum birthrate bmax≪f/(1 -f) ≲ 0.45, for a Salpeter IMF. As a result, only massive (Mgal≳ 1011 M⊙) Sa/Sb spirals may have some chance to survive ˜30 per cent or more beyond a Hubble time. Things may be worse, on the contrary, for dwarf systems, that seem currently on the verge of ceasing their star formation activity unless to drastically reduce their apparent birthrate below the bmax threshold.

  12. The Edwin Hubble papers - Previously unpublished manuscripts on the extragalactic nature of spiral nebulae

    SciTech Connect

    Hetherington, N.S.

    1990-01-01

    Edwin Hubble's previously unpublished manuscripts on the extragalactic nature of spiral nebulae are presented. Manuscripts include the Cepheid criterion and spiral nebulae, Van Maanen's corrobarative evidence, the build up of a star image on a photographic plate, measures of M81 for internal motion, and angular rotations of spiral nebulae.

  13. The basic dynamical mechanism in spiral galaxies.

    PubMed

    Pfenniger, Daniel; Revaz, Yves

    2005-06-01

    This paper explicates the most fundamental mechanism that rules spiral galaxies. Although spiral galaxies are complex systems for which we do not yet have a complete understanding, the dark matter being the most severe unknown, it is possible to pinpoint the few physical factors that determine their most important properties, such as bars and spiral arms. Dynamics linked to the dissipative nature of gas and its transformation into stars provides clues that spiral galaxies are driven by dissipation close to a state of marginal stability with respect to the dynamics in the galaxy plane. Here, we present numerical evidence suggesting that warps play a similar role but in the transverse direction. N-body simulations show that typical galactic disks are also marginally stable with respect to a bending instability, leading to typical observed warps. The frequent occurrence of warps and asymmetries in the outer galactic disks, like bars in the inner disks, give new constraints on the dark matter, but this time in the outer disks.

  14. Magnetic spiral arms in galaxy haloes

    NASA Astrophysics Data System (ADS)

    Henriksen, R. N.

    2017-08-01

    We seek the conditions for a steady mean field galactic dynamo. The parameter set is reduced to those appearing in the α2 and α/ω dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyse the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES) survey.

  15. Hubble Reveals Stellar Fireworks in ‘Skyrocket’ Galaxy

    NASA Image and Video Library

    2016-06-29

    Fireworks shows are not just confined to Earth’s skies. NASA’s Hubble Space Telescope has captured a spectacular fireworks display in a small, nearby galaxy, which resembles a July 4th skyrocket. A firestorm of star birth is lighting up one end of the diminutive galaxy Kiso 5639. The dwarf galaxy is shaped like a flattened pancake, but because it is tilted edge-on, it resembles a skyrocket, with a brilliant blazing head and a long, star-studded tail. Kiso 5639 is a rare, nearby example of elongated galaxies that occur in abundance at larger distances, where we observe the universe during earlier epochs. Astronomers suggest that the frenzied star birth is sparked by intergalactic gas raining on one end of the galaxy as it drifts through space. “I think Kiso 5639 is a beautiful, up-close example of what must have been common long ago,” said lead researcher Debra Elmegreen of Vassar College, in Poughkeepsie, New York. “The current thinking is that galaxies in the early universe grow from accreting gas from the surrounding neighborhood. It’s a stage that galaxies, including our Milky Way, must go through as they are growing up.” Observations of the early universe, such as Hubble’s Ultra-Deep Field, reveal that about 10 percent of all galaxies have these elongated shapes, and are collectively called “tadpoles.” But studies of the nearby universe have turned up only a few of these unusual galaxies, including Kiso 5639. The development of the nearby star-making tadpole galaxies, however, has lagged behind that of their peers, which have spent billions of years building themselves up into many of the spiral galaxies seen today. Elmegreen used Hubble’s Wide Field Camera 3 to conduct a detailed imaging study of Kiso 5639. The images in different filters reveal information about an object by dissecting its light into its component colors. Hubble’s crisp resolution helped Elmegreen and her team analyze the giant star-forming clumps in Kiso 5639 and

  16. The Ultraviolet Attenuation Law in Backlit Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly "gray" law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread

  17. Hubble Space Telescope Observations of the CFA Seyfert 2 Galaxies: The Fueling of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Martini, Paul; Pogge, Richard W.

    1999-12-01

    We present an investigation of possible fueling mechanisms operating in the inner kiloparsec of Seyfert galaxies. We analyze visible and near-infrared Hubble Space Telescope images of 24 Seyfert 2 galaxies from the CfA Redshift Survey sample. In particular, we are searching for the morphological signatures of dynamical processes responsible for transporting gas from kiloparsec scales into the nucleus. The circumnuclear regions are very rich in gas and dust, often taking the form of nuclear spiral dust lanes on scales of a few hundred parsecs. While these nuclear spirals are found in 20 of our 24 Seyfert galaxies, we find only five nuclear bars among the entire sample, strongly reinforcing the conclusions of other investigators that nuclear bars are not the primary means of transporting this material into the nucleus. An estimate of the gas density in the nuclear spirals, based on extinction measurements, suggests that the nuclear spiral dust lanes are probably shocks in nuclear gas disks that are not strongly self-gravitating. Since shocks can dissipate energy and angular momentum, these spiral dust lanes may be the channels by which gas from the host galaxy disks is being fed into the central engines.

  18. Hubble Space Telescope First Observations of the Brightest Stars in the Virgo Galaxy M100 = NGC 4321

    NASA Technical Reports Server (NTRS)

    Freedman, W. L.; Madore, B. F.; Stetson, P. B.; Hughes, S. M. G.; Holtzman, J. A.; Mould, J. R.; Trauger, J. T.; Gallagher, J. S., III; Ballester, G. E.; Burrows, C. J.; Casertano, S.; Clarke, J. T; Crisp, D.; Ferrarese, L.; Ford, H.; Graham, J. A.; Griffiths, R. E.; Hester, J. J.; Hill, R.; Hoessel, J. G.; Huchra, J.; Kennicutt, R. C.; Scowen, P. A.; Sparks, B.; Stapelfeldt, K. R.

    1994-01-01

    As part of both the Early Release Observations fromthe Hubble Space Telescope and the Key PRoject on the Extragalctic Distance Scale, we have obtained multi-wavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M11 = NGC 4321.

  19. The ultraviolet attenuation law in backlit spiral galaxies

    SciTech Connect

    Keel, William C.; Manning, Anna M.; Holwerda, Benne W.; Lintott, Chris J.; Schawinski, Kevin E-mail: ammanning@bama.ua.edu E-mail: Twitter@BenneHolwerda E-mail: Twitter@chrislintott E-mail: Twitter@kevinschawinski

    2014-02-01

    The effective extinction law (attenuation behavior) in galaxies in the emitted ultraviolet (UV) regime is well known only for actively star-forming objects and combines effects of the grain properties, fine structure in the dust distribution, and relative distributions of stars and dust. We use Galaxy Evolution Explorer, XMM Optical Monitor, and Hubble Space Telescope (HST) data to explore the UV attenuation in the outer parts of spiral disks which are backlit by other UV-bright galaxies, starting with the candidate list of pairs provided by Galaxy Zoo participants. New optical images help to constrain the geometry and structure of the target galaxies. Our analysis incorporates galaxy symmetry, using non-overlapping regions of each galaxy to derive error estimates on the attenuation measurements. The entire sample has an attenuation law across the optical and UV that is close to the Calzetti et al. form; the UV slope for the overall sample is substantially shallower than found by Wild et al., which is a reasonable match to the more distant galaxies in our sample but not to the weighted combination including NGC 2207. The nearby, bright spiral NGC 2207 alone gives an accuracy almost equal to the rest of our sample, and its outer arms have a very low level of foreground starlight. Thus, this widespread, fairly 'gray' law can be produced from the distribution of dust alone, without a necessary contribution from differential escape of stars from dense clouds. Our results indicate that the extrapolation needed to compare attenuation between backlit galaxies at moderate redshifts from HST data, and local systems from Sloan Digital Sky Survey and similar data, is mild enough to allow the use of galaxy overlaps to trace the cosmic history of dust in galaxies. For NGC 2207, HST data in the near-UV F336W band show that the covering factor of clouds with small optical attenuation becomes a dominant factor farther into the UV, which opens the possibility that widespread

  20. HUBBLE SURVEYS DYING STARS IN NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    From ground-based telescopes, the glowing gaseous debris surrounding dying, sun-like stars in a nearby galaxy, called the Large Magellanic Cloud, appear as small, shapeless dots of light. But through the 'eyes' of NASA's Hubble Space Telescope, these bright dots take on a variety of shapes, from round- to pinwheel-shaped clouds of gas. Using Hubble's Space Telescope Imaging Spectrograph, scientists probed the glowing gas surrounding 27 dying stars, called planetary nebulae, in the Large Magellanic Cloud. The observations represent the most detailed study of planetary nebulae outside the Milky Way. The six objects in the picture illustrate the assortment of planetary nebulae identified in the galaxy. SMP 16, 30, and 93 are examples of a bipolar nebula, twin lobes of gas projecting away from a dying star. SMP 10 has a pinwheel shape and is known as a 'point-symmetric' nebula. SMP 4 has an elliptical appearance, and SMP 27, consisting of four lobes of gas, is called a 'quadrupolar' nebula. The lines point to the objects' locations in the Large Magellanic Cloud. A ground-based observatory snapped the picture of this galaxy. In the pictures of the planetary nebulae, color corresponds to temperature. Blue represents hotter regions of the nebulae and red, cooler. Scientists are probing these illuminated stellar relics in our neighboring galaxy because they are at relatively the same distance - about 168,000 light-years -- from Earth. Knowing the distance to these objects allows scientists to compare their shapes and sizes, and precisely determine the brightness of their central stars. For this reason, even though these glowing remains of dying stars are about 50 times farther away than the stunning planetary nebulae photographed in the Milky Way, they are of invaluable importance. By sampling this population, scientists noticed that the bipolar nebulae are richer in some heavier elements, such as neon, than those with a more spherical shape. At the dawn of the universe

  1. HUBBLE SURVEYS DYING STARS IN NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    From ground-based telescopes, the glowing gaseous debris surrounding dying, sun-like stars in a nearby galaxy, called the Large Magellanic Cloud, appear as small, shapeless dots of light. But through the 'eyes' of NASA's Hubble Space Telescope, these bright dots take on a variety of shapes, from round- to pinwheel-shaped clouds of gas. Using Hubble's Space Telescope Imaging Spectrograph, scientists probed the glowing gas surrounding 27 dying stars, called planetary nebulae, in the Large Magellanic Cloud. The observations represent the most detailed study of planetary nebulae outside the Milky Way. The six objects in the picture illustrate the assortment of planetary nebulae identified in the galaxy. SMP 16, 30, and 93 are examples of a bipolar nebula, twin lobes of gas projecting away from a dying star. SMP 10 has a pinwheel shape and is known as a 'point-symmetric' nebula. SMP 4 has an elliptical appearance, and SMP 27, consisting of four lobes of gas, is called a 'quadrupolar' nebula. The lines point to the objects' locations in the Large Magellanic Cloud. A ground-based observatory snapped the picture of this galaxy. In the pictures of the planetary nebulae, color corresponds to temperature. Blue represents hotter regions of the nebulae and red, cooler. Scientists are probing these illuminated stellar relics in our neighboring galaxy because they are at relatively the same distance - about 168,000 light-years -- from Earth. Knowing the distance to these objects allows scientists to compare their shapes and sizes, and precisely determine the brightness of their central stars. For this reason, even though these glowing remains of dying stars are about 50 times farther away than the stunning planetary nebulae photographed in the Milky Way, they are of invaluable importance. By sampling this population, scientists noticed that the bipolar nebulae are richer in some heavier elements, such as neon, than those with a more spherical shape. At the dawn of the universe

  2. STELLAR ORBITAL STUDIES IN NORMAL SPIRAL GALAXIES. I. RESTRICTIONS TO THE PITCH ANGLE

    SciTech Connect

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.

    2013-08-01

    We built a family of non-axisymmetric potential models for normal non-barred or weakly barred spiral galaxies as defined in the simplest classification of galaxies: the Hubble sequence. For this purpose, a three-dimensional self-gravitating model for the spiral arm PERLAS is superimposed on the galactic axisymmetric potentials. We analyze the stellar dynamics varying only the pitch angle of the spiral arms, from 4 Degree-Sign to 40 Degree-Sign for an Sa galaxy, from 8 Degree-Sign to 45 Degree-Sign for an Sb galaxy, and from 10 Degree-Sign to 60 Degree-Sign for an Sc galaxy. Self-consistency is indirectly tested through periodic orbital analysis and through density response studies for each morphological type. Based on ordered behavior, periodic orbit studies show that, for pitch angles up to approximately 15 Degree-Sign , 18 Degree-Sign , and 20 Degree-Sign for Sa, Sb, and Sc galaxies, respectively, the density response supports the spiral arms' potential, a requisite for the existence of a long-lasting large-scale spiral structure. Beyond those limits, the density response tends to ''avoid'' the potential imposed by maintaining lower pitch angles in the density response; in that case, the spiral arms may be explained as transient features rather than long-lasting large-scale structures. In a second limit, from a phase-space orbital study based on chaotic behavior, we found that for pitch angles larger than {approx}30 Degree-Sign , {approx}40 Degree-Sign , and {approx}50 Degree-Sign for Sa, Sb, and Sc galaxies, respectively, chaotic orbits dominate the all phase-space prograde region that surrounds the periodic orbits sculpting the spiral arms and even destroying them. This result seems to be in good agreement with observations of pitch angles in typical isolated normal spiral galaxies.

  3. LIFTING THE VEIL OF DUST TO REVEAL THE SECRETS OF SPIRAL GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have combined information from the NASA Hubble Space Telescope's visible- and infrared-light cameras to show the hearts of four spiral galaxies peppered with ancient populations of stars. The top row of pictures, taken by a ground-based telescope, represents complete views of each galaxy. The blue boxes outline the regions observed by the Hubble telescope. The bottom row represents composite pictures from Hubble's visible- and infrared-light cameras, the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Astronomers combined views from both cameras to obtain the true ages of the stars surrounding each galaxy's bulge. The Hubble telescope's sharper resolution allows astronomers to study the intricate structure of a galaxy's core. The galaxies are ordered by the size of their bulges. NGC 5838, an 'S0' galaxy, is dominated by a large bulge and has no visible spiral arms; NGC 7537, an 'Sbc' galaxy, has a small bulge and loosely wound spiral arms. Astronomers think that the structure of NGC 7537 is very similar to our Milky Way. The galaxy images are composites made from WFPC2 images taken with blue (4445 Angstroms) and red (8269 Angstroms) filters, and NICMOS images taken in the infrared (16,000 Angstroms). They were taken in June, July, and August of 1997. Credits for the ground-based images: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for WFPC2 and NICMOS composites: NASA, ESA, and Reynier Peletier (University of Nottingham, United Kingdom)

  4. LIFTING THE VEIL OF DUST TO REVEAL THE SECRETS OF SPIRAL GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Astronomers have combined information from the NASA Hubble Space Telescope's visible- and infrared-light cameras to show the hearts of four spiral galaxies peppered with ancient populations of stars. The top row of pictures, taken by a ground-based telescope, represents complete views of each galaxy. The blue boxes outline the regions observed by the Hubble telescope. The bottom row represents composite pictures from Hubble's visible- and infrared-light cameras, the Wide Field and Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Astronomers combined views from both cameras to obtain the true ages of the stars surrounding each galaxy's bulge. The Hubble telescope's sharper resolution allows astronomers to study the intricate structure of a galaxy's core. The galaxies are ordered by the size of their bulges. NGC 5838, an 'S0' galaxy, is dominated by a large bulge and has no visible spiral arms; NGC 7537, an 'Sbc' galaxy, has a small bulge and loosely wound spiral arms. Astronomers think that the structure of NGC 7537 is very similar to our Milky Way. The galaxy images are composites made from WFPC2 images taken with blue (4445 Angstroms) and red (8269 Angstroms) filters, and NICMOS images taken in the infrared (16,000 Angstroms). They were taken in June, July, and August of 1997. Credits for the ground-based images: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for WFPC2 and NICMOS composites: NASA, ESA, and Reynier Peletier (University of Nottingham, United Kingdom)

  5. Hα Imaging of Early-Type (SA-SAB) Spiral Galaxies. I.

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Devereux, Nick

    1999-08-01

    Hα and continuum images are presented for 27 nearby early-type (Sa-Sab) spiral galaxies. Contrary to popular perception, the images reveal copious massive star formation in some of these galaxies. A determination of the Hα morphology and a measure of the Hα luminosity suggest that early-type spirals can be classified into two broad categories based on the luminosity of the largest H II region in the disk. The first category includes galaxies for which the individual H II regions have L_Hα<10^39 ergs s^-1. Most of the category 1 galaxies appear to be morphologically undisturbed but show a wide diversity in nuclear Hα properties. The second category includes galaxies that have at least one H II region in the disk with L_Hα>=10^39 ergs s^-1. All category 2 galaxies show either prominent dust lanes or other morphological peculiarities such as tidal tails, which suggests that the anomalously luminous H II regions in category 2 galaxies may have formed as a result of a recent interaction. The observations, which are part of an ongoing Hα survey, reveal early-type spirals to be a heterogeneous class of galaxies that are evolving in the current epoch. We have also identified some systematic differences between the classifications of spiral galaxies in the Second General Catalog and the Revised Shapley-Ames Catalog that may be traced to subtle variations in the application of the criteria used for classifying spiral galaxies. An examination of earlier studies suggests that perceptions concerning the Hubble-type dependence of star formation rates among spiral galaxies depends on the choice of catalog.

  6. A Chandra survey of nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Kilgard, R. E.; Krauss, M. I.; Kaaret, P.; Prestwich, A. H.; Ward, M. J.

    We present results from a Chandra survey of 11 nearby, face-on spiral galaxies. 24 observations totalling 900 ks of new and archival Chandra data reveal more than 1000 X-ray point sources associated with the galaxies, diffuse emission, and hundreds of serendipitous sources. We discuss source populations and luminosity functions and show that the slope of the X-ray luminosity function is correlated with the star formation rate in the galaxies. We also discuss ultraluminous X-ray sources in comparison with sources within the Milky Way. Finally, we discuss ongoing work on source classification based upon X-ray colors and spectra, position within the host galaxies, and multiwavelenth counterparts.

  7. A photometrically and spectroscopically confirmed population of passive spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fraser-McKelvie, Amelia; Brown, Michael J. I.; Pimbblet, Kevin A.; Dolley, Tim; Crossett, Jacob P.; Bonne, Nicolas J.

    2016-10-01

    We have identified a population of passive spiral galaxies from photometry and integral field spectroscopy. We selected z < 0.035 spiral galaxies that have WISE colours consistent with little mid-infrared emission from warm dust. Matched aperture photometry of 51 spiral galaxies in ultraviolet, optical and mid-infrared show these galaxies have colours consistent with passive galaxies. Six galaxies form a spectroscopic pilot study and were observed using the Wide-Field Spectrograph to check for signs of nebular emission from star formation. We see no evidence of substantial nebular emission found in previous red spiral samples. These six galaxies possess absorption-line spectra with 4000 Å breaks consistent with an average luminosity-weighted age of 2.3 Gyr. Our photometric and integral field spectroscopic observations confirm the existence of a population of local passive spiral galaxies, implying that transformation into early-type morphologies is not required for the quenching of star formation.

  8. STAR FORMATION IN TWO LUMINOUS SPIRAL GALAXIES

    SciTech Connect

    Hunter, Deidre A.; Ashburn, Allison; Wright, Teresa; Elmegreen, Bruce G.; Rubin, Vera C.; Józsa, Gyula I. G.; Struve, Christian

    2013-10-01

    We examined star formation in two very luminous (M{sub V} = –22 to –23) Sc-type spiral galaxies, NGC 801 and UGC 2885, using ultra-deep Hα images. We combine these Hα images with UBV and Two-Micron All-Sky Survey JHK images and H I maps to explore the star formation characteristics of disk galaxies at high luminosity. Hα traces star formation in these galaxies to 4-6 disk scale lengths, but the lack of detection of Hα further out is likely due to the loss of Lyman continuum photons. Considering gravitational instabilities alone, we find that the gas and stars in the outer regions are marginally stable in an average sense, but considering dissipative gas and radial and azimuthal forcing, the outer regions are marginally unstable to forming spiral arms. Star formation is taking place in spiral arms, which are regions of locally higher gas densities. Furthermore, we have traced smooth exponential stellar disks over four magnitudes in V-band surface brightness and 4-6 disk scale lengths, in spite of a highly variable gravitational instability parameter. Thus, gravitational instability thresholds do not seem relevant to the stellar disk. One possibility for creating an exponential disk is that the molecular cloud densities and star formation rates have exponential profiles and this fact forces the stellar disk to build up such a profile. Another possibility is that the stellar disk is continuously adjusted to an exponential shape regardless of the star formation profile, for example, through global dynamical processes that scatter stars. However, such scattering processes are only known to operate in spiral systems, in which case they cannot explain the same dilemma of smooth exponential disks observed in dwarf irregular galaxies.

  9. Tidal interaction of small satellite galaxies with spiral primaries

    NASA Technical Reports Server (NTRS)

    Byrd, Gene G.

    1988-01-01

    The interaction of the disks of spiral galaxies and small companions is discussed. The gravitational drag effects of the disk on small satellites are of particular interest. Studies of the Andromeda Galaxy and its satellites, M32 and NGC 205, reveal the usefulness of few-body test-particle simulations in explaining many features of spiral galaxies and their satellites.

  10. Secular Evolution of Spiral Galaxies

    DTIC Science & Technology

    2003-01-01

    observationthat dwarf, irregular, and L galaxies share quite sim-ilar distributions; and the prediction of cusp -like darkmatter cores in low surface...which is too clumpy (or can easilybecome too clumpy) on small scales, yet too smoothon large scales. For example, the cusp problem andthe satellite...and dwarfgalaxies are found not to possess such cuspy cores(de Blok, McGaugh, & Rubin 2001). Even invok-ing maximum feedback does not solve the cusp

  11. Model of outgrowths in the spiral galaxies NGC 4921 and NGC 7049 and the origin of spiral arms

    NASA Astrophysics Data System (ADS)

    Carlqvist, Per

    2013-02-01

    NGC 4921 and 7049 are two spiral galaxies presenting narrow, distinct dust features. A detailed study of the morphology of those features has been carried out using Hubble Space Telescope archival images. NGC 4921 shows a few but well-defined dust arms midway to its centre while NGC 7049 displays many more dusty features, mainly collected within a ring-shaped formation. Numerous dark and filamentary structures, called outgrowths, are found to protrude from the dusty arms in both galaxies. The outgrowths point both outwards and inwards in the galaxies. Mostly they are found to be V-shaped or Y-shaped with the branches connected to dark arm filaments. Often the stem of the Y appears to consist of intertwined filaments. Remarkably, the outgrowths show considerable similarities to elephant trunks in H ii regions. A model of the outgrowths, based on magnetized filaments, is proposed. The model provides explanations of both the shapes and orientations of the outgrowths. Most important, it can also give an account for their intertwined structures. It is found that the longest outgrowths are confusingly similar to dusty spiral arms. This suggests that some of the outgrowths can develop into such arms. The time-scale of the development is estimated to be on the order of the rotation period of the arms or shorter. Similar processes may also take place in other spiral galaxies. If so, the model of the outgrowths can offer a new approach to the old winding problem of spiral arms.

  12. Most Massive Spiral Galaxy Known in the Universe

    NASA Astrophysics Data System (ADS)

    2000-12-01

    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

  13. Hubble's Law Implies Benford's Law for Distances to Galaxies

    NASA Astrophysics Data System (ADS)

    Hill, Theodore P.; Fox, Ronald F.

    2016-03-01

    A recent article by Alexopoulos and Leontsinis presented empirical evidence that the first digits of the distances from the Earth to galaxies are a reasonably good fit to the probabilities predicted by Benford's law, the well known logarithmic statistical distribution of significant digits. The purpose of the present article is to give a theoretical explanation, based on Hubble's law and mathematical properties of Benford's law, why galaxy distances might be expected to follow Benford's law. The new galaxy-distance law derived here, which is robust with respect to change of scale and base, to additive and multiplicative computational or observational errors, and to variability of the Hubble constant in both time and space, predicts that conformity to Benford's law will improve as more data on distances to galaxies becomes available. Conversely, with the logical derivation of this law presented here, the recent empirical observations may be viewed as independent evidence of the validity of Hubble's law.

  14. The CALIFA survey across the Hubble sequence. Spatially resolved stellar population properties in galaxies

    NASA Astrophysics Data System (ADS)

    González Delgado, R. M.; García-Benito, R.; Pérez, E.; Cid Fernandes, R.; de Amorim, A. L.; Cortijo-Ferrero, C.; Lacerda, E. A. D.; López Fernández, R.; Vale-Asari, N.; Sánchez, S. F.; Mollá, M.; Ruiz-Lara, T.; Sánchez-Blázquez, P.; Walcher, C. J.; Alves, J.; Aguerri, J. A. L.; Bekeraité, S.; Bland-Hawthorn, J.; Galbany, L.; Gallazzi, A.; Husemann, B.; Iglesias-Páramo, J.; Kalinova, V.; López-Sánchez, A. R.; Marino, R. A.; Márquez, I.; Masegosa, J.; Mast, D.; Méndez-Abreu, J.; Mendoza, A.; del Olmo, A.; Pérez, I.; Quirrenbach, A.; Zibetti, S.

    2015-09-01

    Various different physical processes contribute to the star formation and stellar mass assembly histories of galaxies. One important approach to understanding the significance of these different processes on galaxy evolution is the study of the stellar population content of today's galaxies in a spatially resolved manner. The aim of this paper is to characterize in detail the radial structure of stellar population properties of galaxies in the nearby universe, based on a uniquely large galaxy sample, considering the quality and coverage of the data. The sample under study was drawn from the CALIFA survey and contains 300 galaxies observed with integral field spectroscopy. These cover a wide range of Hubble types, from spheroids to spiral galaxies, while stellar masses range from M⋆ ~ 109 to 7 × 1011 M⊙. We apply the fossil record method based on spectral synthesis techniques to recover the following physical properties for each spatial resolution element in our target galaxies: the stellar mass surface density (μ⋆), stellar extinction (AV), light-weighted and mass-weighted ages (⟨log age⟩L, ⟨log age⟩M), and mass-weighted metallicity (⟨log Z⋆⟩M). To study mean trends with overall galaxy properties, the individual radial profiles are stacked in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd). We confirm that more massive galaxies are more compact, older, moremetal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M⋆, which is evidence that quenching is related to morphology, but not driven by mass. Negative gradients of ⟨log age⟩L are consistent with an inside-out growth of galaxies, with the largest ⟨log age⟩L gradients in Sb-Sbc galaxies. Further, the mean stellar ages of disks and bulges are

  15. HUBBLE'S NEW IMPROVED OPTICS PROBE THE CORE OF A DISTANT GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This comparison image of the core of the galaxy M100 shows the dramatic improvement in Hubble Space Telescope's view of the universe. The new image was taken with the second generation Wide Field and Planetary Camera (WFPC-2) which was installed during the STS-61 Hubble Servicing Mission. The picture beautifully demonstrates that the corrective optics incorporated within the WFPC-2 compensate fully for optical aberration in Hubble's primary mirror. The new camera will allow Hubble to probe the universe with unprecedented clarity and sensitivity, and to fulfill many of the most important scientific objectives for which the telescope was originally built. [ Right ] The core of the grand design spiral galaxy M100, as imaged by Hubble Space Telescope's Wide Field Planetary Camera 2 in its high resolution channel. The WFPC-2 contains modified optics that correct for Hubble's previously blurry vision, allowing the telescope for the first time to cleanly resolve faint structure as small as 30 light-years across in a galaxy which is tens of millions of light years away. The image was taken on December 31, 1993. [Left ] For comparison, a picture taken with the WFPC-1 camera in wide field mode, on November 27, 1993, just a few days prior to the STS-61 servicing mission. The effects of optical aberration in HST's 2.4-meter primary mirror blur starlight, smear out fine detail, and limit the telescope's ability to see faint structure. Both Hubble images are 'raw;' they have not been subject to computer image reconstruction techniques commonly used in aberrated images made before the servicing mission. TARGET INFORMATION: M100 The galaxy M100 (100th object in the Messier Catalog of non-stellar objects) is one of the brightest members of the Virgo Cluster of galaxies. The galaxy is in the spring constellation Coma Berenices and can be seen through a moderate-sized amateur telescope. M100 is spiral shaped, like our Milky Way, and tilted nearly face-on as seen from earth. The

  16. HUBBLE'S NEW IMPROVED OPTICS PROBE THE CORE OF A DISTANT GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This comparison image of the core of the galaxy M100 shows the dramatic improvement in Hubble Space Telescope's view of the universe. The new image was taken with the second generation Wide Field and Planetary Camera (WFPC-2) which was installed during the STS-61 Hubble Servicing Mission. The picture beautifully demonstrates that the corrective optics incorporated within the WFPC-2 compensate fully for optical aberration in Hubble's primary mirror. The new camera will allow Hubble to probe the universe with unprecedented clarity and sensitivity, and to fulfill many of the most important scientific objectives for which the telescope was originally built. [ Right ] The core of the grand design spiral galaxy M100, as imaged by Hubble Space Telescope's Wide Field Planetary Camera 2 in its high resolution channel. The WFPC-2 contains modified optics that correct for Hubble's previously blurry vision, allowing the telescope for the first time to cleanly resolve faint structure as small as 30 light-years across in a galaxy which is tens of millions of light years away. The image was taken on December 31, 1993. [Left ] For comparison, a picture taken with the WFPC-1 camera in wide field mode, on November 27, 1993, just a few days prior to the STS-61 servicing mission. The effects of optical aberration in HST's 2.4-meter primary mirror blur starlight, smear out fine detail, and limit the telescope's ability to see faint structure. Both Hubble images are 'raw;' they have not been subject to computer image reconstruction techniques commonly used in aberrated images made before the servicing mission. TARGET INFORMATION: M100 The galaxy M100 (100th object in the Messier Catalog of non-stellar objects) is one of the brightest members of the Virgo Cluster of galaxies. The galaxy is in the spring constellation Coma Berenices and can be seen through a moderate-sized amateur telescope. M100 is spiral shaped, like our Milky Way, and tilted nearly face-on as seen from earth. The

  17. Non-circular motion estimation of the grand-design spiral galaxy NGC 628

    NASA Astrophysics Data System (ADS)

    Colombo, D.

    2013-09-01

    I present a harmonic decomposition analysis of the grand-design spiral galaxy NGC 628 using the H I data from The H I Nearby Galaxy Survey (THINGS), Walter et al., Astron. J. 136, 2563 (2008). The harmonic decomposition analysis allows the estimation of the peculiar motion magnitude of the galaxy not counted in the rotation of the disk. The rotation curve is obtained through a tilted ring analysis and reaches a maximum velocity not higher than 200 km s-1. The residual from the velocity field shows a morphology shift from a m = 1 to a m = 3 feature at R = 120", typical of two spiral arms perturbation of the potential. The non-circular motion have a magnitude of ~10 km s-1, in agreement with previous studies of similar Hubble type galaxies.

  18. Gargantuan Super Spiral Galaxies Loom Large in the Cosmos

    NASA Image and Video Library

    2016-03-17

    In archived NASA data, researchers have discovered "super spiral" galaxies that dwarf our own spiral galaxy, the Milky Way, and compete in size and brightness with the largest galaxies in the universe. The unprecedented galaxies have long hidden in plain sight by mimicking the appearance of typical spirals. Three examples of super spirals are presented here in images taken by the Sloan Digital Sky Survey. The super spiral on the left (Figure 1), catalogued as 2MASX J08542169+0449308, contains two galactic nuclei, instead of just the usual one, and thus looks like two eggs frying in a pan. The central image (Figure 2) shows a super spiral designated 2MASX J16014061+2718161, and it also contains the double nuclei. On the right (Figure 3), a huge galaxy with the moniker SDSS J094700.08+254045.7 stands as one of the biggest and brightest super spirals. The mega-galaxy's starry disk and spiral arms stretch about 320,000 light-years across, or more than three times the breadth of the Milky Way. These double nuclei, which are known to result from the recent merger of two galaxies, could offer a vital hint about the potential origin of super spirals. Researchers speculate that a special merger involving two, gas-rich spiral galaxies could see their pooled gases settle down into a new, larger stellar disk -- presto, a super spiral. The super spirals were discovered using the NASA/IPAC Extragalactic Database, or NED, an online repository containing information on over 100 million galaxies. NED brings together a wealth of data from many different projects, including ultraviolet light observations from the Galaxy Evolution Explorer, visible light from Sloan Digital Sky Survey, infrared light from the 2-Micron All-Sky Survey, and links to data from other missions such as NASA's Spitzer Space Telescope and Wide-Field Infrared Survey Explorer, or WISE. http://photojournal.jpl.nasa.gov/catalog/PIA20064

  19. Giant cyclones in gaseous discs of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.; Polyachenko, E.; Zasov, A. V.; Sil'chenko, O. K.; Afanas'ev, V. L.; Dodonov, S. N.; Moiseev, A. V.

    1999-12-01

    We report the detection of giant cyclonic vortices in the gaseous disc of the spiral galaxy NGC 3631 in the reference frame rotating with the spiral pattern. A presence of such structures was predicted by the authors for galaxies, where the radial gradient of the perturbed velocity exceeds that of the rotational velocity. This situation really takes place in NGC 3631.

  20. HUBBLE CAPTURES VIEW OF SUPERNOVA BLAST IN REMOTE GALAXY CLUSTER

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In March 1996, the Hubble Space Telescope's Wide Field and Planetary Camera 2 just happened to be pointed at the faraway galaxy cluster MS1054-0321 when it captured the light from an exploding star, called supernova 1996CL. The cluster is 8 billion light-years from Earth. The Hubble telescope can clearly distinguish the supernova light from the glow of its parent galaxy. The larger image on the left shows the entire cluster of galaxies. The galaxy where the supernova was discovered is located in the boxed area. The bright knot of light from the supernova and the fainter glow from the parent galaxy are shown in the inset image on the right. The arrow points to the light from the supernova explosion. The supernova was discovered by members of the Supernova Cosmology Project, led by Saul Perlmutter of Lawrence Berkeley Laboratory in California. Perlmutter and his team made this discovery using images from the Hubble telescope and ground-based observatories. The Hubble data were furnished by Megan Donahue of the Space Telescope Science Institute. Donahue was using the Hubble telescope to study galaxy cluster MS1054-0321. Members of the Supernova Project use ground-based telescopes to search for distant supernovae, such as 1996CL, by comparing multiple, wide-field images of galaxies and clusters of galaxies taken at different times. Supernovae are named for the year and the order in which they are found. Supernova 1996CL is a Type Ia supernova. Exploding stars of this type are particularly useful for cosmology because they share a standard maximum brightness. By measuring this brightness, astronomers can determine a Type Ia's distance from Earth. Astronomers use this information to measure the expansion rate of the universe.

  1. Chemical abundances in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Richer, Michael Gerard

    2015-08-01

    The chemical abundances observed in planetary nebulae in the discs of spiral galaxies are revealing a rich variety of information about their progenitor stars as well as the structure and evolution of the galaxies they inhabit. As concerns galaxy structure and evolution, most of the attention has been on whether gradients in chemical abundances have changed with time, but there is also the issue of the formation and origin of the stellar progenitors of planetary nebulae. The gradients in oxygen abundances for planetary nebulae in M81 and NGC 300 are shallower than the corresponding gradients for H II regions in these galaxies. On the other hand, the gradients for H II regions and planetary nebulae are similar in M33. In the case of M31, there is mounting evidence whose simplest explanation may not be related to internal processes, but instead may lay in the gravitational interaction between it and its neighbours, past and present. As concerns the nucleosynthesis of the stellar progenitors of these planetary nebulae, some results for both nitrogen and oxygen may indicate the production of these elements during the previous evolutionary stages of their progenitor stars. Nominally, this may not be surprising for nitrogen, but the results do not agree quantitatively with canonical theory. At this point, though, there are still too few studies to draw very firm conclusions regrading any of these topics. Even so, the surprises among the results found so far make clear that interpreting the chemical abundances in the planetary nebulae in nearby spirals will require considering the processes affecting both stellar and galactic evolution.

  2. The Nature of Red-Sequence Cluster Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kashur, Lane; Barkhouse, Wayne; Sultanova, Madina; Kalawila Vithanage, Sandanuwa; Archer, Haylee; Foote, Gregory; Mathew, Elijah; Rude, Cody; Lopez-Cruz, Omar

    2017-01-01

    Preliminary analysis of the red-sequence galaxy population from a sample of 57 low-redshift galaxy clusters observed using the KPNO 0.9m telescope and 74 clusters from the WINGS dataset, indicates that a small fraction of red-sequence galaxies have a morphology consistent with spiral systems. For spiral galaxies to acquire the color of elliptical/S0s at a similar luminosity, they must either have been stripped of their star-forming gas at an earlier epoch, or contain a larger than normal fraction of dust. To test these ideas we have compiled a sample of red-sequence spiral galaxies and examined their infrared properties as measured by 2MASS, WISE, Spitzer, and Herschel. These IR data allows us to estimate the amount of dust in each of our red-sequence spiral galaxies. We compare the estimated dust mass in each of these red-sequence late-type galaxies with spiral galaxies located in the same cluster field but having colors inconsistent with the red-sequence. We thus provide a statistical measure to discriminate between purely passive spiral galaxy evolution and dusty spirals to explain the presence of these late-type systems in cluster red-sequences.

  3. A FUNDAMENTAL PLANE OF SPIRAL STRUCTURE IN DISK GALAXIES

    SciTech Connect

    Davis, Benjamin L.; Kennefick, Daniel; Kennefick, Julia; Shields, Douglas W.; Flatman, Russell; Hartley, Matthew T.; Berrier, Joel C.; Martinsson, Thomas P. K.; Swaters, Rob A.

    2015-03-20

    Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is correct. Many versions of the density wave theory demand that the pitch angle be uniquely determined by the distribution of mass in the bulge and disk of the galaxy. We present evidence that the tangent of the pitch angle of logarithmic spiral arms in disk galaxies correlates strongly with the density of neutral atomic hydrogen in the disk and with the central stellar bulge mass of the galaxy. These three quantities, when plotted against each other, form a planar relationship that we argue should be fundamental to our understanding of spiral structure in disk galaxies. We further argue that any successful theory of spiral structure must be able to explain this relationship.

  4. GRAND DESIGN AND FLOCCULENT SPIRALS IN THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S{sup 4}G)

    SciTech Connect

    Elmegreen, Debra Meloy; Yau, Andrew; Elmegreen, Bruce G.; Athanassoula, E.; Bosma, Albert; Helou, George; Sheth, Kartik; Ho, Luis C.; Madore, Barry F.; Menendez-Delmestre, KarIn; Gadotti, Dimitri A.; Knapen, Johan H.; Laurikainen, Eija; Salo, Heikki; Meidt, Sharon E.; Regan, Michael W.; Zaritsky, Dennis; Aravena, Manuel

    2011-08-10

    Spiral arm properties of 46 galaxies in the Spitzer Survey of Stellar Structure in Galaxies (S{sup 4}G) were measured at 3.6 {mu}m, where extinction is small and the old stars dominate. The sample includes flocculent, multiple arm, and grand design types with a wide range of Hubble and bar types. We find that most optically flocculent galaxies are also flocculent in the mid-IR because of star formation uncorrelated with stellar density waves, whereas multiple arm and grand design galaxies have underlying stellar waves. Arm-interarm contrasts increase from flocculent to multiple arm to grand design galaxies and with later Hubble types. Structure can be traced further out in the disk than in previous surveys. Some spirals peak at mid-radius while others continuously rise or fall, depending on Hubble and bar type. We find evidence for regular and symmetric modulations of the arm strength in NGC 4321. Bars tend to be long, high amplitude, and flat-profiled in early-type spirals, with arm contrasts that decrease with radius beyond the end of the bar, and they tend to be short, low amplitude, and exponential-profiled in late Hubble types, with arm contrasts that are constant or increase with radius. Longer bars tend to have larger amplitudes and stronger arms.

  5. High chemical abundances in stripped Virgo spiral galaxies

    NASA Astrophysics Data System (ADS)

    Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

    1993-01-01

    Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

  6. High chemical abundances in stripped Virgo spiral galaxies

    NASA Technical Reports Server (NTRS)

    Skillman, E. D.; Kennicutt, R. C.; Shields, G. A.

    1993-01-01

    Based on a comparison of the oxygen abundances in H 2 regions in field and Virgo cluster late type spiral galaxies, Shields, Skillman, & Kennicutt (1991) suggested that the highly stripped spiral galaxies in the Virgo cluster have systematically higher abundances than comparable field galaxies. In April 1991 and May 1992 we used the blue channel spectrograph on the MMT to obtain new observations of 30 H 2 regions in Virgo spiral galaxies. These spectra cover the wavelength range from (O II) lambda 3727 to (S II) lambda 6731. We now have observed at least 4 H II regions in 9 spiral galaxies in the Virgo cluster. Combining (O II) and (O III) line strengths, we calculate the H II region oxygen abundances based on the empirical calibration of Edmunds & Pagel (1984). These observations show: (1) The stripped, low luminosity Virgo spirals (N4689, N4571) truly have abundances characteristic of much more luminous field spirals; (2) Virgo spirals which show no evidence of stripping (N4651, N4713) have abundances comparable to field galaxies; and (3) Evidence for transition galaxies (e.g., N4254, N4321), with marginally stripped disks and marginal abundance enhancements. The new observations presented here confirm the validity of the oxygen over-abundances in the stripped Virgo spirals. Shields et al. (1991) discussed two different mechanisms for producing the higher abundances in the disks of stripped galaxies in Virgo. The first is the supression of infall of near-primordial material, the second is the suppression of radial inflow of metal-poor gas. Distinguishing between the two cases will require more observations of the Virgo cluster spirals and a better understanding of which parameters determine the variation of abundance with radius in field spirals (cf., Garnett & Shields 1987).

  7. A COMPARATIVE STUDY OF KNOTS OF STAR FORMATION IN INTERACTING VERSUS SPIRAL GALAXIES

    SciTech Connect

    Smith, Beverly J.; Olmsted, Susan; Jones, Keith; Zaragoza-Cardiel, Javier; Struck, Curtis

    2016-03-15

    Interacting galaxies are known to have higher global rates of star formation on average than normal galaxies, relative to their stellar masses. Using UV and IR photometry combined with new and published Hα images, we have compared the star formation rates (SFRs) of ∼700 star forming complexes in 46 nearby interacting galaxy pairs with those of regions in 39 normal spiral galaxies. The interacting galaxies have proportionally more regions with high SFRs than the spirals. The most extreme regions in the interacting systems lie at the intersections of spiral/tidal structures, where gas is expected to pile up and trigger star formation. Published Hubble Space Telescope images show unusually large and luminous star clusters in the highest luminosity regions. The SFRs of the clumps correlate with measures of the dust attenuation, consistent with the idea that regions with more interstellar gas have more star formation. For the clumps with the highest SFRs, the apparent dust attenuation is consistent with the Calzetti starburst dust attenuation law. This suggests that the high luminosity regions are dominated by a central group of young stars surrounded by a shell of clumpy interstellar gas. In contrast, the lower luminosity clumps are bright in the UV relative to Hα, suggesting either a high differential attenuation between the ionized gas and the stars, or a post-starburst population bright in the UV but faded in Hα. The fraction of the global light of the galaxies in the clumps is higher on average for the interacting galaxies than for the spirals. Thus either star formation in interacting galaxies is “clumpier” on average, or the star forming regions in interacting galaxies are more luminous, dustier, or younger on average.

  8. ROSAT observations of Several Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Cui, Wei

    1994-01-01

    We have made observations of several nearby face-on normal spiral galaxies with the ROSAT PSPC to study their 01-2 0 keV diffuse X-ray emission. The cleaned X-ray images of NGC3184, M101, NGC4395, NGC4736 and NGC5055 in the 1/4, 3/4 and 1.5 keV energy bands are presented along with a detailed discussion of how to identify and model known types of non-cosmic X-ray background. Unresolved X-ray emission in the 0.1-2.0 keV range is detected in all the observed galaxies, bright at the center and getting fainter toward the outer edges. It is a combination of diffuse emission and contribution from un-resolved point sources in these galaxies, so represents an upper limit to the diffuse X-ray emission. The derived upper limits on the diffuse emission can be interpreted in terms of upper limits to average emission measure for a putative unabsorbed halo emission, or alternatively as limits on the filling factors of 106 K hot bubbles, similar to the one surrounding the Sun, in the disks of these galaxies. They can also be used to derive limits to the total energy radiated by hot gas as a function of its temperature for various assumed absorbing geometries. Another exciting possibility is to measure shadows of the 1/4 keV extragalactic X-ray background cast by the external galaxies, which then allow us to determine useful limits on it The absorption features observed at the outer edges of some of the galaxies are direct evidence for absorption of this background by matter in there galaxies, and we have derived a 96% confidence lower limit of 32 keV cm-2 s-l sr-l keV-l. This lower limit can be compared directly with the best 95% confidence upper limit derived from observations of the Small Magellanic Cloud, which is 45 keV cm-2 s-l , sr-l keV-l The e lower and upper limits are less than a factor of two apart, and bend to provide a reasonable measurement of the actual value of the 1/4 keV extragalactic X-ray intensity

  9. Circumnuclear Regions In Barred Spiral Galaxies. 1; Near-Infrared Imaging

    NASA Technical Reports Server (NTRS)

    Perez-Ramirez, D.; Knapen, J. H.; Peletier, R. F.; Laine, S.; Doyon, R.; Nadeau, D.

    2000-01-01

    We present sub-arcsecond resolution ground-based near-infrared images of the central regions of a sample of twelve barred galaxies with circumnuclear star formation activity, which is organized in ring-like regions typically one kiloparsec in diameter. We also present Hubble Space Telescope near-infrared images of ten of our sample galaxies, and compare them with our ground-based data. Although our sample galaxies were selected for the presence of circumnuclear star formation activity, our broad-band near-infrared images are heterogeneous, showing a substantial amount of small-scale structure in some galaxies, and practically none in others. We argue that, where it exists, this structure is caused by young stars, which also cause the characteristic bumps or changes in slope in the radial profiles of ellipticity, major axis position angle, surface brightness and colour at the radius of the circumnuclear ring in most of our sample galaxies. In 7 out of 10 HST images, star formation in the nuclear ring is clearly visible as a large number of small emitting regions, organised into spiral arm fragments, which are accompanied by dust lanes. NIR colour index maps show much more clearly the location of dust lanes and, in certain cases, regions of star formation than single broad-band images. Circumnuclear spiral structure thus outlined appears to be common in barred spiral galaxies with circumnuclear star formation.

  10. Arm and interarm abundance gradients in CALIFA spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sánchez-Menguiano, L.; Sánchez, S. F.; Pérez, I.; Debattista, V. P.; Ruiz-Lara, T.; Florido, E.; Cavichia, O.; Galbany, L.; Marino, R. A.; Mast, D.; Sánchez-Blázquez, P.; Méndez-Abreu, J.; de Lorenzo-Cáceres, A.; Catalán-Torrecilla, C.; Cano-Díaz, M.; Márquez, I.; McIntosh, D. H.; Ascasibar, Y.; García-Benito, R.; Gónzalez Delgado, R. M.; Kehrig, C.; López-Sánchez, Á. R.; Mollá, M.; Bland-Hawthorn, J.; Walcher, C. J.; Costantin, L.

    2017-07-01

    Spiral arms are the most singular features in disc galaxies. These structures can exhibit different patterns, namely grand design and flocculent arms, with easily distinguishable characteristics. However, their origin and the mechanisms shaping them are unclear. The overall role of spirals in the chemical evolution of disc galaxies is another unsolved question. In particular, it has not been fully explored if the H ii regions of spiral arms present different properties from those located in the interarm regions. Here we analyse the radial oxygen abundance gradient of the arm and interarm star forming regions of 63 face-on spiral galaxies using CALIFA Integral Field Spectroscopy data. We focus the analysis on three characteristic parameters of the profile: slope, zero-point, and scatter. The sample is morphologically separated into flocculent versus grand design spirals and barred versus unbarred galaxies. We find subtle but statistically significant differences betweenthe arm and interarm distributions for flocculent galaxies, suggesting that the mechanisms generating the spiral structure in these galaxies may be different to those producing grand design systems, for which no significant differences are found. We also find small differences in barred galaxies, not observed in unbarred systems, hinting that bars may affect the chemical distribution of these galaxies but not strongly enough as to be reflected in the overall abundance distribution. In light of these results, we propose bars and flocculent structure as two distinct mechanisms inducing differences in the abundance distribution between arm and interarm star forming regions.

  11. Comparing Stellar Populations of Galaxies across the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Kaleida, Catherine C.; Parkash, Vaishali; Jansen, Rolf

    2014-08-01

    We propose to investigate the spatial distributions of stellar populations within a statistically significant set of galaxies, representing the full range of luminosity and morphological type. By obtaining new, near-infrared images of these galaxies to complement existing optical and near-UV data, we can self-consistently probe the older stellar populations, dust extinction, and metallicity, and ultimately determine ages of and age variations within the stellar components of these galaxies. This information can then be used to compare stellar populations between luminous and faint galaxies of the same Hubble type, and between similar luminosity galaxies of different types. Galaxy candidates for this study were drawn from the Nearby Field Galaxy Survey (Jansen 2000), which provides U, B, and R optical images and both nuclear and globally integrated spectra. Near- infrared J, H, and K_s surface photometry can break the age-dust- metallicity degeneracy in galaxy spectral energy distributions (SEDs), but existing 2MASS image data is not sufficiently deep for this purpose. We therefore request observing time on the Infrared Side Port Imager (ISPI) on the CTIO 4-m Blanco telescope to secure J, H, and K_s images reaching out to the optical radius for 19 NFGS galaxies observable from Cerro Tololo in 2014B. Specific results expected from this sample are the distributions of age, dust, and metallicity across galaxies of differing type and luminosity. These distributions will allow us to address systematic trends in assembly history that can confront simulations of hierarchical galaxy formation.

  12. Comparing Stellar Populations of Galaxies across the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Kaleida, Catherine C.; Parkash, Vaishali; Jansen, Rolf

    2014-02-01

    We propose to investigate the spatial distributions of stellar populations within a statistically significant set of galaxies, representing the full range of luminosity and morphological type. By obtaining new, near-infrared images of these galaxies to complement existing optical and near-UV data, we can self-consistently probe the older stellar populations, dust extinction, and metallicity, and ultimately determine ages of and age variations within the stellar components of these galaxies. This information can then be used to compare stellar populations between luminous and faint galaxies of the same Hubble type, and between similar luminosity galaxies of different types. Galaxy candidates for this study were drawn from the Nearby Field Galaxy Survey (Jansen 2000), which provides U, B, and R optical images and both nuclear and globally integrated spectra. Near- infrared J, H, and K_s surface photometry can break the age-dust- metallicity degeneracy in galaxy spectral energy distributions (SEDs), but existing 2MASS image data is not sufficiently deep for this purpose. We therefore request observing time on the Infrared Side Port Imager (ISPI) on the CTIO 4-m Blanco telescope to secure J, H, and K_s images reaching out to the optical radius for 12 NFGS galaxies observable from Cerro Tololo in 2014A. Specific results expected from this sample are the distributions of age, dust, and metallicity across galaxies of differing type and luminosity. These distributions will allow us to address systematic trends in assembly history that can confront simulations of hierarchical galaxy formation.

  13. 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

  14. 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

  15. Halos of Spiral Galaxies. I. The Tip of the Red Giant Branch as a Distance Indicator

    NASA Astrophysics Data System (ADS)

    Mouhcine, M.; Ferguson, H. C.; Rich, R. M.; Brown, T. M.; Smith, T. E.

    2005-11-01

    We have imaged the halo populations of a sample of nearby spiral galaxies using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope with the aim of studying the stellar population properties and relating them to those of the host galaxies. In four galaxies, the red giant branch is sufficiently well populated to measure the magnitude of the tip of the red giant branch (TRGB), a well-known distance indicator. Using both the Sobel edge-detection technique and maximum likelihood analysis to measure the I-band magnitude of the TRGB, we determine distances to four nearby galaxies: NGC 253, NGC 4244, NGC 4945, and NGC 4258. For the first three galaxies, the TRGB distance is here determined more directly, and is likely to be more accurate, than previous distance estimates. In the case of NGC 4258, our TRGB distance is in good agreement with the geometrical maser distance, supporting the Large Magellanic Cloud distance modulus (m-M)0=18.50 that is generally adopted in recent estimates of the Hubble constant. Based on observations 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.

  16. The CALIFA Survey Across the Hubble Sequence: How Galaxies Grow their Bulges and Disks

    NASA Astrophysics Data System (ADS)

    Gonzáez-Delgado, R. M.; García-Benito, R.; Pérez, E.; Cid Fernandes, R.; de Amorim, A. L.; Cortijo-Ferrero, C.; Lacerda, E. A. D.; López-Fernández, R.; Vale-Asari, R. L.; Sánchez, S.; Califa Collaboration

    2016-10-01

    We characterize in detail the radial structure of the stellar population properties of 300 galaxies in the nearby universe, observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, from spheroidal to spiral galaxies, ranging in stellar masses from M*˜109 to 7×1011 ⊙. We derive the stellar mass surface density (μ⋆), light-weighted and mass-weighted ages («log age»L, «log age»M), and mass-weighted metallicity («logZ⋆ »M), applying the spectral synthesis technique. We study the mean trends with galaxy stellar mass, M⋆, and morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). We confirm that more massive galaxies are more compact, older, more metal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M⋆, which evidences that quenching is related to morphology, but not driven by mass.

  17. Galaxy Zoo: star formation versus spiral arm number

    NASA Astrophysics Data System (ADS)

    Hart, Ross E.; Bamford, Steven P.; Casteels, Kevin R. V.; Kruk, Sandor J.; Lintott, Chris J.; Masters, Karen L.

    2017-06-01

    Spiral arms are common features in low-redshift disc galaxies, and are prominent sites of star formation and dust obscuration. However, spiral structure can take many forms: from galaxies displaying two strong 'grand design' arms to those with many 'flocculent' arms. We investigate how these different arm types are related to a galaxy's star formation and gas properties by making use of visual spiral arm number measurements from Galaxy Zoo 2. We combine ultraviolet and mid-infrared (MIR) photometry from GALEX and WISE to measure the rates and relative fractions of obscured and unobscured star formation in a sample of low-redshift SDSS spirals. Total star formation rate has little dependence on spiral arm multiplicity, but two-armed spirals convert their gas to stars more efficiently. We find significant differences in the fraction of obscured star formation: an additional ˜10 per cent of star formation in two-armed galaxies is identified via MIR dust emission, compared to that in many-armed galaxies. The latter are also significantly offset below the IRX-β relation for low-redshift star-forming galaxies. We present several explanations for these differences versus arm number: variations in the spatial distribution, sizes or clearing time-scales of star-forming regions (i.e. molecular clouds), or contrasting recent star formation histories.

  18. The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Machida, Mami; Kudoh, Takahiro

    2010-10-01

    We propose a primordial-origin model for composite configurations of global magnetic fields in spiral galaxies. We show that a uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S = BSS), axisymmetric spiral (A = ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from a weak primordial uniform field, and that different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce a jet toward the halo. We found that the more vertical was the initial uniform field, the stronger was the formed magnetic field in the galactic disk.

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

    NASA Astrophysics Data System (ADS)

    2009-03-01

    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

  20. Hubble Space Telescope and Very Large Array Observations of the H2O Gigamaser Galaxy TXS 2226-184.

    PubMed

    Falcke; Wilson; Henkel; Brunthaler; Braatz

    2000-02-10

    We present Hubble Space Telescope/Wide-Field and Planetary Camera 2 images in Halpha + [N ii] lambdalambda6548, 6583 lines and continuum radiation and a VLA map at 8 GHz of the H2O gigamaser galaxy TXS 2226-184. This galaxy has the most luminous H2O maser emission known to date. Our red continuum images reveal a highly elongated galaxy with a dust lane crossing the nucleus. The surface brightness profile is best fitted by a bulge plus exponential disk model, favoring classification as a highly inclined spiral galaxy (i=70&j0;). The color map confirms that the dust lane is aligned with the galaxy major axis and is crossing the putative nucleus. The Halpha + [N ii] map exhibits a gaseous, jetlike structure perpendicular to the nuclear dust lane and the galaxy major axis. The radio map shows compact, steep spectrum emission that is elongated in the same direction as the Halpha + [N ii] emission. By analogy with Seyfert galaxies, we therefore suspect that this alignment reflects an interaction between the radio jet and the interstellar medium. The axes of the nuclear dust disk, the radio emission, and the optical line emission apparently define the axis of the active galactic nucleus. The observations suggest that in this galaxy the nuclear accretion disk, obscuring torus, and large-scale molecular gas layer are roughly coplanar. Our classification of the host galaxy strengthens the trend for megamasers to be found preferentially in highly inclined spiral galaxies.

  1. Hα Imaging of Early-type(Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, S.; Devereux, N.

    1997-12-01

    Hα imaging of Early-type (Sa-Sab) Spirals A recent analysis of the IRAS database indicates that the massive star formation rates in early-type(Sa-Sab) spirals are comparable to the massive star formation rates in late-type spirals. We are conducting an Hα imaging survey of a complete sample of nearby (D <= 40Mpc), bright (m(B) <= 12.1), early-type spirals to confirm the results obtained by IRAS. Our preliminary results indicate that a majority of these galaxies show either signs of interaction, and/or host nuclear starbursts. The occurence of nuclear starbursts in early-type spirals may be related to the propensity for such galaxies to also host Seyfert nuclei. The evidence for interactions suggests that early-type spirals are evolving in the current epoch.

  2. Smooth dark spiral arms in the flocculent galaxy NGC2841

    NASA Astrophysics Data System (ADS)

    Block, David L.; Elmegreen, B. G.; Wainscoat, R. J.

    1996-06-01

    OPTICAL images of the arms of spiral galaxies invariably show massive blue stars forming in ridges of interstellar gas and dust1. These are particularly striking in 'grand-design' galaxies, in which the stellar positions are influenced by spiral density waves1. By contrast, many galaxies have a 'flocculent' appearance, with no obvious evidence of spiral structure at visible wavelengths. Here we report infrared observations of the prototype flocculent galaxy NGC2841, which reveal a remarkable system of long, dark spiral arms. These arms arise from concentrations of dust; they are hidden at optical wavelengths by light scattered from the dust. The mechanism that has organized the gas and dust into these dark arms is at present unclear; the arms might be highly sheared dense clouds, or they might correspond to density waves in the interstellar medium driven by an elongated central bulge, which would not affect the stable stellar disk.

  3. The Supermassive Black Hole Mass Function in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, Julia D.; Berrier, J. C.; Kennefick, D.; Davis, B. L.; Seigar, M.; Shields, D.; Barrows, R. S.; Lacy, C. H.; Hughes, J. A.; Galaxy Evolution Survey, Arkansas

    2013-01-01

    The AGES group is exploring a number of techniques to study the relationship between central SMBH black hole mass and spiral arm morphology in disk galaxies. We have developed a new technique which permits us to reliably and accurately measure pitch angle based upon a 2DFFT algorithm. We have then compared pitch angles to directly measured black hole masses in local galaxies and demonstrated a strong correlation between them. Using the relation thus established we have developed a pitch angle distribution function of a statistically complete volume limited sample of nearby galaxies and developed a central black hole mass function for nearby spiral galaxies.

  4. Face on Barred and Ringed Spiral Galaxy NGC 3351

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Ultraviolet image (left) and visual image (right) of the face on barred and ringed spiral galaxy NGC 3351 (M95). The morphological appearance of a galaxy can change dramatically between visual and ultraviolet wavelengths. In the case of M95, the nucleus and bar dominate the visual image. In the ultraviolet, the bar is not even visible and the ring and spiral arms dominate.

  5. THE CONTRIBUTION OF SPIRAL ARMS TO THE THICK DISK ALONG THE HUBBLE SEQUENCE

    SciTech Connect

    Martinez-Medina, L. A.; Pichardo, B.; Moreno, E.; Pérez-Villegas, A. E-mail: barbara@astro.unam.mx

    2015-04-01

    The first mechanism invoked to explain the existence of the thick disk in the Milky Way Galaxy was the spiral arms. Up-to-date work summons several other possibilities that together seem to better explain this component of our Galaxy. All these processes must affect distinct types of galaxies differently, but the contribution of each one has not been straightforward to quantify. In this work, we present the first comprehensive study of the effect of the spiral arms on the formation of thick disks, looking at early- to late-type disk galaxies in an attempt to characterize and quantify this specific mechanism in galactic potentials. To this purpose, we perform test particle numerical simulations in a three-dimensional spiral galactic potential (for early- to late-types spiral galaxies). By varying the parameters of the spiral arms we found that the vertical heating of the stellar disk becomes very important in some cases and strongly depends on the galactic morphology, pitch angle, arm mass, and the arm pattern speed. The later the galaxy type, the larger is the effect on the disk heating. This study shows that the physical mechanism causing the vertical heating is different from simple resonant excitation. The spiral pattern induces chaotic behavior not linked necessarily to resonances but to direct scattering of disk stars, which leads to an increase of the velocity dispersion. We applied this study to the specific example of the Milky Way Galaxy, for which we have also added an experiment that includes the Galactic bar. From this study we deduce that the effect of spiral arms of a Milky-Way-like potential on the dynamical vertical heating of the disk is negligible, unlike later galactic potentials for disks.

  6. Star formation along the Hubble sequence. Radial structure of the star formation of CALIFA galaxies

    NASA Astrophysics Data System (ADS)

    González Delgado, R. M.; Cid Fernandes, R.; Pérez, E.; García-Benito, R.; López Fernández, R.; Lacerda, E. A. D.; Cortijo-Ferrero, C.; de Amorim, A. L.; Vale Asari, N.; Sánchez, S. F.; Walcher, C. J.; Wisotzki, L.; Mast, D.; Alves, J.; Ascasibar, Y.; Bland-Hawthorn, J.; Galbany, L.; Kennicutt, R. C.; Márquez, I.; Masegosa, J.; Mollá, M.; Sánchez-Blázquez, P.; Vílchez, J. M.

    2016-05-01

    The spatially resolved stellar population content of today's galaxies holds important information for understanding the different processes that contribute to the star formation and mass assembly histories of galaxies. The aim of this paper is to characterize the radial structure of the star formation rate (SFR) in galaxies in the nearby Universe as represented by a uniquely rich and diverse data set drawn from the CALIFA survey. The sample under study contains 416 galaxies observed with integral field spectroscopy, covering a wide range of Hubble types and stellar masses ranging from M⋆ ~ 109 to 7 × 1011 M⊙. Spectral synthesis techniques are applied to the datacubes to derive 2D maps and radial profiles of the intensity of the star formation rate in the recent past (ΣSFR), as well as related properties, such as the local specific star formation rate (sSFR), defined as the ratio between ΣSFR and the stellar mass surface density (μ⋆). To emphasize the behavior of these properties for galaxies that are on and off the main sequence of star formation (MSSF), we stack the individual radial profiles in seven bins of galaxy morphology (E, S0, Sa, Sb, Sbc, Sc, and Sd), and several stellar masses. Our main results are: (a) the intensity of the star formation rate shows declining profiles that exhibit very small differences between spirals with values at R = 1 half light radius (HLR) within a factor two of ΣSFR ~ 20 M⊙Gyr-1pc-2. The dispersion in the ΣSFR(R) profiles is significantly smaller in late type spirals (Sbc, Sc, Sd). This confirms that the MSSF is a sequence of galaxies with nearly constant ΣSFR. (b) sSFR values scale with Hubble type and increase radially outward with a steeper slope in the inner 1 HLR. This behavior suggests that galaxies are quenched inside-out and that this process is faster in the central, bulge-dominated part than in the disks. (c) As a whole and at all radii, E and S0 are off the MSSF with SFR much smaller than spirals of the

  7. Comparing Stellar Populations of Galaxies Across the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Etheridge, Sarina Marie; Kaleida, Catherine; Jansen, Rolf

    2017-01-01

    From analysis of radial color gradients, it has been found that many late-type galaxies tend to become redder further out from the center of the galaxy (add references here). There are no feasible galaxy formation models that predict high metallicity in the outskirts of late-type galaxies, and these galaxies tend to show little evidence for significant amounts of dust at large radii. We therefore hypothesize the radial color gradients are primarily affected by stellar population ages. We observed irregular, elliptical, and spiral galaxies with the Infrared Sideport Imager (ISPI) on the 4-meter Blanco Telescope of Cerro Tololo Inter-American Observatory (CTIO) in Chile, using the J, H, and Ks near-infrared (NIR) filters. Elliptical aperture photometry was performed to obtain radial profiles of surface brightness, and of J-H and H-Ks colors. We analyze the relative contributions of stellar population ages, dust extinction and stellar metallicity to the radial color gradients. Detailed information like that gathered from this research, when expanded to statistical samples of nearby galaxies spanning a range of types, masses, and luminosities, is useful for comparison to studies of high-redshift galaxies and can serve as an observational benchmark that galaxy formation and evolution models must be able to reproduce.

  8. PITCH ANGLE RESTRICTIONS IN LATE-TYPE SPIRAL GALAXIES BASED ON CHAOTIC AND ORDERED ORBITAL BEHAVIOR

    SciTech Connect

    Perez-Villegas, A.; Pichardo, B.; Moreno, E.; Peimbert, A.; Velazquez, H. M.

    2012-01-20

    We built models for low bulge mass spiral galaxies (late type as defined by the Hubble classification) using a three-dimensional self-gravitating model for spiral arms, and analyzed the orbital dynamics as a function of pitch angle, ranging from 10 Degree-Sign to 60 Degree-Sign . Indirectly testing orbital self-consistency, we search for the main periodic orbits and studied the density response. For pitch angles up to approximately {approx}20 Degree-Sign , the response closely supports the potential readily permitting the presence of long-lasting spiral structures. The density response tends to 'avoid' larger pitch angles in the potential by keeping smaller pitch angles in the corresponding response. Spiral arms with pitch angles larger than {approx}20 Degree-Sign would not be long-lasting structures but would rather be transient. On the other hand, from an extensive orbital study in phase space, we also find that for late-type galaxies with pitch angles larger than {approx}50 Degree-Sign , chaos becomes pervasive, destroying the ordered phase space surrounding the main stable periodic orbits and even destroying them. This result is in good agreement with observations of late-type galaxies, where the maximum observed pitch angle is {approx}50 Degree-Sign .

  9. Derivation of the Hubble parameter using galaxy clusters

    NASA Astrophysics Data System (ADS)

    Kozmanyan, A.; Bourdin, H.; de Gasperis, G.; Mazzotta, P.; Vittorio, N.

    2017-05-01

    In this work we describe a possible way to use X-ray and microwave observations of nearby galaxy clusters to derive the value of the Hubble constant, that parametrises the expansion rate of the Universe. We provide a brief introduction to the Sunyaev-Zel’dovich effect that allows to detect galaxy clusters at microwave frequencies, and the method to combine it with X-ray observables. We emphasize what kind of considerations should be done when applying the method on real data and study the effect of the geometry of the clusters on the final result.

  10. Galaxy Zoo CANDELS Data Release I: Morphologies of ~50,000 Galaxies With z ≤ 3 in Deep Hubble Legacy Fields

    NASA Astrophysics Data System (ADS)

    Simmons, Brooke; Lintott, Chris; Masters, Karen; Willett, Kyle; Kartaltepe, Jeyhan S.; Closson Ferguson, Henry; Faber, Sandra M.; Galaxy Zoo Team, CANDELS Team

    2016-01-01

    We present quantified visual morphologies of approximately 48,000 galaxies in rest-frame optical to z ~ 3, using galaxies observed in three Hubble Space Telescope legacy fields by the Cosmic And Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and classified by participants in the Galaxy Zoo project. Each galaxy received an average of 43 independent classifications, which we combine into detailed morphological information on galaxy features such as clumpiness, bar instabilities, spiral structure, and merger and tidal signatures. We apply a consensus-based classifier weighting method that preserves classifier independence while effectively down-weighting significantly errant classifications. Comparing the Galaxy Zoo classifications to previous human and machine classifications of the same galaxies shows very good agreement; in some cases the high number of independent classifications provided by Galaxy Zoo provides an advantage in selecting galaxies with a particular morphological profile, while in others the combination of Galaxy Zoo with other classifications is a more promising approach than using any one method alone. We combine the Galaxy Zoo classifications of "smooth" galaxies with parametric morphologies to select a sample of featureless disks at 1 ≤ z ≤ 2, which may represent a dynamically warmer progenitor population to the settled disk galaxies seen at later epochs.

  11. Hubble studies generations of star formation in neighbouring galaxy

    NASA Astrophysics Data System (ADS)

    2004-07-01

    N11B Credits: NASA/ESA and the Hubble Heritage Team (AURA/STScI)/HEIC The iridescent tapestry of star birth The NASA/ESA Hubble Space Telescope captures the iridescent tapestry of star birth in a neighbouring galaxy in this panoramic view of glowing gas, dark dust clouds, and young, hot stars. The star-forming region, catalogued as N11B lies in the Large Magellanic Cloud (LMC), located only 160 000 light-years from Earth. With its high resolution, the Hubble Space Telescope is able to view details of star formation in the LMC as easily as ground-based telescopes are able to observe stellar formation within our own Milky Way galaxy. One neighbouring galaxy, the Large Magellanic Cloud (LMC), lies in the constellation of Dorado and contains a number of regions harbouring recent and ongoing star formation. One of these star-forming region, N11B, is shown in this Hubble image. It is a subregion within a larger area of star formation called N11. N11 is the second largest star-forming region in LMC. It is only surpassed in the size and activity by ‘the king of stellar nurseries’, 30 Doradus, located at the opposite side of LMC. N11B Credits: NASA/ESA and the Hubble Heritage Team (AURA/STScI)/HEIC A view of star formation The NASA/ESA Hubble Space Telescope captures the iridescent tapestry of star birth in a neighbouring galaxy in this panoramic view of glowing gas, dark dust clouds, and young, hot stars. The star-forming region, catalogued as N11B lies in the Large Magellanic Cloud (LMC), located only 160 000 light-years from Earth. With its high resolution, the Hubble Space Telescope is able to view details of star formation in the LMC as easily as ground-based telescopes are able to observe stellar formation within our own Milky Way galaxy. One neighbouring galaxy, the Large Magellanic Cloud (LMC), lies in the constellation of Dorado and contains a number of regions harbouring recent and ongoing star formation. One of these star-forming regions, N11B, is shown in

  12. The Hot Gaseous Halos of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, J.

    2016-06-01

    In the Milky Way, absorption and emission line measurements of O VII and O VIII show that the halo environment is dominated by a nearly spherical halo of temperature 2 × 10^6 K, metallicity of 0.3-0.5 solar, and with a density decreasing as r^{-3/2}. The mass of the hot gas, estimated through extrapolation to the virial radius, is comparable to the stellar mass, but does not account for the missing mass. The Milky Way hot halo appears to be rotating at about 180 km/s, which is consistent with model expectations, depending on the time of infall. Around massive spiral galaxies, hot halos are seen in emission out to about 70 kpc in the best cases. These show similar gas density laws and metallicities in the range 0.1-0.5 solar. The gas mass is comparable to the stellar mass, but does not account for the missing baryons within the virial radius. If the density law can be extrapolated to about three virial radii, the missing baryons would be accounted for.

  13. CHARACTERISTICS OF SPIRAL ARMS IN LATE-TYPE GALAXIES

    SciTech Connect

    Honig, Z. N.; Reid, M. J.

    2015-02-10

    We have measured the positions of large numbers of H II regions in four nearly face-on, late-type, spiral galaxies: NGC 628 (M74), NGC 1232, NGC 3184, and NGC 5194 (M51). Fitting log-periodic spiral models to segments of each arm yields local estimates of spiral pitch angle and arm width. While pitch angles vary considerably along individual arms, among arms within a galaxy, and among galaxies, we find no systematic trend with galactocentric distance. We estimate the widths of the arm segments from the scatter in the distances of the H II regions from the spiral model. All major arms in these galaxies show spiral arm width increasing with distance from the galactic center, similar to the trend seen in the Milky Way. However, in the outermost parts of the galaxies, where massive star formation declines, some arms reverse this trend and narrow. We find that spiral arms often appear to be composed of segments of ∼5 kpc length, which join to form kinks and abrupt changes in pitch angle and arm width; these characteristics are consistent with properties seen in the large N-body simulations of D'Onghia et al. and others.

  14. Optical spectroscopy of the radio-loud nuclei of spiral galaxies: Starbursts or monsters

    SciTech Connect

    Heckman, T.M.; Van Breugel, W.; Miley, G.K.; Butcher, H.R.

    1983-08-01

    We present optical spectroscopic data pertaining to the physical state, kinematics, and spatial extent of the emission-line gas near the radio-loud nuclei of spiral galaxies. These data are combined with published optical, radio, and infrared data to evaluate the suggestions by Condon et al. (1982) that the nuclear radio emission in this class of galaxy is produced by multiple supernova remnants generated as a consequence of a nuclear starburst. As a whole, the radio-loud nuclei have stronger emission lines than radio-quiet nuclei of galaxies of similar Hubble/de Vaucouleurs type. This emission-line gas is generally at least as spatially extended as the radio continuum emission. However, we find that only about 1/3 of the spiral galaxies examined have optical spectroscopic properties consistent with those of ''extranuclear starbursts'' (i.e., giant H II regions). The majority of the nuclei seem to require a form of energy input to the ionized gas which is ''harder'' than the Lyman continuum radiation of OB stars, as their emission-line spectra are of the Seyfert or Liner variety. The nuclei with H II region spectra are distinct from the nuclei with Seyfert spectra in terms of radio morphology and radio spectral index, and tend to occur in spiral galaxies of much later Hubble type than do the Seyfert or Liner nuclei (Sc vs Sa). Moreover, the most luminous nuclear radio sources in our sample (PMHz> or =10/sup 22/ Watts Hz/sup -1/ Sr/sup -1/) are not associated with H II region nuclei. We summarize evidence that the putative nuclear starbursts must differ significantly from extranuclear starbursts.

  15. Turbulence and Star Formation in a Sample of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Maier, Erin; Chien, Li-Hsin; Hunter, Deidre A.

    2016-11-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. on the Small Magellanic Cloud, we use the third and fourth statistical moments, as indicators of structures caused by turbulence, to examine the neutral hydrogen (H i) column density of a sample of spiral galaxies selected from The H i Nearby Galaxy Survey. We apply the statistical moments in three different methods—the galaxy as a whole, divided into a function of radii and then into grids. We create individual grid maps of kurtosis for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with their far-ultraviolet images taken by the Galaxy Evolution Explorer satellite.We find that the moments are largely uniform across the galaxies, in which the variation does not appear to trace any star-forming regions. This may, however, be due to the spatial resolution of our analysis, which could potentially limit the scale of turbulent motions that we are sensitive to greater than ∼700 pc. From comparison between the moments themselves, we find that the gas motions in our sampled galaxies are largely supersonic. This analysis also shows that the Burkhart et al. methods may be applied not just to dwarf galaxies but also to normal spiral galaxies.

  16. Distance determinations to shield galaxies from Hubble space telescope imaging

    SciTech Connect

    McQuinn, Kristen B. W.; Skillman, Evan D.; Cannon, John M.; Cave, Ian; Dolphin, Andrew E.; Salzer, John J.; Haynes, Martha P.; Adams, Elizabeth; Giovanelli, Riccardo; Elson, Ed C.; Ott, Juërgen; Saintonge, Amélie

    2014-04-10

    The Survey of H I in Extremely Low-mass Dwarf (SHIELD) galaxies is an ongoing multi-wavelength program to characterize the gas, star formation, and evolution in gas-rich, very low-mass galaxies. The galaxies were selected from the first ∼10% of the H I Arecibo Legacy Fast ALFA (ALFALFA) survey based on their inferred low H I mass and low baryonic mass, and all systems have recent star formation. Thus, the SHIELD sample probes the faint end of the galaxy luminosity function for star-forming galaxies. Here, we measure the distances to the 12 SHIELD galaxies to be between 5 and 12 Mpc by applying the tip of the red giant method to the resolved stellar populations imaged by the Hubble Space Telescope. Based on these distances, the H I masses in the sample range from 4 × 10{sup 6} to 6 × 10{sup 7} M {sub ☉}, with a median H I mass of 1 × 10{sup 7} M {sub ☉}. The tip of the red giant branch distances are up to 73% farther than flow-model estimates in the ALFALFA catalog. Because of the relatively large uncertainties of flow-model distances, we are biased toward selecting galaxies from the ALFALFA catalog where the flow model underestimates the true distances. The measured distances allow for an assessment of the native environments around the sample members. Five of the galaxies are part of the NGC 672 and NGC 784 groups, which together constitute a single structure. One galaxy is part of a larger linear ensemble of nine systems that stretches 1.6 Mpc from end to end. Three galaxies reside in regions with 1-9 neighbors, and four galaxies are truly isolated with no known system identified within a radius of 1 Mpc.

  17. NASA's Hubble Finds Life is Too Fast, Too Furious for This Runaway Galaxy

    NASA Image and Video Library

    2017-09-27

    This image combines NASA/ESA Hubble Space Telescope observations with data from the Chandra X-ray Observatory. As well as the electric blue ram pressure stripping streaks seen emanating from ESO 137-001, a giant gas stream can be seen extending towards the bottom of the frame, only visible in the X-ray part of the spectrum. Credit: NASA, ESA, CXC The spiral galaxy ESO 137-001 looks like a dandelion caught in a breeze in this new Hubble Space Telescope image. The galaxy is zooming toward the upper right of this image, in between other galaxies in the Norma cluster located over 200 million light-years away. The road is harsh: intergalactic gas in the Norma cluster is sparse, but so hot at 180 million degrees Fahrenheit that it glows in X-rays. The spiral plows through the seething intra-cluster gas so rapidly – at nearly 4.5 million miles per hour — that much of its own gas is caught and torn away. Astronomers call this "ram pressure stripping." The galaxy’s stars remain intact due to the binding force of their gravity. Tattered threads of gas, the blue jellyfish-tendrils trailing ESO 137-001 in the image, illustrate the process. Ram pressure has strung this gas away from its home in the spiral galaxy and out over intergalactic space. Once there, these strips of gas have erupted with young, massive stars, which are pumping out light in vivid blues and ultraviolet. The brown, smoky region near the center of the spiral is being pushed in a similar manner, although in this case it is small dust particles, and not gas, that are being dragged backwards by the intra-cluster medium. Read more here: 1.usa.gov/P0HSFh 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

  18. Hubble Space Telescope Imaging of Brightest Cluster Galaxies

    NASA Astrophysics Data System (ADS)

    Laine, Seppo; van der Marel, Roeland P.; Lauer, Tod R.; Postman, Marc; O'Dea, Christopher P.; Owen, Frazer N.

    2003-02-01

    We used the Hubble Space Telescope Wide Field Planetary Camera 2 to obtain I-band images of the centers of 81 brightest cluster galaxies (BCGs), drawn from a volume-limited sample of nearby BCGs. The images show a rich variety of morphological features, including multiple or double nuclei, dust, stellar disks, point-source nuclei, and central surface brightness depressions. High-resolution surface brightness profiles could be inferred for 60 galaxies. Of those, 88% have well-resolved cores. The relationship between core size and galaxy luminosity for BCGs is indistinguishable from that of Faber et al. (published in 1997, hereafter F97) for galaxies within the same luminosity range. However, the core sizes of the most luminous BCGs fall below the extrapolation of the F97 relationship rb~L1.15V. A shallower relationship, rb~L0.72V, fits both the BCGs and the core galaxies presented in F97. Twelve percent of the BCG sample lacks a well-resolved core; all but one of these BCGs have ``power law'' profiles. Some of these galaxies have higher luminosities than any power-law galaxy identified by F97 and have physical upper limits on rb well below the values observed for core galaxies of the same luminosity. These results support the idea that the central structure of early-type galaxies is bimodal in its physical properties but also suggest that there exist high-luminosity galaxies with power-law profiles (or unusually small cores). The BCGs in the latter category tend to fall at the low end of the BCG luminosity function and tend to have low values of the quantity α (the logarithmic slope of the metric luminosity as a function of radius, at 10 kpc). Since theoretical calculations have shown that the luminosities and α-values of BCGs grow with time as a result of accretion, this suggests a scenario in which elliptical galaxies evolve from power-law profiles to core profiles through accretion and merging. This is consistent with theoretical scenarios that invoke the

  19. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole.

  20. A Survey of nearby, nearly face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Garmire, Gordon

    2014-09-01

    This is a continuation of a survey of nearby, nearly face-on spiral galaxies. The main purpose is to search for evidence of collisions with small galaxies that show up in X-rays by the generation of hot shocked gas from the collision. Secondary objectives include study of the spatial distribution point sources in the galaxy and to detect evidence for a central massive blackhole. These are alternate targets.

  1. Gas Ejection from Spiral Galaxy Disks

    NASA Astrophysics Data System (ADS)

    Durelle, Jeremy

    We present the results of three proposed mechanisms for ejection of gas from a spiral arm into the halo. The mechanisms were modelled using magnetohydrodynamics (MHD) as a theoretical template. Each mechanism was run through simulations using a Fortran code: ZEUS-3D, an MHD equation solver. The first mechanism modelled the gas dynamics with a modified Hartmann flow which describes the fluid flow between two parallel plates. We initialized the problem based on observation of lagging halos; that is, that the rotational velocity falls to a zero at some height above the plane of the disk. When adopting a density profile which takes into account the various warm and cold H I and HII molecular clouds, the system evolves very strangely and does not reproduce the steady velocity gradient observed in edge-on galaxies. This density profile, adopted from Martos and Cox (1998), was used in the remaining models. However, when treating a system with a uniform density profile, a stable simulation can result. Next we considered supernova (SN) blasts as a possible mechanism for gas ejection. While a single SN was shown to be insufficient to promote vertical gas structures from the disk, multiple SN explosions proved to be enough to promote gas ejection from the disk. In these simulations, gas ejected to a height of 0.5 kpc at a velocity of 130 km s--1 from 500 supernovae, extending to an approximate maximum height of 1 kpc at a velocity of 6.7 x 103 km s--1 from 1500 supernovae after 0.15 Myr, the approximate time of propagation of a supernova shock wave. Finally, we simulated gas flowing into the spiral arm at such a speed to promote a jump in the disk gas, termed a hydraulic jump. The height of the jump was found to be slightly less than a kiloparsec with a flow velocity of 41 km s--1 into the halo after 167 Myr. The latter models proved to be effective mechanisms through which gas is ejected from the disk whereas the Hartmann flow (or toy model) mechanism remains unclear as the

  2. HUBBLE IDENTIFIES SOURCE OF ULTRAVIOLET LIGHT IN AN OLD GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Hubble Space Telescope's exquisite resolution has allowed astronomers to resolve, for the first time, hot blue stars deep inside an elliptical galaxy. The swarm of nearly 8,000 blue stars resembles a blizzard of snowflakes near the core (lower right) of the neighboring galaxy M32, located 2.5 million light-years away in the constellation Andromeda. Hubble confirms that the ultraviolet light comes from a population of extremely hot helium-burning stars at a late stage in their lives. Unlike the Sun, which burns hydrogen into helium, these old stars exhausted their central hydrogen long ago, and now burn helium into heavier elements. The observations, taken in October 1998, were made with the camera mode of the Space Telescope Imaging Spectrograph (STIS) in ultraviolet light. The STIS field of view is only a small portion of the entire galaxy, which is 20 times wider on the sky. For reference, the full moon is 70 times wider than the STIS field-of-view. The bright center of the galaxy was placed on the right side of the image, allowing fainter stars to be seen on the left side of the image. These results are to be published in the March 1, 2000 issue of The Astrophysical Journal. Thirty years ago, the first ultraviolet observations of elliptical galaxies showed that they were surprisingly bright when viewed in ultraviolet light. Before those pioneering UV observations, old groups of stars were assumed to be relatively cool and thus extremely faint in the ultraviolet. Over the years since the initial discovery of this unexpected ultraviolet light, indirect evidence has accumulated that it originates in a population of old, but hot, helium-burning stars. Now Hubble provides the first direct visual evidence. Nearby elliptical galaxies are thought to be relatively simple galaxies comprised of old stars. Because they are among the brightest objects in the Universe, this simplicity makes them useful for tracing the evolution of stars and galaxies. Credits: NASA and Thomas

  3. OBSERVATIONAL EVIDENCE AGAINST LONG-LIVED SPIRAL ARMS IN GALAXIES

    SciTech Connect

    Foyle, K.; Rix, H.-W.; Walter, F.; Dobbs, C. L.; Leroy, A. K.

    2011-07-10

    We test whether the spiral patterns apparent in many large disk galaxies should be thought of as dynamical features that are stationary in a corotating frame for {approx}> t{sub dyn}, as implied by the density wave approach for explaining spiral arms. If such spiral arms have enhanced star formation (SF), observational tracers for different stages of the SF sequence should show a spatial ordering, from upstream to downstream in the corotating frame: dense H I, CO, tracing molecular hydrogen gas, 24 {mu}m emission tracing enshrouded SF, and UV emission tracing unobscured young stars. We argue that such a spatial ordering should be reflected in the angular cross-correlation (CC, in polar coordinates) using all azimuthal positions among pairs of these tracers; the peak of the CC should be offset from zero, in different directions inside and outside the corotation radius. Recent spiral SF simulations by Dobbs and Pringle show explicitly that for the case of a stationary spiral arm potential such angular offsets between gas and young stars of differing ages should be observable as cross-correlation offsets. We calculate the angular cross-correlations for different observational SF sequence tracers in 12 nearby spiral galaxies, drawing on a data set with high-quality maps of the neutral gas (H I, THINGS) and molecular gas (CO, HERACLES), along with 24 {mu}m emission (Spitzer, SINGS); we include FUV images (GALEX) and 3.6 {mu}m emission (Spitzer, IRAC) for some galaxies, tracing aging stars and longer timescales. In none of the resulting tracer cross-correlations for this sample do we find systematic angular offsets, which would be expected for a stationary dynamical spiral pattern of well-defined pattern speed. This result indicates that spiral density waves in their simplest form are not an important aspect of explaining spirals in large disk galaxies.

  4. HUBBLE PEEKS INTO A STELLAR NURSERY IN A NEARBY GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    HUBBLE PEEKS INTO A STELLAR NURSERY IN A NEARBY GALAXY NASA's Hubble Space Telescope has peered deep into a neighboring galaxy to reveal details of the formation of new stars. Hubble's target was a newborn star cluster within the Small Magellanic Cloud, a small galaxy that is a satellite of our own Milky Way. The new images show young, brilliant stars cradled within a nebula, or glowing cloud of gas, cataloged as N 81. These massive, recently formed stars inside N 81 are losing material at a high rate, sending out strong stellar winds and shock waves and hollowing out a cocoon within the surrounding nebula. The two most luminous stars, seen in the Hubble image as a very close pair near the center of N 81, emit copious ultraviolet radiation, causing the nebula to glow through fluorescence. Outside the hot, glowing gas is cooler material consisting of hydrogen molecules and dust. Normally this material is invisible, but some of it can be seen in silhouette against the nebular background, as long dust lanes and a small, dark, elliptical-shaped knot. It is believed that the young stars have formed from this cold matter through gravitational contraction. Few features can be seen in N 81 from ground-based telescopes, earning it the informal nick-name 'The Blob.' Astronomers were not sure if just one or a few hot stars were embedded in the cloud, or if it was a stellar nursery containing a large number of less massive stars. Hubble's high-resolution imaging shows the latter to be the case, revealing that numerous young, white-hot stars---easily visible in the color picture---are contained within N 81. This crucial information bears strongly on theories of star formation, and N 81 offers a singular opportunity for a close-up look at the turbulent conditions accompanying the birth of massive stars. The brightest stars in the cluster have a luminosity equal to 300,000 stars like our own Sun. Astronomers are especially keen to study star formation in the Small Magellanic

  5. Can cluster environment modify the dynamical evolution of spiral galaxies?

    NASA Technical Reports Server (NTRS)

    Amram, P.; Balkowski, C.; Cayatte, V.; Marcelin, M.; Sullivan, W. T., III

    1993-01-01

    Over the past decade many effects of the cluster environment on member galaxies have been established. These effects are manifest in the amount and distribution of gas in cluster spirals, the luminosity and light distributions within galaxies, and the segregation of morphological types. All these effects could indicate a specific dynamical evolution for galaxies in clusters. Nevertheless, a more direct evidence, such as a different mass distribution for spiral galaxies in clusters and in the field, is not yet clearly established. Indeed, Rubin, Whitmore, and Ford (1988) and Whitmore, Forbes, and Rubin (1988) (referred to as RWF) presented evidence that inner cluster spirals have falling rotation curves, unlike those of outer cluster spirals or the great majority of field spirals. If falling rotation curves exist in centers of clusters, as argued by RWF, it would suggest that dark matter halos were absent from cluster spirals, either because the halos had become stripped by interactions with other galaxies or with an intracluster medium, or because the halos had never formed in the first place. Even if they didn't disagree with RWF, other researchers pointed out that the behaviour of the slope of the rotation curves of spiral galaxies (in Virgo) is not so clear. Amram, using a different sample of spiral galaxies in clusters, found only 10% of declining rotation curves (2 declining vs 17 flat or rising) in opposition to RWF who find about 40% of declining rotation curves in their sample (6 declining vs 10 flat or rising), we will hereafter briefly discuss the Amram data paper and compare it to the results of RWF. We have measured the rotation curves for a sample of 21 spiral galaxies in 5 nearby clusters. These rotation curves have been constructed from detailed two-dimensional maps of each galaxy's velocity field as traced by emission from the Ha line. This complete mapping, combined with the sensitivity of our CFHT 3.60 m. + Perot-Fabry + CCD observations, allows

  6. The similar stellar populations of quiescent spiral and elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Robaina, Aday R.; Hoyle, Ben; Gallazzi, Anna; Jiménez, Raul; van der Wel, Arjen; Verde, Licia

    2012-12-01

    We compare the stellar population properties in the central regions of visually classified non-star-forming spiral and elliptical galaxies from Galaxy Zoo and Sloan Digital Sky Survey (SDSS) Data Release 7. The galaxies lie in the redshift range 0.04 < z < 0.1 and have stellar masses larger than log M* = 10.4. We select only face-on spiral galaxies in order to avoid contamination by light from the disc in the SDSS fibre and enabling the robust visual identification of spiral structure. Overall, we find that galaxies with larger central stellar velocity dispersions, regardless of morphological type, have older ages, higher metallicities and an increased overabundance of α-elements. Age and α-enhancement, at fixed velocity dispersion, do not depend on morphological type. The only parameter that, at a given velocity dispersion, correlates with morphological type is metallicity, where the metallicity of the bulges of spiral galaxies is 0.07 dex higher than that of the ellipticals. However, for galaxies with a given total stellar mass, this dependence on morphology disappears. Under the assumption that, for our sample, the velocity dispersion traces the mass of the bulge alone, as opposed to the total mass (bulge+disc) of the galaxy, our results imply that the formation epoch of galaxy and the duration of its star-forming period are linked to the mass of the bulge. The extent to which metals are retained within the galaxy, and not removed as a result of outflows, is determined by the total mass of the galaxy.

  7. The evolution of C/O in dwarf galaxies from Hubble Space Telescope FOS observations

    NASA Technical Reports Server (NTRS)

    Garnett, D. R.; Skillman, E. D.; Dufour, R. J.; Peimbert, M.; Torres-Peimbert, S.; Terlevich, R.; Terlevich, E.; Shields, G. A.

    1995-01-01

    We present UV observations of seven H II regions in low-luminosity dwarf irregular galaxies and the Magellanic Clouds obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in order to measure the C/O abundance ratio in the interstellar medium (ISM) of those galaxies. We measure both O III 1666 A and C III 1909 A in our spectra, enabling us to determine C(+2)/O(+2) with relatively small uncertainties. The results from our HST observations show a continuous increase in C/O with increasing O/H, consistent with a power law having an index of 0.43 +/- 0.09 over the range -4.7 to -3.6 in log (O/H). One possible interpretation of this trend is that the most metal-poor galaxies are the youngest and dominated by the products of early enrichment by massive stars, while more metal-rich galaxies show increasing, delayed contributions of carbon from intermediate-mass stars. Our results also suggest that it may not be appropiate to combine abundances in irregular galaxies with those in spiral galaxies to study the evolution of chemical abundances. Our measured C/O ratios in the most metal-poor galaxies are consistent with predictions of nucleosynthesis from massive stars for Weaver & Woosley's best estimate for the 12C(alpha, gamma) 16O nuclear reaction rate, assuming negligible contanmination from carbon produced in intermediate-mass stars in these galaxies. We detect a weak N III 1750 A multiplet in SMC N88A and obtain interesting upper limits for two other objects. Our 2 sigma uppr limits on the 1750 A feature indicate that the N(+2)/O(+2) ratios in these objects are not significantly larger than the N(+)/O(+) ratios measured from optical spectra. This behavior is consistent with predictions of photionization models, although better detections of N III are needed to confirm the results.

  8. Hubble Space Telescope imaging of globular cluster candidates in low surface brightness dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Sharina, M. E.; Puzia, T. H.; Makarov, D. I.

    2005-10-01

    Fifty-seven nearby low surface brightness dwarf galaxies (-10⪆ MV⪆ -16) were searched for globular cluster candidates (GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sample consists of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3 "transition" type (dIrr/dSph) galaxies with angular sizes less than 3.7 kpc situated at distances 2{-}6 Mpc in the field and in the nearby groups: M 81, Centaurus A, Sculptor, Canes Venatici I cloud. We find that 50% of dSph, dIrr/dSph, and dIrr galaxies contain GCCs. The fraction of GCCs located near the center of dwarf spheroidal galaxies is ⪆2 times higher than for dIrrs. The mean integral color of GCCs in dSphs, (V-I)_0=1.04±0.16 mag, coincides with the corresponding value for Galactic globular clusters and is similar to the blue globular cluster sub-populations in massive early-type galaxies. The color distribution for GCCs in dIrrs shows a clear bimodality with peaks near (V-I)0 = 0.5 and 1.0 mag. Blue GCCs are presumably young with ages t⪉1 Gyr, while the red GCC population is likely to be older. The detected GCCs have absolute visual magnitudes between MV=-10 and -5 mag. We find indications for an excess population of faint GCCs with MV⪆-6.5 mag in both dSph and dIrr galaxies, reminiscent of excess populations of faint globular clusters in nearby Local Group spiral galaxies. The measurement of structural parameters using King-profile fitting reveals that most GCCs have structural parameters similar to extended outer halo globular clusters in the Milky Way and M 31, as well as the recently discovered population of "faint fuzzy" clusters in nearby lenticular galaxies.

  9. Hubble Eyes Galactic Refurbishment

    NASA Image and Video Library

    2015-04-30

    The smudge of stars at the center of this NASA/ESA Hubble Space Telescope image is a galaxy known as UGC 5797. UGC 5797 is an emission line galaxy, meaning that it is currently undergoing active star formation. The result is a stellar population that is constantly being refurbished as massive bright blue stars form. Galaxies with prolific star formation are not only veiled in a blue tint, but are key to the continuation of a stellar cycle. In this image UGC 5797 appears in front of a background of spiral galaxies. Spiral galaxies have copious amounts of dust and gas — the main ingredient for stars — and therefore often also belong to the class of emission line galaxies. Spiral galaxies have disk-like shapes that drastically vary in appearance depending on the angle at which they are observed. The collection of spiral galaxies in this frame exhibits this attribute acutely: Some are viewed face-on, revealing the structure of the spiral arms, while the two in the bottom left are seen edge-on, appearing as plain streaks in the sky. There are many spiral galaxies, with varying colors and at different angles, sprinkled across this image — just take a look. Credit: ESA/Hubble & NASA, Acknowledgement: Luca Limatola

  10. Tidal Origin of Spiral Arms in Galaxies Orbiting a Cluster

    NASA Astrophysics Data System (ADS)

    Semczuk, Marcin; Łokas, Ewa L.; del Pino, Andrés

    2017-01-01

    One of the scenarios for the formation of grand-design spiral arms in disky galaxies involves their interactions with a satellite or another galaxy. Here we consider another possibility, where the perturbation is instead due to the potential of a galaxy cluster. Using N-body simulations we investigate the formation and evolution of spiral arms in a Milky-Way-like galaxy orbiting a Virgo-like cluster. The galaxy is placed on a few orbits of different size but similar eccentricity and its evolution are followed for 10 Gyr. The tidally induced, two-armed, approximately logarithmic spiral structure forms on each of them during the pericenter passages. The spiral arms dissipate and wind up with time, to be triggered again at the next pericenter passage. We confirm this transient and recurrent nature of the arms by analyzing the time evolution of the pitch angle and the arm strength. We find that the strongest arms are formed on the tightest orbit; however, they wind up rather quickly and are disturbed by another pericenter passage. The arms on the most extended orbit, which we analyze in more detail, wind up slowly and survive for the longest time. Measurements of the pattern speed of the arms indicate that they are kinematic density waves. We attempt a comparison with observations by selecting grand-design spiral galaxies in the Virgo cluster. Among those, we find nine examples bearing no sign of recent interactions or the presence of companions. For three of them we present close structural analogues among our simulated spiral galaxies.

  11. Hubble tracks down a galaxy cluster's dark matter

    NASA Astrophysics Data System (ADS)

    2003-07-01

    Unique mass map hi-res Size hi-res: 495 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Unique mass map This is a mass map of galaxy cluster Cl0024+1654 derived from an extensive Hubble Space Telescope campaign. The colour image is made from two images: a dark-matter map (the blue part of the image) and a 'luminous-matter' map determined from the galaxies in the cluster (the red part of the image). They were constructed by feeding Hubble and ground-based observations into advanced mathematical mass-mapping models. The map shows that dark matter is present where the galaxies clump together. The mass of the galaxies is shown in red, the mass of the dark matter in blue. The dark matter behaves like a 'glue', holding the cluster together. The dark-matter distribution in the cluster is not spherical. A secondary concentration of dark-matter mass is shown in blue to the upper right of the main concentration. Sky around galaxy cluster Cl0024+1654 hi-res Size hi-res: 3742 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Sky around galaxy cluster Cl0024+1654 This is a 2.5-degree field around galaxy cluster Cl0024+1654. The cluster galaxies are visible in the centre of the image in yellow. The image is a colour composite constructed from three Digitized Sky Survey 2 images: Blue (shown in blue), Red (shown in green), and Infrared (shown in red). HST observes shapes of more than 7000 faint background galaxies hi-res Size hi-res: 5593 kb Credits: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA) Hubble observes shapes of more than 7000 faint background galaxies Five days of observations produced the altogether 39 Hubble Wide Field and Planetary Camera 2 (WFPC2) images required to map the mass of the galaxy cluster Cl0024+1654. Each WFPC2 image has a size of about 1/150 the diameter of the full Moon. In

  12. Star Formation Activity of Barred Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Eunbin; Hwang, Ho Seong; Chung, Haeun; Lee, Gwang-Ho; Park, Changbom; Cervantes Sodi, Bernardo; Kim, Sungsoo S.

    2017-08-01

    We study the star formation activity of nearby galaxies with bars using a sample of late-type galaxies at 0.02≤slant z≤slant 0.05489 and {M}r< -19.5 from the Sloan Digital Sky Survey. We compare the physical properties of strongly and weakly barred galaxies with those of non-barred galaxies that have stellar mass and redshift distributions similar to barred galaxies. We find that the star formation activity of strongly barred galaxies probed by starburstiness, g-r, {NUV}-r, and mid-infrared [3.4]-[12] colors is, on average, lower than that of non-barred galaxies. However, weakly barred galaxies do not show such a difference between barred and non-barred galaxies. The amounts of atomic and molecular gas in strongly barred galaxies are smaller than those in non-barred galaxies, and the gas metallicity is higher in strongly barred galaxies than in non-barred galaxies. The gas properties of weakly barred galaxies again show no difference from those of non-barred galaxies. We stack the optical spectra of barred and non-barred galaxies in several mass bins and fit to the stacked spectra with a spectral fitting code, STARLIGHT. We find no significant difference in stellar populations between barred and non-barred galaxies for both strongly and weakly barred galaxies. Our results are consistent with the idea that the star formation activity of barred galaxies was enhanced in the past along with significant gas consumption, and is currently lower than or similar to that of non-barred galaxies. The past star formation enhancement depends on the strength of bars.

  13. Hubble Sees Monstrous Cloud Boomerang Back to our Galaxy

    NASA Image and Video Library

    2017-09-28

    Hubble Space Telescope astronomers are finding that the old adage “what goes up must come down” even applies to an immense cloud of hydrogen gas outside our Milky Way galaxy. The invisible cloud is plummeting toward our galaxy at nearly 700,000 miles per hour. Though hundreds of enormous, high-velocity gas clouds whiz around the outskirts of our galaxy, this so-called “Smith Cloud” is unique because its trajectory is well known. New Hubble observations suggest it was launched from the outer regions of the galactic disk, around 70 million years ago. The cloud was discovered in the early 1960s by doctoral astronomy student Gail Smith, who detected the radio waves emitted by its hydrogen. This composite image shows the size and location of the Smith Cloud on the sky. The cloud appears in false-color, radio wavelengths as observed by the Green Bank Telescope in West Virginia. The visible-light image of the background star field shows the cloud's location in the direction of the constellation Aquila. Read more: go.nasa.gov/1ZX8Fzo Credits: Saxton/Lockman/NRAO/AUI/NSF/Mellinger

  14. Turbulence and Star Formation in a Sample of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Maier, Erin R.; Hunter, Deidre Ann; Chien, Li-Hsin

    2016-01-01

    We investigate turbulent gas motions in spiral galaxies and their importance to star formation in far outer disks, where the column density is typically far below the critical value for spontaneous gravitational collapse. Following the methods of Burkhart et al. (2010) as applied to the Small Magellanic Cloud, we use the third and fourth statistical moments, skewness and kurtosis, which are indicators of structures caused by turbulence, to examine the integrated neutral hydrogen (Hι) column density of a sample of spiral galaxies selected from The Hι Nearby Galaxy Survey (THINGS, Walter et al. 2008). We examine the kurtosis and skewness values of each galaxy as a whole, as well as their variation as a function of radius and in discrete sub-regions defined by a square, moving 'kernel,' essentially splitting each galaxy into a grid. We then create individual grid maps of kurtosis and skewness for each galaxy. To investigate the relation between these moments and star formation, we compare these maps with maps of each galaxy's far-ultraviolet (FUV) image, taken by the Galaxy Evolution Explorer (GALEX) satellite. We find that the moments are largely uniform across the galaxies: the variation does not appear to trace any star forming regions. This may, however, be due to the spatial resolution of our analysis, which could potentially limit the scale of turbulent motions to at most ~700 pc. From our analysis of the comparison between the two moments themselves, we find that the gas motions in our sample galaxies are largely supersonic. This analysis shows that Burkhart et al. (2010)'s methods may be applied not just to dwarf galaxies but normal spiral galaxies as well.We acknowledge the NSF for their funding of this work through their Research Experience for Undergraduates (REU) program (Grant No. AST-1461200).

  15. Spiral galaxies in clusters. III. Gas-rich galaxies in the Pegasus I cluster of galaxies

    SciTech Connect

    Bothun, G.D.; Schommer, R.A.; Sullivan, W.T. III

    1982-05-01

    We report the results of a 21-cm and optical survey of disk galaxies in the vicinity of the Pegasus I cluster of galaxies. The color--gas content relation (log(M/sub H//L/sub B/) vs (B-V)/sup T//sub 0/ ) for this particular cluster reveals the presence of a substantial number of blue, gas-rich galaxies. With few exceptions, the disk systems in Pegasus I retain large amounts of neutral hydrogen despite their presence in a cluster. This directly shows that environmental processes have not yet removed substantial amounts of gas from these disk galaxies. We conclude that the environment has had little or no observable effect upon the evolution of disk galaxies in Pegasus I. The overall properties of the Pegasus I spirals are consistent with the suggestion that this cluster is now at an early stage in its evolution.

  16. A Hubble Space Telescope Survey of the Mid-Ultraviolet Morphology of Nearby Galaxies

    NASA Astrophysics Data System (ADS)

    Windhorst, Rogier A.; Taylor, Violet A.; Jansen, Rolf A.; Odewahn, Stephen C.; Chiarenza, Claudia A. T.; Conselice, Christopher J.; de Grijs, Richard; de Jong, Roelof S.; MacKenty, John W.; Eskridge, Paul B.; Frogel, Jay A.; Gallagher, John S., III; Hibbard, John E.; Matthews, Lynn D.; O'Connell, Robert W.

    2002-11-01

    We present a systematic imaging survey of 37 nearby galaxies observed with the Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 (WFPC2) in the mid-UV F300W filter, centered at 2930 Å, as well as in the I-band (F814W) filter at 8230 Å. Eleven of these galaxies were also imaged in the F255W filter, centered at 2550 Å. Our sample is carefully selected to include galaxies of sufficiently small radius and high predicted mid-UV surface brightness to be detectable with WFPC2 in one orbit and covers a wide range of Hubble types and inclinations. The mid-UV (2000-3200 Å) spans the gap between ground-based UBVR(IJHK) images, which are available or were acquired for the current study, and far-UV images available from the Astro/UIT missions for 15 galaxies in our sample. The first qualitative results from our study are as follows:1. Early-type galaxies show a significant decrease in surface brightness going from the red to the mid-UV, reflecting the absence of a dominant young stellar population and in some cases the presence of significant (central) dust lanes. Galaxies that are early types in the optical show a variety of morphologies in the mid-UV that can lead to a different morphological classification, although not necessarily as later type. Some early-type galaxies become dominated by a blue nuclear feature or a point source in the mid-UV, e.g., as a result of the presence of a Seyfert nucleus or a LINER. This is in part due to our mid-UV surface brightness selection, but it also suggests that part of the strong apparent evolution of weak AGNs in early-type galaxies may be due to surface brightness dimming of their UV-faint stellar population, which renders the early-type host galaxies invisible at intermediate to higher redshifts.2. About half of the mid-type spiral and star-forming galaxies appear as a later morphological type in the mid-UV, as Astro/UIT also found primarily in the far-UV. Sometimes these differences are dramatic (e.g., NGC 6782

  17. Halo Mass Concentration and the Morphology of Simulated Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Berlanga Medina, Jazmin; Berrier, Joel C.; Kennefick, Daniel; Arkansas Galaxy Evolution Survey

    2015-01-01

    Using a model based on the Milky Way, we vary the central concentration of the dark matter halo component of simulated spiral galaxies. We evolve 11 galaxies in isolation under the effects of gravity for a time of 3 Gyr and look for differences in the disk structure. We primarily quantify morphological differences with measurements of the spiral arms'pitch angle by using a two-dimensional fast Fourier transform code (2DFFT). Preliminary results indicate that while overall spiral arm structure is dynamic throughout the duration of the time range given, pitch angle values tend to restabilize during periods of reemerging spiral structure. This suggests that pitch angle may be fairly stable on timescales of a few Gyr, even if it tends to change at timescales of Myr. While concentration does seem to determine both the relative age at which simulated galaxies develop clearly visible spiral structure and the specific expression of spiral arms, a clear relationship between concentration vs pitch angle cannot be confirmed at this time.

  18. SELF-PERPETUATING SPIRAL ARMS IN DISK GALAXIES

    SciTech Connect

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-20

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  19. Self-perpetuating Spiral Arms in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-01

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  20. Tadpole Galaxies in the Hubble Ultra Deep Field

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy

    2010-10-01

    Tadpole galaxies have a head-tail shape with a large clump of star formation at the head and a diffuse tail or streak of stars off to one side. We measured the head and tail masses, ages, surface brightnesses, and sizes for 66 tadpoles in the Hubble Ultra Deep Field (UDF) and looked at the distribution of neighbor densities and tadpole orientations with respect to neighbors. The heads have masses of 107-108 M sun and photometric ages of ~0.1 Gyr for z ~ 2. The tails have slightly larger masses than the heads and comparable or slightly older ages. The most obvious interpretation of tadpoles as young merger remnants is difficult to verify. They have no enhanced proximity to other resolved galaxies as a class, and the heads, typically <0.2 kpc in diameter, usually have no obvious double-core structure. Another possibility is ram pressure interaction between a gas-rich galaxy and a diffuse cosmological flow. Ram pressure can trigger star formation on one side of a galaxy disk, giving the tadpole shape when viewed edge-on. Ram pressure can also strip away gas from a galaxy and put it into a tail, which then forms new stars and gravitationally drags along old stars with it. Such an effect might have already been observed in the Virgo Cluster. Another possibility is that tadpoles are edge-on disks with large, off-center clumps. Analogous lop-sided star formation in UDF clump clusters is shown.

  1. Rotation and mass in the Milky Way and spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki

    2017-02-01

    Rotation curves are the basic tool for deriving the distribution of mass in spiral galaxies. In this review, we describe various methods to measure rotation curves in the Milky Way and spiral galaxies. We then describe two major methods to calculate the mass distribution using the rotation curve. By the direct method, the mass is calculated from rotation velocities without employing mass models. By the decomposition method, the rotation curve is deconvolved into multiple mass components by model fitting assuming a black hole, bulge, exponential disk, and dark halo. The decomposition is useful for statistical correlation analyses among the dynamical parameters of the mass components. We also review recent observations and derived results.

  2. Dark and luminous properties of low-luminosity spiral galaxies

    NASA Astrophysics Data System (ADS)

    Kogoshvili, N.; Borchkhadze, T.

    2012-08-01

    On the basis of data in our Merged Catalogue of Galaxies (MERCG), for which an online version is now available, we have analysed some properties of spiral galaxies that are members of pairs or small groups of galaxies. Our sample consists of a total of approximately 300 pairs and groups, distributed over the entire sky. In this context, low-luminosity spirals (LLS), here defined as those with an absolute magnitude of MB ≥ -20.6, are of particular interest, since they are thought to harbour dark matter. We find that the mean distance between the two components in LLS/LLS pairs of galaxies is significantly smaller than in LLS/elliptical (E), LLS/high-luminosity spiral (HLS) and HLS/HLS pairs, as well as in groups with at least one LLS. Moreover, LLS from this sample in the mean have larger central surface densities μo and smaller values of the full angular momentum K than HLS. In the second part, we investigate the relative frequencies of LLS galaxies, single as well as in pairs/groups. We find that they are 4-5 times more frequent inside and around three major clusters of galaxies (Virgo, Pegasus I and Perseus) than in the general field. Our findings all support the assumption that LLS galaxies are indeed carriers of dark matter.

  3. STAR FORMATION IN PARTIALLY GAS-DEPLETED SPIRAL GALAXIES

    SciTech Connect

    Rose, James A.; Miner, Jesse; Levy, Lorenza; Robertson, Paul E-mail: paul@astr.as.utexas.edu E-mail: lorenza.levy@yahoo.com

    2010-02-15

    Broadband B and R and H{alpha} images have been obtained with the 4.1 m SOAR telescope atop Cerro Pachon, Chile, for 29 spiral galaxies in the Pegasus I galaxy cluster and for 18 spirals in non-cluster environments. Pegasus I is a spiral-rich cluster with a low-density intracluster medium and a low galaxy velocity dispersion. When combined with neutral hydrogen (H I) data obtained with the Arecibo 305 m radio telescope, acquired by Levy et al. (2007) and by Springob et al. (2005b), we study the star formation rates in disk galaxies as a function of their H I deficiency. To quantify H I deficiency, we use the usual logarithmic deficiency parameter, DEF. The specific star formation rate (SSFR) is quantified by the logarithmic flux ratio of H{alpha} flux to R-band flux, and thus roughly characterizes the logarithmic SFR per unit stellar mass. We find a clear correlation between the global SFR per unit stellar mass and DEF, such that the SFR is lower in more H I-deficient galaxies. This correlation appears to extend from the most gas-rich to the most gas-poor galaxies. We also find a correlation between the central SFR per unit mass relative to the global values, in the sense that the more H I-deficient galaxies have a higher central SFR per unit mass relative to their global SFR values than do gas-rich galaxies. In fact, approximately half of the H I-depleted galaxies have highly elevated SSFRs in their central regions, indicative of a transient evolutionary state. In addition, we find a correlation between gas depletion and the size of the H{alpha} disk (relative to the R-band disk); H I-poor galaxies have truncated disks. Moreover, aside from the elevated central SSFR in many gas-poor spirals, the SSFR is otherwise lower in the H{alpha} disks of gas-poor galaxies than in gas-rich spirals. Thus, both disk truncation and lowered SSFR levels within the star-forming part of the disks (aside from the enhanced nuclear SSFR) correlate with H I deficiency, and both

  4. ENHANCED ABUNDANCES IN SPIRAL GALAXIES OF THE PEGASUS I CLUSTER

    SciTech Connect

    Robertson, Paul; Shields, Gregory A.; Blanc, Guillermo A. E-mail: shields@astro.as.utexas.edu

    2012-03-20

    We study the influence of cluster environment on the chemical evolution of spiral galaxies in the Pegasus I cluster. We determine the gas-phase heavy element abundances of six galaxies in Pegasus derived from H II region spectra obtained from integral-field spectroscopy. These abundances are analyzed in the context of Virgo, whose spirals are known to show increasing interstellar metallicity as a function of H I deficiency. The galaxies in the Pegasus cluster, despite its lower density and velocity dispersion, also display gas loss due to interstellar-medium-intracluster-medium interaction, albeit to a lesser degree. Based on the abundances of three H I deficient spirals and two H I normal spirals, we observe a heavy element abundance offset of +0.13 {+-} 0.07 dex for the H I deficient galaxies. This abundance differential is consistent with the differential observed in Virgo for galaxies with a similar H I deficiency, and we observe a correlation between log (O/H) and the H I deficiency parameter DEF for the two clusters analyzed together. Our results suggest that similar environmental mechanisms are driving the heavy element enhancement in both clusters.

  5. The IRAS galaxy 0421+040P06: An active spiral (?) galaxy with extended radio lobes

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.; Wynn-Williams, C. G.; Lonsdale, C. J.; Persson, S. E.; Heasley, J. N.; Miley, G. K.; Soifer, B. T.; Neugebauer, G.; Becklin, E. E.; Houck, J. R.

    1984-01-01

    The infrared bright galaxy 0421+040P06 detected by IRAS at 25 and 60 microns was studied at optical, infrared, and radio wavelength. It is a luminous galaxy with apparent spiral structure emitting 4 x 10 to the 37th power from far-infrared to optical wavelengths. Optical spectroscopy reveals a Seyfert 2 emission line spectrum, making 0421+040P06 the first active galaxy selected from an unbiased infrared survey of galaxies. The fact that this galaxy shows a flatter energy distribution with more 25 micron emission than other galaxies in the infrared sample may be related to the presence of an intense active nucleus. The radio observations reveal the presence of a non-thermal source that, at 6 cm, shows a prominent double lobed structure 20 to 30 kpc in size extending beyond the optical confines of the galaxy. The radio source is three to ten times larger than structures previously seen in spiral galaxies.

  6. Environmental Dependence of Warps in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Ann, Hong Bae; Bae, Hyun Jeong

    2016-12-01

    We determined the warp parameters of 192 warped galaxies which are selected from 340 edge-on galaxies using color images as well as r-band isophotal maps. We derive the local background density (Σ_{n}) to examine the dependence of the warp amplitudes on the galaxy environment. We find a clear trend that strongly warped galaxies are likely to be found in high density regions where tidal interactions are supposed to be frequent. However, the correlation between α_{w} and Σ_{n} is too weak for weakly warped galaxies (α_{w} < 4°) and the cumulative distributions of weakly warped galaxies are not significantly different from those of galaxies with no detectable warps. This suggests that tidal interactions do not play a decisive role in the formation of weak warps.}

  7. Nonlinear density wave theory for the spiral structure of galaxies.

    PubMed

    Kondoh, S; Teramoto, R; Yoshida, Z

    2000-05-01

    The theory of nonlinear waves for plasmas has been applied to the analysis of the density wave theory of galaxies which are many-body systems of gravity. A nonlinear Schrödinger equation has been derived by applying the reductive perturbation method on the fluid equations that describe the behavior of infinitesimally thin disk galaxies. Their spiral arms are characterized by a soliton and explained as a pattern of a propagating nonlinear density wave.

  8. NASA's Hubble Spots a Relic from a Shredded Galaxy

    NASA Image and Video Library

    2017-09-28

    February 17, 2012: Astronomers using NASA's Hubble Space Telescope may have found evidence for a cluster of young, blue stars encircling HLX-1, one of the first intermediate-mass black holes ever discovered. Astronomers believe the black hole may once have been at the core of a now-disintegrated dwarf galaxy. The discovery of the black hole and the possible star cluster has important implications for understanding the evolution of supermassive black holes and galaxies To read more go to: www.nasa.gov/mission_pages/hubble/science/shredded-relic.... Credit: NASA, ESA, and S. Farrell (Sydney Institute for Astronomy, University of Sydney) 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

  9. Accretion, radial flows and abundance gradients in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Pezzulli, Gabriele; Fraternali, Filippo

    2016-01-01

    The metal-poor gas continuously accreting on to the discs of spiral galaxies is unlikely to arrive from the intergalactic medium (IGM) with exactly the same rotation velocity as the galaxy itself and even a small angular momentum mismatch inevitably drives radial gas flows within the disc, with significant consequences to galaxy evolution. Here, we provide some general analytic tools to compute accretion profiles, radial gas flows and abundance gradients in spiral galaxies as a function of the angular momentum of the accreting material. We generalize existing solutions for the decomposition of the gas flows, required to reproduce the structural properties of galaxy discs, into direct accretion from the IGM and a radial mass flux within the disc. We then solve the equation of metallicity evolution in the presence of radial gas flows with a novel method, based on characteristic lines, which greatly reduces the numerical demand on the computation and sheds light on the crucial role of boundary conditions on the abundance profiles predicted by theoretical models. We also discuss how structural and chemical constraints can be combined to disentangle the contributions of inside-out growth and radial flows in the development of abundance gradients in spiral galaxies. Illustrative examples are provided throughout with parameters plausible for the Milky Way. We find that the material accreting on the Milky Way should rotate at 70-80 per cent of the rotational velocity of the disc, in agreement with previous estimates.

  10. HUBBLE SPACE TELESCOPE PIXEL ANALYSIS OF THE INTERACTING S0 GALAXY NGC 5195 (M51B)

    SciTech Connect

    Lee, Joon Hyeop; Kim, Sang Chul; Ree, Chang Hee; Kim, Minjin; Jeong, Hyunjin; Lee, Jong Chul; Kyeong, Jaemann E-mail: sckim@kasi.re.kr E-mail: mkim@kasi.re.kr E-mail: jclee@kasi.re.kr

    2012-08-01

    We report the properties of the interacting S0 galaxy NGC 5195 (M51B), revealed in a pixel analysis using the Hubble Space Telescope/Advanced Camera for Surveys images in the F435W, F555W, and F814W (BVI) bands. We analyze the pixel color-magnitude diagram (pCMD) of NGC 5195, focusing on the properties of its red and blue pixel sequences and the difference from the pCMD of NGC 5194 (M51A; the spiral galaxy interacting with NGC 5195). The red pixel sequence of NGC 5195 is redder than that of NGC 5194, which corresponds to the difference in the dust optical depth of 2 < {Delta}{tau}{sub V} < 4 at fixed age and metallicity. The blue pixel sequence of NGC 5195 is very weak and spatially corresponds to the tidal bridge between the two interacting galaxies. This implies that the blue pixel sequence is not an ordinary feature in the pCMD of an early-type galaxy, but that it is a transient feature of star formation caused by the galaxy-galaxy interaction. We also find a difference in the shapes of the red pixel sequences on the pixel color-color diagrams (pCCDs) of NGC 5194 and NGC 5195. We investigate the spatial distributions of the pCCD-based pixel stellar populations. The young population fraction in the tidal bridge area is larger than that in other areas by a factor >15. Along the tidal bridge, young populations seem to be clumped particularly at the middle point of the bridge. On the other hand, the dusty population shows a relatively wide distribution between the tidal bridge and the center of NGC 5195.

  11. On wave dark matter in spiral and barred galaxies

    SciTech Connect

    Martinez-Medina, Luis A.; Matos, Tonatiuh; Bray, Hubert L. E-mail: bray@math.duke.edu

    2015-12-01

    We recover spiral and barred spiral patterns in disk galaxy simulations with a Wave Dark Matter (WDM) background (also known as Scalar Field Dark Matter (SFDM), Ultra-Light Axion (ULA) dark matter, and Bose-Einstein Condensate (BEC) dark matter). Here we show how the interaction between a baryonic disk and its Dark Matter Halo triggers the formation of spiral structures when the halo is allowed to have a triaxial shape and angular momentum. This is a more realistic picture within the WDM model since a non-spherical rotating halo seems to be more natural. By performing hydrodynamic simulations, along with earlier test particles simulations, we demonstrate another important way in which wave dark matter is consistent with observations. The common existence of bars in these simulations is particularly noteworthy. This may have consequences when trying to obtain information about the dark matter distribution in a galaxy, the mere presence of spiral arms or a bar usually indicates that baryonic matter dominates the central region and therefore observations, like rotation curves, may not tell us what the DM distribution is at the halo center. But here we show that spiral arms and bars can develop in DM dominated galaxies with a central density core without supposing its origin on mechanisms intrinsic to the baryonic matter.

  12. Interacting Galaxies

    NASA Image and Video Library

    2008-04-24

    This beautiful pair of interacting galaxies consists of NGC 5754, the large spiral on the right, and NGC 5752, the smaller companion in the bottom left corner of the image. This image is from NASA Hubble Space Telescope.

  13. Type Ia Supernova Hubble Residuals and Host-Galaxy Properties

    SciTech Connect

    Nearby Supernova Factory; Kim, A. G.; Aldering, G.; Antilogus, P.; Aragon, C.; Bailey, S.; Baltay, C.; Bongard, S.; Buton, C.; Canto, A.; Cellier-Holzem, F.; Childress, M.; Chotard, N.; Copin, Y.; Fakhouri, H. K.; Feindt, U.; Fleury, M.; Gangler, E.; Greskovic, P.; Guy, J.; Kowalski, M.; Lombardo, S.; Nordin, J.; Nugent, P.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigault, M.; Runge, K.; Saunders, C.; Scalzo, R.; Smadja, G.; Tao, C.; Thomas, R. C.; Weaver, B. A.

    2014-01-17

    Kim et al. (2013) [K13] introduced a new methodology for determining peak- brightness absolute magnitudes of type Ia supernovae from multi-band light curves. We examine the relation between their parameterization of light curves and Hubble residuals, based on photometry synthesized from the Nearby Supernova Factory spec- trophotometric time series, with global host-galaxy properties. The K13 Hubble residual step with host mass is 0.013 ? 0.031 mag for a supernova subsample with data coverage corresponding to the K13 training; at ? 1?, the step is not significant and lower than previous measurements. Relaxing the data coverage requirement the Hubble residual step with host mass is 0.045 ? 0.026 mag for the larger sample; a calculation using the modes of the distributions, less sensitive to outliers, yields a step of 0.019 mag. The analysis of this article uses K13 inferred luminosities, as distinguished from previous works that use magnitude corrections as a function of SALT2 color and stretch param- eters: Steps at> 2? significance are found in SALT2 Hubble residuals in samples split by the values of their K13 x(1) and x(2) light-curve parameters. x(1) affects the light- curve width and color around peak (similar to the∆m15 and stretch parameters), and x(2) affects colors, the near-UV light-curve width, and the light-curve decline 20 to 30 days after peak brightness. The novel light-curve analysis, increased parameter set, and magnitude corrections of K13 may be capturing features of SN Ia diversity arising from progenitor stellar evolution.

  14. Type Ia supernova Hubble residuals and host-galaxy properties

    SciTech Connect

    Kim, A. G.; Aldering, G.; Aragon, C.; Bailey, S.; Fakhouri, H. K.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Fleury, M.; Guy, J.; Baltay, C.; Buton, C.; Feindt, U.; Greskovic, P.; Kowalski, M.; Childress, M.; Chotard, N.; Copin, Y.; Gangler, E. [Université de Lyon, F-69622 Lyon; Université de Lyon 1, Villeurbanne; CNRS and others

    2014-03-20

    Kim et al. introduced a new methodology for determining peak-brightness absolute magnitudes of type Ia supernovae from multi-band light curves. We examine the relation between their parameterization of light curves and Hubble residuals, based on photometry synthesized from the Nearby Supernova Factory spectrophotometric time series, with global host-galaxy properties. The K13 Hubble residual step with host mass is 0.013 ± 0.031 mag for a supernova subsample with data coverage corresponding to the K13 training; at <<1σ, the step is not significant and lower than previous measurements. Relaxing the data coverage requirement of the Hubble residual step with the host mass is 0.045 ± 0.026 mag for the larger sample; a calculation using the modes of the distributions, less sensitive to outliers, yields a step of 0.019 mag. The analysis of this article uses K13 inferred luminosities, as distinguished from previous works that use magnitude corrections as a function of SALT2 color and stretch parameters: steps at >2σ significance are found in SALT2 Hubble residuals in samples split by the values of their K13 x(1) and x(2) light-curve parameters. x(1) affects the light-curve width and color around peak (similar to the Δm {sub 15} and stretch parameters), and x(2) affects colors, the near-UV light-curve width, and the light-curve decline 20-30 days after peak brightness. The novel light-curve analysis, increased parameter set, and magnitude corrections of K13 may be capturing features of SN Ia diversity arising from progenitor stellar evolution.

  15. The emission line sequence of normal spiral galaxies

    NASA Astrophysics Data System (ADS)

    Sodré, L., Jr.; Stasińska, G.

    1999-05-01

    We have analyzed the emission line properties in the integrated spectra of 15 normal spiral galaxies. We show that very clear trends appear when plotting relevant emission line ratios or equivalent widths as a function of galaxy spectral types, obtained with a Principal Component Analysis of the continua and absorption features of spectra. The equivalent widths of all the lines analyzed correlate extremely well with spectral types, implying that each of them can be considered a good indicator of the spectral type in normal galaxies. The position of most galaxies of our sample in classical emission line diagnostic diagrams follows that of individual giant HII regions in spiral galaxies, but for the earliest type galaxies, the emission line pattern resembles more that of LINERs. Therefore, the direct interpretation of equivalent widths in terms of star formation rates would be misleading in such cases. The observed trends in the emission line ratios as a function of galaxy spectral type suggest a decrease of O/H, a decrease of N/O, an increase of the average effective temperature or ionization parameter, and a decrease of the effective internal extinction of galaxies with increasing (early to late) spectral type.

  16. Ultraviolet Halos around Spiral Galaxies. I. Morphology

    NASA Astrophysics Data System (ADS)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N.

    2016-12-01

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 106-107 M ⊙ of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  17. Magnetic field evolution and reversals in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Dobbs, C. L.; Price, D. J.; Pettitt, A. R.; Bate, M. R.; Tricco, T. S.

    2016-10-01

    We study the evolution of galactic magnetic fields using 3D smoothed particle magnetohydrodynamics (SPMHD) simulations of galaxies with an imposed spiral potential. We consider the appearance of reversals of the field, and amplification of the field. We find that magnetic field reversals occur when the velocity jump across the spiral shock is above ≈20 km s-1, occurring where the velocity change is highest, typically at the inner Lindblad resonance in our models. Reversals also occur at corotation, where the direction of the velocity field reverses in the corotating frame of a spiral arm. They occur earlier with a stronger amplitude spiral potential, and later or not at all with weaker or no spiral arms. The presence of a reversal at radii of around 4-6 kpc in our fiducial model is consistent with a reversal identified in the Milky Way, though we caution that alternative Galaxy models could give a similar reversal. We find that relatively high resolution, a few million particles in SPMHD, is required to produce consistent behaviour of the magnetic field. Amplification of the magnetic field occurs in the models, and while some may be genuinely attributable to differential rotation or spiral arms, some may be a numerical artefact. We check our results using ATHENA, finding reversals but less amplification of the field, suggesting that some of the amplification of the field with SPMHD is numerical.

  18. Determining the Co-Rotation Radius of Nearby Spiral Galaxies Using Spiral Arm Overlays

    NASA Astrophysics Data System (ADS)

    Shameer Abdeen, Mohamed; Kennefick, Daniel; Kennefick, Julia D.; Pour Imani, Hamed; Shields, Douglas W.; Eufrasio, Rafael; Berlanga Medina, Jazmin; Monson, Erik

    2017-01-01

    Density wave theory, originally proposed by C.C. Lin and Frank Shu (Lin & Shu 1964), views the spiral arm structures in spiral galaxies as density waves that propagates through the galactic disk. Resonances within orbits create standing wave patterns of density waves that we observe as spiral arms. The theory predicts the existence of a radius known as the co-rotation radius in which the spiral arm pattern speed matches the velocities of the stars within the disk. We introduce a novel way of determining the co-rotation radius, based on an image overlaying technique, which involves tracing the arms of spiral galaxies on images observed from different wavelengths. For the purpose of this study, 12 nearby galaxies were analyzed from four different wavelengths using pitch angle measurements from a previous study (Hamed et al. 2016). We used optical wavelength images (B-Band,440 nm), two infrared wavelength (Infrared; 3.6 µm and 8 µm) Spitzer Space Telescope images and ultraviolet images from GALEX. The results were verified by checking against results compiled from the literature.

  19. Quintessence-like dark matter in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Guzman, F. S.; Matos, T.; Nunez, D.; Ramirez, E.

    2003-06-01

    Through the geodesic analysis of a static and axially symmetric space time, we present conditions on the state equation of an isotropic perfect fluid p = omegad, when it is considered as the dark matter in spiral galaxies. The main conclusion is that it can be an exotic fluid (-1 < omega < -1/3) as it is found for Quintessence at cosmological scale.

  20. The Abundance and Chemical Evolution of Nitrogen in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Thurston, Tad Ralph

    1998-09-01

    The character of nitrogen processing in spiral galaxies is studied in this dissertation. Of particular interest are questions of how the (N/O) ratio changes over time as a result of perturbations of environmental parameters, as well as the importance of primary vs. secondary nitrogen generation and the regimes where one may be the preferred method. A robust numerical chemical evolution code (NICE) was written to model the change in elemental ratios during galactic chemical processing. This code is consistent with standard observational constraints. A new method is developed for the calculation of (N/O) abundances in the absence of observed temperature-diagnostic emission lines. New (N/O) abundances are derived for previously observed HII regions in spiral and dwarf galaxies, and the trends noted in the observations are modeled with the numeric code NICE. I conclude it is likely that early-type spirals once had a higher rate of infalling material relative to late-type galaxies, resulting in both a higher (N/O) ratio as well as a lower gas fraction during later epochs. NICE models also suggest that the star formation rate was suppressed in the extremely metal-poor stages of galaxy chemical processing, as shown by the model fits to the I Zw 18 regions as well as a highly redshifted primeval galaxy. Primary nitrogen production is only realized in stars of 4-8 solar masses, so that this is the first source of nitrogen after an episode of star formation. This is seen in both the observations and the models of low-metallicity dwarf galaxies. At later times, secondary nitrogen is released by stars in the lower mass range (1-4 solar masses), contributing to the steeper slope seen in (N/O) vs. OH for the more chemically advanced spiral galaxies.

  1. Logarithmic Spiral Arm Pitch Angle of Spiral Galaxies: Measurement and Relationship to Galactic Structure and Nuclear Supermassive Black Hole Mass

    NASA Astrophysics Data System (ADS)

    Davis, Benjamin

    In this dissertation, I explore the geometric structure of spiral galaxies and how the visible structure can provide information about the central mass of a galaxy, the density of its galactic disk, and the hidden mass of the supermassive black hole in its nucleus. In order to quantitatively measure the logarithmic spiral pitch angle (a measurement of tightness of the winding) of galactic spiral arms, I led an effort in our research group (the Arkansas Galaxy Evolution Survey) to modify existing two-dimensional fast Fourier transform software to increase its efficacy and accuracy. Using this software, I was able to lead an effort to calculate a black hole mass function (BHMF) for spiral galaxies in our local Universe. This work effectively provides us with a census of local black holes and establishes an endpoint on the evolutionary history of the BHMF for spiral galaxies. Furthermore, my work has indicated a novel fundamental relationship between the pitch angle of a galaxy's spiral arms, the maximum density of neutral atomic hydrogen in its disk, and the stellar mass of its bulge. This result provides strong support for the density wave theory of spiral structure in disk galaxies and poses a critical question of the validity of rival theories for the genesis of spiral structure in disk galaxies.

  2. Dynamics of stars around spiral arms in an N-body/SPH simulated barred spiral galaxy

    NASA Astrophysics Data System (ADS)

    Grand, Robert J. J.; Kawata, Daisuke; Cropper, Mark

    2012-10-01

    We run N-body smoothed particle hydrodynamics (SPH) simulations of a Milky Way-sized galaxy. The code takes into account hydrodynamics, self-gravity, star formation, supernova and stellar wind feedback, radiative cooling and metal enrichment. The simulated galaxy is a barred spiral galaxy consisting of a stellar and gas disc, enveloped in a static dark matter halo. Similar to what is found in our pure N-body simulation of a non-barred galaxy in Grand et al., we find that the spiral arms are transient features whose pattern speeds decrease with radius, in such a way that the pattern speed is similar to the rotation of star particles. Compared to the non-barred case, we find that the spiral arm pattern speed is slightly faster than the rotation speed of star particles: the bar appears to boost the pattern speed ahead of the rotational velocity. We trace particle motion around the spiral arms at different radii, and demonstrate that there are star particles that are drawn towards and join the arm from behind (in front of) the arm and migrate towards the outer (inner) regions of the disc until the arm disappears as a result of their transient nature. We see this migration over the entire radial range analysed, which is a consequence of the spiral arm rotating at similar speeds to star particles at all radii, which is inconsistent with the prediction of classical density wave theory. The bar does not prevent this systematic radial migration, which is shown to largely preserve circular orbits. We also demonstrate that there is no significant offset of different star-forming tracers across the spiral arm, which is also inconsistent with the prediction of classical density wave theory.

  3. Hubble Monitors Supernova In Nearby Galaxy M82

    NASA Image and Video Library

    2017-09-27

    This is a Hubble Space Telescope composite image of a supernova explosion designated SN 2014J in the galaxy M82. At a distance of approximately 11.5 million light-years from Earth it is the closest supernova of its type discovered in the past few decades. The explosion is categorized as a Type Ia supernova, which is theorized to be triggered in binary systems consisting of a white dwarf and another star — which could be a second white dwarf, a star like our sun, or a giant star. Astronomers using a ground-based telescope discovered the explosion on January 21, 2014. This Hubble photograph was taken on January 31, as the supernova approached its peak brightness. The Hubble data are expected to help astronomers refine distance measurements to Type Ia supernovae. In addition, the observations could yield insights into what kind of stars were involved in the explosion. Hubble’s ultraviolet-light sensitivity will allow astronomers to probe the environment around the site of the supernova explosion and in the interstellar medium of the host galaxy. Because of their consistent peak brightness, Type Ia supernovae are among the best tools to measure distances in the universe. They were fundamental to the 1998 discovery of the mysterious acceleration of the expanding universe. A hypothesized repulsive force, called dark energy, is thought to cause the acceleration. Among the other major NASA space-based observatories used in the M82 viewing campaign are Spitzer Space Telescope, Chandra X-ray Observatory, Nuclear Spectroscopic Telescope Array (NuSTAR), Fermi Gamma-ray Space Telescope, Swift Gamma Ray Burst Explorer, and the Stratospheric Observatory for Infrared Astronomy (SOFIA). Image Credit: NASA, ESA, A. Goobar (Stockholm University), and the Hubble Heritage Team (STScI/AURA) 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

  4. Far-infrared emission and star formation in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Trinchieri, G.; Fabbiano, G.; Bandiera, R.

    1989-01-01

    The correlations between the emission in the far-IR, H-alpha, and blue in a sample of normal spiral galaxies are investigated. It is found that the luminosities in these three bands are all tightly correlated, although both the strength of the correlations and their functional dependencies are a function of the galaxies' morphological types. The best-fit power laws to these correlations are different for the comparison of different quantities and deviate significantly from linearity in some cases, implying the presence of additional emission mechanisms not related to the general increase of luminosity with galactic mass. Clear evidence is found of two independent effects in the incidence of warm far-IR emission in late-type spirals. One is a luminosity effect shown by the presence of excess far-IR relative to H-alpha or optical emission in the more luminous galaxies. The other is a dependence on widespread star-formation activity.

  5. TADPOLE GALAXIES IN THE HUBBLE ULTRA DEEP FIELD

    SciTech Connect

    Elmegreen, Bruce G.; Elmegreen, Debra Meloy E-mail: elmegreen@vassar.ed

    2010-10-20

    Tadpole galaxies have a head-tail shape with a large clump of star formation at the head and a diffuse tail or streak of stars off to one side. We measured the head and tail masses, ages, surface brightnesses, and sizes for 66 tadpoles in the Hubble Ultra Deep Field (UDF) and looked at the distribution of neighbor densities and tadpole orientations with respect to neighbors. The heads have masses of 10{sup 7}-10{sup 8} M{sub sun} and photometric ages of {approx}0.1 Gyr for z {approx} 2. The tails have slightly larger masses than the heads and comparable or slightly older ages. The most obvious interpretation of tadpoles as young merger remnants is difficult to verify. They have no enhanced proximity to other resolved galaxies as a class, and the heads, typically <0.2 kpc in diameter, usually have no obvious double-core structure. Another possibility is ram pressure interaction between a gas-rich galaxy and a diffuse cosmological flow. Ram pressure can trigger star formation on one side of a galaxy disk, giving the tadpole shape when viewed edge-on. Ram pressure can also strip away gas from a galaxy and put it into a tail, which then forms new stars and gravitationally drags along old stars with it. Such an effect might have already been observed in the Virgo Cluster. Another possibility is that tadpoles are edge-on disks with large, off-center clumps. Analogous lop-sided star formation in UDF clump clusters is shown.

  6. Galaxy Group Stephan's Quintet Video File HubbleMinute: Battle Royale in Stephan's Quintet

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The Hubble Space Telescope's closeup view of Stephan's Quintet, a group of five galaxies, reveals a string of brighter star clusters that separate like a diamond necklace. Astronomers studying the compact galaxy group Stephan's Quintet have seen creative destruction in the many collisions taking place among its galaxies. This HubbleMinute discusses what astronomers are learning and hope to learn from exploring the quintet.

  7. Galaxy Group Stephan's Quintet Video File HubbleMinute: Battle Royale in Stephan's Quintet

    NASA Astrophysics Data System (ADS)

    2001-07-01

    The Hubble Space Telescope's closeup view of Stephan's Quintet, a group of five galaxies, reveals a string of brighter star clusters that separate like a diamond necklace. Astronomers studying the compact galaxy group Stephan's Quintet have seen creative destruction in the many collisions taking place among its galaxies. This HubbleMinute discusses what astronomers are learning and hope to learn from exploring the quintet.

  8. Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms

    NASA Astrophysics Data System (ADS)

    2004-06-01

    Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the

  9. Gas and stellar spiral structures in tidally perturbed disc galaxies

    NASA Astrophysics Data System (ADS)

    Pettitt, Alex R.; Tasker, Elizabeth J.; Wadsley, James W.

    2016-06-01

    Tidal interactions between disc galaxies and low-mass companions are an established method for generating galactic spiral features. In this work, we present a study of the structure and dynamics of spiral arms driven in interactions between disc galaxies and perturbing companions in 3D N-body/smoothed hydrodynamical numerical simulations. Our specific aims are to characterize any differences between structures formed in the gas and stars from a purely hydrodynamical and gravitational perspective, and to find a limiting case for spiral structure generation. Through analysis of a number of different interacting cases, we find that there is very little difference between arm morphology, pitch angles and pattern speeds between the two media. The main differences are a minor offset between gas and stellar arms, clear spurring features in gaseous arms, and different radial migration of material in the stronger interacting cases. We investigate the minimum mass of a companion required to drive spiral structure in a galactic disc, finding the limiting spiral generation cases with companion masses of the order of 1 × 109 M⊙, equivalent to only 4 per cent of the stellar disc mass, or 0.5 per cent of the total galactic mass of a Milky Way analogue.

  10. Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672

    NASA Technical Reports Server (NTRS)

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J.; Koribalski, B.; Kuntz, K. D.; Levan, A. J.; Ojha, R.; Roberts, T. P.; Ward, M. J.; Zezas, A.

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST) infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (LX 5 * 10(exp 39) erg s(exp -1)) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard (1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 * 10(exp 38) erg s(exp -1). This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  11. Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672

    NASA Technical Reports Server (NTRS)

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J.; Koribalski, B.; Kuntz, K. D.; Levan, A. J.; Ojha, R.; Roberts, T. P.; Ward, M. J.; Zezas, A.

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST) infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (LX 5 * 10(exp 39) erg s(exp -1)) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard (1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 * 10(exp 38) erg s(exp -1). This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  12. INVESTIGATING THE NUCLEAR ACTIVITY OF BARRED SPIRAL GALAXIES: THE CASE OF NGC 1672

    SciTech Connect

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J. M.; Kuntz, K. D.; Koribalski, B.; Levan, A. J.; Ojha, R.; Zezas, A.

    2011-06-10

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST), infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D{sub 25} area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (L{sub X} > 5 x 10{sup 39} erg s{sup -1}) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard ({Gamma} {approx} 1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 x 10{sup 38} erg s{sup -1}. This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  13. Multicolor CCD photometry of six lenticular and spiral galaxies. Stellar population of the galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.

    2006-03-01

    The results of multicolor surface photometry of the S0 galaxies NGC 524, NGC 1138, and NGC 7280 and the spiral galaxies NGC 532, NGC 783, and NGC 1589 are analyzed. UBVRI observations were acquired with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan), while JHK data were taken from the 2MASS catalog. The brightness and color distributions in the galaxies are analyzed. Extinction in dust lanes in three spiral galaxies is estimated. The contributions of the radiation of the spherical and disk components in different photometric bands are estimated. Two-color diagrams are used to estimate the composition of the stellar populations in various galaxy components. The variations of the color characteristics in the S0 galaxies is due mostly to radial metallicity gradients.

  14. Multicolor CCD photometry of six lenticular and spiral galaxies. Structure of the galaxies

    NASA Astrophysics Data System (ADS)

    Gusev, A. S.

    2006-03-01

    The results of multicolor surface photometry of the S0 galaxies NGC 524, NGC 1138, and NGC 7280 and the spiral galaxies NGC 532, NGC 783, and NGC 1589 are reported. U BV RI observations were acquired with the 1.5-m telescope of the Maidanak Observatory (Uzbekistan), while JHK data were taken from the 2MASS catalog. The overall structure of the galaxies is analyzed and the galaxy images decomposed into bulge and disk components. The parameters of the galaxy components—rings, bars, spiral arms, and dust lanes—are determined. The bulge/disk decompositions based on averaged one-dimensional photometric profiles yield incorrect parameters for the bulges of the S0-Sa galaxies with bars and/or rings, whose inner regions are dominated by the radiation of the bulge.

  15. Computer Simulation of Colliding Galaxies

    NASA Image and Video Library

    Simulation of the formation of the galaxy known as "The Mice." The simulation depicts the merger of two spiral galaxies, pausing and rotating at the stage resembling the Hubble Space Telescope Adva...

  16. Photometric Asymmetry Between Clockwise and Counterclockwise Spiral Galaxies in SDSS

    NASA Astrophysics Data System (ADS)

    Shamir, Lior

    2017-02-01

    While galaxies with clockwise and counterclockwise handedness are visually different, they are expected to be symmetric in all of their other characteristics. Previous experiments using both manual analysis and machine vision have shown that the handedness of Sloan Digital Sky Survey galaxies can be predicted with accuracy significantly higher than mere chance using its photometric data alone. However, some of these previous experiments were based on manually classified galaxies, and the results may therefore be subjected to bias originated from the human perception. This paper describes an experiment based on a set of 162,514 galaxies classified automatically to clockwise and counterclockwise spiral galaxies, showing that the source of the asymmetry in Sloan Digital Sky Survey (SDSS) database is not the human perception bias. The results are compared to two smaller datasets, and confirm the observation that the handedness of SDSS galaxies can be predicted by their photometry. The experiment also shows statistically significant differences in the measured magnitude of SDSS galaxies, according which galaxies with clockwise patterns are brighter than galaxies with counterclockwise patterns. The magnitude of that difference changes across RA ranges, and exhibits a strong correlation with the cosine of the right ascension.

  17. Discovery of rare double-lobe radio galaxies hosted in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Sievers, Jonathan; Wadadekar, Yogesh; Hilton, Matt; Beelen, Alexandre

    2015-12-01

    Double-lobe radio galaxies in the local Universe have traditionally been found to be hosted in elliptical or lenticular galaxies. We report the discovery of four spiral-host double-lobe radio galaxies (J0836+0532, J1159+5820, J1352+3126, and J1649+2635) that are discovered by cross-matching a large sample of 187 005 spiral galaxies from SDSS DR7 (Sloan Digital Sky Survey Data Release 7) to the full catalogues of FIRST (Faint Images of the Radio Sky at Twenty-cm) and NVSS (NRAO VLA Sky Survey). J0836+0532 is reported for the first time. The host galaxies are forming stars at an average rate of 1.7-10 M⊙ yr-1 and possess supermassive black holes (SMBHs) with masses of a few times 108 M⊙. Their radio morphologies are similar to Fanaroff-Riley type II radio galaxies with total projected linear sizes ranging from 86 to 420 kpc, but their total 1.4-GHz radio luminosities are only in the range 1024-1025 W Hz-1. We propose that the formation of spiral-host double-lobe radio galaxies can be attributed to more than one factor, such as the occurrence of strong interactions, mergers, and the presence of unusually massive SMBHs, such that the spiral structures are not destroyed. Only one of our sources (J1649+2635) is found in a cluster environment, indicating that processes other than accretion through cooling flows e.g. galaxy-galaxy mergers or interactions could be plausible scenarios for triggering radio-loud active galactic nuclei activity in spiral galaxies.

  18. Infrared emission and tidal interactions of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Byrd, Gene G.

    1987-01-01

    Computer simulations of tidal interactions of spiral galaxies are used to attempt to understand recent discoveries about infrared (IR) emitting galaxies. It is found that the stronger tidal perturbation by a companion the more disk gas clouds are thrown into nucleus crossing orbits and the greater the velocity jumps crossing spiral arms. Both these tidally created characteristics would create more IR emission by high speed cloud collisions and more IR via effects of recently formed stars. This expectation at greater tidal perturbation matches the observation of greater IR emission for spiral galaxies with closer and/or more massive companions. The greater collision velocities found at stronger perturbations on the models will also result in higher dust temperature in the colliding clouds. In the IR pairs examined, most have only one member, the larger, detected and when both are detected, the larger is always the more luminous. In simulations and in a simple analytic description of the strong distance dependence of the tidal force, it is found that the big galaxy of a pair is more strongly affected than the small.

  19. Emission-Line Galaxies from the PEARS Hubble Ultra Deep Field: A 2-D Detection Method and First Results

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Straughn, Amber N.; Meurer, Gerhardt R.; Pirzkal, Norbert; Cohen, Seth H.; Malhotra, Sangeeta; Rhoads, james; Windhorst, Rogier A.; Gardner, Jonathan P.; Hathi, Nimish P.; Xu, Chun; Gronwall, Caryl; Koekemoer, Anton M.; Walsh, Jeremy; diSeregoAlighieri, Sperello

    2007-01-01

    The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) grism PEARS (Probing Evolution And Reionization Spectroscopically) survey provides a large dataset of low-resolution spectra from thousands of galaxies in the GOODS North and South fields. One important subset of objects in these data are emission-line galaxies (ELGs), and we have investigated several different methods aimed at systematically selecting these galaxies. Here we present a new methodology and results of a search for these ELGs in the PEARS observations of the Hubble Ultra Deep Field (HUDF) using a 2D detection method that utilizes the observation that many emission lines originate from clumpy knots within galaxies. This 2D line-finding method proves to be useful in detecting emission lines from compact knots within galaxies that might not otherwise be detected using more traditional 1D line-finding techniques. We find in total 96 emission lines in the HUDF, originating from 81 distinct "knots" within 63 individual galaxies. We find in general that [0 1111 emitters are the most common, comprising 44% of the sample, and on average have high equivalent widths (70% of [0 1111 emitters having rest-frame EW> 100A). There are 12 galaxies with multiple emitting knots; several show evidence of variations in H-alpha flux in the knots, suggesting that the differing star formation properties across a single galaxy can in general be probed at redshifts approximately greater than 0.2 - 0.4. The most prevalent morphologies are large face-on spirals and clumpy interacting systems, many being unique detections owing to the 2D method described here, thus highlighting the strength of this technique.

  20. Formation and evolution of spiral arms in galaxies orbiting a Virgo-like cluster

    NASA Astrophysics Data System (ADS)

    Semczuk, Marcin; Łokas, Ewa L.

    2017-03-01

    The origin of spiral structure in disks of galaxies remains an open question. One of the theories predicts that two-armed, grand design spiral arms originate from tidal interactions with another body. Using N-body simulations we find that a Milky Way-like galaxy can develop spiral arms due to tidal force from a cluster-size dark matter halo.

  1. SPIRAL FLOWS IN COOL-CORE GALAXY CLUSTERS

    SciTech Connect

    Keshet, Uri

    2012-07-10

    We argue that bulk spiral flows are ubiquitous in the cool cores (CCs) of clusters and groups of galaxies. Such flows are gauged by spiral features in the thermal and chemical properties of the intracluster medium, by the multiphase properties of CCs, and by X-ray edges known as cold fronts. We analytically show that observations of piecewise-spiral fronts impose strong constraints on the CC, implying the presence of a cold, fast flow, which propagates below a hot, slow inflow, separated by a slowly rotating, trailing, quasi-spiral, tangential discontinuity surface. This leads to the nearly logarithmic spiral pattern, two-phase plasma, {rho} {approx} r{sup -1} density (or T {approx} r{sup 0.4} temperature) radial profile, and {approx}100 kpc size, characteristic of CCs. By advecting heat and mixing the gas, such flows can eliminate the cooling problem, provided that a feedback mechanism regulates the flow. In particular, we present a quasi-steady-state model for an accretion-quenched, composite flow, in which the fast phase is an outflow, regulated by active galactic nucleus bubbles, reproducing the observed low star formation rates and explaining some features of bubbles such as their R{sub b} {proportional_to}r size. The simplest two-component model reproduces several key properties of CCs, so we propose that all such cores harbor a spiral flow. Our results can be tested directly in the next few years, for example by ASTRO-H.

  2. Hubble Space Telescope and HI Imaging of Strong Ram Pressure Stripping in the Coma Spiral NGC 4921: Dense Cloud Decoupling and Evidence for Magnetic Binding in the ISM

    NASA Astrophysics Data System (ADS)

    Kenney, Jeffrey D. P.; Abramson, Anne; Bravo-Alfaro, Hector

    2015-08-01

    Remarkable dust extinction features in the deep Hubble Space Telescope (HST) V and I images of the face-on Coma cluster spiral galaxy NGC 4921 show in unprecedented ways how ram pressure strips the ISM from the disk of a spiral galaxy. New VLA HI maps show a truncated and highly asymmetric HI disk with a compressed HI distribution in the NW, providing evidence for ram pressure acting from the NW. Where the HI distribution is truncated in the NW region, HST images show a well-defined, continuous front of dust that extends over 90° and 20 kpc. This dust front separates the dusty from dust-free regions of the galaxy, and we interpret it as galaxy ISM swept up near the leading side of the ICM-ISM interaction. We identify and characterize 100 pc-1 kpc scale substructure within this dust front caused by ram pressure, including head-tail filaments, C-shaped filaments, and long smooth dust fronts. The morphology of these features strongly suggests that dense gas clouds partially decouple from surrounding lower density gas during stripping, but decoupling is inhibited, possibly by magnetic fields that link and bind distant parts of the ISM.

  3. HUBBLE SPACE TELESCOPE AND HI IMAGING OF STRONG RAM PRESSURE STRIPPING IN THE COMA SPIRAL NGC 4921: DENSE CLOUD DECOUPLING AND EVIDENCE FOR MAGNETIC BINDING IN THE ISM

    SciTech Connect

    Kenney, Jeffrey D. P.; Abramson, Anne; Bravo-Alfaro, Hector

    2015-08-15

    Remarkable dust extinction features in the deep Hubble Space Telescope (HST) V and I images of the face-on Coma cluster spiral galaxy NGC 4921 show in unprecedented ways how ram pressure strips the ISM from the disk of a spiral galaxy. New VLA HI maps show a truncated and highly asymmetric HI disk with a compressed HI distribution in the NW, providing evidence for ram pressure acting from the NW. Where the HI distribution is truncated in the NW region, HST images show a well-defined, continuous front of dust that extends over 90° and 20 kpc. This dust front separates the dusty from dust-free regions of the galaxy, and we interpret it as galaxy ISM swept up near the leading side of the ICM–ISM interaction. We identify and characterize 100 pc–1 kpc scale substructure within this dust front caused by ram pressure, including head–tail filaments, C-shaped filaments, and long smooth dust fronts. The morphology of these features strongly suggests that dense gas clouds partially decouple from surrounding lower density gas during stripping, but decoupling is inhibited, possibly by magnetic fields that link and bind distant parts of the ISM.

  4. The black hole mass function derived from local spiral galaxies

    SciTech Connect

    Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Daniel; Kennefick, Julia; Seigar, Marc S.; Lacy, Claud H. S.; Hartley, Matthew T.

    2014-07-10

    We present our determination of the nuclear supermassive black hole (SMBH) mass function for spiral galaxies in the local universe, established from a volume-limited sample consisting of a statistically complete collection of the brightest spiral galaxies in the southern (δ < 0°) hemisphere. Our SMBH mass function agrees well at the high-mass end with previous values given in the literature. At the low-mass end, inconsistencies exist in previous works that still need to be resolved, but our work is more in line with expectations based on modeling of black hole evolution. This low-mass end of the spectrum is critical to our understanding of the mass function and evolution of black holes since the epoch of maximum quasar activity. The sample is defined by a limiting luminosity (redshift-independent) distance, D{sub L} = 25.4 Mpc (z = 0.00572) and a limiting absolute B-band magnitude, M{sub B}=−19.12. These limits define a sample of 140 spiral galaxies, with 128 measurable pitch angles to establish the pitch angle distribution for this sample. This pitch-angle distribution function may be useful in the study of the morphology of late-type galaxies. We then use an established relationship between the logarithmic spiral arm pitch angle and the mass of the central SMBH in a host galaxy in order to estimate the mass of the 128 respective SMBHs in this volume-limited sample. This result effectively gives us the distribution of mass for SMBHs residing in spiral galaxies over a lookback time, t{sub L} ≤ 82.1 h{sub 67.77}{sup −1} Myr and contained within a comoving volume, V{sub C} = 3.37 × 10{sup 4} h{sub 67.77}{sup −3} Mpc{sup 3}. We estimate that the density of SMBHs residing in spiral galaxies in the local universe is ρ=5.54{sub −2.73}{sup +6.55} × 10{sup 4} h{sub 67.77}{sup 3} M{sub ☉} Mpc{sup –3}. Thus, our derived cosmological SMBH mass density for spiral galaxies is Ω{sub BH}=4.35{sub −2.15}{sup +5.14} × 10{sup –7} h{sub 67.77}. Assuming that

  5. Global Modeling of Spur Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Shetty, Rahul; Ostriker, Eve C.

    2006-08-01

    We investigate the formation of substructure in spiral galaxies using global MHD simulations, including gas self-gravity. Local modeling by Kim & Ostriker previously showed that self-gravity and magnetic fields cause rapid growth of overdensities in spiral arms; differential compression of gas flowing through the arms then results in the formation of sheared structures in the interarms. These sheared structures resemble features described as spurs or feathers in optical and IR observations of many spiral galaxies. Global modeling extends previous local models by including the full effects of curvilinear coordinates, a realistic log-spiral perturbation, self-gravitational contribution from five radial wavelengths of the spiral shock, and variation of density and epicyclic frequency with radius. We show that with realistic Toomre Q-values self-gravity and galactic differential rotation produce filamentary gaseous structures with kiloparsec-scale separations, regardless of the strength-or even presence-of a stellar spiral potential. However, a sufficiently strong spiral potential is required to produce true spurs, consisting of interarm structures emerging from gas concentrations in the main spiral arms. In models where Q is initially constant, filaments due to interarm self-gravity grow mainly in the outer regions, whereas true arm spurs grow only in the inner regions. For models with Q~R, outer regions are intrinsically more stable, so background interarm filaments do not grow, but arm spurs can develop if the spiral potential is strong. Unlike independently growing background filaments, the orientation of arm spurs depends on galactic location. Inside corotation, spurs emanate outward, on the convex side of the arm; outside corotation, spurs grow inward, on the concave side of the arm. Based on orientation and the relation to arm clumps, it is possible to distinguish true spurs that originate as instabilities in the arms from independently growing background

  6. Extended HI disks in nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Bosma, Albert

    2017-03-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a ``tilted ring model'' allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  7. Evolution of Gas Across Spiral Arms in the Whirlpool Galaxy

    NASA Astrophysics Data System (ADS)

    Louie, Melissa Nicole

    To investigate the dynamic evolution of gas across spiral arms, we conducted a detailed study of the gas and star formation along the spiral arms in the Whirlpool Galaxy, M51. This nearby, face-on spiral galaxy provides a unique laboratory to study the relationship between gas dynamics and star formation. The textbook picture of interstellar medium (ISM) evolution is rapidly changing. Molecular gas was once believed to form along spiral arms from the diffuse atomic gas in the inter-arm regions. Star formation occurs within giant molecular clouds during spiral arm passage. Lastly, the molecular gas is photo-dissociated back into atomic gas by massive stars on the downstream side of the spiral arm. Recent evidence, however, is revealing a new picture of the interstellar medium and the process of star formation. We seek development of a new picture by studying the development and evolution of molecular gas and the role of large scale galactic dynamics in organizing the interstellar medium. This thesis begins by presenting work measuring the geometrical offsets between interstellar gas and recent star formation. Interstellar gas is traced by atomic hydrogen and carbon monoxide (CO). Star formation is traced by ionized hydrogen recombination lines and infrared emission from dust warmed by young bright stars. Measuring these offsets can help determine the underlying large scale galactic dynamics. Along the spiral arms in M51, offsets between CO and the star formation tracers suggest that gas is flowing through the spiral arms, but the offsets do not show the expected signature of a single pattern speed and imply a more complicated pattern. This thesis also examines the intermediate stages of gas evolution, by studying a denser component of the ISM closer to which stars will form. Only a small percent of the bulk molecular gas will become dense enough to form stars. HCN and HCO+ probe densities ˜104 cm-3, where as the bulk gas is 500 cm-3. This thesis looks at HCN and

  8. Effects of Spiral Arms on Gaseous Structures and Mass Drift in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Yonghwi; Kim, Woong-Tae

    2015-01-01

    Stellar spiral arms play a key role in the formation and evolution of gaseous structures in disk galaxies as well as mass drift in the radial direction. Using hydrodynamic simulations, we investigate nonlinear responses of self-gravitating gas to an imposed stellar spiral potential in galactic disks. By considering various models with different arm strength and pattern speed, we find that the physical properties of imposed spiral potential have profound influences on the shapes and extent of gaseous arms as well as the related mass drift rate. To produce quasi-steady spiral shocks, the gas has to not only move faster than the local sound speed relative to the perturbing potential, but also have sufficient time to respond to one arm before encountering the next arm. From our numerical results, we provide a simple expression for the existence of quasi-steady spiral shocks depending on the pitch angle and pattern speed of stellar spiral arms, which appears consistent to the previous study. We also measure the mass drift rates which are in the range of ~0.5-3.0 M⊙/yr inside the corotation radius, and further quantify the relative contribution of shock dissipation (~50%), external torque (~40%), and self-gravitational torque (~10%) to them. The offset between the pitch angles of stellar and gaseous arms is larger for smaller arm strength and larger pattern speed, since a deeper potential tends to form shocks closer to the potential minima of the arms. We demonstrate that the distributions of line-of-sight velocities and spiral shock densities can be a diagnostic tool in distinguishing whether the spiral pattern rotates fast or not.

  9. An observational study of arm structure in normal spiral galaxies

    NASA Astrophysics Data System (ADS)

    Magri, Christopher

    Multivariate data were obtained and analyzed in an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on morphological properties. By comparing morphological measures with the intrinsic parameters on which the new system is based, it can be seen just how fundamentally important a galactic property arm structure truly is. A sample of 492 moderately bright northern Sa, SBa, Sc, and SBc spirals was chosen for statistical analysis. The literature was searched for redshifts, optical and near-infrared photometric data, 20 cm fluxes, and H I 21 cm line parameters. New observations were made at 20 and 21 cm; in addition, IRAS fluxes were obtained from archival data. These data were subjected to principal component analysis, modified in that non-detections were explicitly acknowledged. Spiral galaxies have two fundamental properties, confirming previous work done with fewer data. While scale (bulk) is most important, galaxies of given scale can vary in form (color, bulge/disk ratio, H I surface density). Arm strength is unrelated to other properties. Forty-five spatially isolated spirals were chosen for two-color optical CCD imaging, for 20 cm continuum imaging, and for CO 2.6 mm spectroscopy. Isolated Sa's are often found to be misclassified; they are either armless SO's or else peculiar victims of collisions. Isolated Sc's are surprising in that all but the most isolated examples have symmetric arms over at least part of the disk, contrary to the predictions of stochastic models for arm formation. Given the extreme isolation of all highly chaotic disks, the presence of tidal companions (or at least candidates) for the other normal isolated spirals, the apparent prevalence of violent processes in isolated Sa's, and recent N-body simulations of tidal encounters, it is likely that arm structure in most spirals is produced by tidal encounters with small companions. Arm structure is not an intrinsic property of a given galaxy

  10. Spiral arms and disc stability in the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Tenjes, P.; Tuvikene, T.; Tamm, A.; Kipper, R.; Tempel, E.

    2017-03-01

    Aims: Density waves are often considered as the triggering mechanism of star formation in spiral galaxies. Our aim is to study relations between different star formation tracers (stellar UV and near-IR radiation and emission from H i, CO, and cold dust) in the spiral arms of M 31, to calculate stability conditions in the galaxy disc, and to draw conclusions about possible star formation triggering mechanisms. Methods: We selected fourteen spiral arm segments from the de-projected data maps and compared emission distributions along the cross sections of the segments in different datasets to each other, in order to detect spatial offsets between young stellar populations and the star-forming medium. By using the disc stability condition as a function of perturbation wavelength and distance from the galaxy centre, we calculated the effective disc stability parameters and the least stable wavelengths at different distances. For this we used a mass distribution model of M 31 with four disc components (old and young stellar discs, cold and warm gaseous discs) embedded within the external potential of the bulge, the stellar halo, and the dark matter halo. Each component is considered to have a realistic finite thickness. Results: No systematic offsets between the observed UV and CO/far-IR emission across the spiral segments are detected. The calculated effective stability parameter has a lowest value of Qeff ≃ 1.8 at galactocentric distances of 12-13 kpc. The least stable wavelengths are rather long, with the lowest values starting from ≃ 3 kpc at distances R > 11 kpc. Conclusions: The classical density wave theory is not a realistic explanation for the spiral structure of M 31. Instead, external causes should be considered, such as interactions with massive gas clouds or dwarf companions of M 31.

  11. The (C II) 158 micron line mapping of spiral galaxies

    NASA Technical Reports Server (NTRS)

    Stacey, Gordon J.; Geis, N.; Genzel, Reinhard; Jackson, J. M.; Poglitsch, Albrecht; Townes, Charles H.

    1990-01-01

    Large scale maps of the face of spiral galaxies M51, M83, and NGC 6946 in the 158 micron (C II) fine structure line. The maps are obtained from the Far-infrared Imaging Fabry-Perot Interferometer (FIFI) during its first series of flights on board the Kuiper Airborne Observatory. The (C II) line emission is ubiquitous and easily traced over the mapped regions of each of the galaxies. The (C II) maps are compared with those obtained with similar sized beams in the CO line. The data available from these maps is interpreted.

  12. Molecular gas temperature and density in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-01-01

    We combine beam-matched CO-13, CO-12 J = 3 yields 2 and J = 2 yields 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of infrared-bright external galaxies: NGC253, IC342, M 83, Maffei 2, and NGC6946. Additional observations of the J = 1 yields 0 lines of C-18O and CO-13 set limits on the opacity of the CO-13 J = 1 yields 0 line averaged over the central kiloparsec of these spiral galaxies.

  13. Tidally Induced Offset Disks in Magellanic Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Pardy, Stephen A.; D'Onghia, Elena; Athanassoula, E.; Wilcots, Eric M.; Sheth, Kartik

    2016-08-01

    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar, and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter, causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyr, the time that it takes for the disk to be recentered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the H i center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

  14. Diffuse hot gas in nearby face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Doane, Nathaniel

    2007-08-01

    We present a study of the diffuse thermal emission in three nearby, face-on spiral galaxies, NGC 3631, NGC 628 and NGC 3184, using X-ray data from the Chandra X-ray Observatory and optical data from the WIYN observatory. We are able to separate out the X-ray emission from unresolved point sources from the total unresolved emission in order to study the truly diffuse X-ray emission. We find that in all cases, the spectrum of the hot gas is well fit using a two thermal-component model. In the three galaxies, we find a strong correlation between the X-ray surface brightness and regions of star formation. We also estimate the electron density, pressure and cooling time of the hot gas, finding that the pressure of the hot gas in these three galaxies is higher than the ambient Milky Way pressure. In addition to the standard two temperature spectral model of the hot-gas emission from spiral galaxies, we show a model with the hot gas at a continuum of temperatures provides an equally good fit and a more physical description of the gas. Finally, we discuss the Chandra ACIS background and our method of spectrally modeling it. We also present plots of all our spectral fits to each galaxy and its sub-regions using our background model.

  15. Feeding IC 342: The nuclear spiral of a starburst galaxy

    NASA Technical Reports Server (NTRS)

    Levine, D.; Turner, J. L.; Hurt, Robert L.

    1993-01-01

    IC 342 is a large nearby (1.8 Mpc, Turner and Hurt, 1991, hereafter T&H) spiral galaxy undergoing a moderate nuclear starburst. T&H have previously mapped the inner arcminute in CO-13(1-0) using the Owens Valley Millimeter Interferometer and found evidence that the nuclear molecular gas takes the form of spiral arms in a density wave pattern. They suggest that radial streaming along the arms may channel gas from the exterior of the galaxy into the nucleus, feeding the starburst. We have mapped the CO-12(1-0) emission of the inner 2 kpc of IC 342 at 2.8 inch resolution using the Owens Valley Radio Observatory (OVRO) Millimeter Interferometer. The greater sensitivity of CO-12 observations has allowed us to trace the spiral pattern out to a total extent of greater than 1 kpc. The CO-12 observations extend considerably the structure observed at CO-13 and offer further evidence that a spiral density wave may extend from the disk into the nucleus of IC 342.

  16. Feeding IC 342: The nuclear spiral of a starburst galaxy

    NASA Astrophysics Data System (ADS)

    Levine, D.; Turner, J. L.; Hurt, Robert L.

    1993-01-01

    IC 342 is a large nearby (1.8 Mpc, Turner and Hurt, 1991, hereafter T&H) spiral galaxy undergoing a moderate nuclear starburst. T&H have previously mapped the inner arcminute in CO-13(1-0) using the Owens Valley Millimeter Interferometer and found evidence that the nuclear molecular gas takes the form of spiral arms in a density wave pattern. They suggest that radial streaming along the arms may channel gas from the exterior of the galaxy into the nucleus, feeding the starburst. We have mapped the CO-12(1-0) emission of the inner 2 kpc of IC 342 at 2.8 inch resolution using the Owens Valley Radio Observatory (OVRO) Millimeter Interferometer. The greater sensitivity of CO-12 observations has allowed us to trace the spiral pattern out to a total extent of greater than 1 kpc. The CO-12 observations extend considerably the structure observed at CO-13 and offer further evidence that a spiral density wave may extend from the disk into the nucleus of IC 342.

  17. Enhanced star formation: The importance of bars in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Puxley, P. J.; Hawarden, T. G.; Mountain, C. M.; Leggett, S. K.

    1987-01-01

    It was found that among an IR luminous subset of nearby spiral galaxies, nearly all of the systems with IRAS colors and luminosities indicative of enhanced star formation are barred. Radio continuum and IR spectroscopic results support the hypothesis that this emission originates within the central 2 kpc; possibly in a circumnuclear ring. It was also found that outer rings are over represented among these barred systems and suggest possible reasons for this phenomena.

  18. Galaxy Zoo: spiral galaxy morphologies and their relation to the star-forming main sequence

    NASA Astrophysics Data System (ADS)

    Willett, Kyle; Schawinski, Kevin; Masters, Karen; Melvin, Tom; Skibba, Ramin A.; Nichol, Robert; Cheung, Edmond; Lintott, Chris; Simmons, Brooke D.; Kaviraj, Sugata; Keel, William C.; Fortson, Lucy; Galaxy Zoo volunteers

    2015-01-01

    We examine the relationship between stellar mass and star formation rate in disk galaxies at z<0.085, measuring different populations of spirals as classified by their kiloparsec-scale structure. The morphologies of disk galaxies are obtained from the Galaxy Zoo 2 project, which includes the number of spiral arms, the arm pitch angle, and the presence of strong galactic bars. We show that both the slope and dispersion of the star-forming main sequence (SFMS) is constant no matter what the morphology of the spiral disk. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by 0.3 dex; this is a significant reduction over the increase seen in merging systems at higher redshifts (z > 1). Of the galaxies that do lie significantly above the SFMS in the local Universe, more than 50% are mergers, with a large contribution from the compact green pea galaxies. We interpret our results as evidence that the number and pitch angle of spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms for star formation or are completely overwhelmed by the combination of outflows and feedback.

  19. Relaxation and Thermalization in Spiral Galaxies Mediated by Spiral Wave Scattering

    NASA Astrophysics Data System (ADS)

    Hohlfeld, R. G.; Shalit, D.; Comins, N. F.; Sandri, G. V. H.

    1993-12-01

    We have constructed N-body particle-mesh simulations of disk galaxies in which the relaxation times of the simulated disks (as measured by thermalization of the disk, i.e. increase in Toomre's Q parameter) is comparable to the actual relaxation time scale in actual disk galaxies (several tens of rotation periods). These simulations require 1M to 4M particles (1M = 2(20) ), consistent with the work of White and of Comins and Schroeder on the dependence of relaxation time on N. We observe that during the interval when Q is increasing, that the Fourier power associated with spiral modes is large. When Q has risen to its asymptotic value in the simulation, the Fourier power diminishes to a low level. This suggests a scenario in which stars (simulation particles) scatter off the time-varying spiral potential, as suggested by Carlberg and Sellwood. Eventually random velocities of stars increase to a value which quenches the spiral instability. We compare the heating rates in our simulations at observed spiral wave amplitudes to the expected growth rates as given by Carlberg and Sellwood.

  20. STAR FORMATION EFFICIENCY IN THE BARRED SPIRAL GALAXY NGC 4303

    SciTech Connect

    Momose, Rieko; Okumura, Sachiko K.; Sawada, Tsuyoshi; Koda, Jin E-mail: sokumura@nro.nao.ac.j E-mail: Jin.Koda@stonybrook.ed

    2010-09-20

    We present new {sup 12}CO (J = 1 - 0) observations of the barred galaxy NGC 4303 using the Nobeyama 45 m telescope (NRO45) and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The H{alpha} images of barred spiral galaxies often show active star formation in spiral arms, but less so in bars. We quantify the difference by measuring star formation rate (SFR) and star formation efficiency (SFE) at a scale where local star formation is spatially resolved. Our CO map covers the central 2.'3 region of the galaxy; the combination of NRO45 and CARMA provides a high fidelity image, enabling accurate measurements of molecular gas surface density. We find that SFR and SFE are twice as high in the spiral arms as in the bar. We discuss this difference in the context of the Kennicutt-Schmidt (KS) law, which indicates a constant SFR at a given gas surface density. The KS law breaks down at our native resolution ({approx}250 pc), and substantial smoothing (to 500 pc) is necessary to reproduce the KS law, although with greater scatter.

  1. Atomic hydrogen in the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Knapen, J. H.

    1997-04-01

    New high-resolution, high-sensitivity Westerbork Synthesis Radio Telescope Hi synthesis observations of the spiral galaxy NGC 3631 are presented. In the total atomic hydrogen map, the spiral arms are well distinguished from the interarm regions, while the sensitivity allows detection of Hi in all but a few isolated regions of the areas between the spiral arms. Most of the atomic hydrogen is located within the optical disc, but the Hi extends to some 1.5R_opt. The Hi follows the spiral arms, and streaming motions of up to ~15 km s^-1 (projected) can be identified from the velocity field. Assuming a constant inclination angle of 17 deg, a rotation curve is derived which is declining slightly in the outer parts of the disc. An analysis of a residual velocity field, obtained after the subtraction of an axisymmetric model based on the rotation curve, confirms the existence of streaming motions near the spiral arms in an otherwise undisturbed disc.

  2. Accurate Distances to Important Spiral Galaxies: M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398

    NASA Astrophysics Data System (ADS)

    McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert

    2017-08-01

    Accurate distances are fundamental for interpreting various measured properties of galaxies. Surprisingly, many of the best-studied spiral galaxies in the Local Volume have distance uncertainties that are much larger than can be achieved with modern observation techniques. Using Hubble Space Telescopeoptical imaging, we use the tip of the red giant branch method to measure the distances to six galaxies that are included in the Spitzer Infrared Nearby Galaxies Survey program and its offspring surveys. The sample includes M63, M74, NGC 1291, NGC 4559, NGC 4625, and NGC 5398. We compare our results with distances reported to these galaxies based on a variety of methods. Depending on the technique, there can be a wide range in published distances, particularly from the Tully-Fisher relation. In addition, differences between the planetary nebular luminosity function and surface brightness fluctuation techniques can vary between galaxies, suggesting inaccuracies that cannot be explained by systematics in the calibrations. Our distances improve upon previous results, as we use a well-calibrated, stable distance indicator, precision photometry in an optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  3. Flocculent and grand design spiral structure in field, binary and group galaxies

    NASA Astrophysics Data System (ADS)

    Elmegreen, D. M.; Elmegreen, B. G.

    1982-12-01

    A 12-division morphological system emphasizing arm continuity, length and symmetry has been developed for the classification of all spiral galaxies according to the regularity of their spiral arm structure. Arm classifications were tabulated for 305 barred and nonbarred spiral galaxies; of these, 79 are isolated, 52 are binary and 174 are in groups. Among the isolated SA galaxies, 68 + or - 10% have irregular and fragmented, or 'flocculent', spiral structures. Only 32 + or - 10% have symmetric spiral arms in the classic grand design pattern. Flocculent spirals are the most common structures of galaxies without companions or bars. Since flocculent galaxies may have bars and companions, and grand design galaxies may have neither bars nor companions, such perturbations are neither perfectly effective nor always necessary in the driving of grand design patterns.

  4. Photometric Properties of Face-on Isolated Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bahr, Alexander; Epstein, P.; Durbala, A.

    2011-05-01

    We want to quantify the relative role of nature versus nurture in defining the observed properties of galaxies. In simpler terms we would like to disentangle the ``genetic'’ and the environmental influences in shaping the morphology of galaxies. In order to do that one needs to firstly define a zero-order baseline, i.e., a sample of galaxies that have been minimally perturbed by neighbors in the last few billion years of their existence. Such a sample has been produced and refined in different stages in the context of the AMIGA international project (www.iaa.es/AMIGA.html). The recent catalogue ``The All-Sky Catalog of Isolated Galaxies Selected from 2MASS'’ (Karachentseva, V. E. et al. 2010) allows us to complete and enrich the initial sample constructed within AMIGA with new objects, thus enhancing the statistical relevance of our study. Our focus is to define a subset of isolated disk spiral galaxies. We constrain the sample selection by: 1) orientation, restricting to almost face-on galaxies and 2) availability of good photometric images in SDSS. The goal is to ``dissect'’ (decompose) these galaxies in major components (disk, bulge, bars, etc.) and to study the properties of the components in a statistical context. Having a reasonable representation of all morphological types, we aim to test the bimodality of bulges and bars. We present a progress report of our work.

  5. UBVR and Hubble Space Telescope Mid-Ultraviolet and Near-Infrared Surface Photometry and Radial Color Gradients of Late-Type, Irregular, and Peculiar Galaxies

    NASA Astrophysics Data System (ADS)

    Taylor, Violet A.; Jansen, Rolf A.; Windhorst, Rogier A.; Odewahn, Stephen C.; Hibbard, John E.

    2005-09-01

    We introduce a data set of 142 mostly late-type spiral, irregular, and peculiar (interacting or merging) nearby galaxies observed in UBVR at the Vatican Advanced Technology Telescope (VATT), and we present an analysis of their radial color gradients. We confirm that nearby elliptical and early- to mid-type spiral galaxies show either no or only small color gradients, becoming slightly bluer with radius. In contrast, we find that late-type spiral, irregular, peculiar, and merging galaxies become on average redder with increasing distance from the center. The scatter in radial color gradient trends increases toward later Hubble type. As a preliminary analysis of a larger data set obtained with the Hubble Space Telescope (HST), we also analyze the color gradients of six nearby galaxies observed with NICMOS in the near-IR (H) and with WFPC2 in the mid-UV (F300W) and red (F814W). We discuss the possible implications of these results on galaxy formation and compare our nearby galaxy color gradients to those at high redshift. We present examples of images and UBVR radial surface brightness and color profiles, as well as of the tables of measurements; the full atlas and tables are published in the electronic edition only. 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 8645, 9124, and 9824.

  6. Globular Clusters and Spur Clusters in NGC 4921, the Brightest Spiral Galaxy in the Coma Cluster

    NASA Astrophysics Data System (ADS)

    Lee, Myung Gyoon; Jang, In Sung

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 105 M⊙. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V - I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting MI (max) = -8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H0 = 77.9 ± 3.6 km s-1 Mpc-1. We estimate the GC specific frequency of NGC 4921 to be SN = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  7. A comparison of extinction curves for dust in galaxies of different Hubble types

    NASA Technical Reports Server (NTRS)

    Townsley, Leisa K.; Price, Jill S.

    1993-01-01

    A sample of 25 galaxies of various Hubble types has been observed in a variety of filters. Extinction curves have been generated for absorption regions in these galaxies using a technique which previously had been used on just a few galaxies; for example, NGC 205, NGC 185, NGC 3077, and M31. The results from these studies suggested that there may be systematic trends in dust properties with Hubble type. This would not be surprising; dust properties should vary with metallicity, for example. It is well known that some galaxies and their interstellar materials should reflect this difference.

  8. IN-SPIRALING CLUMPS IN BLUE COMPACT DWARF GALAXIES

    SciTech Connect

    Elmegreen, Bruce G.; Zhang Hongxin; Hunter, Deidre A.

    2012-03-10

    Giant star formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the blue compact dwarf (BCD) phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived. The two examples with clumps closest to the center have the largest relative clump masses and the greatest contributions from old stars. An additional indication that the dense central regions of BCDs are like bulges is the high ratio of the inner disk scale height to the scale length, which is comparable to 1 for four of the galaxies.

  9. Antitruncated stellar light profiles in the outer regions of STAGES spiral galaxies: bulge or disc related?

    NASA Astrophysics Data System (ADS)

    Maltby, David T.; Hoyos, Carlos; Gray, Meghan E.; Aragón-Salamanca, Alfonso; Wolf, Christian

    2012-03-01

    We present a comparison of azimuthally averaged radial surface brightness μ(r) profiles and analytical bulge-disc decompositions (de Vaucouleurs, r1/4 bulge plus exponential disc) for spiral galaxies using Hubble Space Telescope/Advanced Camera for Surveys V-band imaging from the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). In the established classification scheme, antitruncated μ(r) profiles (Type III) have a broken exponential disc with a shallower region beyond the break radius rbrk. The excess light at large radii (r > rbrk) can either be caused by an outer exponential disc (Type III-d) or an extended spheroidal component (Type III-s). Using our comparisons, we determine the contribution of bulge light at r > rbrk for a large sample of 78 (barred/unbarred, Sa-Sd) spiral galaxies with outer disc antitruncations (?). In the majority of cases (˜85 per cent), evidence indicates that excess light at r > rbrk is related to an outer shallow disc (Type III-d). Here, the contribution of bulge light at r > rbrk is either negligible (˜70 per cent) or too little to explain the antitruncation (˜15 per cent). However in the latter cases, bulge light can affect the measured disc properties (e.g. μbrk, outer scalelength). In the remaining cases (˜15 per cent), light at r > rbrk is dominated by the bulge (Type III-s). Here, for most cases the bulge profile dominates at all radii and only occasionally (? galaxies, ˜5 per cent) extends beyond that of a dominant disc and explains the excess light at r > rbrk. We thus conclude that in the vast majority of cases antitruncated outer discs cannot be explained by bulge light and thus remain a pure disc phenomenon.

  10. Hubble Space Telescope Imaging of Decoupled Dust Clouds in the Ram Pressure Stripped Virgo Spirals NGC 4402 and NGC 4522

    NASA Astrophysics Data System (ADS)

    Abramson, Anne; Kenney, Jeffrey D. P.

    2014-03-01

    We present the highest-resolution study to date of the interstellar medium (ISM) in galaxies undergoing ram pressure stripping, using Hubble Space Telescope BVI imaging of NGC 4522 and NGC 4402, Virgo Cluster spirals that are well known to be experiencing intracluster medium (ICM) ram pressure. We find that throughout most of both galaxies, the main dust lane has a fairly well-defined edge, with a population of giant molecular cloud (GMC) sized (tens- to hundreds-of-pc scale), isolated, highly extincting dust clouds located up to ~1.5 kpc radially beyond it. Outside of these dense clouds, the area has little or no diffuse dust extinction, indicating that the clouds have decoupled from the lower-density ISM material that has already been stripped. Several of the dust clouds have elongated morphologies that indicate active ram pressure, including two large (kpc scale) filaments in NGC 4402 that are elongated in the projected ICM wind direction. We calculate a lower limit on the H I + H2 masses of these clouds based on their dust extinctions and find that a correction factor of ~10 gives cloud masses consistent with those measured in CO for clouds of similar diameters, probably due to the complicating factors of foreground light, cloud substructure, and resolution limitations. Assuming that the clouds' actual masses are consistent with those of GMCs of similar diameters (~104-105 M ⊙), we estimate that only a small fraction (~1%-10%) of the original H I + H2 remains in the parts of the disks with decoupled clouds. Based on Hα images, a similar fraction of star formation persists in these regions, 2%-3% of the estimated pre-stripping star formation rate. We find that the decoupled cloud lifetimes may be up to 150-200 Myr.

  11. Hubble space telescope imaging of decoupled dust clouds in the ram pressure stripped Virgo spirals NGC 4402 and NGC 4522

    SciTech Connect

    Abramson, Anne; Kenney, Jeffrey D. P. E-mail: jeff.kenney@yale.edu

    2014-03-01

    We present the highest-resolution study to date of the interstellar medium (ISM) in galaxies undergoing ram pressure stripping, using Hubble Space Telescope BVI imaging of NGC 4522 and NGC 4402, Virgo Cluster spirals that are well known to be experiencing intracluster medium (ICM) ram pressure. We find that throughout most of both galaxies, the main dust lane has a fairly well-defined edge, with a population of giant molecular cloud (GMC) sized (tens- to hundreds-of-pc scale), isolated, highly extincting dust clouds located up to ∼1.5 kpc radially beyond it. Outside of these dense clouds, the area has little or no diffuse dust extinction, indicating that the clouds have decoupled from the lower-density ISM material that has already been stripped. Several of the dust clouds have elongated morphologies that indicate active ram pressure, including two large (kpc scale) filaments in NGC 4402 that are elongated in the projected ICM wind direction. We calculate a lower limit on the H I + H{sub 2} masses of these clouds based on their dust extinctions and find that a correction factor of ∼10 gives cloud masses consistent with those measured in CO for clouds of similar diameters, probably due to the complicating factors of foreground light, cloud substructure, and resolution limitations. Assuming that the clouds' actual masses are consistent with those of GMCs of similar diameters (∼10{sup 4}-10{sup 5} M {sub ☉}), we estimate that only a small fraction (∼1%-10%) of the original H I + H{sub 2} remains in the parts of the disks with decoupled clouds. Based on Hα images, a similar fraction of star formation persists in these regions, 2%-3% of the estimated pre-stripping star formation rate. We find that the decoupled cloud lifetimes may be up to 150-200 Myr.

  12. Automated Quantification of Arbitrary Arm-Segment Structure in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Davis, Darren Robert

    This thesis describes a system that, given approximately-centered images of spiral galaxies, produces quantitative descriptions of spiral galaxy structure without the need for per-image human input. This structure information consists of a list of spiral arm segments, each associated with a fitted logarithmic spiral arc and a pixel region. This list-of-arcs representation allows description of arbitrary spiral galaxy structure: the arms do not need to be symmetric, may have forks or bends, and, more generally, may be arranged in any manner with a consistent spiral-pattern center (non-merging galaxies have a sufficiently well-defined center). Such flexibility is important in order to accommodate the myriad structure variations observed in spiral galaxies. From the arcs produced from our method it is possible to calculate measures of spiral galaxy structure such as winding direction, winding tightness, arm counts, asymmetry, or other values of interest (including user-defined measures). In addition to providing information about the spiral arm "skeleton" of each galaxy, our method can enable analyses of brightness within individual spiral arms, since we provide the pixel regions associated with each spiral arm segment. For winding direction, arm tightness, and arm count, comparable information is available (to various extents) from previous efforts; to the extent that such information is available, we find strong correspondence with our output. We also characterize the changes to (and invariances in) our output as a function of modifications to important algorithm parameters. By enabling generation of extensive data about spiral galaxy structure from large-scale sky surveys, our method will enable new discoveries and tests regarding the nature of galaxies and the universe, and will facilitate subsequent work to automatically fit detailed brightness models of spiral galaxies.

  13. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Watkins, Aaron E.; Mihos, J. Christopher; Harding, Paul

    2016-07-01

    We present results from deep, wide-field surface photometry of three nearby (D = 4-7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches a limiting surface brightness of {μ }B ˜ 28-30 mag arcsec-2 and probes colors down to {μ }B ˜ 27.5 mag arcsec-2. We compare our broadband optical data to available ultraviolet and high column density H i data to better constrain the star-forming history and stellar populations of the outermost parts of each galaxy’s disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies’ outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarity in outer disk properties despite each galaxy showing distinct levels of environmental influence, from a purely isolated galaxy (M94) to one experiencing weak tidal perturbations from its satellite galaxies (M106) to a galaxy recovering from a recent merger (M64), suggesting that a variety of evolutionary histories can yield similar outer disk structure. While this suggests a common secular mechanism for outer disk formation, the large extent of these smooth, red stellar populations—which reach several disk scale lengths beyond the galaxies’ spiral structure—may challenge models of radial migration given the lack of any nonaxisymmetric forcing at such large radii.

  14. Photometric and kinematic DISKFIT models of four nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peters, Wesley; Kuzio de Naray, Rachel

    2017-08-01

    We present optical BVRI photometry, H α integrated field unit velocity fields and H α long-slit rotation curves for a sample of four nearby spiral galaxies having a range of morphologies and inclinations. We show that the DISKFIT code can be used to model the photometric and kinematic data of these four galaxies and explore how well the photometric data can be decomposed into structures like bars and bulges and to look for non-circular motions in the kinematic data. In general, we find good agreement between our photometric and kinematic models for most parameters. We find the best consistency between our photometric and kinematic models for NGC 6674, a relatively face-on spiral with clear and distinct bulge and bar components. We also find excellent consistency for NGC 2841, and find a bar ∼10° south of the disc major axis in the inner 20 arcsec. Due to geometric effects caused by its high inclination, we find the kinematic model for NGC 2654 to be less accurate than its photometry. We find the bar in NGC 2654 to be roughly parallel to the major axis of the galaxy. We are unable to photometrically model our most highly inclined galaxy, NGC 5746, with DISKFIT and instead use the galaxy isophotes to determine that the system contains a bar ∼5° to ∼10° east of the disc major axis. The high inclination and extinction in this galaxy also prevent our kinematic model from accurately determining parameters about the bar, though the data are better modelled when a bar is included.

  15. Hot X-ray Coronae around Spiral Galaxies: A Unique Probe of Galaxy Formation Models

    NASA Astrophysics Data System (ADS)

    Bogdan, Akos; Concepcion Mairey, Florence; Bourdin, Herve; Forman, William R.; Kraft, Ralph P.; Vogelsberger, Mark; Hernquist, Lars E.; Jones, Christine

    2017-08-01

    The presence of hot gaseous coronae in the dark matter halos of massive spiral galaxies is a fundamental prediction of all galaxy formation models. Yet these coronae remained unexplored for several decades, thereby posing a serious challenge to observers and theorists. Recently, a major breakthrough has been made, and several X-ray coronae have been detected around massive spiral galaxies. We have studied the properties of these luminous X-ray coronae in detail and confronted their observed properties with results of the hydrodynamical galaxy formation simulation, Illustris. This comparison pointed out that the properties of these coronae are extremely sensitive to the incorporated physics in the simulations, and hence observations of X-ray coronae provide a powerful method to constrain the physical processes (e.g. stellar and AGN feedback and metal enrichment) that play an essential role in forming galaxies from the early Universe to the present epoch. I will overview the key observational results, discuss the comparison between observations and simulations, and highlight the future prospects of further exploring hot coronae around spiral galaxies.

  16. Radio continuum and H I emission from the spiral galaxies in the Virgo cluster area

    NASA Astrophysics Data System (ADS)

    Gavazzi, G.

    The statistical method used by Hummel (1981) to derive the radioluminosity functions of galaxies is applied to the H I data obtained on a sample of 101 spiral galaxies in the Virgo cluster. The analysis permits a quantitative demonstration of H I deficiency among the Virgo spiral galaxies without invoking the deficiency parameter. In addition, evidence is presented that Virgo spiral galaxies might show a correlation between H I content and radio continuum luminosity, which is more marked among the unperturbed sample. The results are discussed from the viewpoint of stellar and galaxy evolution and its relation with the intergalactic environment.

  17. The interstellar halo of spiral galaxies: NGC 891

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.; Rand, R. J.; Hester, J. Jeff

    1990-01-01

    Researchers have detected the Warm Ionized Medium (WIM) phase in the galaxy NGC 891. They found that the radial distribution of the WIM follows the molecular or young star distribution - an expected dependence. The amount of the WIM in this galaxy exceeds that in our Galaxy. The major surprize is the large thickness of the WIM phase - about 9 kpc instead 3 kpc as in our Galaxy. Clearly, this is the most significant result of the observations. The presence of low ionization gas at high z as well as at large galactocentric radii (where young stars are rare) is an important clue to the origin of the halo and observations such as the one reported here provide important data on this crucial question. In particular, the ionization of gas at high absolute z implies that either the UV photons manage to escape from the disk of the galaxy or that the extragalactic UV background plays an important role. The bulk of the WIM in spiral galaxies is a result of star-formation activity and thus these results can be understood by invoking a high star formation rate in NGC 891. Only the concerted action of supernovae can get the gas to the large z-heights as is observed in this galaxy. Support for this view comes from our detection of many worms i.e., bits and pieces of supershells in the form of kilo-parsec long vertical filaments. Researchers also saw a 600-pc size supershell located nearly one kpc above the plane of the galaxy.

  18. Constraining corotation from shocks in tightly wound spiral galaxies

    NASA Astrophysics Data System (ADS)

    Gittins, D. M.; Clarke, C. J.

    2004-04-01

    We present a new method for estimating the corotation radius in tightly wound spiral galaxies, through analysis of the radial variation of the offset between arms traced by the potential (P-arms) and those traced by dust (D-arms). We have verified the predictions of semi-analytical theory through hydrodynamical simulations and have examined the uniqueness of the galactic parameters that can be deduced by this method. We find that if the range of angular offsets measured at different radii in a galaxy is greater than around π/4, it is possible to locate the radius of corotation to within ~25 per cent. We argue that the relative location of the P- and D-arms provides more robust constraints on the galactic parameters than can be inferred from regions of enhanced star formation (SF-arms), as interpretation of the latter involves uncertainties due to reddening and the assumed star formation law. We thus stress the importance of K-band studies of spiral galaxies.

  19. Does the Milky Way Obey Spiral Galaxy Scaling Relations?

    NASA Astrophysics Data System (ADS)

    Licquia, Timothy C.; Newman, Jeffrey A.; Bershady, Matthew A.

    2016-12-01

    It is crucial to understand how the Milky Way (MW), the galaxy we can study in the most intimate detail, fits in among other galaxies. Key considerations include the Tully-Fisher relation (TFR)—i.e., the tight correlation between luminosity (L) and rotational velocity (V rot)—and the three-dimensional luminosity-velocity-radius (LVR) scaling relation. Several past studies have characterized the MW as a 1-1.5σ outlier to the TFR. This study re-examines such comparisons using new estimates of MW properties that are robust to many of the systematic uncertainties that have been a problem in the past and are based on assumptions consistent with those used for other spiral galaxies. Comparing to scaling relations derived from modern extragalactic data, we find that our Galaxy’s properties are in excellent agreement with TFRs defined using any Sloan Digital Sky Survey-filter absolute magnitude, stellar mass, or baryonic mass as the L proxy. We next utilize disk scale length (R d) measurements to extend this investigation to the LVR relation. Here we find that our Galaxy lies farther from the relation than ˜90% of other spiral galaxies, yielding ˜9.5σ evidence that it is unusually compact for its L and V rot (based on MW errors alone), a result that holds for all of the L proxies considered. The expected R d for the MW from the LVR relation is ˜5 kpc, nearly twice as large as the observed value, with error estimates placing the two in tension at the ˜1.4σ level. The compact scale length of the Galactic disk could be related to other ways in which the MW has been found to be anomalous.

  20. Whirlpool Galaxy

    NASA Image and Video Library

    1999-12-04

    The image from NASA Hubble Telescope shows spiral arms and dust clouds in the nearby Whirlpool galaxy. Visible starlight and light from the emission of glowing hydrogen is seen, which is associated with the most luminous young stars in the spiral arms.

  1. Exploring for Galaxies in the First Billion Years with Hubble and Spitzer - Pathfinding for JWST

    NASA Astrophysics Data System (ADS)

    Illingworth, Garth D.

    2017-01-01

    Hubble has revolutionized the field of distant galaxies through its deep imaging surveys, starting with the Hubble Deep Field (HDF) in 1995. That first deep survey revealed galaxies at redshift z~1-3 that provided insights into the development of the Hubble sequence. Each new HST instrument has explored new regimes, through the peak of star formation at z~2-3, just 2-3 billion years after the Big Bang, to our first datasets at a billion years at z~6, and then earlier to z~11. HST's survey capabilities were enhanced by 40X with ACS, and then similarly with the WFC3/IR, which opened up the first billion years to an unforeseen degree. I will discuss what we have learned from the remarkable HST and Spitzer imaging surveys (HUDF, GOODS, HUDF09/12 and CANDELS), as well as surveys of clusters like the Hubble Frontier Fields (HFF). Lensing clusters provide extraordinary opportunities for characterizing the faintest earliest galaxies, but also present extraordinary challenges. Together these surveys have resulted in the measurement of the volume density of galaxies in the first billion years down to astonishingly faint levels. The role of faint galaxies in reionizing the universe is still much-discussed, but there is no doubt that such galaxies contribute greatly to the UV ionizing flux, as shown by deep luminosity function studies. Together Hubble and Spitzer have also established the stellar-mass buildup over 97% of cosmic history. Yet some of the greatest surprises have come from the discovery of very luminous galaxies at z~8-11, around 400-650 million years after the Big Bang. Spectroscopic followup by Keck of some of these very rare, bright galaxies has confirmed redshifts from z~7 to z~9, and revealed, surprisingly, strong Lyα emission near the peak of reionization when the HI fraction in the IGM is high. The recent confirmation of a z=11.1 galaxy, just 400 million years after the Big Bang, by a combination of Hubble and Spitzer data, moved Hubble into JWST territory

  2. Spiral galaxy HI models, rotation curves and kinematic classifications

    NASA Astrophysics Data System (ADS)

    Wiegert, Theresa B. V.

    Although galaxy interactions cause dramatic changes, galaxies also continue to form stars and evolve when they are isolated. The dark matter (DM) halo may influence this evolution since it generates the rotational behaviour of galactic disks which could affect local conditions in the gas. Therefore we study neutral hydrogen kinematics of non-interacting, nearby spiral galaxies, characterising their rotation curves (RC) which probe the DM halo; delineating kinematic classes of galaxies; and investigating relations between these classes and galaxy properties such as disk size and star formation rate (SFR). To generate the RCs, we use GalAPAGOS (by J. Fiege). My role was to test and help drive the development of this software, which employs a powerful genetic algorithm, constraining 23 parameters while using the full 3D data cube as input. The RC is here simply described by a tanh-based function which adequately traces the global RC behaviour. Extensive testing on artificial galaxies show that the kinematic properties of galaxies with inclination >40 degrees, including edge-on galaxies, are found reliably. Using a hierarchical clustering algorithm on parametrised RCs from 79 galaxies culled from literature generates a preliminary scheme consisting of five classes. These are based on three parameters: maximum rotational velocity, turnover radius and outer slope of the RC. To assess the relationship between DM content and the kinematic classes, we generate mass models for 10 galaxies from the THINGS and WHISP surveys, and J. Irwin's sample. In most cases mass models using GalAPAGOS RCs were similar to those using traditional "tilted-ring'' method RCs. The kinematic classes are mainly distinguished by their rotational velocity. We confirm correlations between increasing velocity and B-magnitude, optical disk size, and find earlier type galaxies among the strong rotators. SFR also increases with maximum rotational velocity. Given our limited subsample, we cannot discern a

  3. Kinematic classification of non-interacting spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wiegert, Theresa; English, Jayanne

    2014-01-01

    Using neutral hydrogen (HI) rotation curves of 79 galaxies, culled from the literature, as well as measured from HI data, we present a method for classifying disk galaxies by their kinematics. In order to investigate fundamental kinematic properties we concentrate on non-interacting spiral galaxies. We employ a simple parameterized form for the rotation curve in order to derive the three parameters: the maximum rotational velocity, the turnover radius and a measure of the slope of the rotation curve beyond the turnover radius. Our approach uses the statistical Hierarchical Clustering method to guide our division of the resultant 3D distribution of galaxies into five classes. Comparing the kinematic classes in this preliminary classification scheme to a number of galaxy properties, we find that our class containing galaxies with the largest rotational velocities has a mean morphological type of Sb/Sbc while the other classes tend to later types. Other trends also generally agree with those described by previous researchers. In particular we confirm correlations between increasing maximum rotational velocity and the following observed properties: increasing brightness in B-band, increasing size of the optical disk (D25) and increasing star formation rate (as derived using radio continuum data). Our analysis also suggests that lower velocities are associated with a higher ratio of the HI mass over the dynamical mass. Additionally, three galaxies exhibit a drop in rotational velocity amplitude of ≳20% after the turnover radius. However recent investigations suggest that they have interacted with minor companions which is a common cause for declining rotation curves.

  4. On the Extraction of Optical Rotation Curves for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sohn, Young-Jong; Rhee, Myung-Hyun; Chun, Mun-Suk

    1998-06-01

    We discussed four different methods - the single, double and triple Gaussian fits, and the intensity weighted centroid fit - which extract rotation curves from several emission lines ([OII], H_beta, [OIII], and H_alpha) of spiral galaxies. Spatial extents and the shapes of rotation curves derived through various methods applying to each emission lines of a sample galaxy UGC 11635 are all in a good agreement with one another. Linewidths of H_beta and H_alpha measured from rotation profiles are in a good agreement with H_alpha linewidth of Courteau (1992). However, linewidths of [OII] seems to be much broader than H_alpha, and the profile of [OIII] does not follow the profile of H_alpha.

  5. ON THE INTRINSIC ALIGNMENTS OF THE LATE-TYPE SPIRAL GALAXIES FROM THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 7

    SciTech Connect

    Lee, Jounghun

    2011-05-10

    A robust detection of the tidally induced intrinsic alignments of the late-type spiral galaxies with high statistical significance is reported. From the spectroscopic galaxy sample of Sloan Digital Sky Survey DR7 compiled by Huertas-Company et al., which lists each galaxy's probabilities of being in five Hubble types, P(E), P(Ell), P(S0), P(Sab), P(Scd), we select the nearby large late-type spiral galaxies which have redshifts of 0 {<=} z {<=} 0.02, probabilities of P(Scd) {>=} 0.5, and angular sizes of D {>=} 7.92 arcsec. The spin axes of the selected nearby large late-type spiral galaxies are determined up to the two-fold ambiguity with the help of the circular thin-disk approximation, and their spatial correlations are measured as a function of the separation distance r. A clear signal of the intrinsic correlation as high as 3.4{sigma} and 2.4{sigma} is found at the separation distance of r {approx} 1 h{sup -1} Mpc and r {approx} 2 h{sup -1} Mpc, respectively. The comparison of this observational results with the analytic model based on the tidal torque theory reveals that the spin correlation function for the late-type spiral galaxies follows the quadratic scaling of the linear density correlation and that the intrinsic correlations of the galaxy spin axes are stronger than that of the underlying dark halos. We investigate a local density dependence of the galaxy spin correlations and found that the correlations are stronger for the galaxies located in dense regions having more than 10 neighbors within 2 h{sup -1} Mpc. We also attempt to measure a luminosity dependence of the galaxy spin correlations, but find that it is impossible with our magnitude-split samples to disentangle a luminosity from a redshift dependence. We provide the physical explanations for these observational results and also discuss the effects of possible residual systematics on the results.

  6. Spiral Galaxies with HST/NICMOS. II. Isophotal Fits and Nuclear Cusp Slopes

    NASA Astrophysics Data System (ADS)

    Seigar, Marc; Carollo, C. Marcella; Stiavelli, Massimo; de Zeeuw, P. Tim; Dejonghe, Herwig

    2002-01-01

    We present surface brightness profiles for 56 of the 78 spiral galaxies observed in the HST/NICMOS2 F160W snapshot survey introduced in Paper I of this series, as well as surface brightness profiles for 23 objects out of the 41 that were also observed in the F110W filter. We fit these surface brightness profiles with the Nuker law of Lauer et al. and use the smooth analytical descriptions of the data to compute the average nuclear stellar cusp slopes <γ> in the 0.1"-0.5" radial range. Our main result is the startling similarity between the nuclear stellar cusp slopes <γ> in the near-infrared compared with those derived in the visual passband. This similarity has several implications: (1) Despite the significant local color variations that are found in the nuclear regions of spirals and that are documented in Paper I, there are typically little or no optical-NIR global color gradients, and thus no global stellar population variations, inside ~50-100 pc from the nucleus in nearby spirals. (2) The large observed range of the strength of the nuclear stellar cusps seen in the HST optical study of spiral galaxies reflects a physical difference between galaxies and is not an artifact caused by nuclear dust and/or recent star formation. (3) The dichotomy between R1/4 bulges, with steep nuclear stellar cusps <γ>~1, and exponential bulges, with shallow nuclear stellar cusps <γ><0.3, is also not an artifact of the effects of dust or recent star formation. (4) The presence of a surrounding massive disk appears to have no effect on the rise of the stellar density distribution within the innermost hundred parsecs of the R1/4 spheroids. These results imply a breakdown within the family of exponential bulges of the nuclear versus global relationships that have been found for the R1/4 spheroids. Such a breakdown is likely to have significant implications concerning the formation of exponential bulges and their connection with the R1/4 spheroids. Based on observations with the

  7. Effects of spiral arms on star formation in nuclear rings of barred-spiral galaxies

    SciTech Connect

    Seo, Woo-Young; Kim, Woong-Tae E-mail: wkim@astro.snu.ac.kr

    2014-09-01

    We use hydrodynamic simulations to study the effect of spiral arms on the star formation rate (SFR) in nuclear rings of barred-spiral galaxies. We find that spiral arms can be an efficient means of gas transport from the outskirts to the central parts, provided that the arms are rotating slower than the bar. While the ring star formation in models with no arms or corotating arms is active only during around the bar growth phase, arm-driven gas accretion both significantly enhances and prolongs the ring star formation in models with slow-rotating arms. The arm-enhanced SFR is larger by a factor of ∼3-20 than in the no-arm model, with larger values corresponding to stronger and slower arms. Arm-induced mass inflows also make dust lanes stronger. Nuclear rings in slow-arm models are ∼45% larger than in the no-arm counterparts. Star clusters that form in a nuclear ring exhibit an age gradient in the azimuthal direction only when the SFR is small, whereas no notable age gradient is found in the radial direction for models with arm-induced star formation.

  8. Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies

    NASA Technical Reports Server (NTRS)

    Magri, Christopher

    1994-01-01

    Multivariate data have been collected as part of an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on subjective morphological properties. A sample of 492 moderately bright northern Sa and Sc spirals was chosen for future statistical analysis. New observations were made at 20 and 21 cm; the latter data are described in detail here. Infrared Astronomy Satellite (IRAS) fluxes were obtained from archival data. Finally, new estimates of arm pattern radomness and of local environmental harshness were compiled for most sample objects.

  9. Arm structure in normal spiral galaxies, 1: Multivariate data for 492 galaxies

    NASA Technical Reports Server (NTRS)

    Magri, Christopher

    1994-01-01

    Multivariate data have been collected as part of an effort to develop a new classification system for spiral galaxies, one which is not necessarily based on subjective morphological properties. A sample of 492 moderately bright northern Sa and Sc spirals was chosen for future statistical analysis. New observations were made at 20 and 21 cm; the latter data are described in detail here. Infrared Astronomy Satellite (IRAS) fluxes were obtained from archival data. Finally, new estimates of arm pattern radomness and of local environmental harshness were compiled for most sample objects.

  10. Broad-band BVRI photometry of isolated spiral galaxies

    NASA Astrophysics Data System (ADS)

    Hernández-Toledo, H. M.; Ortega-Esbrí, S.

    2008-08-01

    Context: Uniform and high resolution observations in samples of isolated galaxies are required to estimate fundamental morphological and structural parameters for comparative studies of environmental effects and for confronting model predictions of galaxy evolution. A subsample of The Catalog of Isolated Galaxies (CIG), Karachentseva (1973), has been uniformly observed at San Pedro Mártir National Observatory in México and a photometric and morphological study of these galaxies has been carried out. Aims: We report multicolor broad band (BVRI) photometry for a subsample of 40 isolated spirals drawn from the CIG. Total magnitudes and colors at various circular apertures as well as a detailed morphological analysis that is extended into the NIR bands are presented. Some structural parameters are estimated from the global light distribution in the optical and NIR bands to complement our morphological analysis and several correlations between the photometric and structural parameters are explored. Emphasis was given to the detection of morphological distortions at high/low intensity levels. Methods: The observations, data reduction, and analysis are described. Morphology is reevaluated from a combination of optical logarithmically scaled R band images, filter-enhanced R band images, (B-I) color index maps, archived near IR {JHK} images from the TwoMicron Survey and optical-NIR ɛ and PA radial profiles after an isophotal analysis. {RGB} images from the SDSS database were retrieved when available to complement our analysis. The {CAS} structural parameters (Concentration, Asymmetry, and Clumpiness) were calculated from the images in each band. Results: The fraction of galaxies with well-identified optical/near-IR bars (SB) is 40%, while another 25% shows evidence of weak or suspected bars (SAB). The sample average value of the maximum bar ellipticity is ɛ_max≈ 0.35. 57.5% of the galaxies in the sample show rings. The {CAS} parameters change with the observed band

  11. THE LARSON-TINSLEY EFFECT IN THE ULTRAVIOLET: INTERACTING VERSUS 'NORMAL' SPIRAL GALAXIES

    SciTech Connect

    Smith, Beverly J.; Struck, Curtis E-mail: curt@iastate.ed

    2010-12-15

    We compare the UV-optical colors of a well-defined set of optically selected pre-merger interacting galaxy pairs with those of normal spirals. The shorter wavelength colors show a larger dispersion for the interacting galaxies than for the spirals. This result can best be explained by higher star formation rates on average in the interacting galaxies, combined with higher extinctions on average. This is consistent with earlier studies which found that the star formation in interacting galaxies tends to be more centrally concentrated than in normal spirals, perhaps due to gas being driven into the center by the interaction. As noted in earlier studies, there is a large variation from galaxy to galaxy in the implied star formation rates of the interacting galaxies, with some galaxies having enhanced rates but others being fairly quiescent.

  12. Galaxy Zoo: comparing the demographics of spiral arm number and a new method for correcting redshift bias

    NASA Astrophysics Data System (ADS)

    Hart, Ross E.; Bamford, Steven P.; Willett, Kyle W.; Masters, Karen L.; Cardamone, Carolin; Lintott, Chris J.; Mackay, Robert J.; Nichol, Robert C.; Rosslowe, Christopher K.; Simmons, Brooke D.; Smethurst, Rebecca J.

    2016-10-01

    The majority of galaxies in the local Universe exhibit spiral structure with a variety of forms. Many galaxies possess two prominent spiral arms, some have more, while others display a many-armed flocculent appearance. Spiral arms are associated with enhanced gas content and star formation in the discs of low-redshift galaxies, so are important in the understanding of star formation in the local universe. As both the visual appearance of spiral structure, and the mechanisms responsible for it vary from galaxy to galaxy, a reliable method for defining spiral samples with different visual morphologies is required. In this paper, we develop a new debiasing method to reliably correct for redshift-dependent bias in Galaxy Zoo 2, and release the new set of debiased classifications. Using these, a luminosity-limited sample of ˜18 000 Sloan Digital Sky Survey spiral galaxies is defined, which are then further sub-categorized by spiral arm number. In order to explore how different spiral galaxies form, the demographics of spiral galaxies with different spiral arm numbers are compared. It is found that whilst all spiral galaxies occupy similar ranges of stellar mass and environment, many-armed galaxies display much bluer colours than their two-armed counterparts. We conclude that two-armed structure is ubiquitous in star-forming discs, whereas many-armed spiral structure appears to be a short-lived phase, associated with more recent, stochastic star-formation activity.

  13. Gas and Stellar Kinematics in the Giant Spiral Galaxy NGC 1961

    NASA Astrophysics Data System (ADS)

    Sacash, Brian; Pinkney, Jason

    2009-04-01

    Long-slit spectroscopy and CCD imaging from the Hubble Space Telescope and the MDM Observatory is presented for the massive spiral galaxy NGC 1961. We aimed to measure the mass of the central supermassive black hole (SMBH). We have developed our own software for spectral extraction and for the fitting of absorption and emission lines. The program subtracts the absorption-line (stellar) component from the emission-line spectra to improve the fidelity of our emission line measurements. We present our line centroids (velocities), widths (velocity dispersions), and strengths for the most prominent emission lines (Hα, [NII], and [SII]). The rotation curve from the ground-based data is in good agreement with previous work by Rubin (1979); its asymmetric appearance suggests a tidal interaction or merger. We use the rotation curve and surface photometry to estimate the enclosed mass profile of the galaxy. The emission lines near the nucleus broaden indicating more intrinsic dispersion than expected for a cold, gas disk. We estimate the BH mass using simple gas disk models. However, the high dispersion and the asymmetry in its inner rotation curve suggest that this approach is unreliable.

  14. NIR surface photometry of a sample of nearby spiral galaxies

    NASA Astrophysics Data System (ADS)

    Castro-Rodríguez, N.; Garzón, F.

    2003-11-01

    The first results of an observational programme aimed at mapping a sample of face-on spiral galaxies in the NIR are presented. This paper shows the surface photometry of the first ten galaxies in the sample. The data were taken in the broad band J (1.2 mu m) and Ks (2.2 mu m) filters. The sources were selected mainly according to their size and brightness in order to suit the characteristics of the CAIN 2D NIR camera on the 1.5-m Carlos Sánchez Telescope (Tenerife, Spain). The primary scientific goal is to provide a comprehensive and uniform database of the main structural and photometric parameters of the sample members from NIR surface photometry. To this end, elliptical isophotal fitting was performed on each galaxy image to extract information about the size and location of its morphological components and provide the azimuthally averaged radial brightness profile. Analytical functions for each component's brightness distribution were then used to match that profile, and their functional parameters obtained from the global fitting. This first report includes data for NGC 3344, NGC 3686, NGC 3938, NGC 3953, NGC 4254, NGC 4303, NGC 4314, NGC 5248, NGC 6384 and NGC 7479.

  15. ON THE STAR FORMATION LAW FOR SPIRAL AND IRREGULAR GALAXIES

    SciTech Connect

    Elmegreen, Bruce G.

    2015-12-01

    A dynamical model for star formation on a galactic scale is proposed in which the interstellar medium is constantly condensing to star-forming clouds on the dynamical time of the average midplane density, and the clouds are constantly being disrupted on the dynamical timescale appropriate for their higher density. In this model, the areal star formation rate scales with the 1.5 power of the total gas column density throughout the main regions of spiral galaxies, and with a steeper power, 2, in the far outer regions and in dwarf irregular galaxies because of the flaring disks. At the same time, there is a molecular star formation law that is linear in the main and outer parts of disks and in dIrrs because the duration of individual structures in the molecular phase is also the dynamical timescale, canceling the additional 0.5 power of surface density. The total gas consumption time scales directly with the midplane dynamical time, quenching star formation in the inner regions if there is no accretion, and sustaining star formation for ∼100 Gyr or more in the outer regions with no qualitative change in gas stability or molecular cloud properties. The ULIRG track follows from high densities in galaxy collisions.

  16. BCD Galaxies from In-spiraling Giant Clumps

    NASA Astrophysics Data System (ADS)

    Elmegreen, Bruce; Zhang, H.; Hunter, D. A.

    2012-01-01

    Giant star-formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the center in less than 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration analogous to a bulge in an earlier-type galaxy. A long history of inward migration will also produce a long-lived starburst in the inner regions as the gas column density remains above a threshold for star formation. Such a burst may be identified with the BCD phase in some dwarfs. Observations of giant star formation clumps in five local dwarf irregulars illustrate the relatively large clump masses that are suggested by this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case they may be gravitationally bound and long-lived. The two examples with clumps closest to the center have the largest relative clump masses and the greatest contributions from old stars. This work was funded in part by the National Science Foundation through grants AST-0707563 and AST-0707426 to DAH and BGE. HZ was partly supported by NSF of China through grants #10425313, #10833006 and #10621303 to Professor Yu Gao.

  17. Kiloparsec-scale molecular gas excitation in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-09-01

    We combine beam-matched (C-13)O, (C-12)O J = 3 - 2 and J = 2 - 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of IR-bright external galaxies: NGC 253, IC 342, M83, Maffei 2, and NGC 6946. We find that the central 170 to 530 pc diameter regions have typical molecular gas densities ranging from approximately less than 10,000/cu cm (in M83) to approximately greater than 100,000/cu cm (in NGC 253) and that, outside of these regions, the densities are likely to be approximately less than 10,000/cu cm. The molecular clouds outside the inner 170-530 pc are at least as warm as the molecular clouds in our Galaxy. Column densities derived from integrated (C-13)O line strengths and H-alpha surface brightnesses suggest that the star formation rate is enhanced in the central 170-530 pc diameters by an order of magnitude over that inferred for the outer star-forming disks in spiral galaxies.

  18. Kiloparsec-scale molecular gas excitation in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Wall, W. F.; Jaffe, D. T.; Bash, F. N.; Israel, F. P.; Maloney, P. R.; Baas, F.

    1993-01-01

    We combine beam-matched (C-13)O, (C-12)O J = 3 - 2 and J = 2 - 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of IR-bright external galaxies: NGC 253, IC 342, M83, Maffei 2, and NGC 6946. We find that the central 170 to 530 pc diameter regions have typical molecular gas densities ranging from approximately less than 10,000/cu cm (in M83) to approximately greater than 100,000/cu cm (in NGC 253) and that, outside of these regions, the densities are likely to be approximately less than 10,000/cu cm. The molecular clouds outside the inner 170-530 pc are at least as warm as the molecular clouds in our Galaxy. Column densities derived from integrated (C-13)O line strengths and H-alpha surface brightnesses suggest that the star formation rate is enhanced in the central 170-530 pc diameters by an order of magnitude over that inferred for the outer star-forming disks in spiral galaxies.

  19. The Evolution of Faint Field Galaxies: Implications from the Hubble Deep Field

    NASA Astrophysics Data System (ADS)

    Gronwall, C.

    1996-12-01

    The Hubble Deep Field (HDF) is a four square arcminute area of the sky imaged for ten consecutive days with the Hubble Space Telescope. It is the deepest optical imaging survey of field galaxies in existence, reaching ~ 2-3 mag fainter than the deepest ground-based observations. In addition to its unprecedented depth, the spatial resolution of the HDF enables the measurement of structural and morphological parameters for an extremely faint sample of galaxies. We (see Gronwall & Koo 1995) have developed a modeling technique which differs from previous work by adopting the very simple assumption that the local galaxy luminosity function and galaxy mix are not well-defined. Instead, we use a non-negative least squares fitting technique to derive a set of best-fitting local luminosity functions for different galaxy spectral types. By only including traditional luminosity evolution (i.e., the photometric evolution of stars over time given reasonable assumptions of the star formation history of various galaxy types), plus the addition of galaxy reddening, we are able to fit the observed optical and near-IR galaxy counts, B-R colors, and redshifts of faint field galaxies extremely well to B ~ 25. We present the extension of the obove modeling technique to the multicolor photometric information and structural parameters (in particular, angular sizes) provided by the HDF. Our newst models also include additional evolutionary components -- merging and starbursting -- to try to constrain the relative importances of different forms of evolution in faint field galaxies.

  20. The Arkansas Galaxy Evolution Survey: SMBH Mass and Spiral Arm Morphology

    NASA Astrophysics Data System (ADS)

    Seigar, M. S.; Berrier, J. C.; Davis, B. L.; Kennefick, D.; Kennefick, J.; Barrows, R. S.; Hartley, M. T.; Shields, D. W.; Bentz, M. C.; Lacy, C. H. S.

    2014-03-01

    We confirm the existence of a previously reported relationship between spiral arm pitch angle P (a measure of the tightness of spiral structure) and the mass MBH of a disk galaxy's central supermassive black hole (SMBH). We use an improved method to determine spiral arm pitch angles and generate quantitative data on this morphological feature for 34 galaxies with directly measured black hole masses, and a further 20 galaxies with measured core velocity dispersions. Such a relationship is predicted by leading theories of spiral structure (density wave theory, swing amplification, and manifold theory). We propose that this relationship be used as a method for estimating SMBH masses in disk galaxies. Spiral arm pitch angle can be measured from imaging data alone, and with the scatter in the presented relationship (0.45 dex), this tool is potentially superior when compared to other SMBH scaling relationship.

  1. A Sneak Peek at the JWST Era: Observing Galaxies Below the Hubble Limit with Gravitational Lensing

    NASA Astrophysics Data System (ADS)

    Livermore, Rachael C.

    2016-01-01

    The installation of WFC3 on the Hubble Space Telescope pushed the frontier of high-redshift galaxy studies to only 500 Myr after the Big Bang. However, observations in this epoch remain challenging and are limited to the brightest galaxies; the fainter sources believed to be responsible for reionizing the Universe remain beyond the grasp of Hubble. With gravitational lensing, however, we can benefit from the magnification of faint sources, which brings them within reach of today's telescopes. The Hubble Frontier Fields program is a deep survey of strongly lensing clusters observed in the optical and near-infrared. Unfortunately, detecting highly magnified, intrinsically faint galaxies in these fields has proved challenging due to the bright foregound cluster galaxies and intracluster light. We have developed a technique using wavelet decomposition to overcome these difficulties and detect galaxies at z~7 with intrinsic UV magnitudes as faint as MUV = -13. We present this method and the resulting luminosity functions, which support a steep faint-end slope extending out to the observational limits. Our method has uncovered hundreds of galaxies at z > 6 fainter than any that have been seen before, providing our first insight into the small galaxy population during the epoch of reionization and a preview of the capabilities of JWST.

  2. Satellites as Probes of the Masses of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Gottesman, S. T.

    1998-11-01

    We discuss HI observations and analyses of the kinematics of 25 satellite-primary galaxy pairs with projected separations between 4.9 and 240 kpc. The satellites have masses less than 3% of their primary spirals. Two estimates for their mass are available, one from their rotation curves and one from the orbital properties of the satellites. Defining \\chi as the ratio of these two estimates, it is a measure of the presence or absence of a significant halo. The \\chi distribution of these 24 pairs is presented and selection effects are considered. In addition, we show that the \\chi distribution of more numerous pairs, with projected separations of less thn 200 kpc, identified by Zartisky and colleagues (employing selection criteria quite different than ours) is similar to ours. We show that the observational biases have a negligible effect; the biased and unbiased distributions are essentially identical. In order to understand this distribution, N-body calculations were executed to simulate the dynamical behavior of relatively low mass satellites orbiting primary disk galaxies with and without extended halos. The models and the real galaxies were 'obseved' in the same fasion. In adition, we made a partially analytical analysis of the behavior of orbits in a logarithmic potential. We find that a 'generic' model, characterizd by a single disk/halo combination, cannot reproduce the observed distribution, P(\\chi). However, a simple two component population of galaxies, composed of not more than 60% with halos and 40% without halos, is successful, if galaxies have dimensions of order 200kpc. If galaxies are considerably larger with sizes extending 400 kpc or more, the constraints become more onerous. No generic model can describe the full range of the observed P(\\chi), particularly if the distribution for r_p<200 kpc is compared with that for r_p>200 kpc. Regardless of the mix of orbital eccentricities, nether pure halo, nor cannonical models (disk and halo masses are

  3. Statistical study of warps in a sample of spiral and lenticular galaxies

    NASA Astrophysics Data System (ADS)

    Hendy, Y. H. M.; Samir, R. M.; Shaker, A. A.; Ibrahim, Alhassan I.

    2016-12-01

    A sample of edge-on (or nearly edge-on) spiral and lenticular galaxies is selected to study the warp phenomenon in their disks. This sample contains 36 disk galaxies selected from Watanabe's catalogue (Watanabe, 1983). We investigate the existence of physical relations between photometric and spectroscopic parameters and the warp degree of galaxies.

  4. Effects of interaction on the properties of spiral galaxies. II. Isolated galaxies: The zero point

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Moles, M.

    1999-04-01

    We analyse the properties of a sample of 22 bright isolated spiral galaxies on the basis of Johnson B,V,I images and optical rotation curves. The fraction of early morphological types in our sample of isolated galaxies (or in other samples of non-interacting spiral galaxies) appears to be smaller than in samples including interacting systems. The overall morphological aspect is regular and symmetric, but all the galaxies present non-axisymmetric components in the form of bars or rings. We find that the color indices become bluer towards the outer parts and that their central values are well correlated with the total colors. The properties of the bulges span a larger range than those of the disks, that thus are more alike between them. None of the galaxies shows a truncated, type II disk profile. It is found that the relation between surface brightness and size for the bulges, the Kormendy relation, is tighter when only isolated galaxies are considered. We find a similar relation for the disk parameters with an unprecedented low scatter. A Principal Component Analysis of the measured parameters shows that 2 eigenvectors suffice to explain more than 95 % of the total variance. These are, as found for other samples including spiral galaxies in different environmental situations, a scale parameter given by the mass or, equivalently, the luminosity or the size; and a form parameter given by the bulge to disk luminosity ratio, B/D, or, equivalently, by the gradient of the solid-body rotation region of the rotation curve, the G-parameter. We report here a tight correlation between G and B/D for our sample of isolated spirals that could be used as a new distance indicator. Based on data obtained at the 1.5m telescope of the Estacion de Observacion de Calar Alto, Instituto Geografico Nacional, which is jointly operated by the Instituto Geografico Nacional and the Consejo Superior de Investigaciones Cientificas through the Instituto de Astrofisica de Andalucia

  5. Velocity dispersions in the bulges of spiral and S0 galaxies. II Further observations and a simple three-component model for spiral galaxies

    NASA Astrophysics Data System (ADS)

    Whitmore, B. C.; Kirshner, R. P.

    1981-11-01

    We have obtained velocity dispersions for 24 galaxies in the Virgo cluster to supplement our earlier results. A 2000 channel intensified Reticon scanner has again been used on the 1.3 m telescope of McGraw-Hill Observatory, and a Fourier quotient technique has been employed to yield dispersions. We have confirmed our earlier result that spiral bulges exhibit a relation between total luminosity and velocity dispersion with the form L ∝ σ4, but with velocity dispersions that are 17 ± 8% smaller than elliptical galaxies at the same absolute magnitude. However, possible systematic errors may still affect the reality of this gap. The scatter in the L ∝ σ4 relationship is substantially larger for the spiral bulges than for the elliptical galaxies. This larger scatter probably indicates that spiral bulges comprise a more heterogeneous sample than do elliptical galaxies. We also find that the bulge components of SO galaxies follow a L ∝ σ4 relation with no gap with the ellipticals. The similarity in this relation for the spheroidal components of spiral, SO, and elliptical galaxies indicates that the systems are dynamically similar. We have compared our velocity dispersions with rotational velocities determined from neutral hydrogen widths. For a totally bulge dominated spiral the ratio of the asymptotic rotational velocity to the velocity dispersion is about 1.4. This suggests that the mass responsible for producing the flat rotation curves (presumably the "halo") resides in a spheroidal component rather than in the disk. Our study also substantiates our earlier result that the massive halo is not merely an extension of the bulge, but is a separate dynamical component for most of our galaxies. A simple three-component model has been constructed to aid in the interpretation of this data. These models provide an independent indication of the existence of massive halos in spiral galaxies.

  6. GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

    SciTech Connect

    Lee, Myung Gyoon; Jang, In Sung E-mail: isjang@astro.snu.ac.kr

    2016-03-01

    We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 10{sup 5} M{sub ⊙}. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag. We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M{sub I} (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H{sub 0} = 77.9 ± 3.6 km s{sup −1} Mpc{sup −1}. We estimate the GC specific frequency of NGC 4921 to be S{sub N} = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.

  7. The luminosity function of star clusters in 20 star-forming galaxies based on Hubble legacy archive photometry

    SciTech Connect

    Whitmore, Bradley C.; Bowers, Ariel S.; Lindsay, Kevin; Ansari, Asna; Evans, Jessica; Chandar, Rupali; Larsen, Soeren

    2014-04-01

    Luminosity functions (LFs) have been determined for star cluster populations in 20 nearby (4-30 Mpc), star-forming galaxies based on Advanced Camera for Surveys source lists generated by the Hubble Legacy Archive (HLA). These cluster catalogs provide one of the largest sets of uniform, automatically generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster LF can be approximated by a power law, dN/dL∝L {sup α}, with an average value for α of –2.37 and rms scatter = 0.18 when using the F814W ('I') band. A comparison of fitting results based on methods that use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum likelihood) method to give slightly more negative values of α for galaxies with steeper LFs. We find that galaxies with high rates of star formation (or equivalently, with the brightest or largest numbers of clusters) have a slight tendency to have shallower values of α. In particular, the Antennae galaxy (NGC 4038/39), a merging system with a relatively high star formation rate (SFR), has the second flattest LF in the sample. A tentative correlation may also be present between Hubble type and values of α, in the sense that later type galaxies (i.e., Sd and Sm) appear to have flatter LFs. Hence, while there do appear to be some weak correlations, the relative similarity in the values of α for a large number of star-forming galaxies suggests that, to first order, the LFs are fairly universal. We examine the bright end of the LFs and find evidence for a downturn, although it only pertains to about 1% of the clusters. Our uniform database results in a small scatter (≈0.4 to 0.5 mag) in the correlation between the magnitude of the brightest cluster (M {sub brightest}) and log of the number

  8. Observational Manifestation of Chaos in Grand Design Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Fridman, Alexei M.; Sagdeev, Roald Z.; Khoruzii, Oleg V.; et al.

    To study dynamic properties of the gaseous disk of the grand design spiral galaxy NGC 3631 we calculate the Lyapunov characteristic numbers (LCN) for different families of streamlines in the disk. For the trajectories near separatrices of the giant vortices and near saddle points presenting in the velocity field, the LCN turned out to be positive. The result is insensitive to the method of the calculation. Both methods -- using two trajectories and based on linearized equations -- give the identical results. The values of the LCN in the gaseous disk of NGC 3631 are independent on the Riemannian metric used for the calculations in agreement with the classical mathematical theorem. The spectra of the 'short-time' LCN (stretching numbers) evaluated for the same trajectories turned out to be non-invariant. We confirmed this result obtained for the real galactic disk on classical model examples.

  9. Infrared observations of the spiral galaxy NGC 891

    NASA Astrophysics Data System (ADS)

    Whaley, Cynthia

    2007-08-01

    This thesis is a detailed, multi-waveband study of the inner 14 kpc of the famous spiral galaxy, NCG 891. The primary data have come from the Infrared Space Observatory's Camera. These data are images of the galaxy in 9 different mid-infrared wavebands. We have supported these data with archived data from the Spitzer Infrared Array Camera in 4 similar wavebands. Surface brightness contour maps of the galaxy were created and examined to determine where the mid-infrared emitters are located with respect to the galactic plane. We have determined that the main mid-infrared emission, due to warm dust and PAHs, lies in a thin disk of width 700 - 800 pc, but has faint emission that reaches up to about 2.3 kpc into the halo. The infrared spectral energy distribution (SED) for four environments in NGC 891 were created from the above mentioned wavebands as well as measurements from Spitzer's Multiband Imaging Photometer (3 Far-Infrared wavebands), the Two Micron All Sky Survey J, H, and K near-infrared wavebands, and the Sub- millimeter Common User Bolometer Array 450 and 850 mm bands. These spectra were fit with a SED model created by Frederic Galliano, and the physical properties of these environments were computed. The maps and SED show that while there is a relatively large amount of dust in NGC 891's halo, there is a depletion of PAHs beyond 2.3 kpc from the mid-plane. This is only the fourth galaxy to date that has PAH emission discovered in the halo, and it is the first in which the SED has been modeled for the halo.

  10. The nearby spiral density-wave structure of the Galaxy

    NASA Astrophysics Data System (ADS)

    Griv, Evgeny; Jiang, Ing-Guey; Hou, Li-Gang

    2017-07-01

    Accurate measurements of distances and line-of-sight velocities of 19291 intermediate-old giant stars in the near-infrared with typical uncertainties in the distances and velocities of 5 per cent and 0.1 km s-1 have recently been carried out to examine the Galactic disc with the APOGEE survey. In the framework of the Lin-Shu density-wave proposal for the galactic spiral structure, we use the APOGEE-RC DR13 data to investigate coherent non-axisymmetric flows within a few kiloparsecs from the Sun which are superimposed on a circular motion in the disc. Systematic wave-like departures of velocities from circular motion for stars are really detected. These systematic non-circular velocities are used to recover the parameters of the spiral arm segments of density waves of the Galaxy in the solar vicinity. The results of the work can be tested with the large amount of data from the Gaia satellite mission in the near future.

  11. Analyzing Non-circular Motions in Spiral Galaxies Through 3D Spectroscopy

    NASA Astrophysics Data System (ADS)

    Fuentes-Carrera, I.; Rosado, M.; Amram, P.

    3D spectroscopic techniques allow the assessment of different types of motions in extended objects. In the case of spiral galaxies, thes type of techniques allow us to trace not only the (almost) circular motion of the ionized gas, but also the motions arising from the presence of structure such as bars, spiral arms and tidal features. We present an analysis of non-circular motions in spiral galaxies in interacting pairs using scanning Fabry-Perot interferometry of emission lines. We show how this analysis can be helpful to differentiate circular from non-circular motions in the kinematical analysis of this type of galaxies.

  12. Galactic Winds and the X-ray Luminous Bulges of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Wilcots, Eric M.; Kaczmarek, J.

    2010-01-01

    Galactic winds are typically associated with galaxies that host AGN or are undergoing vigorous star formation. The discovery of the overpressurized hot gas in the bulge of NGC 3631 inspired the investigation of several more normal, quiescent spiral galaxies_all with an X-ray luminous bulge. The sample was studied with the WIYN 3.5m. We present the results of an integral field unit study of the kinematics of ionized and neutral gas in the bulges of spiral galaxies and discuss the frequency of galactic winds amongst "normal” early-type spirals.

  13. An Infrared Portrait of the Barred Spiral Galaxy Messier 83

    NASA Astrophysics Data System (ADS)

    2001-11-01

    Messier 83 (M83) is a relatively nearby spiral galaxy with a pronounced bar-like structure. It is located in the southern constellation Hydra (The Water-Snake) and is also known as NGC 5236 ; the distance is approximately 12 million light-years. Images of M83 obtained in visible light - like the VLT photo published exactly two years ago ( ESO PR 18/99 ) - show clumpy, well-defined spiral arms that are rich in young stars while the disk reveals a complex system of intricate dust lanes. This galaxy is known to be a site of vigorous star formation and no less than six supernovae (exploding stars) have been observed in M83 during the past century. It is a fairly symmetrical object and possesses no nearby companions. Gas dynamics and galaxy bars Investigations of gas motions in the nucleus and in the main disk play a key role in understanding the structure and evolution of barred spiral galaxies like M83. Inflow of gas towards the center caused by a mass distribution that is not circularly symmetric is often invoked to explain certain observed phenomena, e.g., the feeding of Active Galactic Nuclei (AGNs, see also the report about recent observations in three such galaxies in ESO PR 18/01 ), and the fueling of bursts of star formation in the nuclear region. Some astronomers think that this process may cause a change of a galaxy's (morphological) type, for instance from barred to normal spiral galaxy. It has also been suggested that the development of spiral structures in galactic disks may be due to central stellar bars. Interstellar gas that is subject to periodical perturbations by the non-circularly symmetrical gravitational field in a barred system will develop a "density wave" that attracts neighbouring stars and gas. The local density increases and once a certain ("critical") value is reached, star formation is "ignited" in this area. The mass distribution In order to better understand phenomena like these, it is essential to know in detail the distribution of

  14. The Structure & Stellar Populations of Nuclear Star Clusters in Late-Type Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Carson, Daniel James

    Luminous, compact stellar systems known as nuclear clusters (NCs) are commonly found in the centers of galaxies across the entire Hubble sequence. I present an analysis of the structure and stellar populations of a sample of ten of the nearest and brightest NCs residing in late-type spiral galaxies, using images from Hubble Space Telescope Wide Field Camera 3 in seven bands that span the near-ultraviolet to the near-infrared in wavelength. The intrinsic shapes and sizes of the NCs, disentangled from the effects of point spread function (PSF) blurring, were measured using GALFIT. We find evidence for radial color gradients within the NCs, as well as young disk structures aligned with the host galaxy disk. In color-color diagrams spanning the near-UV through the near-IR, NCs tend to lie far from single-burst evolutionary tracks, indicating the presence of multi-age populations. I developed a Monte Carlo code to fit linear combinations of simple stellar population models to the observed spectral energy distribution (SED) of each NC and assess the uncertainties in the fit parameters. Tests on a catalog of mock SEDs demonstrate that our method gives unbiased mass age, and reddening estimates for populations with U - V colors redder than ˜ -2 mag. Stellar masses computed via SED fitting are in good agreement with previous dynamical studies. The NCs are generally dominated by an old (> 1 Gyr) population component, but are best described by temporally extended star formation histories. On average, populations with ages < 100 Myr contribute 1.8% of the total stellar mass and 10.4% of the total B-band luminosity. From spatially resolved stellar population modeling, we compute maps of stellar density and age, which reveal radial age gradients. Multi-Gaussian Expansion models of NC stellar surface density, which will be used in future dynamical studies, are presented. We report an effective surface density of 6.7 x 105 solar masses per square parsec in IC 342, the densest

  15. STScI-PRC95-30 HUBBLE SEES DETAILED NEW STRUCTURES IN THREE RADIO GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    These Hubble Space Telescope images, combined with radio maps produced by the Very Large Array Radio Interferometer (blue contour lines), show surprisingly varied and intricate structures of gas and stars that suggest the mechanisms powering radio galaxies are more complex than thought previously. The bizarre, never before seen detail may be a combination of light from massive star forming regions, small satellite dwarf galaxies, and bow shocks caused by jets of hot gas blasted out of the galaxies' cores by suspected black holes. [LEFT] - 3C265. Hubble resolves numerous bright star clusters or dwarf 'satellite' galaxies surrounding a bright central compact structure. The line corresponds to the axis of the galaxy's radio emissions, which unlike other radio galaxies, is in a different direction from the optical region. The star forming regions might result from a collision between galaxies. The jet that produces the radio emissions might have further intensified star formation. [CENTER] - 3C324. A number of small interacting components are distributed roughly along the radio axis in this source. Comparison of the Hubble image with that from the United Kingdom Infrared Telescope suggests that the central regions of this galaxy are obscured by a large dust lane. [RIGHT] - 3C368. One of the best studied radio galaxies, this image is composed of a very smooth cigar-shaped emission region closely aligned with the radio axis, upon which is superimposed a string of bright knots that might be stars or dust. This suggests that a jet of high speed gas, presumably ejected from a black hole at the core of the galaxy, might be triggering star formation along its path. Credit: M. Longair (Cambridge University, England), NASA, and NRAO

  16. UIT Ultraviolet Surface Photometry of the Spiral Galaxy M74

    NASA Astrophysics Data System (ADS)

    Cornett, R. H.; Greason, M. R.; Offenberg, J. D.; Bohlin, R. C.; Cheng, K. P.; O'Connell, R. W.; Roberts, M. R.; Smith, A. M.; Smith, E. P.; Angione, R. J.; Talbert, F. D.; Stecher, T. P.

    1993-05-01

    UV photometry from Ultraviolet Imaging Telescope (UIT) images at 1520 Angstroms (magnitudes mbone) and 2490 Angstroms (maone) of the spiral galaxy M74 (NGC628) is compared with ha, R, V, and B surface photometry and models. M74's surface brightness profiles have central peaks with exponential falloffs; the profiles' exponential scale lengths increase with decreasing continuum wavelength. The slope of the continuum-subtracted ha profile is between those of FUV and NUV profiles, consistent with related origins of ha and UV emission in extreme Population I material. M74's color profiles have small gradients, all becoming bluer with increasing radius. The UIT color (mbone-maone) averages near 0.0, the color of an A0 star, over the central 20 arcsec radius, and slopes from ~ -0.2 to ~ -0.4 from 20 to 200 arcsec. Spiral arms dominate surface photometry colors; interarm regions are slightly redder. In the UV, M74's nuclear region resembles disk/spiral arm material in color and morphology, unlike M81. (mbone-maone) colors and models of M74's central region clearly demonstrate that there are no O or B stars in the central 10 arcsec. M74's (mbone-maone) profile is similar to M33's but is ~ 0.5 mag redder. M74 is ~ 0.4 mag bluer than M81 in its outer disk. We investigate explanations for both the color profiles and the differences among the galaxies. M74's maone-V and mbone-V color profiles cannot be explained by a disk of uniform color behind a screen of dust with a known reddening function, distributed like the neutral gas with a fixed gas-to-dust ratio. Known abundance variations could produce the observed color gradient in M74; however, evolutionary cluster models show that sensible time parameters, including star formation start time and exponential decay rate, also produce the observed colors of M74, M33, and M81.

  17. Near-infrared surface photometry and morphology in virgo cluster spiral galaxy nuclear regions

    NASA Astrophysics Data System (ADS)

    Rauscher, Bernard J.

    1995-04-01

    This paper presents very high spatial resolution (seeing 0.75 arcsec FWHM) K band surface photometry of 15 Virgo cluster spiral galaxy nuclear regions (radii less then 1 kpc). It presents B and I CCD images of 13 of these galaxies. The goals of the study were: (1) to begin to establish a K band baseline of normal spiral galaxy nuclear regions against which peculiar galaxies may be compared, (2) to provide better contsraints on N-body models, and (3) to complement near-infrared studies of large scale structure in spiral galaxies with very high resolution imaging of the important nuclear regions. The principle findings are (1) between 1/4 and 1/3 of these nuclear regions show K band evidence of traxiality, (2) approximately 1/2 of these galaxies have axisymmetric nuclear regions, and (3) NGC 4321 has a bar that is not detectable in the optical images.

  18. HOST GALAXY PROPERTIES AND HUBBLE RESIDUALS OF TYPE Ia SUPERNOVAE FROM THE NEARBY SUPERNOVA FACTORY

    SciTech Connect

    Childress, M.; Aldering, G.; Aragon, C.; Bailey, S.; Fakhouri, H. K.; Hsiao, E. Y.; Kim, A. G.; Loken, S.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Guy, J.; Baltay, C.; Buton, C.; Kerschhaggl, M.; Kowalski, M.; Chotard, N.; Copin, Y.; Gangler, E. [Universite de Lyon, F-69622, Lyon; Universite de Lyon 1, Villeurbanne; CNRS and others

    2013-06-20

    We examine the relationship between Type Ia supernova (SN Ia) Hubble residuals and the properties of their host galaxies using a sample of 115 SNe Ia from the Nearby Supernova Factory. We use host galaxy stellar masses and specific star formation rates fitted from photometry for all hosts, as well as gas-phase metallicities for a subset of 69 star-forming (non-active galactic nucleus) hosts, to show that the SN Ia Hubble residuals correlate with each of these host properties. With these data we find new evidence for a correlation between SN Ia intrinsic color and host metallicity. When we combine our data with those of other published SN Ia surveys, we find the difference between mean SN Ia brightnesses in low- and high-mass hosts is 0.077 {+-} 0.014 mag. When viewed in narrow (0.2 dex) bins of host stellar mass, the data reveal apparent plateaus of Hubble residuals at high and low host masses with a rapid transition over a short mass range (9.8 {<=} log (M{sub *}/M{sub Sun }) {<=} 10.4). Although metallicity has been a favored interpretation for the origin of the Hubble residual trend with host mass, we illustrate how dust in star-forming galaxies and mean SN Ia progenitor age both evolve along the galaxy mass sequence, thereby presenting equally viable explanations for some or all of the observed SN Ia host bias.

  19. Disk mass densities in edge-on spiral galaxies

    NASA Technical Reports Server (NTRS)

    Rupen, Michael P.

    1990-01-01

    Very Large Array (VLA) observations of the neutral hydrogen (HI) gas in two nearby edge-on spirals (NGC 4565 and NGC 891) successfully resolve the thickness of the gas layers in both disks over a wide range in radii. The combination of B, C, and D array data produces a 4 arcsec (approx. 200 pc) beam and 21 km s(exp -1) velocity resolution, combined with sensitivity to structures as large as 18 arcmin (approx. 54 kpc). These observations directly constrain the mid-plane disk mass densities, under the assumption of an equilibrium between the thermal pressure of the gas and the gravitational attraction of the disk. The results of a preliminary analysis are given regarding the z-velocity dispersion of the gas, the mass-to-light ratio of the disk in NGC 4565, and the roles of atomic and molecular gases. The data also allow a detailed study of the HI in these galaxies; in general their brightness temperature distributions seem similar to that in the Milky Way. Both galaxies show asymmetric HI extensions beyond the optical disk. In NGC 4565 the extension is a surprisingly abrupt warp, which may bend back to parallel the galactic plane; the velocity structure implies the warp is continuous around the disk.

  20. A misbehaving spiral

    NASA Image and Video Library

    2016-01-29

    Despite its unassuming appearance, the edge-on spiral galaxy captured in the left half of this NASA/ESA Hubble Space Telescope image is actually quite remarkable. Located about one billion light-years away in the constellation of Eridanus, this striking galaxy — known as LO95 0313-192 — has a spiral shape similar to that of the Milky Way. It has a large central bulge, and arms speckled with brightly glowing gas mottled by thick lanes of dark dust. Its companion, sitting pretty in the right of the frame, is known rather unpoetically as [LOY2001] J031549.8-190623. Jets, outbursts of superheated gas moving at close to the speed of light, have long been associated with the cores of giant elliptical galaxies, and galaxies in the process of merging. However, in an unexpected discovery, astronomers found LO95 0313-192 to have intense radio jets spewing out from its centre! The galaxy appears to have two more regions that are also strongly emitting in the radio part of the spectrum, making it even rarer still. The discovery of these giant jets in 2003 — not visible in this image, but indicated in this earlier Hubble composite — has been followed by the unearthing of a further three spiral galaxies containing radio-emitting jets in recent years. This growing class of unusual spirals continues to raise significant questions about how jets are produced within galaxies, and how they are thrown out into the cosmos.

  1. GLOBULAR CLUSTER SYSTEMS OF SPIRAL AND S0 GALAXIES: RESULTS FROM WIYN IMAGING OF NGC 1023, NGC 1055, NGC 7332, AND NGC 7339

    SciTech Connect

    Young, Michael D.; Dowell, Jessica L.; Rhode, Katherine L. E-mail: jlwind@astro.indiana.edu

    2012-10-01

    We present results from a study of the globular cluster (GC) systems of four spiral and S0 galaxies imaged as part of an ongoing wide-field survey of the GC systems of giant galaxies. The target galaxies-the SB0 galaxy NGC 1023, the SBb galaxy NGC 1055, and an isolated pair comprised of the Sbc galaxy NGC 7339 and the S0 galaxy NGC 7332-were observed in BVR filters with the WIYN 3.5 m telescope and Minimosaic camera. For two of the galaxies, we combined the WIYN imaging with previously published data from the Hubble Space Telescope and the Keck Observatory to help characterize the GC distribution in the central few kiloparsecs. We determine the radial distribution (surface density of GCs versus projected radius) of each galaxy's GC system and use it to calculate the total number of GCs (N{sub GC}). We find N{sub GC} = 490 {+-} 30, 210 {+-} 40, 175 {+-} 15, and 75 {+-} 10 for NGC 1023, NGC 1055, NGC 7332, and NGC 7339, respectively. We also calculate the GC specific frequency (N{sub GC} normalized by host galaxy luminosity or mass) and find values typical of those of the other spiral and E/S0 galaxies in the survey. The two lenticular galaxies have sufficient numbers of GC candidates for us to perform statistical tests for bimodality in the GC color distributions. We find evidence at a high confidence level (>95%) for two populations in the B - R distribution of the GC system of NGC 1023. We find weaker evidence for bimodality (>81% confidence) in the GC color distribution of NGC 7332. Finally, we identify eight GC candidates that may be associated with the Magellanic dwarf galaxy NGC 1023A, which is a satellite of NGC 1023.

  2. Gas and stellar spiral arms and their offsets in the grand-design spiral galaxy M51

    NASA Astrophysics Data System (ADS)

    Egusa, Fumi; Mentuch Cooper, Erin; Koda, Jin; Baba, Junichi

    2017-02-01

    Theoretical studies on the response of interstellar gas to a gravitational potential disc with a quasi-stationary spiral arm pattern suggest that the gas experiences a sudden compression due to standing shock waves at spiral arms. This mechanism, called a galactic shock wave, predicts that gas spiral arms move from downstream to upstream of stellar arms with increasing radius inside a corotation radius. In order to investigate if this mechanism is at work in the grand-design spiral galaxy M51, we have measured azimuthal offsets between the peaks of stellar mass and gas mass distributions in its two spiral arms. The stellar mass distribution is created by the spatially resolved spectral energy distribution fitting to optical and near-infrared images, while the gas mass distribution is obtained by high-resolution CO and H I data. For the inner region (r ≤ 150 arcsec), we find that one arm is consistent with the galactic shock while the other is not. For the outer region, results are less certain due to the narrower range of offset values, the weakness of stellar arms, and the smaller number of successful offset measurements. The results suggest that the nature of two inner spiral arms is different, which is likely due to an interaction with the companion galaxy.

  3. Spectrophotometry of H II regions in the spiral galaxy M101

    PubMed Central

    Sedwick, K. E.; Aller, L. H.

    1981-01-01

    Spectral line intensity data are presented for ionized hydrogen regions in the giant spiral galaxy M101. The influence of interstellar extinction is assessed and electron temperatures of the gas clouds are derived. Images PMID:16592999

  4. A radio continuum survey of edge-on spiral galaxies at 90 cm

    NASA Technical Reports Server (NTRS)

    Heikkila, B.; Webber, W. R.; Burns, Jack O.; Walterbos, R. A. M.; Duric, N.

    1993-01-01

    Accurate spectral indices of the radio emission from both the thin disk and thick disk or halo components are critical to understanding the propagation mechanisms of electrons within spiral galaxies. The spectral indices give information of relative importance of diffusion and synchrotron energy loss in the propagation of electrons in the disk. Our goal of this survey is to locate a larger sample of spiral galaxies that exhibit halo phenomena so that a statistical analysis will be possible.

  5. Vertical motions in the gaseous disk of the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Koruzhii, O. V.; Zasov, A. V.; Sil'chenko, O. K.; Moiseev, A. V.; Burlak, A. N.; Afanas'ev, V. L.; Dodonov, S. N.; Knapen, J.

    1998-11-01

    The velocity field of the nearly face-on galaxy NGC 3631 is derived from observations in the Hα line on the 6-m telescope of the Special Astrophysical Observatory. These optical data are compared with radio observations of this galaxy (Knapen 1997). It is argued that the two-armed spiral structure of NGC 3631 has a wave nature, and that the observed vertical gas motions represent motions in a spiral density wave.

  6. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2009-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z greater than 6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z greater than 10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (less than 50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth-Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems, and discuss recent progress in constructing the observatory.

  7. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2007-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts 2x3, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>lO, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  8. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2007-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z>6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  9. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan F.; Barbier, L. M.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Hullinger, D. D.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Sakamoto, T.

    2006-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts 2-6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 27 microns. In addition to JWST s ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  10. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2007-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z>6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  11. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2007-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts 2x3, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>lO, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (<50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  12. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan F.; Barbier, L. M.; Barthelmy, S. D.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Hullinger, D. D.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; hide

    2006-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts 2-6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z>10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth- Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 27 microns. In addition to JWST s ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems.

  13. Studying Galaxy Formation with the Hubble, Spitzer and James Webb Space Telescopes

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2009-01-01

    The deepest optical to infrared observations of the universe include the Hubble Deep Fields, the Great Observatories Origins Deep Survey and the recent Hubble Ultra-Deep Field. Galaxies are seen in these surveys at redshifts z greater than 6, less than 1 Gyr after the Big Bang, at the end of a period when light from the galaxies has reionized Hydrogen in the inter-galactic medium. These observations, combined with theoretical understanding, indicate that the first stars and galaxies formed at z greater than 10, beyond the reach of the Hubble and Spitzer Space Telescopes. To observe the first galaxies, NASA is planning the James Webb Space Telescope (JWST), a large (6.5m), cold (less than 50K), infrared-optimized observatory to be launched early in the next decade into orbit around the second Earth-Sun Lagrange point. JWST will have four instruments: The Near-Infrared Camera, the Near-Infrared multi-object Spectrograph, and the Tunable Filter Imager will cover the wavelength range 0.6 to 5 microns, while the Mid-Infrared Instrument will do both imaging and spectroscopy from 5 to 28.5 microns. In addition to JWST's ability to study the formation and evolution of galaxies, I will also briefly review its expected contributions to studies of the formation of stars and planetary systems, and discuss recent progress in constructing the observatory.

  14. Spiral Galaxy Formation, Shape, Rotation and Evolution: A Perspective withOUT Mysterious Dark Matter

    NASA Astrophysics Data System (ADS)

    Gallo, C. F.; Feng, James Q.

    2013-04-01

    Various models for Spiral Galaxies are compared to arrive at the following viewpoint. (1)Peratt theoretically displays the formation and evolution of galaxies from hot plasma with a combination of gravity and electromagntic plasma effects, particularly circulating currents. The sequence proceeds from Elliptical to Irregular to stable Spiral Disc Galaxies. The spirals are initiated by radial EM plasma jets oriented around magnetic fields. (2)DeSouza observes/analyzes young spiral galaxies in the process of forming their spiral shapes. He observes radial Jets initiating from the central Bulge and evolving into full trailing spirals in agreement with Peratt's EM plasma simulations. (3) Feng and Gallo have successfully analyzed galactic rotation data with Newtonian gravity/dynamics withOUT Mysterious Dark Matter. Our model represents mature spiral disk galaxies whose behavior is dominated by gravity since the plasma has mostly condensed into stars at this late stage. This situation in similar to our gravity dominated Solar System. (4) All three models are based on known verified physics withOUT Mysterious Dark Matter.

  15. The Luminosity Function of Star Clusters in 20 Star-forming Galaxies Based on Hubble Legacy Archive Photometry

    NASA Astrophysics Data System (ADS)

    Whitmore, Bradley C.; Chandar, Rupali; Bowers, Ariel S.; Larsen, Soeren; Lindsay, Kevin; Ansari, Asna; Evans, Jessica

    2014-04-01

    brighter than MI = -9 (log N). We also examine the magnitude of the brightest cluster versus log SFR for a sample including both dwarf galaxies and ULIRGs. This shows that the correlation extends over roughly six orders of magnitude but with scatter that is larger than for our spiral sample, probably because of the high levels of extinction in many of the LIRGs. Based on observations 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 NAS5-26555. Also based on data obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). Support for Program number 11781 was provided by NASA through a grant from the Space Telescope Science Institute.

  16. SpArcFiRe: Scalable automated detection of spiral galaxy arm segments

    SciTech Connect

    Davis, Darren R.; Hayes, Wayne B. E-mail: whayes@uci.edu

    2014-08-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy (possibly masking nearby stars and other objects if necessary in order to isolate the galaxy itself) and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment, allowing image analysis on a per-arm-segment basis. We also perform a least-squares fit of a logarithmic spiral arc to the pixels in that segment, giving per-arc parameters, such as the pitch angle, arm segment length, location, etc. The algorithm takes about one minute per galaxies, and can easily be scaled using parallelism. We have run it on all ∼644,000 Sloan objects that are larger than 40 pixels across and classified as 'galaxies'. We find a very good correlation between our quantitative description of a spiral structure and the qualitative description provided by Galaxy Zoo humans. Our objective, quantitative measures of structure demonstrate the difficulty in defining exactly what constitutes a spiral 'arm', leading us to prefer the term 'arm segment'. We find that pitch angle often varies significantly segment-to-segment in a single spiral galaxy, making it difficult to define the pitch angle for a single galaxy. We demonstrate how our new database of arm segments can be queried to find galaxies satisfying specific quantitative visual criteria. For example, even though our code does not explicitly find rings, a good surrogate is to look for galaxies having one long, low-pitch-angle arm—which is how our code views ring galaxies. SpArcFiRe is available at http://sparcfire.ics.uci.edu.

  17. SpArcFiRe: Scalable Automated Detection of Spiral Galaxy Arm Segments

    NASA Astrophysics Data System (ADS)

    Davis, Darren R.; Hayes, Wayne B.

    2014-08-01

    Given an approximately centered image of a spiral galaxy, we describe an entirely automated method that finds, centers, and sizes the galaxy (possibly masking nearby stars and other objects if necessary in order to isolate the galaxy itself) and then automatically extracts structural information about the spiral arms. For each arm segment found, we list the pixels in that segment, allowing image analysis on a per-arm-segment basis. We also perform a least-squares fit of a logarithmic spiral arc to the pixels in that segment, giving per-arc parameters, such as the pitch angle, arm segment length, location, etc. The algorithm takes about one minute per galaxies, and can easily be scaled using parallelism. We have run it on all ~644,000 Sloan objects that are larger than 40 pixels across and classified as "galaxies." We find a very good correlation between our quantitative description of a spiral structure and the qualitative description provided by Galaxy Zoo humans. Our objective, quantitative measures of structure demonstrate the difficulty in defining exactly what constitutes a spiral "arm," leading us to prefer the term "arm segment." We find that pitch angle often varies significantly segment-to-segment in a single spiral galaxy, making it difficult to define the pitch angle for a single galaxy. We demonstrate how our new database of arm segments can be queried to find galaxies satisfying specific quantitative visual criteria. For example, even though our code does not explicitly find rings, a good surrogate is to look for galaxies having one long, low-pitch-angle arm—which is how our code views ring galaxies. SpArcFiRe is available at http://sparcfire.ics.uci.edu.

  18. Ultraviolet Galaxy Counts From STIS Observations of The Hubble Deep Fields

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Brown, T. M.; Ferguson, H. C.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    We present galaxy counts in the near and far ultraviolet (NUV and FUV) obtained from Space Telescope Imaging Spectrograph (STIS) observations of portions of the Hubble Deep Field North, (HDFN), the Hubble Deep Field South, (HDFS) and a parallel field near the HDFN. All three fields have deep (AB>29) optical imaging, and we determine magnitudes by taking the ultraviolet flux detected within the limiting optical isophote. An analysis of the UV-optical colors of detected objects, combined with a visual inspection of the UV images, indicates that there are no detectable objects in the UV images which are not also detected in the optical. We measure the detection area and completeness as a function of magnitude by taking the size-magnitude distribution of galaxies in the entire HDFN WFPC2 V+I image, applying the measured UV-optical colors from the detected galaxies, and determining the total area over which each galaxy would have been detected in the UV images. The average area for the simulated galaxies in each UV magnitude bin, (including galaxies which would not be detected at all), provides the effective area and completeness for the bin. We test this procedure with Monte Carlo simulations. The galaxy counts reach to AB=29 in both the NUV and FUV; 1 magnitude fainter than the HDF F30OW counts, and 7 magnitudes fainter than balloon-based counts. We compare our measured counts to various models.

  19. Ultraviolet Galaxy Counts From STIS Observations of The Hubble Deep Fields

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Brown, T. M.; Ferguson, H. C.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    We present galaxy counts in the near and far ultraviolet (NUV and FUV) obtained from Space Telescope Imaging Spectrograph (STIS) observations of portions of the Hubble Deep Field North, (HDFN), the Hubble Deep Field South, (HDFS) and a parallel field near the HDFN. All three fields have deep (AB>29) optical imaging, and we determine magnitudes by taking the ultraviolet flux detected within the limiting optical isophote. An analysis of the UV-optical colors of detected objects, combined with a visual inspection of the UV images, indicates that there are no detectable objects in the UV images which are not also detected in the optical. We measure the detection area and completeness as a function of magnitude by taking the size-magnitude distribution of galaxies in the entire HDFN WFPC2 V+I image, applying the measured UV-optical colors from the detected galaxies, and determining the total area over which each galaxy would have been detected in the UV images. The average area for the simulated galaxies in each UV magnitude bin, (including galaxies which would not be detected at all), provides the effective area and completeness for the bin. We test this procedure with Monte Carlo simulations. The galaxy counts reach to AB=29 in both the NUV and FUV; 1 magnitude fainter than the HDF F30OW counts, and 7 magnitudes fainter than balloon-based counts. We compare our measured counts to various models.

  20. A MULTIWAVELENGTH STUDY OF TADPOLE GALAXIES IN THE HUBBLE ULTRA DEEP FIELD

    SciTech Connect

    Straughn, Amber N.; Eufrasio, Rafael T.; Gardner, Jonathan P.; Voyer, Elysse N.; Mello, Duilia de; Soto, Emmaris; Petty, Sara; Kassin, Susan; Ravindranath, Swara

    2015-12-01

    Multiwavelength data are essential in order to provide a complete picture of galaxy evolution and to inform studies of galaxies’ morphological properties across cosmic time. Here we present the results of a multiwavelength investigation of the morphologies of “tadpole” galaxies at intermediate redshift (0.314 < z < 3.175) in the Hubble Ultra Deep Field. These galaxies were previously selected from deep Hubble Space Telescope (HST) F775W data based on their distinct asymmetric knot-plus-tail morphologies. Here we use deep Wide Field Camera 3 near-infrared imaging in addition to the HST optical data in order to study the rest-frame UV/optical morphologies of these galaxies across the redshift range 0.3 < z < 3.2. This study reveals that the majority of these galaxies do retain their general asymmetric morphology in the rest-frame optical over this redshift range, if not the distinct “tadpole” shape. The average stellar mass of tadpole galaxies is lower than that of field galaxies, with the effect being slightly greater at higher redshift within the errors. Estimated from spectral energy distribution fits, the average age of tadpole galaxies is younger than that of field galaxies in the lower-redshift bin, and the average metallicity is lower (whereas the specific star formation rate for tadpoles is roughly the same as field galaxies across the redshift range probed here). These average effects combined support the conclusion that this subset of galaxies is in an active phase of assembly, either late-stage merging or cold gas accretion causing localized clumpy star formation.

  1. Supermassive Black Hole Mass and Spiral Galaxy Pitch Angle at Intermediate to High Redshift

    NASA Astrophysics Data System (ADS)

    Hughes, John A.; Barrows, R. S.; Berrier, J. C.; Davis, B. L.; Kennefick, D.; Kennefick, J. D.; Lacy, C. H. S.; Seigar, M. S.; Shields, D. W.; Zoldak, K. A.

    2012-01-01

    A possible correlation between spiral galaxy pitch angle (P) and the mass of the central supermassive black hole (SMBH) of the galaxy (M) was reported (Seigar et al. 2008) from a sample of 27 nearby galaxies. Here we investigate the extension of this result to intermediate and high redshifts. We have selected AGN showing spiral structure in their host galaxies from the GOODS fields and from a sample of AGN with reverberation mapping SMBH mass estimates. After careful measure of the pitch angle of these galaxies, we compare the mass found from the M-P relation to that reported from reverberation mapping or estimated from their MgII profiles. By extending the sample to higher redshift, we demonstrate how the M-P relationship can be used to estimate the mass of SMBHs in the center of galaxies with imaging data alone, a useful tool in the study of galaxy evolution.

  2. The Hubble Space Telescope Survey of BL Lacertae Objects. IV. Infrared Imaging of Host Galaxies

    NASA Astrophysics Data System (ADS)

    Scarpa, Riccardo; Urry, C. Megan; Padovani, Paolo; Calzetti, Daniela; O'Dowd, Matthew

    2000-11-01

    The Hubble Space Telescope NICMOS Camera 2 was used for H-band imaging of 12 BL Lacertae objects taken from the larger sample observed with the WFPC2 in the R band by Urry and coworkers and Scarpa and coworkers. Ten of the 12 BL Lacs are clearly resolved, and the detected host galaxies are large, bright ellipticals with average absolute magnitude =-26.2+/-0.45 mag and effective radius =10+/-5 kpc. The rest-frame integrated color of the host galaxies is on average =2.3+/-0.3, consistent with the value for both radio galaxies and normal, nonactive elliptical galaxies and indicating that the dominant stellar population is old. The host galaxies tend to be bluer in their outer regions than in their cores, with average color gradient Δ(R-H)/Δlogr=-0.2 mag, again consistent with results for normal nonactive elliptical galaxies. The infrared Kormendy relation, derived for the first time for BL Lac host galaxies, is μe=3.8logre+14.8, fully in agreement with the relation for normal ellipticals. The close similarity between BL Lac host galaxies and normal ellipticals suggests that the active nucleus has surprisingly little effect on the host galaxy. This supports a picture in which all elliptical galaxies harbor black holes that can be actively accreting for some fraction of their lifetime.

  3. Galaxy Formation: Cold Dark Matter, Feedback, and the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Sommer-Larsen, Jesper; Götz, Martin; Portinari, Laura

    2003-10-01

    TreeSPH simulations of galaxy formation in a standard Λ cold dark matter cosmology, including star formation and the effects of energetic stellar feedback processes and of a metagalactic UV field, have been performed, resulting in a mix of realistic disk, lenticular, and elliptical galaxies at redshift z=0. The disk galaxies are deficient in angular momentum by only about a factor of 2 compared with observed disk galaxies for simulations with fairly strong starbursts in early, protogalactic clouds, leading to ``blow-away'' of the remaining gas in the clouds. In this respect the present scenario is hence doing almost as well as the warm dark matter (WDM) scenarios discussed by Sommer-Larsen & Dolgov. The surface density profiles of the stellar disks are approximately exponential, and those of the bulges range from exponential to r1/4, as observed. The bulge-to-disk ratios of the disk galaxies are consistent with observations, as are their integrated B-V colors, which have been calculated using stellar population synthesis techniques. Furthermore, the observed I-band Tully-Fisher relation can be matched, provided that the stellar mass-to-light ratio of disk galaxies is M/LI~0.8, similar to what was found by Sommer-Larsen & Dolgov from their WDM simulations and in fair agreement with several recent observational determinations of M/LI for disk galaxies. The elliptical and lenticular galaxies have approximately r1/4 stellar surface density profiles, are dominated by nondisklike kinematics, and are flattened as a result of nonisotropic stellar velocity distributions, again consistent with observations. Hot halo gas is predicted to cool out and be accreted onto the Galactic disk at a rate of 0.5-1 Msolar yr-1 at z=0, consistent with upper limits deduced from Far Ultraviolet Spectroscopic Explorer observations of O VI. We have analyzed in detail the formation history of two disk galaxies with circular speeds comparable to that of the Milky Way and find gas accretion

  4. A computer-generated galaxy model with long-lived two-armed spiral structure

    NASA Astrophysics Data System (ADS)

    Thomasson, Magnus; Elmegreen, Bruce G.; Donner, Karl Johan; Sundelius, Bjorn

    1990-06-01

    A long-lived two-armed spiral has been generated in an N-body computer simulation of a galaxy with a static bulge and halo and an active disk composed of 60,000 particles. The spiral lasts for about three pattern revolutions without severe distortion and persists for at least two more revolutions with distortions and bifurcations resulting from an increasingly clumpy ISM. This suggests that two-armed grand design spirals in nonbarred noninteracting galaxies can be long-lived if star formation and other heat sources not present in the simulation maintain a steady interstellar medium.

  5. Late-type galaxies - The shapes of the spiral arm filaments

    NASA Astrophysics Data System (ADS)

    Isserstedt, J.; Schindler, R.

    1987-03-01

    A study is conducted of the shapes of spiral arm filaments in 18 late-type galaxies in order to test the SSPSF theory's hyperbolic spiral arm predictions. After subtracting the disk component from the luminosity distribution by image filtering, the directions along which the intensity variations of the extreme Population I are minimal were determined in circular zones around the centers of the deprojected images; this constitutes an objective determination of pitch angles even for galaxies with very short and filamentary arms. The results obtained severely contradict SSPSF theory, instead implying that the spiral arms are wave phenomena exhibiting logarithmic shapes.

  6. Globular Cluster Systems along the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Huizinga, Edwin

    1996-07-01

    Globular Cluster Systems {GCSs} provide a powerful tool to differentiate between competing galaxy formation- and evolution scenarios. However, our current knowledge of GCS in spiral galaxies is based mainly on studies of the Galaxy and M31. Even though GCSs have been detected in other spiral galaxies, ground-based observations barely reach the peak of the Globular-Cluster luminosity function, and do not provide accurate colors. We propose a systematic study of the GCSs in 6 edge-on L* spiral galaxies beyond the Local Group, using WFPC2. These galaxies were carefully selected to meet several stringent criteria. With the new dithering techniques, it will be possible to resolve any faint background galaxies and obtain a clean sample of globular clusters for all galaxies in our sample. This will allow us to study the complete luminosity functions, {V-I} color distributions, and GCS richness for L* galaxies as a function of Hubble type {Sa, Sb, Sc}. These data will be used to study the relations between the galaxies' bulge and {thin/thick} disk properties and their GCSs. If, for example, GCS properties correlate with bulge properties, this will rule out any strong evolution along the Hubble Sequence towards earlier type spirals, from Sc to Sa, as has recently been proposed by Pfenniger et al. {1994}.

  7. AM 0500-620 - Spiral Arms and Bright Knots

    NASA Image and Video Library

    2008-04-24

    AM 0500-620 consists of a highly symmetric spiral galaxy seen nearly face-on and partially backlit by a background galaxy. This image is part of a large collection of images of merging galaxies taken by NASA Hubble Space Telescope.

  8. THE HUBBLE SEQUENCE IN GROUPS: THE BIRTH OF THE EARLY-TYPE GALAXIES

    SciTech Connect

    Feldmann, R.; Carollo, C. M.; Mayer, L.

    2011-08-01

    The physical mechanisms and timescales that determine the morphological signatures and the quenching of star formation of typical ({approx}L*) elliptical galaxies are not well understood. To address this issue, we have simulated the formation of a group of galaxies with sufficient resolution to track the evolution of gas and stars inside about a dozen galaxy group members over cosmic history. Galaxy groups, which harbor many elliptical galaxies in the universe, are a particularly promising environment to investigate morphological transformation and star formation quenching, due to their high galaxy density, their relatively low velocity dispersion, and the presence of a hot intragroup medium. Our simulation reproduces galaxies with different Hubble morphologies and, consequently, enables us to study when and where the morphological transformation of galaxies takes place. The simulation does not include feedback from active galactic nuclei showing that it is not an essential ingredient for producing quiescent, red elliptical galaxies in galaxy groups. Ellipticals form, as suspected, through galaxy mergers. In contrast with what has often been speculated, however, these mergers occur at z > 1, before the merging progenitors enter the virial radius of the group and before the group is fully assembled. The simulation also shows that quenching of star formation in the still star-forming elliptical galaxies lags behind their morphological transformation, but, once started, takes less than a billion years to complete. As long envisaged the star formation quenching happens as the galaxies approach and enter the finally assembled group, due to quenching of gas accretion and (to a lesser degree) stripping. A similar sort is followed by unmerged, disk galaxies, which, as they join the group, are turned into the red-and-dead disks that abound in these environments.

  9. STScI-PRC02-11d HUBBLE'S NEWEST CAMERA TAKES A DEEP LOOK AT TWO MERGING GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Advanced Camera for Surveys (ACS), the newest camera on NASA's Hubble Space Telescope, has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed 'The Mice' because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy. The image shows the most detail and the most stars that have ever been seen in these galaxies. In the galaxy at left, the bright blue patch is resolved into a vigorous cascade of clusters and associations of young, hot blue stars, whose formation has been triggered by the tidal forces of the gravitational interaction. Streams of material can also be seen flowing between the two galaxies. The clumps of young stars in the long, straight tidal tail [upper right] are separated by fainter regions of material. These dim regions suggest that the clumps of stars have formed from the gravitational collapse of the gas and dust that once occupied those areas. Some of the clumps have luminous masses comparable to dwarf galaxies that orbit in the halo of our own Milky Way Galaxy. Computer simulations by astronomers Josh Barnes (University of Hawaii) and John Hibbard (National Radio Astronomy Observatory, Charlottesville, Va.) show that we are seeing two nearly identical spiral galaxies approximately 160 million years after their closest encounter. The long, straight arm is actually curved, but appears straight because we see it edge-on. The simulations also show that the pair will eventually merge, forming a large, nearly spherical galaxy (known as an elliptical galaxy). The stars, gas, and luminous clumps of stars in the tidal tails will either fall back into the merged galaxies or orbit in the halo of the newly formed elliptical galaxy. The Mice presage what may happen to our own

  10. STScI-PRC02-11d HUBBLE'S NEWEST CAMERA TAKES A DEEP LOOK AT TWO MERGING GALAXIES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Advanced Camera for Surveys (ACS), the newest camera on NASA's Hubble Space Telescope, has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed 'The Mice' because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy. The image shows the most detail and the most stars that have ever been seen in these galaxies. In the galaxy at left, the bright blue patch is resolved into a vigorous cascade of clusters and associations of young, hot blue stars, whose formation has been triggered by the tidal forces of the gravitational interaction. Streams of material can also be seen flowing between the two galaxies. The clumps of young stars in the long, straight tidal tail [upper right] are separated by fainter regions of material. These dim regions suggest that the clumps of stars have formed from the gravitational collapse of the gas and dust that once occupied those areas. Some of the clumps have luminous masses comparable to dwarf galaxies that orbit in the halo of our own Milky Way Galaxy. Computer simulations by astronomers Josh Barnes (University of Hawaii) and John Hibbard (National Radio Astronomy Observatory, Charlottesville, Va.) show that we are seeing two nearly identical spiral galaxies approximately 160 million years after their closest encounter. The long, straight arm is actually curved, but appears straight because we see it edge-on. The simulations also show that the pair will eventually merge, forming a large, nearly spherical galaxy (known as an elliptical galaxy). The stars, gas, and luminous clumps of stars in the tidal tails will either fall back into the merged galaxies or orbit in the halo of the newly formed elliptical galaxy. The Mice presage what may happen to our own

  11. Formation des etoiles massives dans les galaxies spirales

    NASA Astrophysics Data System (ADS)

    Lelievre, Mario

    Le but de cette thèse est de décrire la formation des étoiles massives dans les galaxies spirales appartenant à divers types morphologiques. L'imagerie Hα profonde combinée à une robuste méthode d'identification des régions HII ont permis de détecter et de mesurer les propriétés (position, taille, luminosité, taux de formation d'étoiles) de plusieurs régions HII situées dans le disque interne (R < R25) de dix galaxies mais aussi à leur périphérie (R ≥ R 25). De façon générale, la répartition des régions HII ne montre aucune évidence de structure morphologique à R < R25 (bras spiraux, anneau, barre) à moins de limiter l'analyse aux régions HII les plus grosses ou les plus lumineuses. La répartition des régions HII, de même que leur taille et leur luminosité, sont toutefois sujettes à de forts effets de sélection qui dépendent de la distance des galaxies et qu'il faut corriger en ramenant l'échantillon à une résolution spatiale commune. Les fonctions de luminosité montrent que les régions HII les plus brillantes ont tendance à se former dans la portion interne du disque. De plus, l'analyse des pentes révèle une forte corrélation linéaire par rapport au type morphologique. Aucun pic n'est observé dans les fonctions de luminosité à log L-37 qui révèlerait la transition entre les régions HII bornées par l'ionisation et par la densité. Une relation cubique est obtenue entre la taille et la luminosité des régions HII, cette relation variant toutefois de façon significative entre le disque interne et la périphérie d'une même galaxie. La densité et la dynamique du gaz et des étoiles pourraient influencer de façon significative la stabilité des nuages moléculaires face à l'effondrement gravitationnel. D'une part, l'étendue du disque de régions HII pour cinq galaxies de l'échantillon coïncide avec celle de l'hydrogène atomique. D'autre part, en analysant la stabilité des disques galactiques, on conclue

  12. HUBBLE OBSERVES THE LOST ANCESTORS TO OUR MILKY WAY GALAX

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope (HST) image of the central portion of a remote cluster of galaxies (CL 0939+4713) as it looked when the universe was two-thirds of its present age. Hubble's high resolution allows astronomers to study, for the first time, the shapes of galaxies as they were long ago. The Space Telescope pictures are sharp enough to distinguish between various forms of spiral galaxies. Most of the spiral, or disk, galaxies have odd features, suggesting they were easily distorted within the environment of the rich cluster. Hubble reveals a number of mysterious 'fragments' of galaxies interspersed through the cluster. The HST picture confirms that billions of years ago, clusters of galaxies contained not only the types of galaxies dominating their descendant clusters today, but also several times as many spiral galaxies. These spiral galaxies have since disappeared through mergers and disruptions, as evident in the Hubble image. This visible light image was taken with HST's Wide Field Planetary Camera 2 in Wide Field Camera mode, on January 10 and 12, 1994. Credit: Alan Dressler (Carnegie Institution) and NASA

  13. HUBBLE OBSERVES THE LOST ANCESTORS TO OUR MILKY WAY GALAX

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope (HST) image of the central portion of a remote cluster of galaxies (CL 0939+4713) as it looked when the universe was two-thirds of its present age. Hubble's high resolution allows astronomers to study, for the first time, the shapes of galaxies as they were long ago. The Space Telescope pictures are sharp enough to distinguish between various forms of spiral galaxies. Most of the spiral, or disk, galaxies have odd features, suggesting they were easily distorted within the environment of the rich cluster. Hubble reveals a number of mysterious 'fragments' of galaxies interspersed through the cluster. The HST picture confirms that billions of years ago, clusters of galaxies contained not only the types of galaxies dominating their descendant clusters today, but also several times as many spiral galaxies. These spiral galaxies have since disappeared through mergers and disruptions, as evident in the Hubble image. This visible light image was taken with HST's Wide Field Planetary Camera 2 in Wide Field Camera mode, on January 10 and 12, 1994. Credit: Alan Dressler (Carnegie Institution) and NASA

  14. Young Galaxy Candidates in the Hubble Frontier Fields. IV. MACS J1149.5+2223

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Zitrin, Adi; Infante, Leopoldo; Laporte, Nicolas; Huang, Xingxing; Moustakas, John; Ford, Holland C.; Shu, Xinwen; Wang, Junxian; Diego, Jose M.; Bauer, Franz E.; Troncoso Iribarren, Paulina; Broadhurst, Tom; Molino, Alberto

    2017-02-01

    We search for high-redshift dropout galaxies behind the Hubble Frontier Fields (HFF) galaxy cluster MACS J1149.5+2223, a powerful cosmic lens that has revealed a number of unique objects in its field. Using the deep images from the Hubble and Spitzer space telescopes, we find 11 galaxies at z > 7 in the MACS J1149.5+2223 cluster field, and 11 in its parallel field. The high-redshift nature of the bright z ≃ 9.6 galaxy MACS1149-JD, previously reported by Zheng et al., is further supported by non-detection in the extremely deep optical images from the HFF campaign. With the new photometry, the best photometric redshift solution for MACS1149-JD reduces slightly to z = 9.44 ± 0.12. The young galaxy has an estimated stellar mass of (7+/- 2)× {10}8 {M}⊙ , and was formed at z={13.2}-1.6+1.9 when the universe was ≈300 Myr old. Data available for the first four HFF clusters have already enabled us to find faint galaxies to an intrinsic magnitude of {M}{UV}≃ -15.5, approximately a factor of 10 deeper than the parallel fields.

  15. Spiral Density Wave Triggering of Star Formation in SA and SAB Galaxies

    NASA Astrophysics Data System (ADS)

    Martínez-García, Eric E.; González-Lópezlira, Rosa A.; Bruzual-A, Gustavo

    2009-03-01

    Azimuthal color (age) gradients across spiral arms are one of the main predictions of density wave theory; gradients are the result of star formation triggered by the spiral waves. In a sample of 13 spiral galaxies of types A and AB, we find that ten of them present regions that match the theoretical predictions. By comparing the observed gradients with stellar population synthesis models, the pattern speed and the location of major resonances have been determined. The resonance positions inferred from this analysis indicate that nine of the objects have spiral arms that extend to the outer Lindblad resonance; for one of the galaxies, the spiral arms reach the corotation radius. The effects of dust, and of stellar densities, velocities, and metallicities on the color gradients are also discussed.

  16. Feathers in CO: CARMA CO(1-0) Observations of Four Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    La Vigne, Misty A.; Vogel, S. N.

    2007-12-01

    Feathers are striking extinction features that emerge from a spiral arm dust lane and arch into the interarm. Based on a study of HST archival images, La Vigne et al. 2006 find that feathers are common in a range of spiral galaxy types, and that observations of M51 suggest feathers emerge from giant molecular associations (GMAs) and can be associated with much of the star formation in a spiral galaxy. To evaluate whether the conclusions based on M51 can be more generally applied, we have observed CO(1-0) emission in four spiral galaxies at 2-3” resolution using the newly operational CARMA millimeter wave array. Maps of NGC 0628, NGC 3627, NGC 4637, and NGC 5055 are presented and implications for theories for the origin of feathers are discussed. CARMA operations are supported by the NSF under a cooperative agreement, and by the partner universities.

  17. The Distribution of Supernovae Relative to Spiral Arms of Host Disc Galaxies

    NASA Astrophysics Data System (ADS)

    Aramyan, L. S.; Hakobyan, A. A.; Petrosian, A. R.; de Lapparent, V.; Bertin, E.; Mamon, G. A.; Kunth, D.; Nazaryan, T. A.; Adibekyan, V.; Turatto, M.

    2017-07-01

    Using a sample of 215 supernovae (SNe), we analyse their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. Our results suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of core-collapse (CC) SNe (known to have short-lived progenitors). The closer locations of SNe Ibc vs. SNe II relative to the leading edges of the arms supports the belief that SNe Ibc have more massive progenitors. SNe Ia having less massive and older progenitors, show symmetric distribution with respect to the peaks of spiral arms.

  18. VizieR Online Data Catalog: Southern sky survey of 1355 spiral galaxies (Mathewson+, 1992)

    NASA Astrophysics Data System (ADS)

    Mathewson, D. S.; Ford, V. L.; Buchhorn, M.

    2003-06-01

    Photometry of spiral galaxies less than about 5' in diameter was obtained in the Kron-Cousins I passband at the 1m f/8 telescope at Siding Sping Observatory. The 64m radio telescope at Parkes Observatory, CSIRO,was used to obtain HI profiles of 551 galaxies. (3 data files).

  19. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Technical Reports Server (NTRS)

    Ferrarese, Laura; Bosch, Frank C. Van Den; Ford, Holland C.; Jaffe, Walter; O'Connell, Robert W.

    1994-01-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  20. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 3: Brightness profiles

    NASA Astrophysics Data System (ADS)

    Ferrarese, L.; van den Bosch, F. C.; Ford, H. C.; Jaffe, W.; O'Connell, R. W.

    1994-11-01

    We have used the Planetary Camera on the Hubble Space Telescope (HST) to study the morphology and surface brightness parameters of a luminosity-limited sample of fourteen elliptical galaxies in the Virgo cluster. The total apparent blue magnitudes of the galaxies range between 9.4 and 13.4. In this paper, the core brightness profiles are presented, while the overall morphology and the isophotal shapes are discussed in two companion papers (Jaffe et al. (1994); van den Bosch et al. (1994)). We show that, in spite of the spherical aberration affecting the HST primary mirror, deconvolution techniques allow recovery of the brightness profile up to 0.2 arcsec from the center of the galaxies. We find that none of the galaxies has an isothermal core. On the basis of their morphological and photometrical properties, the galaxies can be divided in two physically distinct groups, referred to as Type I and Type II. All of the Type I galaxies are classified as E1 to E3 in the Revised Shapley Ames Catalog (Sandage & Tammann 1981), while Type II galaxies are classified as E5 to E7. The characteristics of Type II galaxies are explained by the presence of disks component on both the 1 arcsec and the 10 arcsec scales, while Type I galaxies correspond to the classical disk-free ellipticals.

  1. Bar pattern speeds in CALIFA galaxies. I. Fast bars across the Hubble sequence

    NASA Astrophysics Data System (ADS)

    Aguerri, J. A. L.; Méndez-Abreu, J.; Falcón-Barroso, J.; Amorin, A.; Barrera-Ballesteros, J.; Cid Fernandes, R.; García-Benito, R.; García-Lorenzo, B.; González Delgado, R. M.; Husemann, B.; Kalinova, V.; Lyubenova, M.; Marino, R. A.; Márquez, I.; Mast, D.; Pérez, E.; Sánchez, S. F.; van de Ven, G.; Walcher, C. J.; Backsmann, N.; Cortijo-Ferrero, C.; Bland-Hawthorn, J.; del Olmo, A.; Iglesias-Páramo, J.; Pérez, I.; Sánchez-Blázquez, P.; Wisotzki, L.; Ziegler, B.

    2015-04-01

    Context. The bar pattern speed (Ωb) is defined as the rotational frequency of the bar, and it determines the bar dynamics. Several methods have been proposed for measuring Ωb. The non-parametric method proposed by Tremaine & Weinberg (1984, ApJ, 282, L5; TW) and based on stellar kinematics is the most accurate. This method has been applied so far to 17 galaxies, most of them SB0 and SBa types. Aims: We have applied the TW method to a new sample of 15 strong and bright barred galaxies, spanning a wide range of morphological types from SB0 to SBbc. Combining our analysis with previous studies, we investigate 32 barred galaxies with their pattern speed measured by the TW method. The resulting total sample of barred galaxies allows us to study the dependence of Ωb on galaxy properties, such as the Hubble type. Methods: We measured Ωb using the TW method on the stellar velocity maps provided by the integral-field spectroscopy data from the CALIFA survey. Integral-field data solve the problems that long-slit data present when applying the TW method, resulting in the determination of more accurate Ωb. In addition, we have also derived the ratio ℛ of the corotation radius to the bar length of the galaxies. According to this parameter, bars can be classified as fast (ℛ < 1.4) and slow (ℛ > 1.4). Results: For all the galaxies, ℛ is compatible within the errors with fast bars. We cannot rule out (at 95% level) the fast bar solution for any galaxy. We have not observed any significant trend between ℛ and the galaxy morphological type. Conclusions: Our results indicate that independent of the Hubble type, bars have been formed and then evolve as fast rotators. This observational result will constrain the scenarios of formation and evolution of bars proposed by numerical simulations.

  2. The Cluster Environment of a Triple-Double Episodic Radio Spiral Galaxy BCG

    NASA Astrophysics Data System (ADS)

    Irwin, Jimmy

    2012-10-01

    SDSS J140948.85-030232.5 (also referred to as or Speca) is unique in that it is the only known galaxy that is both a spiral radio galaxy and harbors three distinct pairs of radio relic lobes indicative of episodic radio outbursts. Furthermore, it is the brightest cluster galaxy of a cluster despite being a spiral. We propose a short XMM-Newton snapshot observation of the environment of Speca to determine the X-ray flux of the previously unobserved host cluster as a prelude to deeper X-ray observations to investigate the radio relic lobes interaction with the hot intracluster medium of the cluster.

  3. Hubble Helps Find Smallest Known Galaxy Containing a Supermassive Black Hole

    NASA Image and Video Library

    2017-09-28

    This is an illustration of a supermassive black hole, weighing as much as 21 million suns, located in the middle of the ultradense galaxy M60-UCD1. The dwarf galaxy is so dense that millions of stars fill the sky as seen by an imaginary visitor. Because no light can escape from the black hole, it appears simply in silhouette against the starry background. The black hole's intense gravitational field warps the light of the background stars to form ring-like images just outside the dark edges of the black hole's event horizon. Combined observations by the Hubble Space Telescope and Gemini North telescope determined the presence of the black hole inside such a small and dense galaxy. More info: Astronomers using data from NASA’s Hubble Space Telescope and ground observation have found an unlikely object in an improbable place -- a monster black hole lurking inside one of the tiniest galaxies ever known. The black hole is five times the mass of the one at the center of our Milky Way galaxy. It is inside one of the densest galaxies known to date -- the M60-UCD1 dwarf galaxy that crams 140 million stars within a diameter of about 300 light-years, which is only 1/500th of our galaxy’s diameter. If you lived inside this dwarf galaxy, the night sky would dazzle with at least 1 million stars visible to the naked eye. Our nighttime sky as seen from Earth’s surface shows 4,000 stars. The finding implies there are many other compact galaxies in the universe that contain supermassive black holes. The observation also suggests dwarf galaxies may actually be the stripped remnants of larger galaxies that were torn apart during collisions with other galaxies rather than small islands of stars born in isolation. “We don’t know of any other way you could make a black hole so big in an object this small,” said University of Utah astronomer Anil Seth, lead author of an international study of the dwarf galaxy published in Thursday’s issue of the journal Nature. Seth

  4. DEPENDENCE OF NEBULAR HEAVY-ELEMENT ABUNDANCE ON H I CONTENT FOR SPIRAL GALAXIES

    SciTech Connect

    Robertson, Paul; Shields, Gregory A.; Wright, Audrey; Dave, Romeel; Blanc, Guillermo A.

    2013-08-10

    We analyze the galactic H I content and nebular log (O/H) for 60 spiral galaxies in the Moustakas et al. (2006a) spectral catalog. After correcting for the mass-metallicity relationship, we show that the spirals in cluster environments show a positive correlation for log (O/H) on DEF, the galactic H I deficiency parameter, extending the results of previous analyses of the Virgo and Pegasus I clusters. Additionally, we show for the first time that galaxies in the field obey a similar dependence. The observed relationship between H I deficiency and galactic metallicity resembles similar trends shown by cosmological simulations of galaxy formation including inflows and outflows. These results indicate the previously observed metallicity-DEF correlation has a more universal interpretation than simply a cluster's effects on its member galaxies. Rather, we observe in all environments the stochastic effects of metal-poor infall as minor mergers and accretion help to build giant spirals.

  5. Chemical abundances in Virgo cluster spirals - what drives the environmental dependence of galaxy metallicity?

    NASA Astrophysics Data System (ADS)

    Ellison, Sara; Skillman, Evan; Chung, Aeree

    2009-08-01

    The Virgo cluster is not only our nearest massive cluster, but its dynamical infancy also renders it an ideal laboratory for studies of cluster formation and galaxy evolution. Given the intense interest in Virgo, it is astounding that only 9 out of over 100 spirals in its firmament have chemical abundance measurements. We propose to simultaneously address this gap in our fundamental knowledge of Virgo cluster spirals and investigate how the metallicity and abundance gradients of star forming galaxies are sensitive to environment. Our sample consists of 13 Virgo cluster spiral galaxies, preferentially gas-poor early types, which complement the existing metallicity measurements. We also sample a range of clustercentric distances (0.3 -- 3 Mpc from M87), local densities and include several galaxies which exhibit evidence for interactions with the intra-cluster medium.

  6. How do spiral arm contrasts relate to bars, disc breaks and other fundamental galaxy properties?

    NASA Astrophysics Data System (ADS)

    Bittner, Adrian; Gadotti, Dimitri A.; Elmegreen, Bruce G.; Athanassoula, Evangelie; Elmegreen, Debra M.; Bosma, Albert; Muñoz-Mateos, Juan-Carlos

    2017-10-01

    We investigate how the properties of spiral arms relate to other fundamental galaxy properties, including bars and disc breaks. We use previously published measurements of those properties, and our own measurements of arm and bar contrasts for a large sample of galaxies, using 3.6 μm images from the Spitzer Survey of Stellar Structure in Galaxies. Flocculent galaxies are clearly distinguished from other spiral arm classes, especially by their lower stellar mass and surface density. Multi-armed and grand-design galaxies are similar in most of their fundamental parameters, excluding some bar properties and the bulge-to-total ratio. Based on these results, we revisit the sequence of spiral arm classes, and discuss classical bulges as a necessary condition for standing spiral wave modes in grand-design galaxies. We find a strong correlation between bulge-to-total ratio and bar contrast, and a weaker correlation between arm and bar contrasts. Barred and unbarred galaxies exhibit similar arm contrasts, but the highest arm contrasts are found exclusively in barred galaxies. Interestingly, the bar contrast, and its increase from flocculent to grand-design galaxies, is systematically more significant than that of the arm contrast. We corroborate previous findings concerning a connection between bars and disc breaks. In particular, in grand-design galaxies, the bar contrast correlates with the normalized disc break radius. This does not hold for other spiral arm classes or the arm contrast. Our measurements of arm and bar contrast and radial contrast profiles are publicly available.

  7. Hubble Residuals of Nearby SN Ia Are Correlated with Host Galaxy Masses

    SciTech Connect

    Kelly, Patrick L.; Hicken, Malcolm; Burke, David L.; Mandel, Kaisey S.; Kirshner, Robert P.; /Harvard-Smithsonian Ctr. Astrophys.

    2010-05-03

    From Sloan Digital Sky Survey u{prime} g{prime} r{prime} i{prime} z{prime} imaging, we estimate the stellar masses of the host galaxies of 70 low redshift SN Ia (0.015 < z < 0.08) from the hosts absolute luminosities and mass-to-light ratios. These nearby SN were discovered largely by searches targeting luminous galaxies, and we find that their host galaxies are substantially more massive than the hosts of SN discovered by the flux-limited Supernova Legacy Survey. Testing four separate light curve fitters, we detect {approx}2.5{sigma} correlations of Hubble residuals with both host galaxy size and stellar mass, such that SN Ia occurring in physically larger, more massive hosts are {approx}10% brighter after light curve correction. The Hubble residual is the deviation of the inferred distance modulus to the SN, calculated from its apparent luminosity and light curve properties, away from the expected value at the SN redshift. Marginalizing over linear trends in Hubble residuals with light curve parameters shows that the correlations cannot be attributed to a light curve-dependent calibration error. Combining 180 higher-redshift ESSENCE, SNLS, and HigherZ SN with 30 nearby SN whose host masses are less than 10{sup 10.8} M{circle_dot} n a cosmology fit yields 1 + w = 0.22{sub -0.108}{sup +0.152}, while a combination where the 30 nearby SN instead have host masses greater than 10{sup 10.8} M{circle_dot} yields 1 + w = ?0.03{sub -0.143}{sup +0.217}. Progenitor metallicity, stellar population age, and dust extinction correlate with galaxy mass and may be responsible for these systematic effects. Host galaxy measurements will yield improved distances to SN Ia.

  8. Distant encounters between disk galaxies and the origin of S 0 spirals

    NASA Astrophysics Data System (ADS)

    Icke, V.

    1985-03-01

    Numerical calculations of the hydrodynamics of a gaseous disk in a galaxy perturbed by an intruder flying in a hyperbolic orbit are presented. It is shown that if the pericenter of the distance between the galaxy and the intruder object becomes so large that stellar bridges and tails become unimportant, gravitational shocks may occur. It is suggested that the theoretical calculations may help explain the physical mechanisms of S 0 spiral galaxy formation. Computer-generated illustrations of the numerical results are provided.

  9. IMPACT OF CHANDRA CALIBRATION UNCERTAINTIES ON GALAXY CLUSTER TEMPERATURES: APPLICATION TO THE HUBBLE CONSTANT

    SciTech Connect

    Reese, Erik D.; Kawahara, Hajime; Suto, Yasushi; Kitayama, Tetsu; Ota, Naomi; Sasaki, Shin

    2010-09-20

    We perform a uniform, systematic X-ray spectroscopic analysis of a sample of 38 galaxy clusters with three different Chandra calibrations. The temperatures change systematically between calibrations. Cluster temperatures change on average by roughly {approx}6% for the smallest changes and roughly {approx}13% for the more extreme changes between calibrations. We explore the effects of the Chandra calibration on cluster spectral properties and the implications on Sunyaev-Zel'dovich effect (SZE) and X-ray determinations of the Hubble constant. The Hubble parameter changes by +10% and -13% between the current calibration and two previous Chandra calibrations, indicating that changes in the cluster temperature basically explain the entire change in H{sub 0}. Although this work focuses on the difference in spectral properties and resultant Hubble parameters between the calibrations, it is intriguing to note that the newer calibrations favor a lower value of the Hubble constant, H{sub 0} {approx} 60 km s{sup -1} Mpc{sup -1}, typical of results from SZE/X-ray distances. Both galaxy clusters themselves and the details of the instruments must be known precisely to enable reliable precision cosmology with clusters, which will be feasible with combined efforts from ongoing observations and planned missions and observatories covering a wide range of wavelengths.

  10. AN INTENSIVE HUBBLE SPACE TELESCOPE SURVEY FOR z>1 TYPE Ia SUPERNOVAE BY TARGETING GALAXY CLUSTERS

    SciTech Connect

    Dawson, K. S.; Aldering, G.; Barbary, K.; Faccioli, L.; Fakhouri, H. K.; Goldhaber, G.; Amanullah, R.; Barrientos, L. F.; Brodwin, M.; Connolly, N.; Dey, A.; Doi, M.; Donahue, M.; Eisenhardt, P.; Ellingson, E.; Fadeyev, V.; Fruchter, A. S.; Gilbank, D. G.; Gladders, M. D.; Gonzalez, A. H.

    2009-11-15

    We present a new survey strategy to discover and study high-redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 < z < 1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of 3 improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides an SN sample that can be used to decouple the effects of host-galaxy extinction and intrinsic color in high-redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology.

  11. The isolated dSph galaxy KKs3 in the local Hubble flow

    NASA Astrophysics Data System (ADS)

    Karachentsev, I. D.; Kniazev, A. Yu.; Sharina, M. E.

    2015-09-01

    We present SALT spectroscopy of a globular cluster in the center of the nearby isolated dSph galaxy KKs3 situated at a distance of 2.12 Mpc. Its heliocentric radial velocity is 316 ± 7 km s-1 that corresponds to V_LG = 112 km s-1 in the Local Group (LG) reference frame. We use its distance and velocity along with the data on other 35 field galaxies in the proximity of the LG to trace the local Hubble flow. The following basic properties of the local field galaxies are briefly discusse: morphology, absolute magnitudes, average surface brightnesses, specific star formation rates, and hydrogen mass-to-stellar mass ratios. Surprisingly, the sample of the neighboring isolated galaxies displays no signs of compression under the influence of the expanding Local Void.

  12. Cloning Hubble Deep Fields. II. Models for Evolution by Bright Galaxy Image Transformation

    NASA Astrophysics Data System (ADS)

    Bouwens, Rychard; Broadhurst, Tom; Silk, Joseph

    1998-10-01

    In a companion paper, we outlined a methodology for generating parameter-free, model-independent ``no-evolution'' fields of faint galaxy images, demonstrating the need for significant evolution in the Hubble Deep Field (HDF) at faint magnitudes. Here we incorporate evolution into our procedure, by transforming the input bright galaxy images with redshift, for comparison with the HDF at faint magnitudes. Pure luminosity evolution is explored with the assumption that galaxy surface brightness evolves uniformly, at a rate chosen to reproduce the I-band counts. This form of evolution exacerbates the size discrepancy identified by our no-evolution simulations by increasing the area of a galaxy visible to a fixed isophote. Reasonable dwarf-augmented models are unable to generate the count excess invoking moderate rates of stellar evolution. A plausible fit to the counts and sizes is provided by ``mass-conserving'' density-evolution, consistent with small-scale hierarchical growth, in which the product of disk area and space density is conserved with redshift. Here the increased surface brightness generated by stellar evolution is accommodated by the reduced average galaxy size, for a wide range of geometries. These models are useful for calculating the rates of incompleteness and the degree of overcounting. Finally we demonstrate the potential for improvement in quantifying evolution at fainter magnitudes using the Hubble Space Telescope Advanced Camera, with its superior UV and optical performance.

  13. Hubble Space Telescope photometry of the central regions of Virgo cluster elliptical galaxies. 2: Isophote shapes

    NASA Technical Reports Server (NTRS)

    Bosch, Frank C. Van Den; Ferrarese, Laura; Jaffe, Walter; Ford, Holland C.; O'Connell, Robert W.

    1994-01-01

    The isophotal shapes of a magnitude limited sample of Virgo ellipticals are presented. These are derived from high resolution Hubble Space Telescope (HST) photometry. The absence of atmospheric seeing and accurate knowledge of the Point Spread Function (PSF) allows us to perform an accurate deconvolution. Model galaxies were constructed to test the deconvolution algorithms used, and showed that we can accurately recover isophotal shape parameters down to 0.5 sec. From the isophotal parameters we can classify the galaxies in two subsamples: disky and non-disky galaxies. In three of these disky galaxies we found evidence for a nuclear stellar disk in the inner 1.5 sec. In addition these galaxies also have an outer disk, that seems to break up inside 2 sec - 3 sec. In the two galaxies for which there is kinematic evidence from the literature of a decoupled core, we found no indication for such subsystem from the isophotal shape analysis. In 80% of these early type galaxies there are indications for dust. For eight of these galaxies the dust has not been detected before.

  14. Gas motions in the plane of the spiral galaxy NGC 3631

    NASA Astrophysics Data System (ADS)

    Fridman, A. M.; Khoruzhii, O. V.; Polyachenko, E. V.; Zasov, A. V.; Sil'chenko, O. K.; Moiseev, A. V.; Burlak, A. N.; Afanasiev, V. L.; Dodonov, S. N.; Knapen, J. H.

    2001-05-01

    The velocity field of the nearly face-on galaxy NGC 3631, derived from observations in the Hα line and Hi radio line, is analysed to study perturbations related to the spiral structure of the galaxy. We confirm our previous conclusion that the line-of-sight velocity field gives evidence of the wave nature of the observed two-armed spiral structure. Fourier analysis of the observed velocity field is used to determine the location of corotation of the spiral structure of this galaxy, and the radius of corotation Rc is found to be about 42arcsec, or 3.2kpc. The vector velocity field of the gas in the plane of the disc is restored, and, taking into account that we previously investigated vertical motions, we now have a full three-dimensional gaseous velocity field of the galaxy. We show clear evidence of the existence of two anticyclonic and four cyclonic vortices near corotation in a frame of reference rotating with the spiral pattern. The centres of the anticyclones lie between the observed spiral arms. The cyclones lie close to the observed spirals, but their centres are shifted from the maxima in brightness.

  15. Herschel-ATLAS/GAMA: dusty early-type galaxies and passive spirals

    NASA Astrophysics Data System (ADS)

    Rowlands, K.; Dunne, L.; Maddox, S.; Bourne, N.; Gomez, H. L.; Kaviraj, S.; Bamford, S. P.; Brough, S.; Charlot, S.; da Cunha, E.; Driver, S. P.; Eales, S. A.; Hopkins, A. M.; Kelvin, L.; Nichol, R. C.; Sansom, A. E.; Sharp, R.; Smith, D. J. B.; Temi, P.; van der Werf, P.; Baes, M.; Cava, A.; Cooray, A.; Croom, S. M.; Dariush, A.; de Zotti, G.; Dye, S.; Fritz, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Liske, J.; Loveday, J.; Madore, B.; Norberg, P.; Popescu, C. C.; Rigby, E. E.; Robotham, A.; Rodighiero, G.; Seibert, M.; Tuffs, R. J.

    2012-01-01

    We present the dust properties and star formation histories of local submillimetre-selected galaxies, classified by optical morphology. Most of the galaxies are late types and very few are early types. The early-type galaxies (ETGs) that are detected contain as much dust as typical spirals, and form a unique sample that has been blindly selected at submillimetre wavelengths. Additionally, we investigate the properties of the most passive, dusty spirals. We morphologically classify 1087 galaxies detected in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) Science Demonstration Phase data. Comparing to a control sample of optically selected galaxies, we find 5.5 per cent of luminous ETGs are detected in H-ATLAS. The H-ATLAS ETGs contain a significant mass of cold dust: the mean dust mass is 5.5 × 107 M⊙, with individual galaxies ranging from 9 × 105 to 4 × 108 M⊙. This is comparable to that of spiral galaxies in our sample, and is an order of magnitude more dust than that found for the control early-types, which have a median dust mass inferred from stacking of (0.8-4.0) × 106 M⊙ for a cold dust temperature of 25-15 K. The early-types detected in H-ATLAS tend to have bluer NUV - r colours, higher specific star formation rates and younger stellar populations than early-types which are optically selected, and may be transitioning from the blue cloud to the red sequence. We also find that H-ATLAS and control early-types inhabit similar low-density environments. We investigate whether the observed dust in H-ATLAS early-types is from evolved stars, or has been acquired from external sources through interactions and mergers. We conclude that the dust in H-ATLAS and control ETGs cannot be solely from stellar sources, and a large contribution from dust formed in the interstellar medium or external sources is required. Alternatively, dust destruction may not be as efficient as predicted. We also explore the properties of the most passive spiral

  16. The host galaxies and explosion sites of long-duration gamma ray bursts: Hubble Space Telescope near-infrared imaging

    NASA Astrophysics Data System (ADS)

    Lyman, J. D.; Levan, A. J.; Tanvir, N. R.; Fynbo, J. P. U.; McGuire, J. T. W.; Perley, D. A.; Angus, C. R.; Bloom, J. S.; Conselice, C. J.; Fruchter, > A. S.; Hjorth, J.; Jakobsson, P.; Starling, R. L. C.

    2017-01-01

    We present the results of a Hubble Space Telescope WFC3/F160W SNAPSHOT survey of the host galaxies of 39 long-duration gamma-ray bursts (LGRBs) at z < 3. We have non-detections of hosts at the locations of 4 bursts. Sufficient accuracy to astrometrically align optical afterglow images and determine the location of the LGRB within its host was possible for 31/35 detected hosts. In agreement with other work, we find the luminosity distribution of LGRB hosts is significantly fainter than that of a star formation rate-weighted field galaxy sample over the same redshift range, indicating LGRBs are not unbiasedly tracing the star formation rate. Morphologically, the sample of LGRB hosts are dominated by spiral-like or irregular galaxies. We find evidence for evolution of the population of LGRB hosts towards lower-luminosity, higher concentrated hosts at lower redshifts. Their half-light radii are consistent with other LGRB host samples where measurements were made on rest-frame UV observations. In agreement with recent work, we find their 80 per cent enclosed flux radii distribution to be more extended than previously thought, making them intermediate between core-collapse supernova (CCSN) and super-luminous supernova (SLSN) hosts. The galactocentric projected-offset distribution confirms LGRBs as centrally concentrated, much more so than CCSNe and similar to SLSNe. LGRBs are strongly biased towards the brighter regions in their host light distributions, regardless of their offset. We find a correlation between the luminosity of the LGRB explosion site and the intrinsic column density, NH, towards the burst.

  17. The host galaxies and explosion sites of long-duration gamma ray bursts: Hubble Space Telescope near-infrared imaging

    NASA Astrophysics Data System (ADS)

    Lyman, J. D.; Levan, A. J.; Tanvir, N. R.; Fynbo, J. P. U.; McGuire, J. T. W.; Perley, D. A.; Angus, C. R.; Bloom, J. S.; Conselice, C. J.; Fruchter, A. S.; Hjorth, J.; Jakobsson, P.; Starling, R. L. C.

    2017-05-01

    We present the results of a Hubble Space Telescope WFC3/F160W Snapshot survey of the host galaxies of 39 long-duration gamma-ray bursts (LGRBs) at z < 3. We have non-detections of hosts at the locations of four bursts. Sufficient accuracy to astrometrically align optical afterglow images and determine the location of the LGRB within its host was possible for 31/35 detected hosts. In agreement with other work, we find the luminosity distribution of LGRB hosts is significantly fainter than that of a star formation rate-weighted field galaxy sample over the same redshift range, indicating LGRBs are not unbiasedly tracing the star formation rate. Morphologically, the sample of LGRB hosts is dominated by spiral-like or irregular galaxies. We find evidence for evolution of the population of LGRB hosts towards lower luminosity, higher concentrated hosts at lower redshifts. Their half-light radii are consistent with other LGRB host samples where measurements were made on rest-frame UV observations. In agreement with recent work, we find their 80 per cent enclosed flux radii distribution to be more extended than previously thought, making them intermediate between core-collapse supernova (CCSN) and superluminous supernova (SLSN) hosts. The galactocentric projected-offset distribution confirms LGRBs as centrally concentrated, much more so than CCSNe and similar to SLSNe. LGRBs are strongly biased towards the brighter regions in their host light distributions, regardless of their offset. We find a correlation between the luminosity of the LGRB explosion site and the intrinsic column density, NH, towards the burst.

  18. Spirality: Spiral arm pitch angle measurement

    NASA Astrophysics Data System (ADS)

    Shields, Douglas W.; Boe, Benjamin; Pfountz, Casey; Davis, Benjamin L.; Hartley, Matthew; Pour Imani, Hamed; Slade, Zac; Kennefick, Daniel; Kennefick, Julia

    2015-12-01

    Spirality measures spiral arm pitch angles by fitting galaxy images to spiral templates of known pitch. Written in MATLAB, the code package also includes GenSpiral, which produces FITS images of synthetic spirals, and SpiralArmCount, which uses a one-dimensional Fast Fourier Transform to count the spiral arms of a galaxy after its pitch is determined.

  19. VizieR Online Data Catalog: Hα in HII regions in spiral galaxies (Marquez+, 2002)

    NASA Astrophysics Data System (ADS)

    Marquez, I.; Masegosa, J.; Moles, M.; Varela, J.; Bettoni, D.; Galletta, G.

    2002-07-01

    In this paper we study long slit spectra in the region of Hα emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected H II regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/Hα ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/Hα ratios measured for disk H II regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of Hα equivalent width. (1 data file).

  20. Supernovae and their host galaxies - IV. The distribution of supernovae relative to spiral arms

    NASA Astrophysics Data System (ADS)

    Aramyan, L. S.; Hakobyan, A. A.; Petrosian, A. R.; de Lapparent, V.; Bertin, E.; Mamon, G. A.; Kunth, D.; Nazaryan, T. A.; Adibekyan, V.; Turatto, M.

    2016-07-01

    Using a sample of 215 supernovae (SNe), we analyse their positions relative to the spiral arms of their host galaxies, distinguishing grand-design (GD) spirals from non-GD (NGD) galaxies. We find that: (1) in GD galaxies, an offset exists between the positions of Ia and core-collapse (CC) SNe relative to the peaks of arms, while in NGD galaxies the positions show no such shifts; (2) in GD galaxies, the positions of CC SNe relative to the peaks of arms are correlated with the radial distance from the galaxy nucleus. Inside (outside) the corotation radius, CC SNe are found closer to the inner (outer) edge. No such correlation is observed for SNe in NGD galaxies nor for SNe Ia in either galaxy class; (3) in GD galaxies, SNe Ibc occur closer to the leading edges of the arms than do SNe II, while in NGD galaxies they are more concentrated towards the peaks of arms. In both samples of hosts, the distributions of SNe Ia relative to the arms have broader wings. These observations suggest that shocks in spiral arms of GD galaxies trigger star formation in the leading edges of arms affecting the distributions of CC SNe (known to have short-lived progenitors). The closer locations of SNe Ibc versus SNe II relative to the leading edges of the arms supports the belief that SNe Ibc have more massive progenitors. SNe Ia having less massive and older progenitors, have more time to drift away from the leading edge of the spiral arms.

  1. A spiral galaxy's mass distribution uncovered through lensing and dynamics

    NASA Astrophysics Data System (ADS)

    Trick, Wilma H.; van de Ven, Glenn; Dutton, Aaron A.

    2016-12-01

    We investigate the matter distribution of a spiral galaxy with a counter-rotating stellar core, SDSS J1331+3628 (J1331), independently with gravitational lensing and stellar dynamical modelling. By fitting a gravitational potential model to a quadruplet of lensing images around J1331's bulge, we tightly constrain the mass inside the Einstein radius Rein = (0.91 ± 0.02) arcsec (≃1.83 ± 0.04 kpc) to within 4 per cent: Mein = (7.8 ± 0.3) × 1010 M⊙. We model observed long-slit major axis stellar kinematics in J1331's central regions by finding Multi-Gaussian Expansion (MGE) models for the stellar and dark matter distribution that solve the axisymmetric Jeans equations. The lens and dynamical model are independently derived, but in very good agreement with each other around ˜Rein. We find that J1331's centre requires a steep total mass-to-light ratio gradient. A dynamical model including an NFW halo (with virial velocity v200 ≃ 240 ± 40 km s-1 and concentration c200 ≃ 8 ± 2) and moderate tangential velocity anisotropy (βz ≃ -0.4 ± 0.1) can reproduce the signatures of J1331's counter-rotating core and predict the stellar and gas rotation curve at larger radii. However, our models do not agree with the observed velocity dispersion at large radii. We speculate that the reason could be a non-trivial change in structure and kinematics due to a possible merger event in J1331's recent past.

  2. Modeling Spiral Galaxy Surface Luminosity to Explain Non-Uniform Inclination Distributions

    NASA Astrophysics Data System (ADS)

    Rozum, Jordan C.; Larson, S. L.

    2014-01-01

    The distribution of spiral and bar galaxy orientations is expected to be uniform. However, analysis of several major galaxy catalogs shows this is not always reflected in data. In an attempt to explain this discrepancy, we have developed a galaxy simulation code to compute the appearance of a spiral type galaxy as a function of its morphological parameters. We examine the dependence of observed brightness upon inclination angle by using smooth luminous mass density and interstellar medium (ISM) density distributions. The luminous mass component is integrated along a particular line of sight, thus producing a mass distribution, from which a surface luminosity profile is derived. The ISM component is integrated alongside the luminous mass component to account for light extinction. Using this model, we present simulated galaxy inclination distributions that account for potential selection effects.

  3. Galaxy Zoo Hubble: First results of the redshift evolution of disk fraction in the red sequence

    NASA Astrophysics Data System (ADS)

    Galloway, Melanie; Willett, Kyle; Fortson, Lucy; Scarlata, Claudia; Beck, Melanie; Masters, Karen; Melvin, Tom

    2016-01-01

    The transition of galaxies from the blue cloud to the red sequence is commonly linked to a morphological transformation from disk to elliptical structure. However, the correlation between color and morphology is not one-to-one, as evidenced by the existence of a significant population of red disks. As this stage in a galaxy's evolution is likely to be transitory, the mechanism by which red disks are formed offers insight to the processes that trigger quenching of star formation and the galaxy's position on the star-forming sequence. To study the population of disk galaxies in the red sequence as a function of cosmic time, we utilize data from the Galaxy Zoo: Hubble project, which uses crowdsourced visual classifications of images of galaxies selected from the AEGIS, COSMOS, GEMS, and GOODS surveys. We construct a large sample of over 10,000 disk galaxies spanning a wide (0 < z < 1.0) redshift range. We use this sample to examine the change in the fraction of disks in the red sequence with respect to all disks from z˜1 to the present day. Preliminary results confirm that the fraction of disks in the red sequence decreases as the Universe evolves. We discuss the quenching processes which may explain this trend, and which morphological transformations are most affected by it.

  4. Effect of dark matter halo on global spiral modes in galaxies

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumavo; Saini, Tarun Deep; Jog, Chanda J.

    2016-02-01

    Low surface brightness (LSB) galaxies form a major class of galaxies, and are characterized by low disc surface density and low star formation rate. These are known to be dominated by dark matter halo from the innermost regions. Here, we study the role of the dark matter halo on the grand-design, m = 2, spiral modes in a galactic disc by carrying out a global mode analysis in the WKB approximation. The Bohr-Sommerfeld quantization rule is used to determine how many discrete global spiral modes are permitted. First, a typical superthin, LSB galaxy UGC 7321 is studied by taking only the galactic disc, modelled as a fluid; and then the disc embedded in a dark matter halo. We find that both cases permit the existence of global spiral modes. This is in contrast to earlier results where the inclusion of dark matter halo was shown to nearly fully suppress local, swing-amplified spiral features. Although technically global modes are permitted in the fluid model as shown here, we argue that due to lack of tidal interactions, these are not triggered in LSB galaxies. For comparison, we carried out a similar analysis for the Galaxy, for which the dark matter halo does not dominate in the inner regions. We show that here too the dark matter halo has little effect, hence the disc embedded in a halo is also able to support global modes. The derived pattern speed of the global mode agrees fairly well with the observed value for the Galaxy.

  5. Synthetic HI observations of spiral structure in the outer disk in galaxies

    NASA Astrophysics Data System (ADS)

    Khoperskov, Sergey A.; Bertin, Giuseppe

    2015-12-01

    > By means of 3D hydrodynamical simulations, in a separate paper we have discussed the properties of non-axisymmetric density wave trains in the outermost regions of galaxy disks, based on the picture that self-excited global spiral modes in the bright optical stellar disk are accompanied by low-amplitude short trailing wave signals outside corotation; in the gas, such wave trains can penetrate through the outer Lindblad resonance and propagate outwards, forming prominent spiral patterns. In this paper we present the synthetic 21 cm velocity maps expected from simulated models of the outer gaseous disk, focusing on the case when the disk is dominated by a two-armed spiral pattern, but considering also other more complex situations. We discuss some aspects of the spiral pattern in the gaseous periphery of galaxy disks noted in our simulations that might be interesting to compare with specific observed cases.

  6. Large and small-scale structures and the dust energy balance problem in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Saftly, W.; Baes, M.; De Geyter, G.; Camps, P.; Renaud, F.; Guedes, J.; De Looze, I.

    2015-04-01

    The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a Sérsic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical input models. This factor is in agreement with previous energy balance studies of real edge-on spiral galaxies. On the other hand, fitting the same basic model to less complex input models (e.g. a smooth exponential disc with a spiral perturbation or with random clumps), does recover the dust mass of the input model almost perfectly. Thus it seems that the complex asymmetries and the inhomogeneous structure of real and hydrodynamically simulated galaxies are a lot more efficient at hiding dust than the rather contrived geometries in typical quasi-analytical models. This effect may help explain the discrepancy between the dust emission predicted by radiative transfer models and the observed emission in energy balance studies for edge-on spiral galaxies.

  7. AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

    SciTech Connect

    Singal, J.; Jones, E.; Dunlap, H.; Kogut, A.

    2015-01-20

    We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

  8. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    NASA Astrophysics Data System (ADS)

    de Souza, R. S.; Dantas, M. L. L.; Krone-Martins, A.; Cameron, E.; Coelho, P.; Hattab, M. W.; de Val-Borro, M.; Hilbe, J. M.; Elliott, J.; Hagen, A.; COIN Collaboration

    2016-09-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, M200, and the normalized cluster centric distance, r/r200. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within an HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g. whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a binary variable. Furthermore, we demonstrate how an HBM can incorporate information of each particular galaxy morphological type in an unified framework. In elliptical galaxies our analysis indicates a strong correlation of Seyfert-AGN activity with r/r200, and a weaker correlation with the mass of the host cluster. In spiral galaxies these trends do not appear, suggesting that the link between Seyfert activity and the properties of spiral galaxies are independent of the environment.

  9. Hubble's Cosmic Atlas

    NASA Image and Video Library

    2017-09-27

    Morphologies, masses, and structures - oh, my! This beautiful clump of glowing gas, dark dust and glittering stars is the spiral galaxy NGC 4248, located about 24 million light-years away in the constellation of Canes Venatici (The Hunting Dogs). This image was produced by the NASA/ESA Hubble Space Telescope as it embarked upon compiling the first Hubble ultraviolet “atlas,” for which the telescope targeted 50 nearby star-forming galaxies. The collection spans all kinds of different morphologies, masses, and structures. Studying this sample can help us to piece together the star-formation history of the Universe. By exploring how massive stars form and evolve within such galaxies, astronomers can learn more about how, when, and where star formation occurs, how star clusters change over time, and how the process of forming new stars is related to the properties of both the host galaxy and the surrounding interstellar medium (the gas and dust that fills the space between individual stars). This galaxy was imaged with observations from Hubble’s Wide Field Camera 3. Image credit: ESA/Hubble & NASA

  10. Galaxy NGC 4013

    NASA Image and Video Library

    1999-12-15

    An amazing edge-on view of a spiral galaxy 55 million light years from Earth has been captured by the Hubble Space Telescope. The image reveals in great detail huge clouds of dust and gas extending along and above the galaxy main disk.

  11. Determination of Disk Thickness of Face-on Spiral Galaxies and Its Image Processing Method

    NASA Astrophysics Data System (ADS)

    Hu, T.; Peng, Q. H.

    2014-11-01

    It is uneasy to obtain the disk thickness of face-on spiral galaxies by measuring the galactic light distributions. Here we obtain the spiral galactic disk thickness based on an asymptotic expression of Poisson's equation for a logarithmic perturbation of matter density in spiral galaxies. For measuring the key parameter of the innermost position of the spiral arm (forbidden radius r_0) freed from the contamination by the light of bulge, an improved image processing method is used in this study by subtracting a decomposition brightness model from the galactic observed image. On the basis of measuring some fundamental parameters of spiral structures, we obtain the disk thickness and some other parameters of two (types S and SB) face-on spiral galaxies, and their ratio parameters (r_{b}/r_{d} and r_{d}/H) are also derived. By using this improved subtracted-method, it is easy to measure the forbidden radius r_0, which is smaller than that obtained from unsubtracted-method.

  12. VizieR Online Data Catalog: Nuclear star clusters in 228 spiral galaxies (Georgiev+, 2014)

    NASA Astrophysics Data System (ADS)

    Georgiev, I. Y.; Boker, T.

    2015-02-01

    We searched the HST/WFPC2 archive for all exposures of galaxies with late Hubble type (t>=3.5) to avoid the most luminous bulges, an inclination of i<=88° to avoid edge-on galaxies, and distances of <=40Mpc, (m-M)<~33mag to be able to reliably measure the size of the Nuclear Star Clusters. (5 data files).

  13. The relation between the gas, dust and total mass in edge-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Allaert, Flor

    2015-02-01

    Each component of a galaxy plays its own unique role in regulating the galaxy's evolution. In order to understand how galaxies form and evolve, it is therefore crucial to study the distribution and properties of each of the various components, and the links between them, both radially and vertically. The latter is only possible in edge-on systems. We present the HEROES project, which aims to investigate the 3D structure of the interstellar gas, dust, stars and dark matter in a sample of 7 massive early-type spiral galaxies based on a multi-wavelength data set including optical, NIR, FIR and radio data.

  14. Formation and evolution of molecular hydrogen in disc galaxies with different masses and Hubble types

    NASA Astrophysics Data System (ADS)

    Bekki, Kenji

    2014-10-01

    We investigate the physical properties of molecular hydrogen (H2) in isolated and interacting disc galaxies with different masses and Hubble types by using chemodynamical simulations with H2 formation on dust grains and dust growth and destruction in interstellar medium. We particularly focus on the dependences of H2 gas mass fractions (f_H_2), spatial distributions of H I and H2, and local H2-scaling relations on initial halo masses (Mh), baryonic fractions (fbary), gas mass fractions (fg), and Hubble types. The principal results are as follows. The final f_H_2 can be larger in disc galaxies with higher Mh, fbary, and fg. Some low-mass disc models with Mh smaller than 1010 M⊙ show extremely low f_H_2 and thus no/little star formation, even if initial fg is quite large (>0.9). Big galactic bulges can severely suppress the formation of H2 from H I on dust grains whereas strong stellar bars cannot only enhance f_H_2 but also be responsible for the formation of H2-dominated central rings. The projected radial distributions of H2 are significantly more compact than those of H I and the simulated radial profiles of H2-to-H I-ratios (Rmol) follow roughly R-1.5 in Milky Way-type disc models. Galaxy interaction can significantly increase f_H_2 and total H2 mass in disc galaxies. The local surface mass densities of H2 can be correlated with those of dust in a galaxy. The observed correlation between Rmol and gas pressure (R_mol ∝ P_g^{0.92}) can be well reproduced in the simulated disc galaxies.

  15. Hubble and Chandra Find Evidence for Densest Galaxy in Nearby Universe

    NASA Image and Video Library

    2017-09-28

    SEPTEMBER 24, 2013: Astronomers may have found the densest galaxy in the nearby universe. The galaxy, known as M60-UCD1, is located near a massive elliptical galaxy NGC 4649, also called M60, about 54 million light-years from Earth. This composite image shows M60 and the region around it, where data from NASA's Chandra X-ray Observatory are pink and data from NASA's Hubble Space Telescope are red, green, and blue. The Chandra image shows hot gas and double stars containing black holes and neutron stars, and the Hubble image reveals stars in M60 and neighboring galaxies including M60-UCD1. The arrow points to M60-UCD1. Packed with an extraordinary number of stars, M60-UCD1 is an "ultra-compact dwarf galaxy." It is one of the most massive galaxies of its kind, weighing 200 million times more than our Sun, based on observations with the Keck 10-meter telescope in Hawaii. Remarkably, about half of this mass is found within a radius of only about 80 light-years. This would make the density of stars about 15,000 times greater than found in Earth's neighborhood in the Milky Way, meaning that the stars are about 25 times closer. For more information about M60-UCD1, visit chandra.si.edu/press/13_releases/press_092413.html Credit: NASA, ESA, CXC, and J. Strader (Michigan State University) 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

  16. Ultraviolet photometry from the Orbiting Astronomical Observatory. XL - The energy distributions of spiral and irregular galaxies

    NASA Technical Reports Server (NTRS)

    Code, A. D.; Welch, G. A.

    1982-01-01

    Measurements of the total light of 40 spiral and irregular galaxies are presented. The photometry covers the wavelength range 1550-4250 A and is calibrated on an absolute basis. On the average later-type galaxies are not only bluer at short wavelengths than ellipticals but significantly bluer than visual colors would imply. This reflects a recent history of more vigorous formation of massive stars. The shape of the upper part of the initial mass function apparently varies more among early-type galaxies, producing a wide scatter in their energy distributions. In at least some galaxies interstellar dust appears to have little influence upon the emerging radiation. The local volume luminosity spectrum due to galaxies turns up steeply at short wavelengths, and is shaped largely by contributions from late-type galaxies. The observed ultraviolet background cannot be produced by normal galaxies, although the large corrections implied by theoretical evolutionary models may account for the measurements.

  17. Low-mass spiral galaxies with little molecular gas and prodigious star formation

    NASA Technical Reports Server (NTRS)

    Kenney, Jeffrey D.; Young, Judith S.

    1988-01-01

    A comparison of CO and H I properties is used here to demonstrate that many CO-poor low-mass Virgo spiral galaxies are rich in atomic gas, which implies that the lack of CO emission from them is due, at least partly, to a lack of molecular gas. Despite the paucity of molecular gas, these H I-rich, CO-poor, low-mass spiral galaxies are undergoing extensive massive star formation. A column density of 10 to the 21st nuclei/sq cm is a necessary but insufficient condition for the creation of an H2-dominated interstellar medium.

  18. A sub-millimetre survey of dust enshrouded galaxies in the Hubble Deep Field region

    NASA Astrophysics Data System (ADS)

    Borys, Colin James Kelvin

    This thesis investigates the emission of sub-millimetre- wave radiation from galaxies in the Hubble Deep Field North region. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope. The data were combined using techniques specifically developed here for low signal-to-noise source recovery. The sources found represent over 10% of all cosmological sources SCUBA has detected since it was commissioned. The number of sub-mm galaxies we detect account for a significant fraction of the sub-mm back-ground, and we show that mild extrapolations can reproduce it entirely. We comment on their clustering properties, both with themselves and other high-redshift galaxy types. A multi-wavelength analysis of these galaxies shows that SCUBA sources do not all have similar properties, and are made of a collection including: star-forming radio galaxies; optically invisible objects; active galactic nuclei; and extremely red objects. Reasonable attempts to determine the redshift distribution of the sample show that SCUBA galaxies have a median redshift of around 2, and suggest that the global star formation rate may be dominated by such objects at redshifts beyond about 1. The thesis summarises the current state of extra-galactic sub-mm astronomy, and comments on how new surveys and detectors will allow us to place stronger constraints on the evolution properties of the high-redshift Universe.

  19. High-z massive galaxies in the Hubble Deep Field South

    NASA Astrophysics Data System (ADS)

    Saracco, P.; Longhetti, M.; Giallongo, E.; Arnouts, S.; Cristiani, S.; D'Odorico, S.; Fontana, A.; Nonino, M.; Vanzella, E.

    2004-06-01

    A census of massive galaxies at redshift increasingly higher than z˜1 may provide strong constraints for the history of mass assembly and star formation. Here we report the analysis of three galaxies selected in the Hubble Deep Field South at K s≤22 on the basis of their unusually red near-IR color J-K≥3. We have used population synthesis models to constrain their redshifts and their stellar masses. One galaxy (HDFS-1269) is at redshift zphot≃2.4 while the other two (HDFS-822 and HDFS-850) are at zphot≃2.9{-}3.0. All three galaxies have already assembled a stellar mass of about 1011 M⊙ at the observed redshift, placing the possible merging event of their formation at z⪆ 3.5. The inferred mass weighted age of their stellar populations implies that the bulk of the stars formed at zf>3.5. The resulting co-moving density of Mstars⪆ 1011 M⊙ galaxies at < z>≃2.7 is ρ=1.2 ± 0.7× 10-4 Mpc-3, about a factor two higher than the predictions of hierarchical models. The comparison with the local density of galaxies implies that the three galaxies must have already formed most of their stellar mass and that they cannot follow an evolution significantly different from a passive aging. The comparison with the density of local L≥L* early types (passively evolved galaxies) suggests that their co-moving density cannot decrease by more than a factor 2.5-3 from z=0 to z≃3 suggesting that up to 40% of the stellar mass content of bright (L≥L*) local early type galaxies was already in place at z>2.5.

  20. Supernovae and their host galaxies - II. The relative frequencies of supernovae types in spirals

    NASA Astrophysics Data System (ADS)

    Hakobyan, A. A.; Nazaryan, T. A.; Adibekyan, V. Zh.; Petrosian, A. R.; Aramyan, L. S.; Kunth, D.; Mamon, G. A.; de Lapparent, V.; Bertin, E.; Gomes, J. M.; Turatto, M.

    2014-11-01

    We present an analysis of the relative frequencies of different supernova (SN) types in spirals with various morphologies and in barred or unbarred galaxies. We use a well-defined and homogeneous sample of spiral host galaxies of 692 SNe from the Sloan Digital Sky Survey in different stages of galaxy-galaxy interaction and activity classes of nucleus. We propose that the underlying mechanisms shaping the number ratios of SNe types can be interpreted within the framework of interaction-induced star formation, in addition to the known relations between morphologies and stellar populations. We find a strong trend in behaviour of the NIa/NCC ratio depending on host morphology, such that early spirals include more Type Ia SNe. The NIbc/NII ratio is higher in a broad bin of early-type hosts. The NIa/NCC ratio is nearly constant when changing from normal, perturbed to interacting galaxies, then declines in merging galaxies, whereas it jumps to the highest value in post-merging/remnant galaxies. In contrast, the NIbc/NII ratio jumps to the highest value in merging galaxies and slightly declines in post-merging/remnant subsample. The interpretation is that the star formation rates and morphologies of galaxies, which are strongly affected in the final stages of interaction, have an impact on the number ratios of SNe types. The NIa/NCC (NIbc/NII) ratio increases (decreases) from star-forming to active galactic nuclei (AGN) classes of galaxies. These variations are consistent with the scenario of an interaction-triggered starburst evolving into AGN during the later stages of interaction, accompanied with the change of star formation and transformation of the galaxy morphology into an earlier type.

  1. On the nature and correction of the spurious S-wise spiral galaxy winding bias in Galaxy Zoo 1

    NASA Astrophysics Data System (ADS)

    Hayes, Wayne B.; Davis, Darren; Silva, Pedro

    2017-04-01

    The Galaxy Zoo 1 catalogue displays a bias towards the S-wise winding direction in spiral galaxies, which has yet to be explained. The lack of an explanation confounds our attempts to verify the Cosmological Principle, and has spurred some debate as to whether a bias exists in the real Universe. The bias manifests not only in the obvious case of trying to decide if the universe as a whole has a winding bias, but also in the more insidious case of selecting which Galaxies to include in a winding direction survey. While the former bias has been accounted for in a previous image-mirroring study, the latter has not. Furthermore, the bias has never been corrected in the GZ1 catalogue, as only a small sample of the GZ1 catalogue was reexamined during the mirror study. We show that the existing bias is a human selection effect rather than a human chirality bias. In effect, the excess S-wise votes are spuriously 'stolen' from the elliptical and edge-on-disc categories, not the Z-wise category. Thus, when selecting a set of spiral galaxies by imposing a threshold T so that max (PS, PZ) > T or PS + PZ > T, we spuriously select more S-wise than Z-wise galaxies. We show that when a provably unbiased machine selects which galaxies are spirals independent of their chirality, the S-wise surplus vanishes, even if humans still determine the chirality. Thus, when viewed across the entire GZ1 sample (and by implication, the Sloan catalogue), the winding direction of arms in spiral galaxies as viewed from Earth is consistent with the flip of a fair coin.

  2. The Black Hole Mass - Pitch Angle Relation of Type I AGN In Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Schilling, Amanda; Jones, Logan; Hughes, John A.; Barrows, R. Scott; Kennefick, Julia D.

    2017-01-01

    A relationship between the mass of supermassive black holes, M, at the center of galaxies and the pitch angle, P, a measure of tightness of spiral arms, was recently reported by Berrier, et al. (2013 ApJ 769, 132) for late type galaxies. The relationship, established for a local sample, shows that spiral galaxies with tighter pitch angles host higher mass black holes. In this work, we explore the M-P relation for a sample of 50 low to moderate redshift (0.04spiral galaxies that host Type 1 Active Galactic Nuclei, AGN. These objects were selected from the SDSS quasar catalog and various studies involving HST imaging. Broad Hβ, Hα, and MgII and narrow [OIII]λ5007 emission lines were used with established mass scaling relations to estimate black-hole mass. Pitch angles were measured using a 2DFFT technique (Davis, et al., 2012 ApJS 199, 33). We find that the M-P relation for the higher redshift, AGN sample differs from that of the local sample and discuss the possibility of AGN feedback by looking at a proposed Fundamental Plane for late-type galaxies - a correlation between bulge mass, disk mass, and spiral-arm pitch angle (Davis, et al. 2015, ApJ 802, L13).

  3. Galaxy And Mass Assembly (GAMA): Gas Fueling of Spiral Galaxies in the Local Universe. I. The Effect of the Group Environment on Star Formation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Norberg, P.; Robotham, A. S. G.; Liske, J.; Andrae, E.; Baldry, I. K.; Gunawardhana, M.; Kelvin, L. S.; Madore, B. F.; Seibert, M.; Taylor, E. N.; Alpaslan, M.; Brown, M. J. I.; Cluver, M. E.; Driver, S. P.; Bland-Hawthorn, J.; Holwerda, B. W.; Hopkins, A. M.; Lopez-Sanchez, A. R.; Loveday, J.; Rushton, M.

    2017-03-01

    We quantify the effect of the galaxy group environment (for group masses of 1012.5–1014.0 M ⊙) on the current star formation rate (SFR) of a pure, morphologically selected sample of disk-dominated (i.e., late-type spiral) galaxies with redshift ≤0.13. The sample embraces a full representation of quiescent and star-forming disks with stellar mass M * ≥ 109.5 M ⊙. We focus on the effects on SFR of interactions between grouped galaxies and the putative intrahalo medium (IHM) of their host group dark matter halos, isolating these effects from those induced through galaxy–galaxy interactions, and utilizing a radiation transfer analysis to remove the inclination dependence of derived SFRs. The dependence of SFR on M * is controlled for by measuring offsets Δlog(ψ *) of grouped galaxies about a single power-law relation in specific SFR, {\\psi }* \\propto {M}* -0.45+/- 0.01, exhibited by non-grouped “field” galaxies in the sample. While a small minority of the group satellites are strongly quenched, the group centrals and a large majority of satellites exhibit levels of ψ * statistically indistinguishable from their field counterparts, for all M *, albeit with a higher scatter of 0.44 dex about the field reference relation (versus 0.27 dex for the field). Modeling the distributions in Δlog(ψ *), we find that (i) after infall into groups, disk-dominated galaxies continue to be characterized by a similar rapid cycling of gas into and out of their interstellar medium shown prior to infall, with inflows and outflows of ∼1.5–5 x SFR and ∼1–4 x SFR, respectively; and (ii) the independence of the continuity of these gas flow cycles on M * appears inconsistent with the required fueling being sourced from gas in the circumgalactic medium on scales of ∼100 kpc. Instead, our data favor ongoing fueling of satellites from the IHM of the host group halo on ∼Mpc scales, i.e., from gas not initially associated with the galaxies upon infall. Consequently

  4. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    NASA Astrophysics Data System (ADS)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 < z < 0.06 from the Sloan Digital Sky Survey, I will present results illustrating the role of mergers in triggering bars, rings, spiral arms and AGN as a function of close pair separation and merger ratios as well as their dependence on morphology and other physical properties of the galaxies. Time permitting, I will show how resolved IFU observations from SDSS MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  5. SPIN ALIGNMENTS OF SPIRAL GALAXIES WITHIN THE LARGE-SCALE STRUCTURE FROM SDSS DR7

    SciTech Connect

    Zhang, Youcai; Yang, Xiaohu; Luo, Wentao; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C. E-mail: xyang@sjtu.edu.cn

    2015-01-01

    Using a sample of spiral galaxies selected from the Sloan Digital Sky Survey Data Release 7 and Galaxy Zoo 2, we investigate the alignment of spin axes of spiral galaxies with their surrounding large-scale structure, which is characterized by the large-scale tidal field reconstructed from the data using galaxy groups above a certain mass threshold. We find that the spin axes only have weak tendencies to be aligned with (or perpendicular to) the intermediate (or minor) axis of the local tidal tensor. The signal is the strongest in a cluster environment where all three eigenvalues of the local tidal tensor are positive. Compared to the alignments between halo spins and the local tidal field obtained in N-body simulations, the above observational results are in best agreement with those for the spins of inner regions of halos, suggesting that the disk material traces the angular momentum of dark matter halos in the inner regions.

  6. The Supermassive Black Hole Mass - Pitch Angle Relation in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Kennefick, Daniel; Berrier, J. C.; Kennefick, J. D.; Seigar, M.; Davis, B. L.; Barrows, R. S.; Shields, D.; Lacy, C. H.

    2013-01-01

    We present new and improved evidence for a strong correlation, with low scatter, between supermassive black hole mass and spiral arm pitch angle in disk galaxies. Such a correlation could be a useful tool for developing a SMBH mass function for both local and distant galaxies, because other host galaxy features which correlate with black hole mass either require expensive spectroscopy (as in the M-sigma relation) or work less well for spiral than for other galaxies because of the need to disentangle the bulge component from the disk and bar components (Bulge luminosity or Sersic index). A late-type SMBH mass function derived from pitch angle measurements could complement nicely early-type mass functions derived from these other measurements, especially because the late-type mass function has so far received less attention than the early-type mass function.

  7. The 2X-Hi disks of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Koribalski, Bärbel S.

    2017-03-01

    The outskirts of galaxies - especially the very extended Hi disks of galaxies - are strongly affected by their local environment. I highlight the giant 2X-Hi disks of nearby galaxies (M 83, NGC 3621, and NGC 1512), studied as part of the Local Volume Hi Survey (LVHIS), their kinematics and relation to XUV disks, signatures of tidal interactions and accretion events, the M HI - D HI relation as well as the formation of tidal dwarf galaxies. - Using multi-wavelength data, I create 3D visualisations of the gas and stars in galaxies, with the shape of their warped disks obtained through kinematic modelling of their Hi velocity fields.

  8. SPECTROSCOPIC CONFIRMATION OF FAINT LYMAN BREAK GALAXIES NEAR REDSHIFT FIVE IN THE HUBBLE ULTRA DEEP FIELD

    SciTech Connect

    Rhoads, James E.; Malhotra, Sangeeta; Cohen, Seth; Grogin, Norman; Hathi, Nimish; Ryan, Russell; Straughn, Amber; Windhorst, Rogier A. Pirzkal, Norbert; Xu Chun; Koekemoer, Anton; Panagia, Nino; Dickinson, Mark; Ferreras, Ignacio; Gronwall, Caryl; Kuemmel, Martin; Walsh, Jeremy; Meurer, Gerhardt; Pasquali, Anna; Yan, H.-J.

    2009-05-20

    We present the faintest spectroscopically confirmed sample of z {approx} 5 Lyman break galaxies (LBGs) to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the Grism ACS Program for Extragalactic Science (GRAPES) and Probing Evolution and Reionization Spectroscopically (PEARS) projects, using the G800L grism on the Hubble Space Telescope Advanced Camera for Surveys. We report here confirmations of 39 galaxies, preselected as candidate LBGs using photometric selection criteria. We compare a 'traditional' V-dropout selection, based on the work of Giavalisco et al., to a more liberal one (with V - i > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Ly{alpha} emission properties of our sample. We find that Ly{alpha} emission is detected in {approx}1/4 of the sample, and that the liberal V-dropout color selection includes {approx}55% of previously published line-selected Ly{alpha} sources. Finally, we examine our stacked two-dimensional spectra. We demonstrate that strong, spatially extended ({approx}1'') Ly{alpha} emission is not a generic property of these LBGs, but that a modest extension of the Ly{alpha} photosphere (compared to the starlight) may be present in those galaxies with prominent Ly{alpha} emission.

  9. Spectroscopic Confirmation of Faint Lyman Break Galaxies Near Redshift Five in the Hubble Ultra Deep Field

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, Sangeeta; Pirzkal, Norbert; Dickinson, Mark; Cohen, Seth; Grogin, Norman; Hathi, Nimish; Xu, Chun; Ferreras, Ignacio; Gronwall, Caryl; Koekemoer, Anton; Kümmel, Martin; Meurer, Gerhardt; Panagia, Nino; Pasquali, Anna; Ryan, Russell; Straughn, Amber; Walsh, Jeremy; Windhorst, Rogier A.; Yan, Hao-Jing

    2009-05-01

    We present the faintest spectroscopically confirmed sample of z ~ 5 Lyman break galaxies (LBGs) to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the Grism ACS Program for Extragalactic Science (GRAPES) and Probing Evolution and Reionization Spectroscopically (PEARS) projects, using the G800L grism on the Hubble Space Telescope Advanced Camera for Surveys. We report here confirmations of 39 galaxies, preselected as candidate LBGs using photometric selection criteria. We compare a "traditional" V-dropout selection, based on the work of Giavalisco et al., to a more liberal one (with V - i > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Lyα emission properties of our sample. We find that Lyα emission is detected in ~1/4 of the sample, and that the liberal V-dropout color selection includes ~55% of previously published line-selected Lyα sources. Finally, we examine our stacked two-dimensional spectra. We demonstrate that strong, spatially extended (~1'') Lyα emission is not a generic property of these LBGs, but that a modest extension of the Lyα photosphere (compared to the starlight) may be present in those galaxies with prominent Lyα emission.

  10. The Cluster Population of the Irregular Galaxy NGC 4449 as Seen by the Hubble Advanced Camera for Surveys

    NASA Astrophysics Data System (ADS)

    Annibali, F.; Tosi, M.; Aloisi, A.; van der Marel, R. P.

    2011-10-01

    We present a study of the star cluster population in the starburst irregular galaxy NGC 4449 based on B, V, I, and Hα images taken with the Advanced Camera for Surveys on the Hubble Space Telescope. We derive cluster properties such as size, ellipticity, and total magnitude. Cluster ages and masses are derived fitting the observed spectral energy distributions with different population synthesis models. Our analysis is strongly affected by the age-metallicity degeneracy; however, if we assume a metallicity of ~1/4 solar, as derived from spectroscopy of H II regions, we find that the clusters have ages distributed quite continuously over a Hubble time, and they have masses from ~103 M sun up to ~2 × 106 M sun, assuming a Salpeter initial mass function down to 0.1 M sun. Young clusters are preferentially located in regions of young star formation (SF), while old clusters are distributed over the whole NGC 4449 field of view, like the old stars (although we note that some old clusters follow linear structures, possibly a reflection of past satellite accretion). The high SF activity in NGC 4449 is confirmed by its specific frequency of young massive clusters, higher than the average value found in nearby spirals and in the Large Magellanic Cloud (but lower than in other starburst dwarfs such as NGC 1705 and NGC 1569), and by the flat slope of the cluster luminosity function (dN(LV )vpropL -1.5 V dL for clusters younger than 1 Gyr). We use the upper envelope of the cluster log(mass) versus log(age) distribution to quantify cluster disruption, and do not find evidence for the high (90%) long-term infant mortality found by some studies. For the red clusters, we find correlations between size, ellipticity, luminosity, and mass: brighter and more massive clusters tend to be more compact, and brighter clusters also tend to be more elliptical. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute which is operated

  11. A spiral in the Air Pump

    NASA Image and Video Library

    2013-09-02

    Lying over 110 million light-years away from Earth in the constellation of Antlia (The Air Pump) is the spiral galaxy IC 2560, shown here in an image from NASA/ESA Hubble Space Telescope. At this distance it is a relatively nearby spiral galaxy, and is part of the Antlia cluster — a group of over 200 galaxies held together by gravity. This cluster is unusual; unlike most other galaxy clusters, it appears to have no dominant galaxy within it. In this image, it is easy to spot IC 2560's spiral arms and barred structure. This spiral is what astronomers call a Seyfert-2 galaxy, a kind of spiral galaxy characterised by an extremely bright nucleus and very strong emission lines from certain elements — hydrogen, helium, nitrogen, and oxygen. The bright centre of the galaxy is thought to be caused by the ejection of huge amounts of super-hot gas from the region around a central black hole. There is a story behind the naming of this quirky constellation — Antlia was originally named antlia pneumatica by French astronomer Abbé Nicolas Louis de Lacaille, in honour of the invention of the air pump in the 17th century. A version of this image was entered into the Hubble's Hidden Treasures image processing competition by contestant Nick Rose.

  12. The opacity of spiral galaxy disks: IX. Dust and gas surface densities

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Allen, R. J.; de Blok, W. J. G.; Bouchard, A.; González-Lópezlira, R. A.; van der Kruit, P. C.; Leroy, A.

    2013-03-01

    Our aim is to explore the relation between gas, atomic and molecular, and dust in spiral galaxies. Gas surface densities are from atomic hydrogen and CO line emission maps. To estimate the dust content, we use the disk opacity as inferred from the number of distant galaxies identified in twelve HST/WFPC2 fields of ten nearby spiral galaxies. The observed number of distant galaxies is calibrated for source confusion and crowding with artificial galaxy counts and here we verify our results with sub-mm surface brightnesses from archival Herschel-SPIRE data. We find that the opacity of the spiral disk does not correlate well with the surface density of atomic (H I) or molecular hydrogen (H_2) alone implying that dust is not only associated with the molecular clouds but also the diffuse atomic disk in these galaxies. Our result is a typical dust-to-gas ratio of 0.04, with some evidence that this ratio declines with galactocentric radius, consistent with recent Herschel results. We discuss the possible causes of this high dust-to-gas ratio; an over-estimate of the dust surface-density, an under-estimate of the molecular hydrogen density from CO maps or a combination of both. We note that while our value of the mean dust-to-gas ratio is high, it is consistent with the metallicity at the measured radii if one assumes the Pilyugin & Thuan (2005) calibration of gas metallicity.

  13. A neutral hydrogen study of the barred spiral galaxy NGC 3319

    NASA Astrophysics Data System (ADS)

    Moore, E. M.; Gottesman, S. T.

    1998-03-01

    Neutral hydrogen line observations of the late-type barred spiral galaxy NGC 3319 are presented. The distribution and kinematics of the galaxy are studied using the Very Large Array, with spatial resolutions between 11 and 50 arcsec and a channel separation of 10.33 km/s. As is typical for late-type galaxies, NGC 3319 is rich in H I, with a gaseous bar and spiral features. Several large, low-density regions are present, and the H I spiral structure is distorted, especially in the south. The gas distribution is asymmetric and extends significantly further to the southeast due to a long, off-center tail. Noncircular motions caused by the bar, spiral structure, and low-density regions are present in the radial velocity field, complicating the rotation curve analysis. These nonaxisymmetric structures cause the values of the position angle and inclination derived from the velocity field to vary across the disk. In addition, beyond a radius of 180 arcsec, the velocity field is severely perturbed on the approaching (southern) side of the galaxy, and the disk becomes nonplanar. However, the galaxy does not show the typical 'integral sign' shape of a warped system. We detect a small system approximately 11 arcmin south of the center of NGC 3319. It is seen in eight velocity channels and is coincident with a small, resolved object in the Palomar Sky Survey. A tidal interaction between this object and NGC 3319 is the most likely cause of the distorted spiral structure, the H I tail, and the velocity perturbations found in the southern half of the galaxy. Infalling tidal debris from such an event may account for the large, low-density regions found in the disk, several of which show kinematic evidence that suggest they are expanding superstructures.

  14. Les Abondances Chimiques dans les Galaxies Spirales de Type Precoce

    NASA Astrophysics Data System (ADS)

    Dutil, Yvan

    1998-09-01

    Les galaxies spriales presentent une distribution continue de formes et de proprietes physiques. A l'heure actuelle, il existe deux ecoles de pensee au sujet de la nature de ces proprietes morphologiques des galaxies. Pour certains elles sont innees, pour d'autres elles sont acquises. Les gradients d'abondance nebulaires, de par leur sensibilite aux mouvements a grande echelle du gaz et au taux de formation stellaire, offrent une possibilite de trancher dans ce debat. Toutefois, jusqu'ici, on a surtout observe les gradients d'abondance dans les galaxies de type tardif. Le premier objectif de cette these est d'enrichir l'echantillon de galaxies de type precoce observees. Le second objectif est de demontrer qu'il y a deja eu une barre dans les galaxies de type precoce et, si possible, de chercher des traces d'interactions dans ces galaxies. Dans le cadre de cette these, j'ai observe huit galaxies de type precoce. Mes observations indiquent que ces galaxies presentent des profils d'abondance dont les caracteristiques se rapprochent des galaxies barrees, meme si certaines ne presentent pas de barres. Ce resultat renforce l'hypothese selon laquelle les galaxies changent de type morphologique au cours du temps sous l'effet d'instabilites comme les barres.

  15. Hubble and Keck team up to find farthest known galaxy in the Universe

    NASA Astrophysics Data System (ADS)

    2004-02-01

    Galaxy cluster Abell 2218 hi-res Size hi-res: 5212 Kb Credits: European Space Agency, NASA, J.-P. Kneib (Observatoire Midi-Pyrénées) and R. Ellis (Caltech) Close-up of the large galaxy cluster Abell 2218 This close-up of the large galaxy cluster Abell 2218 shows how this cluster acts as one of nature’s most powerful ‘gravitational telescopes’ and amplifies and stretches all galaxies lying behind the cluster core (seen as red, orange and blue arcs). Such natural gravitational ‘telescopes’ allow astronomers to see extremely distant and faint objects that could otherwise not be seen. A new galaxy (split into two ‘images’ marked with an ellipse and a circle) was detected in this image taken with the Advanced Camera for Surveys on board the NASA/ESA Hubble Space Telescope. The extremely faint galaxy is so far away that its visible light has been stretched into infrared wavelengths, making the observations particularly difficult. The galaxy may have set a new record in being the most distant known galaxy in the Universe. Located an estimated 13 billion light-years away (z~7), the object is being viewed at a time only 750 million years after the big bang, when the Universe was barely 5 percent of its current age. In the image the distant galaxy appears as multiple ‘images’, an arc (left) and a dot (right), as its light is forced along different paths through the cluster’s complex clumps of mass (the yellow galaxies) where the magnification is quite large. The colour of the different lensed galaxies in the image is a function of their distances and galaxy types. The orange arc is for instance an elliptical galaxy at moderate redshift (z=0.7) and the blue arcs are star forming galaxies at intermediate redshift (z between 1 and 2.5). An image of Abell 2218 hi-res Size hi-res: 29 563 Kb Credits: European Space Agency, NASA, J.-P. Kneib (Observatoire Midi-Pyrénées) and R. Ellis (Caltech) A ground-based wide-angle image of Abell 2218 This wide

  16. Probing Bursty Star Formation in Faint Galaxies with the Hubble Frontier Fields

    NASA Astrophysics Data System (ADS)

    Finkelstein, Steven; Livermore, Rachael; Song, Mimi

    2015-08-01

    The Hubble Frontier Fields have magnified our view into the formation and evolution of galaxies in the first billion years after the Big Bang. One key issue these data can probe is how galaxies grow their stellar masses. Do they grow smoothly with time, dominated by steady gas inflow? Or is their growth more stochastic, dominated by starburst triggering events such as mergers or clumpy gas inflows? A bevy of observational studies have shown that the star formation rates (SFRs) of distant galaxies increase with time, while theoretical studies, which broadly agree on long timescales, show that the SFRs may vary significantly on shorter timescales. We have compiled a sample of galaxies over a wide dynamic range in SFR by combining the HFF imaging with the CANDELS and HUDF datasets. By comparing the scatter in SFRs to SPH and semi-analytic models with known star formation histories, we directly measure the fraction of galaxies at a given epoch undergoing starbursts. This has a variety of implications on the distant universe, including reionization, as a significant burst fraction could both increase the number of ionizing photons being produced, as well as disturb the interstellar medium enough to allow these photons to escape.

  17. Spectrophotometry of faint cluster galaxies and the Hubble diagram - An approach to cosmology

    NASA Technical Reports Server (NTRS)

    Gunn, J. E.; Oke, J. B.

    1975-01-01

    New spectrophotometric data are presented for large-redshift galaxies in clusters. A new approach to aperture corrections and the analysis of the Hubble diagram is outlined, including the explicit incorporation of evolutionary effects. The importance of selection effects on the usual methods of analysis are in principle overcome in the analysis, although the heterogeneity of the sample still makes conclusions about cosmology slightly suspect. Formal values of the deceleration parameter are derived under several sets of assumptions, yielding results between +0.33 and -1.27 with formal standard deviations of order 0.7.

  18. Kinematics of 10 Early-Type Galaxies from Hubble Space Telescope and Ground-based Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pinkney, Jason; Gebhardt, Karl; Bender, Ralf; Bower, Gary; Dressler, Alan; Faber, S. M.; Filippenko, Alexei V.; Green, Richard; Ho, Luis C.; Kormendy, John; Lauer, Tod R.; Magorrian, John; Richstone, Douglas; Tremaine, Scott

    2003-10-01

    We present stellar kinematics for a sample of 10 early-type galaxies observed using the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope and the Modular Spectrograph on the MDM Observatory 2.4 m telescope. These observations are a part of an ongoing program to understand the coevolution of supermassive black holes and their host galaxies. Our spectral ranges include either the calcium triplet absorption lines at 8498, 8542, and 8662 Å or the Mg b absorption at 5175 Å. The lines are used to derive line-of-sight velocity distributions (LOSVDs) of the stars using a maximum penalized likelihood method. We use Gauss-Hermite polynomials to parameterize the LOSVDs and find predominantly negative h4 values (boxy distributions) in the central regions of our galaxies. One galaxy, NGC 4697, has significantly positive central h4 (high tail weight). The majority of galaxies have a central velocity dispersion excess in the STIS kinematics over ground-based velocity dispersions. The galaxies with the strongest rotational support, as quantified with vmax/σSTIS, have the smallest dispersion excess at STIS resolution. The best-fitting, general, axisymmetric dynamical models (described in a companion paper) require black holes in all cases, with masses ranging from 106.5 to 109.3 Msolar. We replot these updated masses on the MBH-σ relation and show that the fit to only these 10 galaxies has a slope consistent with the fits to larger samples. The greatest outlier is NGC 2778, a dwarf elliptical with relatively poorly constrained black hole mass. The two best candidates for pseudobulges, NGC 3384 and NGC 7457, do not deviate significantly from the established relation between MBH and σ. Neither do the three galaxies that show the most evidence of a recent merger, NGC 3608, NGC 4473, and NGC 4697. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the

  19. Formation of S0 galaxies through mergers. Explaining angular momentum and concentration change from spirals to S0s

    NASA Astrophysics Data System (ADS)

    Querejeta, M.; Eliche-Moral, M. C.; Tapia, T.; Borlaff, A.; van de Ven, G.; Lyubenova, M.; Martig, M.; Falcón-Barroso, J.; Méndez-Abreu, J.

    2015-07-01

    The CALIFA team has recently found that the stellar angular momentum and concentration of late-type spiral galaxies are incompatible with those of lenticular galaxies (S0s), concluding that fading alone cannot satisfactorily explain the evolution from spirals into S0s. Here we explore whether major mergers can provide an alternative way to transform spirals into S0s by analysing the spiral-spiral major mergers from the GalMer database that lead to realistic, relaxed S0-like galaxies. We find that the change in stellar angular momentum and concentration can explain the differences in the λRe-R90/R50 plane found by the CALIFA team. Major mergers thus offer a feasible explanation for the transformation of spirals into S0s. Table 1 is available in electronic form at http://www.aanda.org

  20. HUBBLE SPACE TELESCOPE Imaging of the Host Galaxies of High-RedshiftRadio-loud Quasars

    NASA Astrophysics Data System (ADS)

    Lehnert, Matthew D.; van Breugel, Wil J. M.; Heckman, Timothy M.; Miley, George K.

    1999-09-01

    We present rest-frame UV and Lyα images of spatially resolved structures (``hosts'') around five high-redshift radio-loud quasars obtained with the WFPC2 camera on the Hubble Space Telescope (HST). The quasars were imaged with the PC1 through the F555W (``V''-band) filter, which at the redshifts of the quasars (2.1galaxies that appeared to have properties similar to those of high-redshift radio galaxies. Our HST observations allow a more detailed investigation of quasar host morphologies and a comparison with similar HST studies of radio galaxies by others. Using several methods to measure and quantify the host properties we find that all five quasars are extended and that this ``fuzz'' contains ~5%-40% of the total continuum flux and 15%-65% of the Lyα flux within a radius of about 1.5". The rest-frame UV luminosities of the hosts are log λPλ~11.9-12.5 Lsolar (assuming no internal dust extinction), comparable to the luminous radio galaxies at similar redshifts and a factor 10 higher than both radio-quiet field galaxies at z~2-3 and the most UV-luminous low-redshift starburst galaxies. The Lyα luminosities of the hosts are log LLyα~44.3-44.9 ergs s-1, which are also similar to the those of luminous high-redshift radio galaxies and considerably larger than the Lyα luminosities of high-redshift field galaxies. To generate the Lyα luminosities of the hosts would require roughly a few percent of the total observed ionizing luminosity of the quasar. The UV continuum morphologies of the hosts appear complex and knotty at the relatively high surface brightness levels of our exposures (about 24 V mag arcsec-2). In two quasars we find evidence for foreground galaxies that confuse the

  1. Massive Star Formation in Early-type(Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, S.

    1999-12-01

    We have conducted an Hα imaging survey of 57 bright, nearby, early-type spiral galaxies. The new Hα images have revealed them to be a heterogeneous class of galaxies with Hα morphologies ranging from filamentary, low luminosity nuclear emission line spirals to what we suspect are compact, luminous nuclear starbursts. Contrary to popular perception, our images have revealed a significant number(15-20%) of Sa-Sab galaxies with massive star formation rates comparable to the most prolifically star forming Sc galaxies. A determination of the Hα morphology and a measure of the Hα luminosity suggests that early-type spirals can be classified into two broad categories. The first category includes galaxies for which the individual HII regions have L(Hα ) < 1039 erg/s. Most of the category 1 galaxies appear to be morphologically undisturbed, but show a wide diversity in nuclear Hα properties. The second category includes galaxies which have at least one HII region in the disk with L(Hα ) >= 1039 erg/s. All category 2 galaxies show morphological peculiarities, such as tidal tails, which suggests that the anomalously luminous HII regions may have formed as a result of a recent interaction. We have also determined HII region luminosity functions for a subset of our sample and find that the shape of the HII region LF is different when a giant HII region is present compared to a galaxy which contains only HII regions of modest luminosity. The difference may point to corresponding differences in massive star formation triggering mechanisms.

  2. MEASUREMENT OF GALACTIC LOGARITHMIC SPIRAL ARM PITCH ANGLE USING TWO-DIMENSIONAL FAST FOURIER TRANSFORM DECOMPOSITION

    SciTech Connect

    Davis, Benjamin L.; Berrier, Joel C.; Shields, Douglas W.; Kennefick, Julia; Kennefick, Daniel; Seigar, Marc S.; Lacy, Claud H. S.; Puerari, Ivanio

    2012-04-01

    A logarithmic spiral is a prominent feature appearing in a majority of observed galaxies. This feature has long been associated with the traditional Hubble classification scheme, but historical quotes of pitch angle of spiral galaxies have been almost exclusively qualitative. We have developed a methodology, utilizing two-dimensional fast Fourier transformations of images of spiral galaxies, in order to isolate and measure the pitch angles of their spiral arms. Our technique provides a quantitative way to measure this morphological feature. This will allow comparison of spiral galaxy pitch angle to other galactic parameters and test spiral arm genesis theories. In this work, we detail our image processing and analysis of spiral galaxy images and discuss the robustness of our analysis techniques.

  3. Hubble Space Telescope Medium Deep Survey. 2: Deconvolution of Wide Field Camera field galaxy images in the 13 hour + 43 deg field

    NASA Technical Reports Server (NTRS)

    Windhorst, R. A.; Schmidtke, P. C.; Pascarelle, S. M.; Gordon, J. M.; Griffiths, R. E.; Ratnatunga, K. U.; Neuschaefer, L. W.; Ellis, R. S.; Gilmore, G.; Glazebrook, K.

    1994-01-01

    We present isophotal profiles of six faint field galaxies from some of the first deep images taken for the Hubble Space Telescope (HST) Medium Deep Survey (MDS). These have redshifts in the range z = 0.126 to 0.402. The images were taken with the Wide Field Camera (WFC) in `parallel mode' and deconvolved with the Lucy method using as the point-spread function nearby stars in the image stack. The WFC deconvolutions have a dynamic range of 16 to 20 dB (4 to 5 mag) and an effective resolution approximately less than 0.2 sec (FWHM). The multiorbit HST images allow us to trace the morphology, light profiles, and color gradients of faint field galaxies down to V approximately equal to 22 to 23 mag at sub-kpc resolution, since the redshift range covered is z = 0.1 to 0.4. The goals of the MDS are to study the sub-kpc scale morphology, light profiles, and color gradients for a large samole of faint field galaxies down to V approximately equal to 23 mag, and to trace the fraction of early to late-type galaxies as function of cosmic time. In this paper we study the brighter MDS galaxies in the 13 hour + 43 deg MDS field in detail, and investigate to what extent model fits with pure exponential disks or a(exp 1/4) bulges are justified at V approximately less than 22 mag. Four of the six field galaxies have light profiles that indicate (small) inner bulges following r(exp 1/4) laws down to 0.2 sec resolution, plus a dominant surrounding exponential disk with little or no color gradients. Two occur in a group at z = 0.401, two are barred spiral galaxies at z = 0.179 and z = 0.302, and two are rather subluminous (and edge-on) disk galaxies at z = 0.126 and z = 0.179. Our deep MDS images can detect galaxies down to V, I approximately less than 25 to 26 mag, and demonstrate the impressive potential of HST--even with its pre-refurbished optics--to resolve morphological details in galaxies at cosmologically significant distances (v approximately less than 23 mag). Since the median

  4. Hα Imaging of Early-Type Sa-Sab Spiral Galaxies. II. Global Properties

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Devereux, Nick

    2005-06-01

    New results, based on one of the most comprehensive Hα imaging surveys of nearby Sa-Sab spirals completed to date, reveals early-type spirals to be a diverse group of galaxies that span a wide range in massive star formation rates. While the majority of Sa-Sab galaxies in our sample are forming stars at a modest rate, a significant fraction (~29%) exhibit star formation rates greater than 1 Msolar yr-1, rivaling the most prolifically star-forming late-type spirals. A similar diversity is apparent in the star formation history of Sa-Sab spirals as measured by their Hα equivalent widths. Consistent with our preliminary results presented in the first paper in this series, we find giant H II regions [L(Hα)>=1039 ergs s-1] in the disks of ~37% of early-type spirals. We suspect that recent minor mergers or past interactions are responsible for the elevated levels of Hα emission and, perhaps, for the presence of giant H II regions in these galaxies. Our results, however, are not in total agreement with the Hα study of Kennicutt & Kent, who did not find any early-type spirals with Hα equivalent widths >14 Å. A close examination of the morphological classification of galaxies, however, suggests that systematic differences between the Revised Shapley-Ames Catalog and the Second Reference Catalogue may be responsible for the contrasting results. Based on observations obtained with the 3.5 m telescope at Apache Point Observatory (APO) and the 0.9 m telescope at Kitt Peak National Observatory (KPNO). The APO 3.5 m telescope is owned and operated by the Astrophysical Research Consortium.

  5. Unveiling the nature of bright z ≃ 7 galaxies with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Bowler, R. A. A.; Dunlop, J. S.; McLure, R. J.; McLeod, D. J.

    2017-04-01

    We present new Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) imaging of 25 extremely luminous (-23.2 ≤ MUV ≲ -21.2) Lyman-break galaxies (LBGs) at z ≃ 7. The sample was initially selected from 1.65 deg2 of ground-based imaging in the UltraVISTA/COSMOS and UDS/SXDS fields, and includes the extreme Lyman α emitters, 'Himiko' and 'CR7'. A deconfusion analysis of the deep Spitzer photometry available suggests that these galaxies exhibit strong rest-frame optical nebular emission lines (EW0(Hβ + [O III]) > 600 Å). We find that irregular, multiple-component morphologies suggestive of clumpy or merging systems are common (fmulti > 0.4) in bright z ≃ 7 galaxies, and ubiquitous at the very bright end (MUV < -22.5). The galaxies have half-light radii in the range r1/2 ∼ 0.5-3 kpc. The size measurements provide the first determination of the size-luminosity relation at z ≃ 7 that extends to MUV ∼ -23. We find the relation to be steep with r1/2 ∝ L1/2. Excluding clumpy, multicomponent galaxies however, we find a shallower relation that implies an increased star formation rate surface density in bright LBGs. Using the new, independent, HST/WFC3 data we confirm that the rest-frame UV luminosity function at z ≃ 7 favours a power-law decline at the bright end, compared to an exponential Schechter function drop-off. Finally, these results have important implications for the Euclid mission, which we predict will detect >1000 similarly bright galaxies at z ≃ 7. Our new HST imaging suggests that the vast majority of these galaxies will be spatially resolved by Euclid, mitigating concerns over dwarf star contamination.

  6. The morphology of nine radio-selected faint galaxies from deep Hubble Space Telescope imaging

    NASA Astrophysics Data System (ADS)

    Roche, Nathan D.; Lowenthal, James D.; Koo, David C.

    2002-12-01

    Using the Hubble Space Telescope (HST) WFPC2 we perform deep I-band imaging of nine radio-selected [F(8.5 GHz) >=14 μJy] faint galaxies from the Roche, Lowenthal & Koo (2002) sample. Two are also observed in V using HST STIS. Six of the galaxies have known redshifts, in the range 0.4 < z < 1.0. Radial intensity profiles indicate that seven are disc galaxies and two are bulge-dominated. Four of the six with redshifts have a high optical surface brightness in comparison with previous studies of disc galaxies at similar redshifts (e.g. Lilly et al. 1998). The HST imaging reveals that two of the nine galaxies are in close interacting pairs and another five show morphological evidence of recent interactions - two are very asymmetric (Aasym~ 0.4) and three have large, luminous rings resembling the collisional starburst rings in the Cartwheel galaxy. For the two ring galaxies with redshifts, we measure ring radii of 7.05 and 10.0 h-150 kpc, which suggest post-collision ages 0.1-0.2 Gyr. One has a fainter inner ring, like the original Cartwheel. The remaining two appear to be late-type barred galaxies and relatively undisturbed. Our HST imaging confirms the high incidence of interactions and dynamical disturbance in faint radio-selected galaxies, as reported by Windhorst et al. and Serjeant et al., for example. In the great majority of these galaxies the high radio luminosities are probably the result of interaction-triggered starbursts. However, one interacting galaxy is a very radio-luminous giant elliptical, with red V-I colours, a normal surface brightness and no evidence of star-forming regions, so its radio source is probably an obscured active galactic nucleus (AGN). The mixture of observed morphologies suggests that enhanced radio luminosities often persist to a late stage of interaction, i.e. at least ~0.2 Gyr after the perigalactic encounter.

  7. A close nuclear black-hole pair in the spiral galaxy NGC 3393.

    PubMed

    Fabbiano, G; Wang, Junfeng; Elvis, M; Risaliti, G

    2011-08-31

    The current picture of galaxy evolution advocates co-evolution of galaxies and their nuclear massive black holes, through accretion and galactic merging. Pairs of quasars, each with a massive black hole at the centre of its galaxy, have separations of 6,000 to 300,000 light years (refs 2 and 3; 1 parsec = 3.26 light years) and exemplify the first stages of this gravitational interaction. The final stages of the black-hole merging process, through binary black holes and final collapse into a single black hole with gravitational wave emission, are consistent with the sub-light-year separation inferred from the optical spectra and light-variability of two such quasars. The double active nuclei of a few nearby galaxies with disrupted morphology and intense star formation (such as NGC 6240 with a separation of about 2,600 light years and Mrk 463 with a separation of about 13,000 light years between the nuclei) demonstrate the importance of major mergers of equal-mass spiral galaxies in this evolution; such mergers lead to an elliptical galaxy, as in the case of the double-radio-nucleus elliptical galaxy 0402+379 (with a separation of about 24 light years between the nuclei). Minor mergers of a spiral galaxy with a smaller companion should be a more common occurrence, evolving into spiral galaxies with active massive black-hole pairs, but have hitherto not been seen. Here we report the presence of two active massive black holes, separated by about 490 light years, in the Seyfert galaxy NGC 3393 (50 Mpc, about 160 million light years). The regular spiral morphology and predominantly old circum-nuclear stellar population of this galaxy, and the closeness of the black holes embedded in the bulge, provide a hitherto missing observational point to the study of galaxy/black hole evolution. Comparison of our observations with current theoretical models of mergers suggests that they are the result of minor merger evolution.

  8. Far infrared structure of spiral galaxies from the IRAS CPC images

    NASA Technical Reports Server (NTRS)

    Wainscoat, Richard J.; Chokshi, Arati; Doyle, Laurance R.

    1989-01-01

    Significant extended far infrared (50 micron and 100 micron) structure was found for five face-on spiral galaxies (NGC2403, M51, M83, NGC6946, and IC342) from fourteen galaxies searched in the Infrared Astronomy Satellite (IRAS) chopped photometric channel (CPC) catalogue. Images were initially processed to remove instrumental and background artifacts, the isophotal centroids of each image determined, and multiple images of each galaxy (for each wavelength) superimposed and averaged to improve signal-to-noise. Calibration of these images was performed using IRAS survey array data. Infrared isophotes were then superimposed on optical (blue) images so that direct structural comparisons could be made.

  9. The Discovery of Seven Extremely Low Surface Brightness Galaxies in the Field of the Nearby Spiral Galaxy M101

    NASA Astrophysics Data System (ADS)

    Merritt, Allison; van Dokkum, Pieter; Abraham, Roberto

    2014-06-01

    Dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, which makes it difficult to identify and study them outside of the Local Group. We used a low surface brightness-optimized telescope, the Dragonfly Telephoto Array, to search for dwarf galaxies in the field of the massive spiral galaxy M101. We identify seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of μ g ~ 25.5-27.5 mag arcsec-2. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Assuming the galaxies are dwarf satellites of M101, their absolute magnitudes are in the range -11.6 <~ MV <~ -9.3 and their effective radii are 350 pc-1.3 kpc. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (n ~ 0.3-0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Distance measurements are required to determine whether these galaxies are in fact associated with M101 or are in its foreground or background.

  10. The Hubble Heritage Image of the Polar-Ring Galaxy NGC 4650A

    NASA Astrophysics Data System (ADS)

    Kinney, A. L.; Gallagher, J.; Matthews, L.; Sparke, L.; Bond, H. E.; Christian, C. A.; English, J.; Frattare, L.; Hamilton, F.; Levay, Z.; Noll, K.; Hubble Heritage Team

    1999-05-01

    The Hubble Heritage Project has the aim of providing the public with pictorially striking images of celestial objects obtained with the Hubble Space Telescope. As part of the Heritage Project, we have used HST to obtain a multi-color image of the peculiar galaxy NGC 4650A. This was the first Heritage observation for which the public joined in the target selection. NGC 4650A was chosen in the winter of 1998-99 from among several candidate objects by over 8,000 members of the public, who used the Heritage web site (heritage.stsci.edu) to register their votes. The WFPC2 observations were obtained in April 1999, in the wide B (F450W), wide V (F606W), and I (F814W) bands. The resulting full-color image will be presented at the AAS meeting and on our web site, and the actual data frames are available publicly in the HST archive for use by interested scientists. NGC 4650A, located at a distance of about 40 Mpc, is the best-known and most spectacular example of the rare class of ``polar-ring'' galaxies. These objects are probably the remnants of collisions, in which the debris from a disrupted, gas-rich smaller galaxy has gone into orbit around a larger galaxy. The HST image of NGC 4650A shows a rotating, almost edge-on inner disk of old red stars, around which orbits a younger ring of dust, gas, and stars, in a plane that is nearly perpendicular to that of the old disk. Numerous young blue star clusters reveal that active star formation is occurring within the polar ring, triggered by the collision process. Polar rings are particularly useful for probing the distribution of dark matter in galactic halos.

  11. 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

  12. Spiral Arm Pitch Angle and its Significance for Theories of Galactic Structure

    NASA Astrophysics Data System (ADS)

    Kennefick, D.

    2014-03-01

    I argue that the pitch angle of spiral arms in disk galaxies is one of a number of characteristics of galaxies (which we may refer to as “traits” of a galaxy) which correlate reasonably well with each other, most of them probably determined by the mass of the galaxy's central bulge. Although often dealt with qualitatively in the past, as in Hubble's galaxy classification scheme, quantifying pitch angle opens up the prospect of using it as a probe of the mass distribution of a galaxy and as a tool for testing various theories of the origins of spiral structure in disk galaxies.

  13. Environmental Variations in the Atomic and Molecular Gas Radial Profiles of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, Christine; JCMT Nearby Galaxies Legacy Survey

    2017-01-01

    We present an analysis of the radial profiles of a sample of 43 HI-flux selected spiral galaxies from the Nearby Galaxies Legacy Survey (NGLS) with resolved James Clerk Maxwell Telescope (JCMT) CO J= 3-2 and/or Very Large Array (VLA) HI maps. Comparing the Virgo and non-Virgo populations, we confirm that the HI disks are truncated in the Virgo sample, even for these relatively HI-rich galaxies. On the other hand, the H2 distribution is enhanced for Virgo galaxies near their centres, resulting in higher H2 to HI ratios and steeper H2 and total gas radial profiles. This is likely due to the effects of moderate ram pressure stripping in the cluster environment, which would preferentially remove low density gas in the outskirts while enhancing higher density gas near the centre. Combined with Hα star formation rate data, we find that the star formation efficiency (SFR/H2) is relatively constant with radius for both samples, but Virgo galaxies have a ˜40% lower star formation efficiency than non-Virgo galaxies. These results suggest that the environment of spiral galaxies can play an important role in the formation of molecular gas and the star formation process.

  14. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Greene, J. E.; Seth, A.; Kim, M.; Läsker, R.; Goulding, A.; Gao, F.; Braatz, J. A.; Henkel, C.; Condon, J.; Lo, K. Y.; Zhao, W.

    2016-08-01

    We use new precision measurements of black hole (BH) masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive BH mass. The megamaser-derived BH masses span 106-108 {M}⊙ , while all the galaxy properties that we examine (including total stellar mass, central mass density, and central velocity dispersion) lie within a narrower range. Thus, no galaxy property correlates tightly with {M}{BH} in ˜L* spiral galaxies as traced by megamaser disks. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed {σ }* the mean megamaser {M}{BH} are offset by -0.6 ± 0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not appear to show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to an inability to resolve their spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  15. RELATIVE ORIENTATION OF PAIRS OF SPIRAL GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

    SciTech Connect

    Buxton, Jesse; Ryden, Barbara S. E-mail: ryden@astronomy.ohio-state.edu

    2012-09-10

    From our study of binary spiral galaxies in the Sloan Digital Sky Survey Data Release 6, we find that the relative orientation of disks in binary spiral galaxies is consistent with their being drawn from a random distribution of orientations. For 747 isolated pairs of luminous disk galaxies, the distribution of {phi}, the angle between the major axes of the galaxy images, is consistent with a uniform distribution on the interval [0 Degree-Sign , 90 Degree-Sign ]. With the assumption that the disk galaxies are oblate spheroids, we can compute cos {beta}, where {beta} is the angle between the rotation axes of the disks. In the case that one galaxy in the binary is face-on or edge-on, the tilt ambiguity is resolved, and cos {beta} can be computed unambiguously. For 94 isolated pairs with at least one face-on member, and for 171 isolated pairs with at least one edge-on member, the distribution of cos {beta} is statistically consistent with the distribution of cos i for isolated disk galaxies. This result is consistent with random orientations of the disks within pairs.

  16. The Near-Infrared Ca II Triplet-σ Relation for Bulges of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Falcón-Barroso, Jesús; Peletier, Reynier F.; Vazdekis, Alexandre; Balcells, Marc

    2003-05-01

    We present measurements of the near-infrared Ca II triplet (CaT, CaT*), Paschen (PaT), and magnesium (Mg I) indices for a well-studied sample of 19 bulges of early to intermediate spiral galaxies. We find that both the CaT* and CaT indices decrease with central velocity dispersion σ with small scatter. This dependence is similar to that recently found by Cenarro for elliptical galaxies, implying a uniform CaT*-σ relation that applies to galaxies from ellipticals to intermediate-type spirals. The decrease of CaT and CaT* with σ contrasts with the well-known increase of another α-element index, Mg2, with σ. We discuss the role of Ca underabundance ([Ca/Fe]<0) and initial mass function variations in the onset of the observed relations.

  17. The Surface Brightness of the Cores of Elliptical Galaxies from Hubble Space Telescope High Resolution Imaging

    NASA Astrophysics Data System (ADS)

    Ferrarese, L.; Ford, H. C.; Jaffe, W.; van den Bosch, F.; O'Connell, R. W.

    1993-12-01

    High resolution studies of the cores of elliptical galaxies are needed in order to understand the mechanisms of galaxy formation and evolution. Because ground based imaging is severely impaired by atmopheric seeing, we have undertaken a program of high resolution Hubble Space Telescope (HST) imaging of a magnitude-limited sample of 12 elliptical galaxies in the Virgo cluster. The data has been obtained using the Planetary Camera (PC) and the F555W filter (very close to the Johnson V band). The plate scale of the PC is 0.043 arcsec/pixel = 3.1 pc/pixel at an assumed distance of 14.7 Mpc to the Virgo cluster. In spite of the spherical aberration affecting the HST primary mirror, our modelling shows that deconvolution techniques allow us to recover to surface brightness parameters up to 0.3 arcsec from the centre of the galaxy, an order of magnitude improvement with respect to ground based data. For each galaxy we have determined the ellipticity, position angle of the major axis, deviations of the isophotes from pure ellipses, and the brightness profile inside a 15 arcsec radius, by iteratively fitting the isophotes. All of the galaxies studied show a unique morphology in the inner 10 arcsec. Five galaxies are found to harbour dust, in agreement with previous estimates (e.g. Lauer 1985b, Ebner et al. 1988), seven of the galaxies have isophotes deviating from pure ellipses more than 1% (cfr Peletier et al. 1990). For three galaxies, NGC4342, NGC4570, and NGC4623, we find the presence of a thin (less than 10 parsecs) elongated (~150 parsecs) nuclear structure, resembling an edge-on disk, although kinematic data is needed to confirm the presence of a separate disk component. None of the galaxies shows an isothermal core. This may be the due to the presence of a large nuclear mass concentrations, such as a nuclear black hole, the occurence of merging processes, or anisotropies in the velocity distribution.

  18. Rotation curves and metallicity gradients from HII regions in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Márquez, I.; Masegosa, J.; Moles, M.; Varela, J.; Bettoni, D.; Galletta, G.

    2002-10-01

    In this paper we study long slit spectra in the region of Hα emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected HII regions, thus producing a composite metallicity profile for different types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The [NII]/Hα ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The [NII]/Hα ratios measured for disk HII regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of Hα Equivalent Width. Tables 3 and 4 and Figs. 6, 7 and 21 are only available in electronic form at http://www.edpsciences.org. Table 5 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/389 Based on data obtained Asiago/Ekar Observatory. Also based on observations made

  19. Infall of nearby galaxies into the Virgo cluster as traced with Hubble space telescope

    SciTech Connect

    Karachentsev, Igor D.; Tully, R. Brent; Wu, Po-Feng; Shaya, Edward J.; Dolphin, Andrew E.

    2014-02-10

    We measured the tip of the red giant branch distances to nine galaxies in the direction to the Virgo cluster using the Advanced Camera for Surveys on the Hubble Space Telescope. These distances put seven galaxies (GR 34, UGC 7512, NGC 4517, IC 3583, NGC 4600, VCC 2037, and KDG 215) in front of Virgo and two galaxies (IC 3023 and KDG 177) likely inside the cluster. Distances and radial velocities of the galaxies situated between us and the Virgo core clearly exhibit the infall phenomenon toward the cluster. In the case of spherically symmetric radial infall, we estimate the radius of the 'zero-velocity surface' to be (7.2 ± 0.7) Mpc, which yields a total mass of the Virgo cluster of (8.0 ± 2.3) × 10{sup 14} M {sub ☉}, in good agreement with its virial mass estimates. We conclude that the Virgo outskirts do not contain significant amounts of dark matter beyond their virial radius.

  20. Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. 3; Measurement for URSA Minor

    NASA Technical Reports Server (NTRS)

    Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

    2005-01-01

    This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field contains a quasi-stellar object that serves as the "reference point". Integrating the motion of Ursa Minor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 40 (10, 76) and 89 (78, 160) kpc, respectively, where the values in the parentheses represent the 95% confidence intervals derived from Monte Carlo experiments. The eccentricity of the orbit is 0.39 (0.09, 0.79), and the orbital period is 1.5 (1.1, 2.7) Gyr. The orbit is retrograde and inclined by 124 degrees (94 deg, 36 deg ) to the Galactic plane. Ursa Minor is not a likely member of a proposed stream of galaxies on similar orbits around the Milky Way, nor is the plane of its orbit coincident with a recently proposed planar alignment of galaxies around the Milky Way. Comparing the orbits of Ursa Minor and Carina shows no reason for the different star formation histories of these two galaxies. Ursa Minor must contain dark matter to have a high probability of having survived disruption by the Galactic tidal force until the present.

  1. Hubble space telescope emission line galaxies at z ∼ 2: the Lyα escape fraction

    SciTech Connect

    Ciardullo, Robin; Zeimann, Gregory R.; Gronwall, Caryl; Gebhardt, Henry; Schneider, Donald P.; Hagen, Alex; Malz, A. I. E-mail: grzeimann@psu.edu E-mail: gebhardt@psu.edu E-mail: hagen@psu.edu; and others

    2014-11-20

    We compare the Hβ line strengths of 1.90 < z < 2.35 star-forming galaxies observed with the near-IR grism of the Hubble Space Telescope with ground-based measurements of Lyα from the HETDEX Pilot Survey and narrow-band imaging. By examining the line ratios of 73 galaxies, we show that most star-forming systems at this epoch have a Lyα escape fraction below ∼6%. We confirm this result by using stellar reddening to estimate the effective logarithmic extinction of the Hβ emission line (c {sub Hβ} = 0.5) and measuring both the Hβ and Lyα luminosity functions in a ∼100, 000 Mpc{sup 3} volume of space. We show that in our redshift window, the volumetric Lyα escape fraction is at most 4.4{sub −1.2}{sup +2.1}%, with an additional systematic ∼25% uncertainty associated with our estimate of extinction. Finally, we demonstrate that the bulk of the epoch's star-forming galaxies have Lyα emission line optical depths that are significantly greater than that for the underlying UV continuum. In our predominantly [O III] λ5007-selected sample of galaxies, resonant scattering must be important for the escape of Lyα photons.

  2. The Herschel Reference Survey: Dust in Early-type Galaxies and across the Hubble Sequence

    NASA Astrophysics Data System (ADS)

    Smith, M. W. L.; Gomez, H. L.; Eales, S. A.; Ciesla, L.; Boselli, A.; Cortese, L.; Bendo, G. J.; Baes, M.; Bianchi, S.; Clemens, M.; Clements, D. L.; Cooray, A. R.; Davies, J. I.; De Looze, I.; di Serego Alighieri, S.; Fritz, J.; Gavazzi, G.; Gear, W. K.; Madden, S.; Mentuch, E.; Panuzzo, P.; Pohlen, M.; Spinoglio, L.; Verstappen, J.; Vlahakis, C.; Wilson, C. D.; Xilouris, E. M.

    2012-04-01

    We present Herschel observations of 62 early-type galaxies (ETGs), including 39 galaxies morphologically classified as S0+S0a and 23 galaxies classified as ellipticals using SPIRE at 250, 350, and 500 μm as part of the volume-limited Herschel Reference Survey (HRS). We detect dust emission in 24% of the ellipticals and 62% of the S0s. The mean temperature of the dust is langTd rang = 23.9 ± 0.8 K, warmer than that found for late-type galaxies in the Virgo Cluster. The mean dust mass for the entire detected early-type sample is logMd = 6.1 ± 0.1 M ⊙ with a mean dust-to-stellar-mass ratio of log(Md /M *) = -4.3 ± 0.1. Including the non-detections, these parameters are logMd = 5.6 ± 0.1 and log(Md /M *) = -5.1 ± 0.1, respectively. The average dust-to-stellar-mass ratio for the early-type sample is fifty times lower, with larger dispersion, than the spiral galaxies observed as part of the HRS, and there is an order-of-magnitude decline in Md /M * between the S0s and ellipticals. We use UV and optical photometry to show that virtually all the galaxies lie close to the red sequence yet the large number of detections of cool dust, the gas-to-dust ratios, and the ratios of far-infrared to radio emission all suggest that many ETGs contain a cool interstellar medium similar to that in late-type galaxies. We show that the sizes of the dust sources in S0s are much smaller than those in early-type spirals and the decrease in the dust-to-stellar-mass ratio from early-type spirals to S0s cannot simply be explained by an increase in the bulge-to-disk ratio. These results suggest that the disks in S0s contain much less dust (and presumably gas) than the disks of early-type spirals and this cannot be explained simply by current environmental effects, such as ram-pressure stripping. The wide range in the dust-to-stellar-mass ratio for ETGs and the lack of a correlation between dust mass and optical luminosity suggest that much of the dust in the ETGs detected by Herschel has

  3. Hubble Frontier Fields: systematic errors in strong lensing models of galaxy clusters - implications for cosmography

    NASA Astrophysics Data System (ADS)

    Acebron, Ana; Jullo, Eric; Limousin, Marceau; Tilquin, André; Giocoli, Carlo; Jauzac, Mathilde; Mahler, Guillaume; Richard, Johan

    2017-09-01

    Strong gravitational lensing by galaxy clusters is a fundamental tool to study dark matter and constrain the geometry of the Universe. Recently, the Hubble Space Telescope Frontier Fields programme has allowed a significant improvement of mass and magnification measurements but lensing models still have a residual root mean square between 0.2 arcsec and few arcseconds, not yet completely understood. Systematic errors have to be better understood and treated in order to use strong lensing clusters as reliable cosmological probes. We have analysed two simulated Hubble-Frontier-Fields-like clusters from the Hubble Frontier Fields Comparison Challenge, Ares and Hera. We use several estimators (relative bias on magnification, density profiles, ellipticity and orientation) to quantify the goodness of our reconstructions by comparing our multiple models, optimized with the parametric software lenstool, with the input models. We have quantified the impact of systematic errors arising, first, from the choice of different density profiles and configurations and, secondly, from the availability of constraints (spectroscopic or photometric redshifts, redshift ranges of the background sources) in the parametric modelling of strong lensing galaxy clusters and therefore on the retrieval of cosmological parameters. We find that substructures in the outskirts have a significant impact on the position of the multiple images, yielding tighter cosmological contours. The need for wide-field imaging around massive clusters is thus reinforced. We show that competitive cosmological constraints can be obtained also with complex multimodal clusters and that photometric redshifts improve the constraints on cosmological parameters when considering a narrow range of (spectroscopic) redshifts for the sources.

  4. A sub-millimetre survey of dust enshrouded galaxies in the Hubble Deep Field North region

    NASA Astrophysics Data System (ADS)

    Borys, C. J.

    2002-12-01

    This thesis investigates the emission of sub-millimetre-wave radiation from galaxies in the Hubble Deep Field North region. The data were obtained from dedicated observing runs from our group and others using the SCUBA camera on the James Clerk Maxwell Telescope. The data were combined using techniques specifically developed here for low signal-to-noise source recovery. The sources found represent over 10% of all cosmological sources SCUBA has detected since it was commissioned. The number of sub-mm galaxies we detect account for a significant fraction of the sub-mm background, and we show that mild extrapolations can reproduce it entirely. We comment on their clustering properties, both with themselves and other high-redshift galaxy types. A multi-wavelength analysis of these galaxies shows that SCUBA sources do not all have similar properties, and are made of a collection including: star-forming radio galaxies; optically invisible objects; active galactic nuclei; and extremely red objects. Reasonable attempts to determine the redshift distribution of the sample show that SCUBA galaxies have a median redshift of around 2, and suggest that the global star formation rate may be dominated by such objects at redshifts beyond about 1. The thesis summarises the current state of extra-galactic sub-mm astronomy, and comments on how new surveys and detectors will allow us to place stronger constraints on the evolution properties of the high-redshift Universe. The research described here was made possible from grants by the Natural Science and Engineering Research Council of Canada, and a generous scholarship from the University of British Columbia.

  5. THE RELATIONSHIP BETWEEN THE DENSE NEUTRAL AND DIFFUSE IONIZED GAS IN THE THICK DISKS OF TWO EDGE-ON SPIRAL GALAXIES

    SciTech Connect

    Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.

    2013-03-15

    We present high-resolution, optical images (BVI + H{alpha}) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z {approx}2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our H{alpha} images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed H{alpha} emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions.

  6. High velocity dispersion in a rare grand-design spiral galaxy at redshift z = 2.18.

    PubMed

    Law, David R; Shapley, Alice E; Steidel, Charles C; Reddy, Naveen A; Christensen, Charlotte R; Erb, Dawn K

    2012-07-18

    Although grand-design spiral galaxies are relatively common in the local Universe, only one has been spectroscopically confirmed to lie at redshift z > 2 (HDFX 28; z = 2.011); and it may prove to be a major merger that simply resembles a spiral in projection. The rarity of spirals has been explained as a result of disks being dynamically 'hot' at z > 2 (refs 2-5), which may instead favour the formation of commonly observed clumpy structures. Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe. At z < 2, the velocity dispersion of disks decreases, and spiral galaxies are more numerous by z ≈ 1 (refs 7, 13-15). Here we report observations of the grand-design spiral galaxy Q2343-BX442 at z = 2.18. Spectroscopy of ionized gas shows that the disk is dynamically hot, implying an uncertain origin for the spiral structure. The kinematics of the galaxy are consistent with a thick disk undergoing a minor merger, which can drive the formation of short-lived spiral structure. A duty cycle of <100 Myr for such tidally induced spiral structure in a hot massive disk is consistent with its rarity.

  7. The Chemical Evolution Carousel of Spiral Galaxies: Azimuthal Variations of Oxygen Abundance in NGC1365

    NASA Astrophysics Data System (ADS)

    Ho, I.-Ting; Seibert, Mark; Meidt, Sharon E.; Kudritzki, Rolf-Peter; Kobayashi, Chiaki; Groves, Brent A.; Kewley, Lisa J.; Madore, Barry F.; Rich, Jeffrey A.; Schinnerer, Eva; D’Agostino, Joshua; Poetrodjojo, Henry

    2017-09-01

    The spatial distribution of oxygen in the interstellar medium of galaxies is the key to understanding how efficiently metals that are synthesized in massive stars can be redistributed across a galaxy. We present here a case study in the nearby spiral galaxy NGC 1365 using 3D optical data obtained in the TYPHOON Program. We find systematic azimuthal variations of the H ii region oxygen abundance imprinted on a negative radial gradient. The 0.2 dex azimuthal variations occur over a wide radial range of 0.3–0.7 R 25 and peak at the two spiral arms in NGC 1365. We show that the azimuthal variations can be explained by two physical processes: gas undergoes localized, sub-kiloparsec-scale self-enrichment when orbiting in the inter-arm region, and experiences efficient, kiloparsec-scale mixing-induced dilution when spiral density waves pass through. We construct a simple chemical evolution model to quantitatively test this picture and find that our toy model can reproduce the observations. This result suggests that the observed abundance variations in NGC 1365 are a snapshot of the dynamical local enrichment of oxygen modulated by spiral-driven, periodic mixing and dilution.

  8. A Technique for Separating the Gravitational Torques of Bars and Spirals in Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Buta, R.; Block, D. L.; Knapen, J. H.

    2003-09-01

    We describe a Fourier-based method of separating bars from spirals in near-infrared images. The method takes advantage of the fact that a bar is typically a feature with a relatively fixed position angle and uses the simple assumption that the relative Fourier amplitudes due to the bar decline with radius past a maximum in the same or a similar manner as they rose to that maximum. With such an assumption, the bar can be extrapolated into the spiral region and removed from an image, leaving just the spiral and the axisymmetric background disk light. We refer to such a bar-subtracted image as the ``spiral plus disk'' image. The axisymmetric background (Fourier index m=0 image) can then be added back to the bar image to give the ``bar plus disk'' image. The procedure allows us to estimate the maximum gravitational torque per unit mass per unit square of the circular speed for the bar and spiral forcing separately, parameters that quantitatively define the bar strength Qb and the spiral strength Qs following the recent study of Buta & Block. For the first time, we are able to measure the torques generated by spiral arms alone, and we can now define spiral torque classes, in the same manner as bar torque classes are delineated. We outline the complete procedure here using a 2.1 μm image of NGC 6951, a prototypical SAB(rs)bc spiral having an absolute blue magnitude of -21 and a maximum rotation velocity of 230 km s-1. Comparison between a rotation curve predicted from the m=0 near-infrared light distribution and an observed rotation curve suggests that NGC 6951 is maximum disk in its bar and main spiral region, implying that our assumption of a constant mass-to-light ratio in our analysis is probably reliable. We justify our assumption on how to make the bar extrapolation using an analysis of NGC 4394, a barred spiral with only weak near-infrared spiral structure, and we justify the number of needed Fourier terms using NGC 1530, one of the most strongly barred galaxies

  9. The Secret Lives of Galaxies

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The ground-based image in visible light locates the hub imaged with the Hubble Space Telescope. This barred galaxy feeds material into its hub, igniting star birth. The Hubble NICMOS instrument penetrates beneath the dust to reveal clusters of young stars. Footage shows ground-based, WFPC2, and NICMOS images of NGS 1365. An animation of a large spiral galaxy zooms from the edge to the galactic bulge.

  10. The Secret Lives of Galaxies

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The ground-based image in visible light locates the hub imaged with the Hubble Space Telescope. This barred galaxy feeds material into its hub, igniting star birth. The Hubble NICMOS instrument penetrates beneath the dust to reveal clusters of young stars. Footage shows ground-based, WFPC2, and NICMOS images of NGS 1365. An animation of a large spiral galaxy zooms from the edge to the galactic bulge.

  11. The Role of Interactions in the Evolution of Highly Star-forming Early-Type (Sa-Sab) Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Hameed, Salman; Young, Lisa M.

    2003-06-01

    We present a search for the signatures of galaxy-galaxy interactions in the neutral gas of early-type spirals. New neutral hydrogen observations for four highly star-forming early-type spirals are presented here, along with H I data for three additional galaxies from other sources. H I maps of six of seven galaxies reveal unambiguous signs of a recent encounter, via tidal tails and H I bridges. Most of these galaxies appear undisturbed in the optical, and these interactions probably would have gone unnoticed without H I mapping. Such high rates of interaction suggest that galactic encounters may play an important role in the evolution of early-type spiral galaxies.

  12. Hubble spies NGC 3274

    NASA Image and Video Library

    2016-11-21

    This image of the spiral galaxy NGC 3274 comes courtesy of the NASA/ESA Hubble Space Telescope’s Wide Field Camera 3 (WFC3). Hubble’s WFC3 vision spreads from the ultraviolet light through to the near infrared , allowing astronomers to study a wide range of targets, from nearby star formation through to galaxies in the most remote regions of the cosmos. This particular image combines observations gathered in five different filters, bringing together ultraviolet, visible, and infrared light to show off NGC 3274 in all its glory. As with all of the data Hubble sends back to Earth, it takes advantage of the telescope’s location in space above our planet’s distorting atmosphere. WFC3 returns clear, crisp, and detailed images time after time. NGC 3274 is a relatively faint galaxy located over 20 million light-years away in the constellation of Leo (The Lion). The galaxy was discovered by Wilhelm Herschel in 1783. The galaxy PGC 213714 is also visible on the upper right of the frame, located much further away from Earth.

  13. The Elaboration of Spiral Galaxies: Morpho-Kinematics Analyses of their Progenitors with IMAGES

    NASA Astrophysics Data System (ADS)

    Hammer, F.; Images Collaboration

    2009-12-01

    The IMAGES (Intermediate MAss Galaxy Evolution Sequence) project aims at measuring the velocity fields of a representative sample of 100 massive galaxies at z=0.4-0.75, selected in the CDFS, the CFRS and the HDFS fields. It uses the world-unique mode of multiple integral field units of FLAMES/ GIRAFFE at VLT. The resolved-kinematics data allow us to sample the large scale motions at ˜ few kpc scale for each galaxy. They have been combined with the deepest HST/ACS, Spitzer (MIPS and IRAC) and VLT/FORS2 ever achieved observations. Most intermediate redshift galaxies show anomalous velocity fields: 6 Gyrs ago, half of the present day spirals were out of equilibrium and had peculiar morphologies. The wealth of the data in these fields allow us to modelize the physical processes in each galaxy with an accuracy almost similar to what is done in the local Universe. These detailed analyses reveal the importance of merger processes, including their remnant phases. Together with the large evolution of spiral properties, this points out the importance of disk survival and strengthens the disk rebuilding scenario. This suggests that the hierarchical scenario may apply to the elaboration of disk galaxies as it does for ellipticals.

  14. High-Resolution Hα Velocity Fields of Nearby Spiral Galaxies with the Southern African Large Telescope

    NASA Astrophysics Data System (ADS)

    Mitchell, Carl; Williams, Ted; Spekkens, Kristine; Lee-Waddell, Karen; Kuzio de Naray, Rachel; Sellwood, Jerry

    2016-01-01

    In an effort to test ΛCDM predictions of galaxy mass distributions, we have obtained spectrophotometric observations of several nearby spiral galaxies with the Southern African Large Telescope (SALT) Fabry-Pérot (FP) interferometer as part of the RSS Imaging spectroscopy Nearby Galaxy Survey. Utilizing the SALT FP's 8 arcmin field of view and 2 arcsec angular resolution, we have derived 2D velocity fields of the Hα emission line to high spatial resolution at large radii. We have modeled these velocity fields with the DiskFit software package and found them to be in good agreement with lower-resolution velocity fields of the HI 21 cm line for the same galaxies. Here we present our Hα kinematic map of the barred spiral galaxy NGC 578. At the distance to this galaxy (22 Mpc), our kinematic data has a spatial resolution of 185 pc and extends to galactocentric radii of 13 kpc. The high spatial resolution of this data allows us to resolve the inner rising part of the rotation curves, which is compromised by beam smearing in lower-resolution observations. We are using these Hα kinematic data, combined with HI 21 cm kinematics and broadband photometric observations, to place constraints on NGC 578's mass distribution.

  15. The relationship between the carbon monoxide intensity and the radio continuum emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Adler, David S.; Lo, K. Y.; Allen, Ronald J.

    1991-01-01

    The relationship between the velocity-integrated CO emission and the nonthermal radio continuum brightness in the disks of normal spiral galaxies is examined on a variety of length scales. On a global scale, the total CO intensity correlates strongly with the total radio continuum flux density for a sample of 31 galaxies. On scales of about 2 kpc or more in the disk of individual galaxies, it is found that the ratio I(CO)/T(20) remains fairly constant over the entire disk as well as from galaxy to galaxy. For the eight spirals in the sample, the disk-averaged values of I(CO)/T(20) range from 0.6-2.4, with the average over all eight galaxies being 1.3 +/- 0.6. It is concluded that what these various length scales actually trace are differences in the primary heating mechanism of the gas in the beam. The observed relationship between CO and nonthermal radio continuum emission can be explained by assuming that molecular gas in galactic disks is heated primarily by cosmic rays. The observed relationship is used to show that the brightness of synchrotron emission is proportional to n(cr) exp 0.4 - 0.9 in galactic disks.

  16. Environmental Effects on the ISM and Star Formation Properties of Nearby Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Mok, Angus; Wilson, Christine

    2015-08-01

    We present the results from a sample of HI flux-selected spiral galaxies within 25 Mpc from the JCMT Nearby Galaxies Legacy Survey (NGLS), subdivided into isolated, group, and Virgo cluster samples. The CO J=3-2 line was observed with the James Clerk Maxwell Telescope (JCMT), a tracer for the dense molecular gas linked to star formation. We combine the CO data with integrated star formation rates using H-alpha measurements and stellar masses from the S4G Survey in order to study the link between the gas and stars inside these galaxies. We find that while the mean atomic gas mass is lower for the Virgo galaxies compared to the isolated galaxies, the distributions of molecular gas masses are not significantly different between the three samples. The specific star formation rate is also lower for the Virgo sample, followed by the group and isolated galaxies. Finally, the molecular gas depletion time is longer for the Virgo galaxies compared to the group and isolated galaxies, which suggests the possible effects of environment on the galaxy's star formation properties.

  17. Stellar disc truncations and extended haloes in face-on spiral galaxies

    NASA Astrophysics Data System (ADS)

    Peters, S. P. C.; van der Kruit, P. C.; Knapen, J. H.; Trujillo, I.; Fliri, J.; Cisternas, M.; Kelvin, L. S.

    2017-09-01

    We use data from the IAC Stripe82 Legacy Project to study the surface photometry of 22 nearby, face-on to moderately inclined spiral galaxies. The reprocessed and combined Stripe 82 g',r' and i' images allow us to probe the galaxy down to 29-30 r'-magnitudes arcsec-2 and thus reach into the very faint outskirts of the galaxies. Truncations are found in three galaxies. An additional 15 galaxies are found to have an apparent extended stellar halo. Simulations show that the scattering of light from the inner galaxy by the point spread function (PSF) can produce faint structures resembling haloes, but this effect is insufficient to fully explain the observed haloes. The presence of these haloes and of truncations is mutually exclusive, and we argue that the presence of a stellar halo and/or light scattered by the PSF can hide truncations. Furthermore, we find that the onset of the stellar halo and the truncations scales tightly with galaxy size. Interestingly, the fraction of light does not correlate with dynamic mass. Nineteen galaxies are found to have breaks in their profiles, the radius of which also correlates with galaxy size.

  18. GAMA/H-ATLAS: The Dust Opacity-Stellar Mass Surface Density Relation for Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Grootes, M. W.; Tuffs, R. J.; Popescu, C. C.; Pastrav, B.; Andrae, E.; Gunawardhana, M.; Kelvin, L. S.; Liske, J.; Seibert, M.; Taylor, E. N.; Graham, Alister W.; Baes, M.; Baldry, I. K.; Bourne, N.; Brough, S.; Cooray, A.; Dariush, A.; De Zotti, G.; Driver, S. P.; Dunne, L.; Gomez, H.; Hopkins, A. M.; Hopwood, R.; Jarvis, M.; Loveday, J.; Maddox, S.; Madore, B. F.; Michałowski, M. J.; Norberg, P.; Parkinson, H. R.; Prescott, M.; Robotham, A. S. G.; Smith, D. J. B.; Thomas, D.; Valiante, E.

    2013-03-01

    We report the discovery of a well-defined correlation between B-band face-on central optical depth due to dust, τ ^f_B, and the stellar mass surface density, μ*, of nearby (z <= 0.13) spiral galaxies: {log}(τ ^{f}_{B}) = 1.12(+/- 0.11) \\cdot {log}({μ _{*}}/{{M}_{⊙ } {kpc}^{-2}}) - 8.6(+/- 0.8). This relation was derived from a sample of spiral galaxies taken from the Galaxy and Mass Assembly (GAMA) survey, which were detected in the FIR/submillimeter (submm) in the Herschel-ATLAS science demonstration phase field. Using a quantitative analysis of the NUV attenuation-inclination relation for complete samples of GAMA spirals categorized according to stellar mass surface density, we demonstrate that this correlation can be used to statistically correct for dust attenuation purely on the basis of optical photometry and Sérsic-profile morphological fits. Considered together with previously established empirical relationships of stellar mass to metallicity and gas mass, the near linearity and high constant of proportionality of the τ ^f_B - μ_{*} relation disfavors a stellar origin for the bulk of refractory grains in spiral galaxies, instead being consistent with the existence of a ubiquitous and very rapid mechanism for the growth of dust in the interstellar medium. We use the τ ^f_B - μ_{*} relation in conjunction with the radiation transfer model for spiral galaxies of Popescu & Tuffs to derive intrinsic scaling relations between specific star formation rate (SFR), stellar mass, and stellar surface density, in which attenuation of the UV light used for the measurement of SFR is corrected on an object-to-object basis. A marked reduction in scatter in these relations is achieved which we demonstrate is due to correction of both the inclination-dependent and face-on components of at