Improving the ability of image sensors to detect faint stars and moving objects using image deconvolution techniques.

PubMed

Fors, Octavi; Núñez, Jorge; Otazu, Xavier; Prades, Albert; Cardinal, Robert D

2010-01-01

In this paper we show how the techniques of image deconvolution can increase the ability of image sensors as, for example, CCD imagers, to detect faint stars or faint orbital objects (small satellites and space debris). In the case of faint stars, we show that this benefit is equivalent to double the quantum efficiency of the used image sensor or to increase the effective telescope aperture by more than 30% without decreasing the astrometric precision or introducing artificial bias. In the case of orbital objects, the deconvolution technique can double the signal-to-noise ratio of the image, which helps to discover and control dangerous objects as space debris or lost satellites. The benefits obtained using CCD detectors can be extrapolated to any kind of image sensors.

Confirming Planetary Mass Candidate Companions in Ophiuchus

NASA Astrophysics Data System (ADS)

Fontanive, Clemence

2016-10-01

We propose for follow-up observations to confirm common proper motion for two candidate planetary mass companions, identified as part of our GO 12944 (PI Allers) search for companions to the youngest ( 0.5 Myr) brown dwarfs in the nearby Ophiuchus star-forming region. If confirmed to be co-moving, these would be among the lowest mass planetary mass companions imaged to date, with estimated masses <5 Jupiter Masses and would be vital benchmark objects for evolutionary models at these young ages. With our multi-band optical and IR photometric approach based on the SpT-Q relation seen for Ophiuchus brown dwarfs (Allers in prep.), we have already estimated the spectral type of our candidate companions. This approach distinguishes substellar objects from background interlopers based on the strength of the 1.4 um water feature robustly observed in MLTY objects but not in reddened background stars - both our candidates show clear evidence of absorption at 1.4 um. If confirmed, these candidate companions would significantly increase the census of young planetary mass companions around extremely young brown dwarfs. These candidate companions are too faint to be observed with ground-based laser guide star adaptive optics (LGS AO) nor is the 1.4 um water feature observable from the ground for such faint objects due to telluric absorption, thus HST is the only telescope in the world suitable for these observations.

Infrared spectrum of an extremely cool white-dwarf star

PubMed

Hodgkin; Oppenheimer; Hambly; Jameson; Smartt; Steele

2000-01-06

White dwarfs are the remnant cores of stars that initially had masses of less than 8 solar masses. They cool gradually over billions of years, and have been suggested to make up much of the 'dark matter' in the halo of the Milky Way. But extremely cool white dwarfs have proved difficult to detect, owing to both their faintness and their anticipated similarity in colour to other classes of dwarf stars. Recent improved models indicate that white dwarfs are much more blue than previously supposed, suggesting that the earlier searches may have been looking for the wrong kinds of objects. Here we report an infrared spectrum of an extremely cool white dwarf that is consistent with the new models. We determine the star's temperature to be 3,500 +/- 200 K, making it the coolest known white dwarf. The kinematics of this star indicate that it is in the halo of the Milky Way, and the density of such objects implied by the serendipitous discovery of this star is consistent with white dwarfs dominating the dark matter in the halo.

ARC-1989-A89-7015

NASA Image and Video Library

1989-08-21

Range : 4.8 million km. ( 3 million miles ) P-34648 This Voyager 2, sixty-one second exposure, shot through clear filters, of Neptunes rings. The Voyager cameras were programmed to make a systematic search of the entire ring system for new material. The previously ring arc is visible as a long bright streak at the bottom of the image. Extening beyond the bright arc is a much fainter component which follows the arc in its orbit. this faint material was also visible leading the ring arc and, in total, covers at least half of the orbit before it becomes too faint to identify. Also visible in this image, is a continuous ring of faint material previously identified as a possible ring arc by Voyager. this continuous ring is located just outside the orbit of the moon 1989N3, which was also discovered by Voyager. This moon is visible as a streak in the lower left. the smear of 1989N3 is due to its own orbital motion during the exposure. Extreme computer processing of this image was made to enhance the extremely faint features of Neptunes moon system. the dark area surrounding the moon as well as the bright corners are due to this special processing.

Chemical enrichment in Ultra-Faint Dwarf galaxies

NASA Astrophysics Data System (ADS)

Romano, Donatella

2016-08-01

Our view of the Milky Way's satellite population has radically changed after the discovery, ten years ago, of the first Ultra-Faint Dwarf galaxies (UFDs). These extremely faint, dark-matter dominated, scarcely evolved stellar systems are found in ever-increasing number in our cosmic neighbourhood and constitute a gold-mine for studies of early star formation conditions and early chemical enrichment pathways. Here we show what can be learned from the measurements of chemical abundances in UFD stars read through the lens of chemical evolution studies, point out the limitations of the classic approach, and discuss the way to go to improve the models.

The faint intergalactic-medium red-shifted emission balloon: future UV observations with EMCCDs

NASA Astrophysics Data System (ADS)

Kyne, Gillian; Hamden, Erika T.; Lingner, Nicole; Morrissey, Patrick; Nikzad, Shouleh; Martin, D. Christopher

2016-08-01

We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing dark current, via cooling and substrate voltage adjustment. We present result of laboratory noise measurements including dark current. Furthermore, we will briefly present some initial results from our first set of on-sky observations using a delta-doped EMCCD on the 200 inch telescope at Palomar using the Palomar Cosmic Web Imager (PCWI).

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

NASA Astrophysics Data System (ADS)

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

2009-03-01

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

X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

NASA Astrophysics Data System (ADS)

Terashima, Yuichi; Suganuma, Makoto; Akiyama, Masayuki; Greene, Jenny E.; Kawaguchi, Toshihiro; Iwasawa, Kazushi; Nagao, Tohru; Noda, Hirofumi; Toba, Yoshiki; Ueda, Yoshihiro; Yamashita, Takuji

2018-01-01

We construct a sample of X-ray-bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. Fifty-three X-ray sources satisfying i-band magnitude fainter than 23.5 mag and X-ray counts with the EPIC-PN detector larger than 70 are selected from 9.1 deg2, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. Forty-four objects with an X-ray to i-band flux ratio FX/Fi > 10 are classified as extreme X-ray-to-optical flux sources. Spectral energy distributions of 48 among 53 are represented by templates of type 2 AGNs or star-forming galaxies and show the optical signature of stellar emission from host galaxies in the source rest frame. Infrared/optical SEDs indicate a significant contribution of emission from dust to the infrared fluxes, and that the central AGN is dust obscured. The photometric redshifts determined from the SEDs are in the range of 0.6-2.5. The X-ray spectra are fitted by an absorbed power-law model, and the intrinsic absorption column densities are modest (best-fit log NH = 20.5-23.5 cm-2 in most cases). The absorption-corrected X-ray luminosities are in the range of 6 × 1042-2 × 1045 erg s-1. Twenty objects are classified as type 2 quasars based on X-ray luminsosity and NH. The optical faintness is explained by a combination of redshifts (mostly z > 1.0), strong dust extinction, and in part a large ratio of dust/gas.

Theoretical colours and isochrones for some Hubble Space Telescope colour systems. II

NASA Technical Reports Server (NTRS)

Paltoglou, G.; Bell, R. A.

1991-01-01

A grid of synthetic surface brightness magnitudes for 14 bandpasses of the Hubble Space Telescope Faint Object Camera is presented, as well as a grid of UBV, uvby, and Faint Object Camera surface brightness magnitudes derived from the Gunn-Stryker spectrophotometric atlas. The synthetic colors are used to examine the transformations between the ground-based Johnson UBV and Stromgren uvby systems and the Faint Object Camera UBV and uvby. Two new four-color systems, similar to the Stromgren system, are proposed for the determination of abundance, temperature, and surface gravity. The synthetic colors are also used to calculate color-magnitude isochrones from the list of theoretical tracks provided by VandenBerg and Bell (1990). It is shown that by using the appropriate filters it is possible to minimize the dependence of this color difference on metallicity. The effects of interstellar reddening on various Faint Object Camera colors are analyzed as well as the observational requirements for obtaining data of a given signal-to-noise for each of the 14 bandpasses.

New Window on the Universe.

ERIC Educational Resources Information Center

Reynolds, Ronald F.

1984-01-01

Describes the basic components of a space telescope that will be launched during a 1986 space shuttle mission. These components include a wide field/planetary camera, faint object spectroscope, high-resolution spectrograph, high-speed photometer, faint object camera, and fine guidance sensors. Data to be collected from these instruments are…

Evidence for a New Class of Extreme Ultraviolet Sources

NASA Technical Reports Server (NTRS)

Maoz, Dan; Ofek, Eran O.; Shemi, Amotz

1997-01-01

Most of the sources detected in the extreme ultraviolet (EUV; 100-600 A) by the ROSAT/WFC and EUVE all-sky surveys have been identified with active late-type stars and hot white dwarfs that are near enough to the Earth to escape absorption by interstellar gas. However, about 15 per cent of EUV sources are as yet unidentified with any optical counterparts. We examine whether the unidentified EUV sources may consist of the same population of late-type stars and white dwarfs. We present B and R photometry of stars in the fields of seven of the unidentified EUV sources. We detect in the optical the entire main-sequence and white dwarf population out to the greatest distances where they could still avoid absorption. We use color-magnitude diagrams to demonstrate that, in most of the fields, none of the observed stars has the colours and magnitudes of late-type dwarfs at distances less than 100 pc. Similarly, none of the observed stars is a white dwarf within 500 pc that is hot enough to be a EUV emitter. The unidentified EUV sources we study are not detected in X-rays, while cataclysmic variables, X-ray binaries, and active galactic nuclei generally are. We conclude that some of the EUV sources may be a new class of nearby objects, which are either very faint at optical bands or which mimic the colours and magnitudes of distant late-type stars or cool white dwarfs. One candidate for optically faint objects is isolated old neutron stars, slowly accreting interstellar matter. Such neutron stars are expected to be abundant in the Galaxy, and have not been unambiguously detected.

Lyman-α emitters in the context of hierarchical galaxy formation: predictions for VLT/MUSE surveys

NASA Astrophysics Data System (ADS)

Garel, T.; Guiderdoni, B.; Blaizot, J.

2016-02-01

The VLT/Multi Unit Spectrograph Explorer (MUSE) integral-field spectrograph can detect Lyα emitters (LAE) in the redshift range 2.8 ≲ z ≲ 6.7 in a homogeneous way. Ongoing MUSE surveys will notably probe faint Lyα sources that are usually missed by current narrow-band surveys. We provide quantitative predictions for a typical wedding-cake observing strategy with MUSE based on mock catalogues generated with a semi-analytic model of galaxy formation coupled to numerical Lyα radiation transfer models in gas outflows. We expect ≈1500 bright LAEs (FLyα ≳ 10-17 erg s-1 cm-2) in a typical shallow field (SF) survey carried over ≈100 arcmin2 , and ≈2000 sources as faint as 10-18 erg s-1 cm-2 in a medium-deep field (MDF) survey over 10 arcmin2 . In a typical deep field (DF) survey of 1 arcmin2 , we predict that ≈500 extremely faint LAEs (FLyα ≳ 4 × 10-19 erg s-1 cm-2) will be found. Our results suggest that faint Lyα sources contribute significantly to the cosmic Lyα luminosity and SFR budget. While the host haloes of bright LAEs at z ≈ 3 and 6 have descendants with median masses of 2 × 1012 and 5 × 1013 M⊙, respectively, the faintest sources detectable by MUSE at these redshifts are predicted to reside in haloes which evolve into typical sub-L* and L* galaxy haloes at z = 0. We expect typical DF and MDF surveys to uncover the building blocks of Milky Way-like objects, even probing the bulk of the stellar mass content of LAEs located in their progenitor haloes at z ≈ 3.

Faint Compact Galaxy in the Early Universe

NASA Image and Video Library

2015-12-03

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

COMPLETE ELEMENT ABUNDANCES OF NINE STARS IN THE r -PROCESS GALAXY RETICULUM II

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

Ji, Alexander P.; Frebel, Anna; Chiti, Anirudh

We present chemical abundances derived from high-resolution Magellan /Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (−3.5 < [Fe/H] < −2). Seven of the nine stars have extremely high levels of r -process material ([Eu/Fe] ∼ 1.7), in contrast to the extremely low neutron-capture element abundances found in every other ultra-faint dwarf galaxy studied to date. The other two stars are the most metal-poor stars in the system ([Fe/H] < −3), and they have neutron-capture elementmore » abundance limits similar to those in other ultra-faint dwarf galaxies. We confirm that the relative abundances of Sr, Y, and Zr in these stars are similar to those found in r -process halo stars, but they are ∼0.5 dex lower than the solar r -process pattern. If the universal r -process pattern extends to those elements, the stars in Ret II display the least contaminated known r -process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r -process sites besides the source of r -process elements in Ret II. Galaxies like Ret II may be the original birth sites of r -process enhanced stars now found in the halo.« less

High-precision Orbit Fitting and Uncertainty Analysis of (486958) 2014 MU69

NASA Astrophysics Data System (ADS)

Porter, Simon B.; Buie, Marc W.; Parker, Alex H.; Spencer, John R.; Benecchi, Susan; Tanga, Paolo; Verbiscer, Anne; Kavelaars, J. J.; Gwyn, Stephen D. J.; Young, Eliot F.; Weaver, H. A.; Olkin, Catherine B.; Parker, Joel W.; Stern, S. Alan

2018-07-01

NASA’s New Horizons spacecraft will conduct a close flyby of the cold-classical Kuiper Belt Object (KBO) designated (486958) 2014 MU69 on 2019 January 1. At a heliocentric distance of 44 au, “MU69” will be the most distant object ever visited by a spacecraft. To enable this flyby, we have developed an extremely high-precision orbit fitting and uncertainty processing pipeline, making maximal use of the Hubble Space Telescope’s Wide Field Camera 3 (WFC3) and pre-release versions of the ESA Gaia Data Release 2 (DR2) catalog. This pipeline also enabled successful predictions of a stellar occultation by MU69 in 2017 July. We describe how we process the WFC3 images to match the Gaia DR2 catalog, extract positional uncertainties for this extremely faint target (typically 140 photons per WFC3 exposure), and translate those uncertainties into probability distribution functions for MU69 at any given time. We also describe how we use these uncertainties to guide New Horizons, plan stellar occultions of MU69, and derive MU69's orbital evolution and long-term stability.

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-angle image spans 0.4 by 0.4 degrees and was taken by the 12k camera on Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, United States. The image is composited by three exposures through blue (B), red (R), and infrared (I) filters. The primeval galaxy was identified by combining the power of the NASA/ESA Hubble Space Telescope and CARA's W. M. Keck Telescopes on Mauna Kea in Hawaii. These great observatories got a boost from the added magnification of a natural ‘cosmic gravitational lens’ in space that further amplifies the brightness of the distant object. The newly discovered galaxy is likely to be a young galaxy shining during the end of the so-called "Dark Ages" - the period in cosmic history which ended with the first galaxies and quasars transforming opaque, molecular hydrogen into the transparent, ionized Universe we see today. The new galaxy was detected in a long exposure of the nearby cluster of galaxies Abell 2218, taken with the Advanced Camera for Surveys on board the Hubble Space Telescope. This cluster is so massive that the light of distant objects passing through the cluster actually bends and is amplified, much as a magnifying glass bends and magnifies objects seen through it. Such natural gravitational ‘telescopes’ allow astronomers to see extremely distant and faint objects that could otherwise not be seen. The extremely faint galaxy is so far away its visible light has been stretched into infrared wavelengths, making the observations particularly difficult. "As we were searching for distant galaxies magnified by Abell 2218, we detected a pair of strikingly similar images whose arrangement and colour indicate a very distant object," said astronomer Jean-Paul Kneib (Observatoire Midi-Pyrénées and California Institute of Technology), who is lead author reporting the discovery in a forthcoming article in the Astrophysical Journal. Analysis of a sequence of Hubble images indicate the object lies between a redshift of 6.6 and 7.1, making it the most distant source currently known. However, long exposures in the optical and infrared taken with spectrographs on the 10-meter Keck telescopes suggests that the object has a redshift towards the upper end of this range, around redshift 7. Redshift is a measure of how much the wavelengths of light are shifted to longer wavelengths. The greater the shift in wavelength toward the redder regions of the spectrum, the more distant the object is. "The galaxy we have discovered is extremely faint, and verifying its distance has been an extraordinarily challenging adventure," said Dr. Kneib. "Without the 25 x magnification afforded by the foreground cluster, this early object could simply not have been identified or studied in any detail at all with the present telescopes available. Even with aid of the cosmic lens, the discovery has only been possible by pushing our current observatories to the limits of their capabilities!" Using the combination of the high resolution of Hubble and the large magnification of the cosmic lens, the astronomers estimate that this object, although very small - only 2,000 light-years across - is forming stars extremely actively. However, two intriguing properties of the new source are the apparent lack of the typically bright hydrogen emission line and its intense ultraviolet light which is much stronger than that seen in star-forming galaxies closer by. "The properties of this distant source are very exciting because, if verified by further study, they could represent the hallmark of a truly young stellar system that ended the Dark Ages" added Dr. Richard Ellis, Steele Professor of Astronomy at Caltech, and a co-author in the article. The team is encouraged by the success of their technique and plans to continue the search for more examples by looking through other cosmic lenses in the sky. Hubble's exceptional resolution makes it ideally suited for such searches. "Estimating the abundance and characteristic properties of sources at early times is particularly important in understanding how the Universe reionized itself, thus ending the Dark Ages," said Mike Santos, a former Caltech graduate student, now a postdoctoral researcher at the Institute of Astronomy, Cambridge, UK. "The cosmic lens has given us a first glimpse into this important epoch. We are now eager to learn more by finding further examples, although it will no doubt be challenging." "We are looking at the first evidence of our ancestors on the evolutionary tree of the entire Universe," said Dr. Frederic Chaffee, director of the W. M. Keck Observatory, home to the twin 10-meter Keck telescopes that confirmed the discovery. "Telescopes are virtual time machines, allowing our astronomers to look back to the early history of the cosmos, and these marvellous observations are of the earliest time yet."

Exploring the Universe with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

1990-01-01

A general overview is given of the operations, engineering challenges, and components of the Hubble Space Telescope. Deployment, checkout and servicing in space are discussed. The optical telescope assembly, focal plane scientific instruments, wide field/planetary camera, faint object spectrograph, faint object camera, Goddard high resolution spectrograph, high speed photometer, fine guidance sensors, second generation technology, and support systems and services are reviewed.

VizieR Online Data Catalog: Deep Herschel PACS point spread functions (Bocchio+, 2016)

NASA Astrophysics Data System (ADS)

Bocchio, M.; Bianchi, A.; Abergel, S.

2016-06-01

Herschel PACS dedicated PSF observations are scanmaps centred on various objects taken at 70 (blue channel), 100 (green channel) and 160 (red channel) um. The core of the PSF is best characterised observing faint objects (e.g. the asteroid Vesta), while the wings of the PSF can only be seen in observations of bright objects (e.g. Mars). Using a combination of images of bright and faint objects it is therefore possible to have a good characterisation of the PACS PSFs. (2 data files).

An Automatic Technique for Finding Faint Moving Objects in Wide Field CCD Images

NASA Astrophysics Data System (ADS)

Hainaut, O. R.; Meech, K. J.

1996-09-01

The traditional method used to find moving objects in astronomical images is to blink pairs or series of frames after registering them to align the background objects. While this technique is extremely efficient in terms of the low signal-to-noise ratio that the human sight can detect, it proved to be extremely time-, brain- and eyesight-consuming. The wide-field images provided by the large CCD mosaic recently built at IfA cover a field of view of 20 to 30' over 8192(2) pixels. Blinking such images is an enormous task, comparable to that of blinking large photographic plates. However, as the data are available digitally (each image occupying 260Mb of disk space), we are developing a set of computer codes to perform the moving object identification in sets of frames. This poster will describe the techniques we use in order to reach a detection efficiency as good as that of a human blinker; the main steps are to find all the objects in each frame (for which we rely on ``S-Extractor'' (Bertin & Arnouts (1996), A&ASS 117, 393), then identify all the background objects, and finally to search the non-background objects for sources moving in a coherent fashion. We will also describe the results of this method applied to actual data from the 8k CCD mosaic. {This work is being supported, in part, by NSF grant AST 92-21318.}

X-ray Counterparts of Infrared Faint Radio Sources

NASA Astrophysics Data System (ADS)

Schartel, Norbert

2011-10-01

Infrared Faint Radio Sources (IFRS) are radio sources with extremely faint or even absent infrared emission in deep Spitzer Surveys. Models of their spectral energy distributions, the ratios of radio to infrared flux densities and their steep radio spectra strongly suggest that IFRS are AGN at high redshifts (2

THE ORIGIN OF LOW [α/Fe] RATIOS IN EXTREMELY METAL-POOR STARS

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

Kobayashi, Chiaki; Ishigaki, Miho N.; Tominaga, Nozomu

2014-04-10

We show that the low ratios of α elements (Mg, Si, and Ca) to Fe recently found for a small fraction of extremely metal-poor stars can be naturally explained with the nucleosynthesis yields of core-collapse supernovae, i.e., 13-25 M {sub ☉} supernovae, or hypernovae. For the case without carbon enhancement, the ejected iron mass is normal, consistent with observed light curves and spectra of nearby supernovae. On the other hand, the carbon enhancement requires much smaller iron production, and the low [α/Fe] of carbon-enhanced metal-poor stars can also be reproduced with 13-25 M {sub ☉} faint supernovae or faint hypernovae.more » Iron-peak element abundances, in particular Zn abundances, are important to put further constraints on the enrichment sources from galactic archaeology surveys.« less

Globular Clusters for Faint Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions.The most striking feature of these galaxies, however, is that they are surrounded by a large number of compact objects that appear to be globular clusters. From the observations, Van Dokkum and collaborators estimate that Dragonfly 44 and DFX1 have approximately 74 and 62 globulars, respectively significantly more than the low numbers expected for galaxies of this luminosity.Armed with this knowledge, the authors went back and looked at archival observations of 14 other UDGs also located in the Coma cluster. They found that these smaller and fainter galaxies dont host quite as many globular clusters as Dragonfly 44 and DFX1, but more than half also show significant overdensities of globulars.Main panel: relation between the number of globular clusters and total absolute magnitude for Coma UDGs (solid symbols) compared to normal galaxies (open symbols). Top panel: relation between effective radius and absolute magnitude. The UDGs are significantly larger and have more globular clusters than normal galaxies of the same luminosity. [van Dokkum et al. 2017]Evidence of FailureIn general, UDGs appear to have more globular clusters than other galaxies of the same total luminosity, by a factor of nearly 7. These results are consistent with the scenario in which UDGs are failed galaxies: they likely have the halo mass to have formed a large number of globular clusters, but they were quenched before they formed a disk and bulge. Because star formation never got going in UDGs, they are now much dimmer than other galaxies of the same size.The authors suggest that the next step is to obtain dynamical measurements of the UDGs to determine whether these faint galaxies really do have the halo mass suggested by their large numbers of globulars. Future observations will continue to help us pin down the origin of these dim giants.CitationPieter van Dokkum et al 2017 ApJL 844 L11. doi:10.3847/2041-8213/aa7ca2

Observations of the planetary nebula RWT 152 with OSIRIS/GTC

NASA Astrophysics Data System (ADS)

Aller, A.; Miranda, L. F.; Olguín, L.; Solano, E.; Ulla, A.

2016-11-01

RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Hα imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy/Gran Telescopio Canarias) with the goal of analysing its properties. The Hα image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low excitation nebula with weak emission lines from H+, He+ and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [N II] λ6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity (˜ 92-131 km s-1), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor (˜1 M⊙) formed in a metal-poor environment.

CHARACTERIZING FAINT GALAXIES IN THE REIONIZATION EPOCH: LBT CONFIRMS TWO L < 0.2 L* SOURCES AT z = 6.4 BEHIND THE CLASH/FRONTIER FIELDS CLUSTER MACS0717.5+3745

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

Vanzella, E.; Cusano, F.; Fontana, A.

2014-03-01

We report the LBT/MODS1 spectroscopic confirmation of two images of faint Lyα emitters at z = 6.4 behind the Frontier Fields galaxy cluster MACSJ0717.5+3745. A wide range of lens models suggests that the two images are highly magnified, with a strong lower limit of μ > 5. These are the faintest z > 6 candidates spectroscopically confirmed to date. These may also be multiple images of the same z = 6.4 source as supported by their similar intrinsic properties, but the lens models are inconclusive regarding this interpretation. To be cautious, we derive the physical properties of each image individually.more » Thanks to the high magnification, the observed near-infrared (restframe ultraviolet) part of the spectral energy distributions and Lyα lines are well detected with S/N(m {sub 1500}) ≳ 10 and S/N(Lyα) ≅ 10-15. Adopting μ > 5, the absolute magnitudes, M {sub 1500}, and Lyα fluxes are fainter than –18.7 and 2.8 × 10{sup –18} erg s{sup –1} cm{sup –2}, respectively. We find a very steep ultraviolet spectral slope β = –3.0 ± 0.5 (F {sub λ} = λ{sup β}), implying that these are very young, dust-free, and low metallicity objects, made of standard stellar populations or even extremely metal poor stars (age ≲ 30 Myr, E(B – V) = 0 and metallicity 0.0-0.2 Z/Z {sub ☉}). The objects are compact (<1 kpc{sup 2}) and with a stellar mass M {sub *} < 10{sup 8} M {sub ☉}. The very steep β, the presence of the Lyα line, and the intrinsic FWHM (<300 km s{sup –1}) of these newborn objects do not exclude a possible leakage of ionizing radiation. We discuss the possibility that such faint galaxies may resemble those responsible for cosmic reionization.« less

WISE Discovery of Hyper Luminous Galaxies at z=2-4 and Their Implications for Galaxy and AGN Evolution

NASA Technical Reports Server (NTRS)

Tsai, Chao Wei; Eisenhardt, Peter; Wu, Jingwen; Bridge, Carrie; Assef, Roberto; Benford, Dominic; Blain, Andrew; Cutri, Roc; Griffith, Robert L.; Jarrett, Thomas;

AN ENIGMATIC POINT-LIKE FEATURE WITHIN THE HD 169142 TRANSITIONAL DISK ,

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

Biller, Beth A.; Males, Jared; Morzinski, Katie

2014-09-01

We report the detection of a faint point-like feature possibly related to ongoing planet-formation in the disk of the transition disk star HD 169142. The point-like feature has a Δmag(L) ∼ 6.4, at a separation of ∼0.''11 and position angle ∼0°. Given its lack of an H or K{sub S} counterpart despite its relative brightness, this candidate cannot be explained by purely photospheric emission and must be a disk feature heated by an as yet unknown source. Its extremely red colors make it highly unlikely to be a background object, but future multi-wavelength follow up is necessary for confirmation and characterization ofmore » this feature.« less

Finding new sub-stellar co-moving companion candidates - the case of CT Cha

NASA Astrophysics Data System (ADS)

Schmidt, Tobias; Neuhäuser, Ralph

2008-05-01

We have searched for close and faint companions around T Tauri stars in the Chamaeleon star forming region. Two epochs of direct imaging data were taken with the VLT Adaptive Optics instrument NaCo in February 2006 and March 2007 in Ks band for the classical T Tauri star CT Cha together with a Hipparcos binary for astrometric calibration. Moreover a J band image was taken in March 2007 to get color information. We found CT Cha to have a very faint companion (Ks0=14.6 mag) of 2.67” separation corresponding to 440AU. We show that CT Cha A and the faint object form a common proper motion pair and that the companion is not a non-moving background object (with 4σ significance).

High-resolution imaging of the Pluto-Charon system with the Faint Object Camera of the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Albrecht, R.; Barbieri, C.; Adorf, H.-M.; Corrain, G.; Gemmo, A.; Greenfield, P.; Hainaut, O.; Hook, R. N.; Tholen, D. J.; Blades, J. C.

1994-01-01

Images of the Pluto-Charon system were obtained with the Faint Object Camera (FOC) of the Hubble Space Telescope (HST) after the refurbishment of the telescope. The images are of superb quality, allowing the determination of radii, fluxes, and albedos. Attempts were made to improve the resolution of the already diffraction limited images by image restoration. These yielded indications of surface albedo distributions qualitatively consistent with models derived from observations of Pluto-Charon mutual eclipses.

NIFTE: The Near Infrared Faint-Object Telescope Experiment

NASA Technical Reports Server (NTRS)

Bock, James J.; Lange, Andrew E.; Matsumoto, T.; Eisenhardt, Peter B.; Hacking, Perry B.; Schember, Helene R.

1994-01-01

The high sensitivity of large format InSb arrays can be used to obtain deep images of the sky at 3-5 micrometers. In this spectral range cool or highly redshifted objects (e.g. brown dwarfs and protogalaxies) which are not visible at shorter wavelengths may be observed. Sensitivity at these wavelengths in ground-based observations is severly limited by the thermal flux from the telescope and from the earth's atmosphere. The Near Infrared Faint-Object Telescope Experiment (NIFTE), a 50 cm cooled rocket-borne telescope combined with large format, high performance InSb arrays, can reach a limiting flux less than 1 micro-Jy(1-sigma) over a large field-of-view in a single flight. In comparison, the Infrared Space Observatory (ISO) will require days of observation to reach a sensitivity more than one order of magnitude worse over a similar area of the sky. The deep 3-5 micrometer images obtained by the rocket-borne telescope will assist in determining the nature of faint red objects detected by ground-based telescopes at 2 micrometers, and by ISO at wavelengths longer than 5 micrometers.

Exploring three faint source detections methods for aperture synthesis radio images

NASA Astrophysics Data System (ADS)

Peracaula, M.; Torrent, A.; Masias, M.; Lladó, X.; Freixenet, J.; Martí, J.; Sánchez-Sutil, J. R.; Muñoz-Arjonilla, A. J.; Paredes, J. M.

2015-04-01

Wide-field radio interferometric images often contain a large population of faint compact sources. Due to their low intensity/noise ratio, these objects can be easily missed by automated detection methods, which have been classically based on thresholding techniques after local noise estimation. The aim of this paper is to present and analyse the performance of several alternative or complementary techniques to thresholding. We compare three different algorithms to increase the detection rate of faint objects. The first technique consists of combining wavelet decomposition with local thresholding. The second technique is based on the structural behaviour of the neighbourhood of each pixel. Finally, the third algorithm uses local features extracted from a bank of filters and a boosting classifier to perform the detections. The methods' performances are evaluated using simulations and radio mosaics from the Giant Metrewave Radio Telescope and the Australia Telescope Compact Array. We show that the new methods perform better than well-known state of the art methods such as SEXTRACTOR, SAD and DUCHAMP at detecting faint sources of radio interferometric images.

THE EXTREMELY RED HOST GALAXY OF GRB 080207

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

Hunt, Leslie; Cresci, Giovanni; Palazzi, Eliana

2011-08-01

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

Calibration of EFOSC2 Broadband Linear Imaging Polarimetry

NASA Astrophysics Data System (ADS)

Wiersema, K.; Higgins, A. B.; Covino, S.; Starling, R. L. C.

2018-03-01

The European Southern Observatory Faint Object Spectrograph and Camera v2 is one of the workhorse instruments on ESO's New Technology Telescope, and is one of the most popular instruments at La Silla observatory. It is mounted at a Nasmyth focus, and therefore exhibits strong, wavelength and pointing-direction-dependent instrumental polarisation. In this document, we describe our efforts to calibrate the broadband imaging polarimetry mode, and provide a calibration for broadband B, V, and R filters to a level that satisfies most use cases (i.e. polarimetric calibration uncertainty 0.1%). We make our calibration codes public. This calibration effort can be used to enhance the yield of future polarimetric programmes with the European Southern Observatory Faint Object Spectrograph and Camera v2, by allowing good calibration with a greatly reduced number of standard star observations. Similarly, our calibration model can be combined with archival calibration observations to post-process data taken in past years, to form the European Southern Observatory Faint Object Spectrograph and Camera v2 legacy archive with substantial scientific potential.

HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: LEO IV

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

Simon, Joshua D.; McWilliam, Andrew; Thompson, Ian B.

2010-06-10

We present high-resolution Magellan/MIKE spectroscopy of the brightest star in the ultra-faint dwarf galaxy Leo IV. We measure an iron abundance of [Fe/H] = -3.2, adding to the rapidly growing sample of extremely metal-poor (EMP) stars being identified in Milky Way satellite galaxies. The star is enhanced in the {alpha} elements Mg, Ca, and Ti by {approx}0.3 dex, very similar to the typical Milky Way halo abundance pattern. All of the light and iron-peak elements follow the trends established by EMP halo stars, but the neutron-capture elements Ba and Sr are significantly underabundant. These results are quite similar to thosemore » found for stars in the ultra-faint dwarfs Ursa Major II, Coma Berenices, Booetes I, and Hercules, suggesting that the chemical evolution of the lowest-luminosity galaxies may be universal. The abundance pattern we observe is consistent with predictions for nucleosynthesis from a Population III supernova explosion. The extremely low metallicity of this star also supports the idea that a significant fraction ({approx}>10%) of the stars in the faintest dwarfs have metallicities below [Fe/H] = -3.0.« less

Deadly Dark Matter Cusps versus Faint and Extended Star Clusters: Eridanus II and Andromeda XXV

NASA Astrophysics Data System (ADS)

Amorisco, Nicola C.

2017-07-01

The recent detection of two faint and extended star clusters in the central regions of two Local Group dwarf galaxies, Eridanus II and Andromeda XXV, raises the question of whether clusters with such low densities can survive the tidal field of cold dark matter halos with central density cusps. Using both analytic arguments and a suite of collisionless N-body simulations, I show that these clusters are extremely fragile and quickly disrupted in the presence of central cusps ρ ˜ {r}-α with α ≳ 0.2. Furthermore, the scenario in which the clusters were originally more massive and sank to the center of the halo requires extreme fine tuning and does not naturally reproduce the observed systems. In turn, these clusters are long lived in cored halos, whose central regions are safe shelters for α ≲ 0.2. The only viable scenario for hosts that have preserved their primordial cusp to the present time is that the clusters formed at rest at the bottom of the potential, which is easily tested by measurement of the clusters proper velocity within the host. This offers means to readily probe the central density profile of two dwarf galaxies as faint as {L}V˜ 5× {10}5 {L}⊙ and {L}V˜ 6× {10}4 {L}⊙ , in which stellar feedback is unlikely to be effective.

A low-energy core-collapse supernova without a hydrogen envelope.

PubMed

Valenti, S; Pastorello, A; Cappellaro, E; Benetti, S; Mazzali, P A; Manteca, J; Taubenberger, S; Elias-Rosa, N; Ferrando, R; Harutyunyan, A; Hentunen, V P; Nissinen, M; Pian, E; Turatto, M; Zampieri, L; Smartt, S J

2009-06-04

The final fate of massive stars depends on many factors. Theory suggests that some with initial masses greater than 25 to 30 solar masses end up as Wolf-Rayet stars, which are deficient in hydrogen in their outer layers because of mass loss through strong stellar winds. The most massive of these stars have cores which may form a black hole and theory predicts that the resulting explosion of some of them produces ejecta of low kinetic energy, a faint optical luminosity and a small mass fraction of radioactive nickel. An alternative origin for low-energy supernovae is the collapse of the oxygen-neon core of a star of 7-9 solar masses. No weak, hydrogen-deficient, core-collapse supernovae have hitherto been seen. Here we report that SN 2008ha is a faint hydrogen-poor supernova. We propose that other similar events have been observed but have been misclassified as peculiar thermonuclear supernovae (sometimes labelled SN 2002cx-like events). This discovery could link these faint supernovae to some long-duration gamma-ray bursts, because extremely faint, hydrogen-stripped core-collapse supernovae have been proposed to produce such long gamma-ray bursts, the afterglows of which do not show evidence of associated supernovae.

A Tool for Optimizing Observation Planning for Faint Moving Objects

NASA Astrophysics Data System (ADS)

Arredondo, Anicia; Bosh, Amanda S.; Levine, Stephen

2016-10-01

Observations of small solar system bodies such as trans-Neptunian objects and Centaurs are vital for understanding the basic properties of these small members of our solar system. Because these objects are often very faint, large telescopes and long exposures may be necessary, which can result in crowded fields in which the target of interest may be blended with a field star. For accurate photometry and astrometry, observations must be planned to occur when the target is free of background stars; this restriction results in limited observing windows. We have created a tool that can be used to plan observations of faint moving objects. Features of the tool include estimates of best times to observe (when the object is not too near another object), a finder chart output, a list of possible astrometric and photometric reference stars, and an exposure time calculator. This work makes use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (S.E. Levine and D.G. Monet 2000), the JPL Horizons online ephemeris service (Giorgini et al. 1996), the Minor Planet Center's MPChecker (http://cgi.minorplanetcenter.net/cgi-bin/checkmp.cgi), and source extraction software SExtractor (Bertin & Arnouts 1996). Support for this work was provided by NASA SSO grant NNX15AJ82G.

Chemical Abundance Measurements of Ultra-Faint Dwarf Galaxies Discovered by the Dark Energy Survey

NASA Astrophysics Data System (ADS)

Nagasawa, Daniel; Marshall, Jennifer L.; Simon, Joshua D.; Hansen, Terese; Li, Ting; Bernstein, Rebecca; Balbinot, Eduardo; Drlica-Wagner, Alex; Pace, Andrew; Strigari, Louis; Pellegrino, Craig; DePoy, Darren L.; Suntzeff, Nicholas; Bechtol, Keith; Dark Energy Suvey

2018-01-01

We present chemical abundance analysis results derived from high-resolution spectroscopy of ultra-faint dwarfs discovered by the Dark Energy Survey. Ultra-faint dwarf galaxies preserve a fossil record of the chemical abundance patterns imprinted by the first stars in the Universe. High-resolution spectroscopic observations of member stars in several recently discovered Milky Way satellites reveal a range of abundance patterns among ultra-faint dwarfs suggesting that star formation processes in the early Universe were quite diverse. The chemical content provides a glimpse not only of the varied nucleosynthetic processes and chemical history of the dwarfs themselves, but also the environment in which they were formed. We present the chemical abundance analysis of these objects and discuss possible explanations for the observed abundance patterns.

Astrometric and Photometric Follow-up of Faint Near Earth Objects

NASA Technical Reports Server (NTRS)

Morgan, T. (Technical Monitor); Spahr, Timothy

2005-01-01

During the period April 2003 - April 2005, roughly 150 different faint NEO's were observed using the 1.2-m telescope at Mt. Hopkins. Among these were a couple of spacecraft/radar targets, including support observations in support of the Deep Impact mission. While not strictly an NEO target, comet P/Tempel 1 was nonetheless observed as an object of very high importance. During this time and independent contractor, Kyle Smalley, was trained in the use of the telescope and provided some basic software support for the project.

A Study of the Effects of Faint Dust Comae on the Spectra of Asteroids

NASA Astrophysics Data System (ADS)

Rondón, E.; Carvano, J.; Lorenz-Martins, S.

2017-09-01

The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of Active Asteroids is to use large multi-colour surveys or catalogs, like SDSS Moving Object Catalog. In this work we analyze the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude, and radial profile of asteroids.

On the Nature of Ultra-faint Dwarf Galaxy Candidates. II. The Case of Cetus II

NASA Astrophysics Data System (ADS)

Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

2018-04-01

We obtained deep Gemini GMOS-S g, r photometry of the ultra-faint dwarf galaxy candidate Cetus II with the aim of providing stronger constraints on its size, luminosity, and stellar population. Cetus II is an important object in the size–luminosity plane, as it occupies the transition zone between dwarf galaxies and star clusters. All known objects smaller than Cetus II (r h ∼ 20 pc) are reported to be star clusters, while most larger objects are likely dwarf galaxies. We found a prominent excess of main-sequence stars in the color–magnitude diagram of Cetus II, best described by a single stellar population with an age of 11.2 Gyr, metallicity of [Fe/H] = ‑1.28 dex, an [α/Fe] = 0.0 dex at a heliocentric distance of 26.3 ± 1.2 kpc. As well as being spatially located within the Sagittarius dwarf tidal stream, these properties are well matched to the Sagittarius galaxy’s Population B stars. Interestingly, like our recent findings on the ultra-faint dwarf galaxy candidate Tucana V, the stellar field in the direction of Cetus II shows no evidence of a concentrated overdensity despite tracing the main sequence for over six magnitudes. These results strongly support the picture that Cetus II is not an ultra-faint stellar system in the Milky Way halo, but made up of stars from the Sagittarius tidal stream.

Faintest Methane Brown Dwarf Discovered with the NTT and VLT

NASA Astrophysics Data System (ADS)

1999-08-01

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

First results from the faint object camera - High-resolution observations of the central object R136 in the 30 Doradus nebula

NASA Technical Reports Server (NTRS)

Weigelt, G.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.

1991-01-01

R136 is the luminous central object of the giant H II region 30 Doradus in the LMC. The first high-resolution observations of R136 with the Faint Object Camera on board the Hubble Space Telescope are reported. The physical nature of the brightest component R136a has been a matter of some controversy over the last few years. The UV images obtained show that R136a is a very compact star cluster consisting of more than eight stars within 0.7 arcsec diameter. From these high-resolution images a mass upper limit can be derived for the most luminous stars observed in R136.

High Contrast Programmable Field Masks for JWST NIRSpec

NASA Technical Reports Server (NTRS)

Kutyrev, Alexander S.

2008-01-01

Microshutter arrays are one of the novel technologies developed for the James Webb Space Telescope (JWST). It will allow Near Infrared Spectrometer (NIRSpec) to acquire spectra of hundreds of objects simultaneously therefore increasing its efficiency tremendously. We have developed these programmable arrays that are based on Micro-Electro Mechanical Structures (MEMS) technology. The arrays are 2D addressable masks that can operate in cryogenic environment of JWST. Since the primary JWST science requires acquisition of spectra of extremely faint objects, it is important to provide very high contrast of the open to closed shutters. This high contrast is necessary to eliminate any possible contamination and confusion in the acquired spectra by unwanted objects. We have developed and built a test system for the microshutter array functional and optical characterization. This system is capable of measuring the contrast of the microshutter array both in visible and infrared light of the NIRSpec wavelength range while the arrays are in their working cryogenic environment. We have measured contrast ratio of several microshutter arrays and demonstrated that they satisfy and in many cases far exceed the NIRSpec contrast requirement value of 2000.

THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

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

Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu

2015-01-01

We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). Wemore » have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.« less

Exploring the Faint End of the Luminosity-Metallicity Relation with Hα Dots

NASA Astrophysics Data System (ADS)

Hirschauer, Alec S.; Salzer, John J.

2015-01-01

The well-known correlation between a galaxy's luminosity and its gas-phase oxygen abundance (the luminosity-metallicity (L-Z) relation) offers clues toward our understanding of chemical enrichment histories and evolution. Bright galaxies are comparatively better studied than faint ones, leaving a relative dearth of observational data points to constrain the L-Z relation in the low-luminosity regime. We present high S/N nebular spectroscopy of low-luminosity star-forming galaxies observed with the KPNO 4m using the new KOSMOS spectrograph to derive direct-method metallicities. Our targets are strong point-like emission-line sources discovered serendipitously in continuum-subtracted narrowband images from the ALFALFA Hα survey. Follow-up spectroscopy of these "Hα dots" shows that these objects represent some of the lowest luminosity star-forming systems in the local Universe. Our KOSMOS spectra cover the full optical region and include detection of [O III] λ4363 in roughly a dozen objects. This paper presents some of the first scientific results obtained using this new spectrograph, and demonstrates its capabilities and effectiveness in deriving direct-method metallicities of faint objects.

High Contrast Imaging in the Visible: First Experimental Results at the Large Binocular Telescope

NASA Astrophysics Data System (ADS)

Pedichini, F.; Stangalini, M.; Ambrosino, F.; Puglisi, A.; Pinna, E.; Bailey, V.; Carbonaro, L.; Centrone, M.; Christou, J.; Esposito, S.; Farinato, J.; Fiore, F.; Giallongo, E.; Hill, J. M.; Hinz, P. M.; Sabatini, L.

2017-08-01

In 2014 February, the System for High contrast And coronography from R to K at VISual bands (SHARK-VIS) Forerunner, a high contrast experimental imager operating at visible wavelengths, was installed at the Large Binocular Telescope (LBT). Here we report on the first results obtained by recent on-sky tests. These results show the extremely good performance of the LBT Extreme Adaptive Optics (ExAO) system at visible wavelengths, both in terms of spatial resolution and contrast achieved. Similarly to what was done by Amara & Quanz (2012), we used the SHARK-VIS Forerunner data to quantitatively assess the contrast enhancement. This is done by injecting several different synthetic faint objects in the acquired data and applying the angular differential imaging (ADI) technique. A contrast of the order of 5 × 10-5 is obtained at 630 nm for angular separations from the star larger than 100 mas. These results are discussed in light of the future development of SHARK-VIS and compared to those obtained by other high contrast imagers operating at similar wavelengths.

Seeing Red and Shooting Blanks: A Study of Red Quasars and Blank Field X-Ray Sources

NASA Technical Reports Server (NTRS)

Elvis, Martin; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

We have identified a population of 'blank field sources' (or 'blanks') among the ROSAT (Roentgen Satellite) bright unidentified X-ray sources with faint optical counterparts. The extreme X-ray over optical flux ratio of blank field sources is not compatible with the main classes of X-ray emitters except for extreme BL Lacertae objects at fx/fv is equal to or less than 35. From the analysis of ROSAT archival data we found evidence for only three sources, out of 16, needing absorption in excess of the Galactic value and no indication of variability. We also found evidence for an extended nature for only one of the five blanks with a serendipitous HRI (High Resolution Imager) detection; this source (1WGA J1226.9+3332) was confirmed as a z=0.89 cluster of galaxies. Palomar images reveal the presence of a red (O - E is equal to or greater than 2) counterpart in the X-ray error circle for six blanks. The identification process brought to the discovery of another high z cluster of galaxies, one (possibly extreme) BL Lac and two apparently normal type 1 AGNs (Active Galactic Nuclei). These AGNs, together with four more AGN-like objects seem to form a well defined group: they present type 1 X-ray spectra but red Palomar counterparts. We discuss the possible explanations for the discrepancy between the X-ray and optical data, among which: a suppressed big blue bump emission, an extreme dust to gas (approximately 40 - 60 the Galactic ratio) ratio value and a high redshift (z is greater than or equal to 3.5) QSO (Quasi-Stellar Object) nature. These AGN-like blanks seem to be the bright (and easier to study) analogs of the sources which are being found in deep Chandra observations. Five more blanks have a still an unknown nature.

The population of faint Jupiter family comets near the Earth

NASA Astrophysics Data System (ADS)

Fernández, Julio A.; Morbidelli, Alessandro

2006-11-01

We study the population of faint Jupiter family comets (JFCs) that approach the Earth (perihelion distances q<1.3 AU) by applying a debiasing technique to the observed sample. We found for the debiased cumulative luminosity function (CLF) of absolute total magnitudes H a bimodal distribution in which brighter comets ( H≲9) follow a linear relation with a steep slope α=0.65±0.14, while fainter comets follow a much shallower slope α=0.25±0.06 down to H˜18. The slope can be pushed up to α=0.35±0.09 if a second break in the H distribution to a much shallower slope is introduced at H˜16. We estimate a population of about 10 3 faint JFCs with q<1.3 AU and 10

In-flight performance of the Faint Object Camera of the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Greenfield, P.; Paresce, F.; Baxter, D.; Hodge, P.; Hook, R.; Jakobsen, P.; Jedrzejewski, R.; Nota, A.; Sparks, W. B.; Towers, N.

1991-01-01

An overview of the Faint Object Camera and its performance to date is presented. In particular, the detector's efficiency, the spatial uniformity of response, distortion characteristics, detector and sky background, detector linearity, spectrography, and operation are discussed. The effect of the severe spherical aberration of the telescope's primary mirror on the camera's point spread function is reviewed, as well as the impact it has on the camera's general performance. The scientific implications of the performance and the spherical aberration are outlined, with emphasis on possible remedies for spherical aberration, hardware remedies, and stellar population studies.

Hubble Space Telescope, Faint Object Camera

NASA Technical Reports Server (NTRS)

1981-01-01

This drawing illustrates Hubble Space Telescope's (HST's), Faint Object Camera (FOC). The FOC reflects light down one of two optical pathways. The light enters a detector after passing through filters or through devices that can block out light from bright objects. Light from bright objects is blocked out to enable the FOC to see background images. The detector intensifies the image, then records it much like a television camera. For faint objects, images can be built up over long exposure times. The total image is translated into digital data, transmitted to Earth, and then reconstructed. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST detects objects 25 times fainter than the dimmest objects seen from Earth and provides astronomers with an observable universe 250 times larger than visible from ground-based telescopes, perhaps as far away as 14 billion light-years. The HST views galaxies, stars, planets, comets, possibly other solar systems, and even unusual phenomena such as quasars, with 10 times the clarity of ground-based telescopes. The HST was deployed from the Space Shuttle Discovery (STS-31 mission) into Earth orbit in April 1990. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

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

NASA Astrophysics Data System (ADS)

Guo, Yicheng

2017-08-01

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

CEMP Stars in the Halo and Their Origin in Ultra-Faint Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Beers, Timothy C.

2018-06-01

The very metal-poor (VMP; [Fe/H] < –2.0) and extremely metal-poor (EMP; [Fe/H] < –3.0) stars provide a direct view of Galactic chemical and dynamical evolution; detailed spectroscopic studies of these objects are the best way to identify and distinguish between various scenarios for the enrichment of early star-forming gas clouds soon after the Big Bang. It has been recognized that a large fraction of VMP (15-20%) and EMP stars (30-40%) possess significant over-abundances of carbon relative to iron, [C/Fe] > +0.7. This fraction rises to at least 80% for stars with [Fe/H] < –4.0. Recent studies show that the majority of CEMP stars with [Fe/H] < –3.0 belong to the CEMP-no sub-class, characterized by the lack of strong enhancements in the neutron-capture elements (e.g., [Ba/Fe] < 0.0). The CEMP-no abundance signature is commonly observed among stars ultra-faint dwarf spheroidal galaxies such as SEGUE-1. In addition, kinematic studies of CEMP-no stars strongly suggest an association with the outer-halo population of the Galaxy, which was likely formed from the accretion of low-mass mini-halos. These observations, and other lines of evidence, indicate that the CEMP-no stars of the Milky Way were born in low-mass dwarf galaxies, and later subsumed into the halo.

Deep Imaging of Extremely Metal-Poor Galaxies

NASA Astrophysics Data System (ADS)

Corbin, Michael

2006-07-01

Conflicting evidence exists regarding whether the most metal-poor and actively star-forming galaxies in the local universe such as I Zw 18 contain evolved stars. We propose to help settle this issue by obtaining deep ACS/HRC U, narrow-V, I, and H-alpha images of nine nearby {z < 0.01} extremely metal-poor {12 + O/H < 7.65} galaxies selected from the Sloan Digital Sky Survey. These objects are only marginally resolved from the ground and appear uniformly blue, strongly motivating HST imaging. The continuum images will establish: 1.} If underlying populations of evolved stars are present, by revealing the objects' colors on scales 10 pc, and 2.} The presence of any faint tidal features, dust lanes, and globular or super star clusters, all of which constrain the objects' evolutionary states. The H-alpha images, in combination with ground-based echelle spectroscopy, will reveal 1.} Whether the objects are producing "superwinds" that are depleting them of their metals; ground-based images of some of them indeed show large halos of ionized gas, and 2.} The correspondence of their nebular and stellar emission on scales of a few parsecs, which is important for understanding the "feedback" process by which supernovae and stellar winds regulate star formation. One of the sample objects, CGCG 269-049, lies only 2 Mpc away, allowing the detection of individual red giant stars in it if any are present. We have recently obtained Spitzer images and spectra of this galaxy to determine its dust content and star formation history, which will complement the proposed HST observations. [NOTE: THIS PROPOSAL WAS REDUCED TO FIVE ORBITS, AND ONLY ONE OF THE ORIGINAL TARGETS, CGCG 269-049, AFTER THE PHASE I REVIEW

The Simbol-X Perspective on the Physics of Quasar Outflows

NASA Astrophysics Data System (ADS)

Giustini, M.; Cappi, M.; Vignali, C.; Palumbo, G. G. C.; Fiore, F.; Malaguti, G.

2009-05-01

There is increasing evidence that quasar outflows may play a key role in providing the feedback between AGN/QSOs and their surrounding (and feeding) media, in regulating the central supermassive black hole growth and the galaxy formation and, on larger scales, in shaping the growth of cosmic structures (see e.g. [1]). X-ray observations of quasar outflows are crucial to probe their innermost parts and assess the global energetics entrained in the outflow by studying its most extreme (in terms of velocity, ionization state, mass outflow rate) phases. Simbol-X-with its high effective area in the Fe K energy band and above-will allow the detection and the characterization of powerful outflows in bright, nearby AGN and notably also in moderately faint AGN, thus shedding light on feedback processes in these objects.

Does faint galaxy clustering contradict gravitational instability?

NASA Technical Reports Server (NTRS)

Melott, Adrian L.

1992-01-01

It has been argued, based on the weakness of clustering of faint galaxies, that these objects cannot be the precursors of present galaxies in a simple Einstein-de Sitter model universe with clustering driven by gravitational instability. It is shown that the assumptions made about the growth of clustering were too restrictive. In such a universe, the growth of clustering can easily be fast enough to match the data.

AO 0235+164 and Surrounding Field: Surprising HST Results

NASA Technical Reports Server (NTRS)

Burbidge, E. M.; Beaver, E. A.; Cohen, Ross D.; Junkkarinen, V. T.; Lyons, R. W.

1996-01-01

Results obtained with the Hubble Space Telescope on the highly variable radio, x-ray, and gamma-ray emitting QSO (or BL Lac object) AO 0235 + 164 are presented and analyzed. WFPC2 images were obtained in 1994 June, when AO 0235 + 164 was bright (m approx. 17), and the results are described in Sec. 3. After subtraction of the PSF of the QSO, hereafter called AO following the nomenclature of Yanny et al. (1989), the companion object named A, 2 sec south of AO, is discovered not to be an elliptical galaxy as hypothesized earlier, but to be an AGN object, with a central UV-bright point-source nucleus and faint surrounding nebulosity extending to AO. The second companion object 1.3 sec east of AO discovered by Yanny et al. (1989) and named object Al, appears more like a normal spiral galaxy. We have measured the positions, luminosities, and colors of some 30 faint objects in the field around AO 0235 + 16; most are extended and may be star-forming galaxies in a loose group or cluster. Our most surprising result of the HST observations comes from FOS spectra obtained in 1995 July, discussed in Sec. 4. Because of a positioning error of the telescope and AO's faintness at that time (m approx. 20), object A was observed instead of the intended target AO. Serendipitously, we discovered A to have broad deep BALQSO-type absorptions of C IV, Si IV, N V shortward of broad emissions. A is thus ejecting high velocity, highly ionized gas into the surrounding IGM. We discuss in Sec. 5 the relationship of the objects in the central 10 sec X 1O sec region around AO, where redshifts z(sub e) = 0.94, z(sub a) = 0.524, 0.851 in AO, (sub e) = 0.524 and Z(sub BAL)=0.511 in A, are found. We hypothesize that some of the 30 faint objects in the 77 sec. x 77 sec. field may be part of a large star-forming region at z approx. 0.5, as suggested for a few objects by Yanny et al. (1989). The proximity of two highly active extragalactic objects, AO 0235+164 and its AGN companion A, is remarkable and one of the authors (EMB) suggests it may require consideration of a non-cosmological component of redshift in AO 0235+164.

Rocket instrument for far-UV spectrophotometry of faint astronomical objects.

PubMed

Hartig, G F; Fastie, W G; Davidsen, A F

1980-03-01

A sensitive sounding rocket instrument for moderate (~10-A) resolution far-UV (lambda1160-lambda1750-A) spectrophotometry of faint astronomical objects has been developed. The instrument employs a photon-counting microchannel plate imaging detector and a concave grating spectrograph behind a 40-cm Dall-Kirkham telescope. A unique remote-control pointing system, incorporating an SIT vidicon aspect camera, two star trackers, and a tone-encoded command telemetry link, permits the telescope to be oriented to within 5 arc sec of any target for which suitable guide stars can be found. The design, construction, calibration, and flight performance of the instrument are discussed.

Infrared Faint Radio Sources in the Extended Chandra Deep Field South

NASA Astrophysics Data System (ADS)

Huynh, Minh T.

2009-01-01

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey (ATLAS) which have no observable counterpart in the Spitzer Wide-area Infrared Extragalactic Survey (SWIRE). The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6 to 70 micron) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the SED of these objects shows that they are consistent with high redshift AGN (z > 2).

Are the infrared-faint radio sources pulsars?

NASA Astrophysics Data System (ADS)

Cameron, A. D.; Keith, M.; Hobbs, G.; Norris, R. P.; Mao, M. Y.; Middelberg, E.

2011-07-01

Infrared-faint radio sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50 per cent duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

Dwarfs in Coma Cluster

NASA Technical Reports Server (NTRS)

2007-01-01

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

This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

FIGGS 2: An HI survey of extremely faint irregular galaxies

NASA Astrophysics Data System (ADS)

Patra, N. N.; Chengalur, J. N.; Karachentsev, I. D.; Sharina, M. E.

2016-10-01

We present observations and first results from the FIGGS2 survey. FIGGS2 is an extension of the earlier Faint Irregular Galaxies GMRT survey (FIGGS) towards faint luminosity end. The sample consists of 20 galaxies, 15 of which were detected in HI 21 cm line using the Giant Meterwave Radio Telescope (GMRT). The median blue band magnitude of our sample is approximately -11.m 6, which is more than one magnitude fainter than earlier FIGGS survey. From our GMRT observations we found that, for many of our sample galaxies, the HI disks are offset from their optical disks. The HI diameters of the FIGGS2 galaxies show a tight correlation with their HI mass. The slope of the correlation is 2.08 ± 0.20 similar to what is found for FIGGS galaxies. We also found that for almost all galaxies, the HI disks are larger than the optical disks which is a common trend for dwarf or spiral galaxies. The mean value of the ratio of HI to optical diameter is about 1.54.

Kinematics of Extremely Metal-poor Galaxies: Evidence for Stellar Feedback

NASA Astrophysics Data System (ADS)

Olmo-García, A.; Sánchez Almeida, J.; Muñoz-Tuñón, C.; Filho, M. E.; Elmegreen, B. G.; Elmegreen, D. M.; Pérez-Montero, E.; Méndez-Abreu, J.

2017-01-01

The extremely metal-poor (XMP) galaxies analyzed in a previous paper have large star-forming regions with a metallicity lower than the rest of the galaxy. Such a chemical inhomogeneity reveals the external origin of the metal-poor gas fueling star formation, possibly indicating accretion from the cosmic web. This paper studies the kinematic properties of the ionized gas in these galaxies. Most XMPs have a rotation velocity around a few tens of km s-1. The star-forming regions appear to move coherently. The velocity is constant within each region, and the velocity dispersion sometimes increases within the star-forming clump toward the galaxy midpoint, suggesting inspiral motion toward the galaxy center. Other regions present a local maximum in velocity dispersion at their center, suggesting a moderate global expansion. The Hα line wings show a number of faint emission features with amplitudes around a few per cent of the main Hα component, and wavelength shifts between 100 and 400 km s-1. The components are often paired, so that red and blue emission features with similar amplitudes and shifts appear simultaneously. Assuming the faint emission to be produced by expanding shell-like structures, the inferred mass loading factor (mass loss rate divided by star formation rate) exceeds 10. Since the expansion velocity far exceeds the rotational and turbulent velocities, the gas may eventually escape from the galaxy disk. The observed motions involve energies consistent with the kinetic energy released by individual core-collapse supernovae. Alternative explanations for the faint emission have been considered and discarded.

KINEMATICS OF EXTREMELY METAL-POOR GALAXIES: EVIDENCE FOR STELLAR FEEDBACK

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

Olmo-García, A.; Sánchez Almeida, J.; Muñoz-Tuñón, C.

2017-01-10

The extremely metal-poor (XMP) galaxies analyzed in a previous paper have large star-forming regions with a metallicity lower than the rest of the galaxy. Such a chemical inhomogeneity reveals the external origin of the metal-poor gas fueling star formation, possibly indicating accretion from the cosmic web. This paper studies the kinematic properties of the ionized gas in these galaxies. Most XMPs have a rotation velocity around a few tens of km s{sup −1}. The star-forming regions appear to move coherently. The velocity is constant within each region, and the velocity dispersion sometimes increases within the star-forming clump toward the galaxymore » midpoint, suggesting inspiral motion toward the galaxy center. Other regions present a local maximum in velocity dispersion at their center, suggesting a moderate global expansion. The H α line wings show a number of faint emission features with amplitudes around a few per cent of the main H α component, and wavelength shifts between 100 and 400 km s{sup −1}. The components are often paired, so that red and blue emission features with similar amplitudes and shifts appear simultaneously. Assuming the faint emission to be produced by expanding shell-like structures, the inferred mass loading factor (mass loss rate divided by star formation rate) exceeds 10. Since the expansion velocity far exceeds the rotational and turbulent velocities, the gas may eventually escape from the galaxy disk. The observed motions involve energies consistent with the kinetic energy released by individual core-collapse supernovae. Alternative explanations for the faint emission have been considered and discarded.« less

Discarded candidate companions to low-mass members of Chamaeleon I

NASA Astrophysics Data System (ADS)

Comerón, F.

2012-01-01

Context. Direct detections of brown dwarfs and planetary-mass companions to members of nearby star-forming regions provide important clues about the process of star formation, core fragmentation, and protoplanetary disk evolution. Aims: We study two faint objects at a very small angular distance from the low-mass star ESO-Hα-558 and the possible massive brown dwarf ESO-Hα-566, both of which are members of the Chamaeleon I star-forming region, to establish whether they are physical companions to those sources. If they are, their low luminosities should imply L or T spectral types, which have clearly detectable spectral features. Methods: Adaptive optics-assisted imaging and spectroscopy of both faint candidate companions has been obtained with the NACO instrument at the Very Large Telescope (VLT). Results: Photometry shows that the colors of both objects are compatible with them being moderately reddened, normal stars in the background of the Chamaeleon I clouds. This interpretation is confirmed spectroscopically, as the spectrum between 1.4 and 2.4 μm of both objects has a featureless, monotonic slope lacking the strong H2O absorption features that dominate cool stellar and substellar spectra in that domain. Conclusions: We demonstrate that the two faint sources seen very close to ESO-Hα-558 and ESO-Hα-566 are unrelated background stars, instead of giant planetary-mass companions as might be expected based on their faintness and angular proximity. Based on observations collected with the Very Large Telescope (VLT) at the European Southern Observatory, Paranal, Chile, under observing programmes 075.C-0809(B) and 078.C-0429(C).

Morphology and astrometry of Infrared-Faint Radio Sources

NASA Astrophysics Data System (ADS)

Middelberg, Enno; Norris, Ray; Randall, Kate; Mao, Minnie; Hales, Christopher

2008-10-01

Infrared-Faint Radio Sources, or IFRS, are an unexpected class of object discovered in the Australia Telescope Large Area Survey, ATLAS. They are compact 1.4GHz radio sources with no visible counterparts in co-located (relatively shallow) Spitzer infrared and optical images. We have detected two of these objects with VLBI, indicating the presence of an AGN. These observations and our ATLAS data indicate that IFRS are extended on scales of arcseconds, and we wish to image their morphologies to obtain clues about their nature. These observations will also help us to select optical counterparts from very deep, and hence crowded, optical images which we have proposed. With these data in hand, we will be able to compare IFRS to known object types and to apply for spectroscopy to obtain their redshifts.

Space telescope scientific instruments

NASA Technical Reports Server (NTRS)

Leckrone, D. S.

1979-01-01

The paper describes the Space Telescope (ST) observatory, the design concepts of the five scientific instruments which will conduct the initial observatory observations, and summarizes their astronomical capabilities. The instruments are the wide-field and planetary camera (WFPC) which will receive the highest quality images, the faint-object camera (FOC) which will penetrate to the faintest limiting magnitudes and achieve the finest angular resolution possible, and the faint-object spectrograph (FOS), which will perform photon noise-limited spectroscopy and spectropolarimetry on objects substantially fainter than those accessible to ground-based spectrographs. In addition, the high resolution spectrograph (HRS) will provide higher spectral resolution with greater photometric accuracy than previously possible in ultraviolet astronomical spectroscopy, and the high-speed photometer will achieve precise time-resolved photometric observations of rapidly varying astronomical sources on short time scales.

Do the enigmatic ``Infrared-Faint Radio Sources'' include pulsars?

NASA Astrophysics Data System (ADS)

Hobbs, George; Middelberg, Enno; Norris, Ray; Keith, Michael; Mao, Minnie; Champion, David

2009-04-01

The Australia Telescope Large Area Survey (ATLAS) team have surveyed seven square degrees of sky at 1.4GHz. During processing some unexpected infrared-faint radio sources (IFRS sources) were discovered. The nature of these sources is not understood, but it is possible that some of these sources may be pulsars within our own galaxy. We propose to observe the IFRS sources with steep spectral indices using standard search techniques to determine whether or not they are pulsars. A pulsar detection would 1) remove a subset of the IFRS sources from the ATLAS sample so they would not need to be observed with large optical/IR telescopes to find their hosts and 2) be intrinsically interesting as the pulsar would be a millisecond pulsar and/or have an extreme spatial velocity.

Hot DOGs: The Most Luminous Galaxies Found by WISE

NASA Astrophysics Data System (ADS)

Eisenhardt, Peter; Tsai, Chao-Wei; Wu, Jingwen; Griffith, Roger; Yan, Lin; Stern, Daniel; Stanford, Adam; Blain, Andrew; Benford, Dominic; Bridge, Carrie; Assef, Roberto; Petty, Sara

2013-02-01

NASA's Wide-field Infrared Survey Explorer (WISE) has achieved its fundamental goal by delivering its all-sky survey at 3.4, 4.6, 12 and 22 (micron) (W1, W2, W3, and W4), reaching sensitivities hundreds of times deeper than IRAS. One of the two primary science objectives for WISE is to identify the most luminous galaxies in the Universe (Ultra-Luminous IR Galaxies, or ULIRGs). We have used WISE photometry to select an all- sky sample of objects which are extremely luminous, and for which Herschel far-IR follow-up observations are underway. The objects are prominent in W3 and W4, but faint or undetected in W1 and W2. Available spectroscopy and far IR photometry for these objects show they typically have redshifts z > 2 and luminosities over 10^13 L_odot, with about 10% exceeding 10^14 L_odot and rivaling the brightest known QSOs. Their dust is more than twice as hot as other IR luminous objects: they are hot dust obscured galaxies or ``hot DOGs," and may represent a new phase in galaxy evolution. We request NOAO time to obtain redshifts and optical and near IR photometry for the all-sky sample of the brightest hot DOGs, all of which are in our Herschel program. With existing and allocated observations, this request should complete the acquisition of these crucial data for this primary WISE science objective.

Hot DOGs: The Most Luminous Galaxies Found by WISE

NASA Astrophysics Data System (ADS)

Eisenhardt, Peter; Tsai, Chao-Wei; Wu, Jingwen; Assef, Roberto; Stern, Daniel; Wright, Edward

2013-08-01

NASA's Wide-field Infrared Survey Explorer (WISE) has achieved its fundamental goal by delivering an all-sky survey at 3.4, 4.6, 12 and 22 (micron) (W1, W2, W3, and W4), reaching sensitivities hundreds of times deeper than IRAS. One of the two primary science objectives for WISE is to identify the most luminous galaxies in the Universe. We have used WISE photometry to select an all-sky sample of objects which are extremely luminous, and for which Herschel far-IR follow-up observations are 99% complete. The objects are prominent in W3 and W4, but faint or undetected in W1 and W2. The spectroscopy and far IR photometry for these objects show they typically have redshifts z > 2 and luminosities over 10^13 L_⊙, with about 5 - 10% exceeding 10^14 L_⊙ and rivaling the brightest known QSOs. Their dust is more than twice as hot as other IR luminous objects: they are hot dust obscured galaxies or ``hot DOGs," and may represent a new phase in galaxy evolution. Because our 2012B allocation had mixed weather, we request 2013B NOAO time to complete the collection of redshifts and optical and near IR photometry for this all-sky sample of the brightest hot DOGs. With existing and allocated observations, this request should complete the acquisition of these crucial data for this primary WISE science objective.

Hubble Space Telescope faint object camera instrument handbook (Post-COSTAR), version 5.0

NASA Technical Reports Server (NTRS)

Nota, A. (Editor); Jedrzejewski, R. (Editor); Greenfield, P. (Editor); Hack, W. (Editor)

1994-01-01

The faint object camera (FOC) is a long-focal-ratio, photon-counting device capable of taking high-resolution two-dimensional images of the sky up to 14 by 14 arc seconds squared in size with pixel dimensions as small as 0.014 by 0.014 arc seconds squared in the 1150 to 6500 A wavelength range. Its performance approaches that of an ideal imaging system at low light levels. The FOC is the only instrument on board the Hubble Space Telescope (HST) to fully use the spatial resolution capabilities of the optical telescope assembly (OTA) and is one of the European Space Agency's contributions to the HST program.

Evidence for Infrared-faint Radio Sources as z > 1 Radio-loud Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Huynh, Minh T.; Norris, Ray P.; Siana, Brian; Middelberg, Enno

2010-02-01

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 μm) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z >~ 1) active galactic nuclei.

EVIDENCE FOR INFRARED-FAINT RADIO SOURCES AS z > 1 RADIO-LOUD ACTIVE GALACTIC NUCLEI

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

Huynh, Minh T.; Norris, Ray P.; Siana, Brian

2010-02-10

Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 {mu}m) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z {approx}> 1) active galactic nuclei.

The science enabled by the Maunakea Spectroscopic Explorer

NASA Astrophysics Data System (ADS)

Martin, N. F.; Babusiaux, C.

2017-12-01

With its unique wide-field, multi-object, and dedicated spectroscopic capabilities, the Maunakea Spectroscopic Explorer (MSE) is a powerful facility to shed light on the faint Universe. Built around an upgrade of the Canada-France Hawaii Telescope (CFHT) to a 11.25-meter telescope with a dedicated ˜1.5 deg^2, 4,000-fiber wide-field spectrograph that covers the optical and near-infrared wavelengths at resolutions between 2,500 and 40,000, the MSE is the essential follow-up complement to the current and next generations of multi-wavelength imaging surveys, such as the LSST, Gaia, Euclid, eROSITA, SKA, and WFIRST, and is an ideal feeder facility for the extremely large telescopes that are currently being built (E-ELT, GMT, and TMT). The science enabled by the MSE is vast and would have an impact on almost all aspects of astronomy research.

EMITTING ELECTRONS AND SOURCE ACTIVITY IN MARKARIAN 501

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

Mankuzhiyil, Nijil; Ansoldi, Stefano; Persic, Massimo

2012-07-10

We study the variation of the broadband spectral energy distribution (SED) of the BL Lac object Mrk 501 as a function of source activity, from quiescent to flaring. Through {chi}{sup 2}-minimization we model eight simultaneous SED data sets with a one-zone synchrotron self-Compton (SSC) model, and examine how model parameters vary with source activity. The emerging variability pattern of Mrk 501 is complex, with the Compton component arising from {gamma}-e scatterings that sometimes are (mostly) Thomson and sometimes (mostly) extreme Klein-Nishina. This can be seen from the variation of the Compton to synchrotron peak distance according to source state. Themore » underlying electron spectra are faint/soft in quiescent states and bright/hard in flaring states. A comparison with Mrk 421 suggests that the typical values of the SSC parameters are different in the two sources: however, in both jets the energy density is particle-dominated in all states.« less

A possible brown dwarf companion to Gliese 569

NASA Technical Reports Server (NTRS)

Forrest, W. J.; Shure, Mark; Skrutskie, M. F.

1988-01-01

A faint cool companion to Gliese 569, discovered during an IR imaging survey of nearby stars, may be the lowest-mass stellar object yet found. The companion is somewhat cooler in its 1.65-3.75-micron energy distribution than the coolest known main-sequence stars, indicating a low mass. Despite its lower temperature, it is more luminous than similar extremely low-mass stars, suggesting that it is either a young low-mass star evolving toward the main sequence or a cooling substellar brown dwarf. The primary star has emission lines and a low space velocity and exhibits flaring, all of which imply youth for this system. Observations of Gliese 569 and its companion over a period of 2 yr confirm the common proper motion expected of a true binary. The 5-arcsec apparent separation (50 AU) implies an orbital period of roughly 500 yr, which will permit an eventual direct determination of the mass of the companion.

ALMA Observations of SMM11 Reveal an Extremely Young Protostar in Serpens Main Cluster

NASA Astrophysics Data System (ADS)

Aso, Yusuke; Ohashi, Nagayoshi; Aikawa, Yuri; Machida, Masahiro N.; Saigo, Kazuya; Saito, Masao; Takakuwa, Shigehisa; Tomida, Kengo; Tomisaka, Kohji; Yen, Hsi-Wei; Williams, Jonathan P.

2017-11-01

We report the discovery of an extremely young protostar, SMM11, located in the associated submillimeter condensation in the Serpens Main cluster using the Atacama Large Millimeter/submillimeter Array (ALMA) during its Cycle 3 at 1.3 mm and an angular resolution of ˜ 0\\buildrel{\\prime\\prime}\\over{.} 5˜ 210 {AU}. SMM11 is a Class 0 protostar without any counterpart at 70 μm or shorter wavelengths. The ALMA observations show 1.3 mm continuum emission associated with a collimated 12CO bipolar outflow. Spitzer and Herschel data show that SMM11 is extremely cold ({T}{bol} = 26 K) and faint ({L}{bol} ≲ 0.9 {L}⊙ ). We estimate the inclination angle of the outflow to be ˜ 80^\\circ , almost parallel to the plane of the sky, from simple fitting using a wind-driven-shell model. The continuum visibilities consist of Gaussian and power-law components, suggesting a spherical envelope with a radius of ˜600 au around the protostar. The estimated low C18O abundance, X(C18O) = 1.5-3 × {10}-10, is also consistent with its youth. The high outflow velocity, a few 10 {km} {{{s}}}-1 at a few 1000 au, is much higher than theoretical simulations of first hydrostatic cores, and we suggest that SMM11 is a transitional object right after the second collapse of the first core.

Origin of Outer Solar System

NASA Technical Reports Server (NTRS)

Holman, Matthew J.; Boyce, J. (Technical Monitor)

2003-01-01

We feel that at the present moment the available theoretical models of the Kuiper belt are still in advance of the data, and thus our main task has been to conduct observational work guided by theoretical motivations. Our efforts over the past year can be divided into four categories: A) Wide-field Searches for Kuiper Belt Objects; B) Pencil-beam Searches for Kuiper Belt Objects; C) Wide-field Searches for Moons of the Outer Planets; D) Pencil-beam Searches for Faint Uranian and Neptunian Moons; E) Recovery Observations. As of April 2002, we have conducted several searches for Kuiper belt objects using large-format mosaic CCD camera on 4-meter class telescopes. In May 1999, we used the Kitt Peak 4-meter with the NOAO Mosaic camera we attempted a search for KBOs at a range of ecliptic latitudes. In addition to our wide-field searches, we have conducted three 'pencil-beam' searches in the past year. In a pencil-beam search we take repeated integrations of the same field throughout a night. After preprocessing the resulting images we shift and recombine them along a range of rates and directions consistent with the motion of KBOs. Stationary objects then smear out, while objects moving at near the shift rate appear as point sources. In addition to our searches for Kuiper belt objects, we are completing the inventory of the outer solar system by search for faint satellites of the outer planets. In August 2001 we conducted pencil beam searches for faint Uranian and Neptunian satellites at CFHT and CTIO. These searches resulted in the discover of two Neptunian and four Uranian satellite candidates. The discovery of Kuiper belt objects and outer planet satellites is of little use if the discoveries are not followed by systematic, repeated astrometric observations that permit reliable estimates of their orbits.

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

Micheva, Genoveva; Oey, M. S.; Jaskot, Anne E.

We present the remarkable discovery that the dwarf irregular galaxy NGC 2366 is an excellent analog of the Green Pea (GP) galaxies, which are characterized by extremely high ionization parameters. The similarities are driven predominantly by the giant H ii region Markarian 71 (Mrk 71). We compare the system with GPs in terms of morphology, excitation properties, specific star-formation rate, kinematics, absorption of low-ionization species, reddening, and chemical abundance, and find consistencies throughout. Since extreme GPs are associated with both candidate and confirmed Lyman continuum (LyC) emitters, Mrk 71/NGC 2366 is thus also a good candidate for LyC escape. Themore » spatially resolved data for this object show a superbubble blowout generated by mechanical feedback from one of its two super star clusters (SSCs), Knot B, while the extreme ionization properties are driven by the ≲1 Myr-old, enshrouded SSC Knot A, which has ∼10 times higher ionizing luminosity. Very massive stars (>100 M {sub ⊙}) may be present in this remarkable object. Ionization-parameter mapping indicates that the blowout region is optically thin in the LyC, and the general properties also suggest LyC escape in the line of sight. Mrk 71/NGC 2366 does differ from GPs in that it is one to two orders of magnitude less luminous. The presence of this faint GP analog and candidate LyC emitter (LCE) so close to us suggests that LCEs may be numerous and commonplace, and therefore could significantly contribute to the cosmic ionizing budget. Mrk 71/NGC 2366 offers an unprecedentedly detailed look at the viscera of a candidate LCE, and could clarify the mechanisms of LyC escape.« less

Asteroid families - An initial search

NASA Technical Reports Server (NTRS)

Williams, James G.

1992-01-01

A stereo examination was conducted for clusters in three-dimensional proper element space within a sample of both numbered and faint Palomar-Leiden Survey (PLS) asteroids. The clusters were then objectively filtered for small Poisson probability of chance occurrence; 104 were accepted as families with 4- to 12-member populations, and are interpreted as impact-generated. Structure is common in the well-populated families: the better-sampled families are accordingly discussed in terms of their geometry and taxonomy. Some families are very rich in faint PLS members.

CONSTRAINTS ON MACHO DARK MATTER FROM COMPACT STELLAR SYSTEMS IN ULTRA-FAINT DWARF GALAXIES

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

Brandt, Timothy D.

2016-06-20

I show that a recently discovered star cluster near the center of the ultra-faint dwarf galaxy Eridanus II provides strong constraints on massive compact halo objects (MACHOs) of ≳5 M {sub ⊙} as the main component of dark matter. MACHO dark matter will dynamically heat the cluster, driving it to larger sizes and higher velocity dispersions until it dissolves into its host galaxy. The stars in compact ultra-faint dwarf galaxies themselves will be subject to the same dynamical heating; the survival of at least 10 such galaxies places independent limits on MACHO dark matter of masses ≳10 M {sub ⊙}.more » Both Eri II’s cluster and the compact ultra-faint dwarfs are characterized by stellar masses of just a few thousand M {sub ⊙} and half-light radii of 13 pc (for the cluster) and ∼30 pc (for the ultra-faint dwarfs). These systems close the ∼20–100 M {sub ⊙} window of allowed MACHO dark matter and combine with existing constraints from microlensing, wide binaries, and disk kinematics to rule out dark matter composed entirely of MACHOs from ∼10{sup −7} M {sub ⊙} up to arbitrarily high masses.« less

Space Telescope maintenance and refurbishment

NASA Technical Reports Server (NTRS)

Trucks, H. F.

1983-01-01

The Space Telescope (ST) represents a new concept regarding spaceborne astronomical observatories. Maintenance crews will be brought to the orbital worksite to make repairs and replace scientific instruments. For major overhauls the telescope can be temporarily returned to earth with the aid of the Shuttle. It will, thus, be possible to conduct astronomical studies with the ST for two decades or more. The five first-generation scientific instruments used with the ST include a wide field/planetary camera, a faint object camera, a faint object spectrograph, a high resolution spectrograph, and a high speed photometer. Attention is given to the optical telescope assembly, the support systems module, aspects of mission and science operations, unscheduled maintenance, contingency orbital maintenance, planned on-orbit maintenance, ground maintenance, ground refurbishment, and ground logistics.

Hubble Space Telescope: Faint object camera instrument handbook. Version 2.0

NASA Technical Reports Server (NTRS)

Paresce, Francesco (Editor)

1990-01-01

The Faint Object Camera (FOC) is a long focal ratio, photon counting device designed to take high resolution two dimensional images of areas of the sky up to 44 by 44 arcseconds squared in size, with pixel dimensions as small as 0.0007 by 0.0007 arcseconds squared in the 1150 to 6500 A wavelength range. The basic aim of the handbook is to make relevant information about the FOC available to a wide range of astronomers, many of whom may wish to apply for HST observing time. The FOC, as presently configured, is briefly described, and some basic performance parameters are summarized. Also included are detailed performance parameters and instructions on how to derive approximate FOC exposure times for the proposed targets.

The morphology of faint galaxies in Medium Deep Survey images using WFPC2

NASA Technical Reports Server (NTRS)

Griffiths, R. E.; Casertano, S.; Ratnatunga, K. U.; Neuschaefer, L. W.; Ellis, R. S.; Gilmore, G. F.; Glazebrook, K.; Santiago, B.; Huchra, J. P.; Windhorst, R. A.

1994-01-01

First results from Hubble Space Telescope (HST) Medium Deep Survey images taken with Wide Field/Planetary Camera-2 (WFPC2) demonstrate that galaxy classifications can be reliably performed to magnitudes I814 approximately less than 22.0 in the F815W band. Published spectroscopic surveys to this depth indicate a mean redshift of bar-z approximately 0.5. We have classified over 200 galaxies in nine WFPC2 fields according to a basic morphological scheme. The majority of these faint galaxies appear to be similar to regular Hubble-sequence examples observed at low redshift. To the precision of our classification scheme, the relative proportion of spheroidal and disk systems of normal appearance is as expected from nearby samples, indicating that the bulk of the local galaxy population was in place at half the Hubble time. However, the most intriguing result is the relatively high proportion (approximately 40%) of objects which are in some way anomalous, and which may be of relevance in understanding the origin of the familiar excess population of faint galaxies established by others. These diverse objects include apparently interacting pairs whose multiple structure is only revealed with HST's angular resolution, galaxies with superluminous star-forming regions, diffuse low surface brightness galaxies of various forms, and compact galaxies. These anomalous galaxies contribute a substantial fraction of the excess counts at our limiting magnitude, and may provide insights into the 'faint blue galaxy' problem.

Unidentified point sources in the IRAS minisurvey

NASA Technical Reports Server (NTRS)

Houck, J. R.; Soifer, B. T.; Neugebauer, G.; Beichman, C. A.; Aumann, H. H.; Clegg, P. E.; Gillett, F. C.; Habing, H. J.; Hauser, M. G.; Low, F. J.

1984-01-01

Nine bright, point-like 60 micron sources have been selected from the sample of 8709 sources in the IRAS minisurvey. These sources have no counterparts in a variety of catalogs of nonstellar objects. Four objects have no visible counterparts, while five have faint stellar objects visible in the error ellipse. These sources do not resemble objects previously known to be bright infrared sources.

The Role of the Goldstone Apple Valley Radio Telescope Project in Promoting Scientific Efficacy among Middle and High School Students.

ERIC Educational Resources Information Center

Ibe, Mary; Deutscher, Rebecca

This study investigated the effects on student scientific efficacy after participation in the Goldstone Apple Valley Radio Telescope (GAVRT) project. In the GAVRT program, students use computers to record extremely faint radio waves collected by the telescope and analyze real data. Scientific efficacy is a type of self-knowledge a person uses to…

Faint Object Camera observations of a globular cluster nova field

NASA Technical Reports Server (NTRS)

Margon, Bruce; Anderson, Scott F.; Downes, Ronald A.; Bohlin, Ralph C.; Jakobsen, Peter

1991-01-01

The Faint Object Camera onboard Hubble Space Telescope has obtained U and B images of the field of Nova Ophiuchi 1938 in the globular cluster M14 (NGC 6402). The candidate for the quiescent nova suggested by Shara et al. (1986) is clearly resolved into at least six separate images, probably all stellar, in a region of 0.5 arcsec. Although two of these objects are intriguing as they are somewhat ultraviolet, the actual nova counterpart remains ambiguous, as none of the images in the field has a marked UV excess. Many stars within the 1.4 arcsec (2 sigma) uncertainty of the nova outburst position are viable counterparts if only astrometric criteria are used for selection. The 11 x 11 arcsec frames easily resolve several hundred stars in modest exposures, implying that HST even in its current optical configuration will be unique for studies of very crowded fields at moderate (B = 22) limiting magnitudes.

Calibration of HST wide field camera for quantitative analysis of faint galaxy images

NASA Technical Reports Server (NTRS)

Ratnatunga, Kavan U.; Griffiths, Richard E.; Casertano, Stefano; Neuschaefer, Lyman W.; Wyckoff, Eric W.

1994-01-01

We present the methods adopted to optimize the calibration of images obtained with the Hubble Space Telescope (HST) Wide Field Camera (WFC) (1991-1993). Our main goal is to improve quantitative measurement of faint images, with special emphasis on the faint (I approximately 20-24 mag) stars and galaxies observed as a part of the Medium-Deep Survey. Several modifications to the standard calibration procedures have been introduced, including improved bias and dark images, and a new supersky flatfield obtained by combining a large number of relatively object-free Medium-Deep Survey exposures of random fields. The supersky flat has a pixel-to-pixel rms error of about 2.0% in F555W and of 2.4% in F785LP; large-scale variations are smaller than 1% rms. Overall, our modifications improve the quality of faint images with respect to the standard calibration by about a factor of five in photometric accuracy and about 0.3 mag in sensitivity, corresponding to about a factor of two in observing time. The relevant calibration images have been made available to the scientific community.

Simulations for Improved Imaging of Faint Objects at Maui Space Surveillance Site

NASA Astrophysics Data System (ADS)

Holmes, R.; Roggemann, M.; Werth, M.; Lucas, J.; Thompson, D.

A detailed wave-optics simulation is used in conjunction with advanced post-processing algorithms to explore the trade space between image post-processing and adaptive optics for improved imaging of low signal-to-noise ratio (SNR) targets. Target-based guidestars are required for imaging of most active Earth-orbiting satellites because of restrictions on using laser-backscatter-based guidestars in the direction of such objects. With such target-based guidestars and Maui conditions, it is found that significant reductions in adaptive optics actuator and subaperture density can result in improved imaging of fainter objects. Simulation indicates that elimination of adaptive optics produces sub-optimal results for all of the faint-object cases considered. This research was developed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions, and/or findings expressed are those of the author(s) and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.

Spectroscopic observations of comets

NASA Technical Reports Server (NTRS)

1982-01-01

Development of a spectrograph using a microchannel plate intensifier for observing faint comets is described. The spectrograph is capable of obtaining useful spectra of objects as faint as M(2) = 18. The increased guiding efficiency achieved by the optical coupling of the ISIT vidicon of the 154 cm telescope has resulted in a better signal to noise ratio. The ability to take a direct image of the comet aids in the interpretation of the spatial profile of the emissions. Spectra of comets Schwassmann-Wachmann 1, Bradfield, Encke, Tuttle, and Stephen-Oterma are discussed.

The Origin of Ultra-Faint Galaxies

NASA Astrophysics Data System (ADS)

Sand, David

2017-08-01

We request 24 orbits of HST/ACS to obtain imaging in F606W and F814W of apparent tidal features in two ultra-faint dwarf galaxies: Hercules and Leo V. This will enable us to test whether the stars in ultra- faint galaxies-as a population-have been affected by Galactic tides. Most of the new dwarfs show signs of tidal interaction in ground-based photometry, several have measured ellipticities greater than 0.5, and kinematics of a subset show velocity gradients. These ubiquitous hints for tidal effects among distant dwarfs is particularly surprising and suggestive. If most ultra-faint dwarfs are disturbed by tides, then recent tests of galaxy formation in the near field have unstable foundations.HST resolution provides an opportunity to assess whether tidal features (accompanied by tentative kinematic gradients) seen in ground-based observations of Hercules and Leo V are genuine or are instead clumps of compact background galaxies masquerading as stellar debris. In Hercules, a further test is possible: searching for a distance gradient along the stretched body of the galaxy. Parallel pointings will sample similar dwarf-centric radii away from the tidal features, assuring an unambiguous result. Whether we confirm or rule out the presence of stellar loss in these objects, the consequences are important-the origin of the ultra-faint dwarfs tells us the lower limit to both galaxy formation and the number of dark matter subhalos inhabiting the Milky Way.This program is only possible with HST: its exquisite resolution can separate compact galaxies from main sequence dwarf stars at faint magnitudes, which even the best multi-band ground-based schemes struggle with.

The Discovery of Herbig–Haro Objects in LDN 673

NASA Astrophysics Data System (ADS)

Rector, T. A.; Shuping, R. Y.; Prato, L.; Schweiker, H.

2018-01-01

We report the discovery of 12 faint Herbig–Haro (HH) objects in LDN 673 found using a novel color-composite imaging method that reveals faint Hα emission in complex environments. Follow-up observations in [S II] confirmed their classification as HH objects. Potential driving sources are identified from the Spitzer c2d Legacy Program catalog and other infrared observations. The 12 new HH objects can be divided into three groups: four are likely associated with a cluster of eight young stellar object class I/II IR sources that lie between them; five are colinear with the T Tauri multiple star system AS 353, and are likely driven by the same source as HH 32 and HH 332 and three are bisected by a very red source that coincides with an infrared dark cloud. We also provide updated coordinates for the three components of HH 332. Inaccurate numbers were given for this object in the discovery paper. The discovery of HH objects and associated driving sources in this region provides new evidence for star formation in the Aquila clouds, implying a much larger T Tauri population in a seldom-studied region.

The space telescope scientific instruments

NASA Technical Reports Server (NTRS)

Leckrone, D. S.

1980-01-01

The paper describes the space telescope with a 2.4 m aperture to be launched at 500 km altitude in late 1983. Four axial-bay and one radial-bay scientific instrument, a wide-field and planetary camera, a faint-object camera, a faint-object spectrograph, and a high-speed photometer are to be installed to conduct the initial observations. The axial instruments are constrained to envelopes with dimensions 0.9 x 0.9 x 2.2 m and their masses cannot exceed 317 kg. The observatory will also be equipped with fine-guidance sensors and a microprocessor. The design concepts of the instruments are outlined and some of the astronomical capabilities including studies of distant and local galaxies, physical properties of quasars, interrelations between quasars and active galactic nuclei are mentioned.

Portable Telescopic Observations of the 3 June 2017 Stellar Occultation by New Horizons Kuiper Extended Mission Target (486958) 2014 MU69

NASA Astrophysics Data System (ADS)

Verbiscer, Anne J.; Buie, Marc W.; Porter, Simon Bernard; Tamblyn, Peter; Terrell, Dirk; Benecchi, Susan; Parker, Alex; Soto, Alejandro; Wasserman, Lawrence H.; Young, Eliot F.; Zangari, Amanda Marie; New Horizons MU69 Occultation Team

2017-10-01

The New Horizons spacecraft will encounter the cold classical Kuiper Belt Object (486958) 2014 MU69 on 1 January 2019. Because it is extremely faint (V mag ~27), MU69 has only been directly observed by the Hubble Space Telescope since its discovery (by HST) in 2014 (Spencer et al. 2015 EPSC 10, 417S). Current knowledge of the physical properties of MU69 is therefore limited to its red color (F606W-F814W = 0.99 ± 0.18, Benecchi et al. 2017) and a crude estimate on its size (20-40 km) based on association with other cold classical KBO visible albedos (0.04-0.15). Stellar occultations are powerful tools with which to measure the size and shape of objects whose distance and faintness precludes any spatially resolved observations. Here we report the results of a stellar occultation of a g’=15.33 magnitude star by MU69 on 3 June 2017. The shadow path crossed both southern Africa and South America. We deployed 12 portable telescopes from Mendoza, Argentina and 13 portable telescopes from Clanwilliam, Western Cape, South Africa. Although 24 of these 25 telescopes successfully observed the occultation star at the predicted event time, no solid body detection appeared in any of the acquired lightcurves. Following the successful detection of MU69 by stellar occultation on 17 July 2017, revised predictions of the location of the shadow path on 3 June now allow the lightcurves obtained on 3 June to place important constraints on the environment surrounding MU69 as well as upper limits on the size of any small satellites in the regions probed. This work would not have been possible without the financial support of NASA, the New Horizons Project, the astrometric support of the Gaia mission, and logistical support from the South African Astronomical Observatory, the US Embassies in Buenos Aires and Pretoria and the US Consulate in Cape Town.

Stellar Populations with the LSST

NASA Astrophysics Data System (ADS)

Saha, Abhijit; Olsen, K.; LSST Stellar Populations Collaboration

2006-12-01

The LSST will produce a multi-color map and photometric object catalog of half the sky to g 27.5(5σ). Strategically cadenced time-space sampling of each field spanning ten years will allow variability, proper motion and parallax measurements for objects brighter than g 25. As part of providing an unprecedented map of the Galaxy, the accurate multi-band photometry will permit photometric parallaxes, chemical abundances and a handle on ages via colors at turn-off for main-sequence stars at all distances within the Galaxy, permitting a comprehensive study of star formation histories (SFH) and chemical evolution for field stars. With a geometric parallax accuracy of 1mas, LSST will produce a robust complete sample of the solar neighborhood stars. While delivering parallax accuracy comparable to HIPPARCOS, LSST will extend the catalog to more than a 10 magnitudes fainter limit, and will be complete to MV 15. In the Magellanic Clouds too, the photometry will reach MV +8, allowing the SFH and chemical signatures in the expansive outer extremities to be gleaned from their main sequence stars. This in turn will trace the detailed interaction of the Clouds with the Galaxy halo. The LSST time sampling will identify and characterize variable stars of all types, from time scales of 1hr to several years, a feast for variable star astrophysics. Cepheids and LPVs in all galaxies in the Sculptor, M83 and Cen-A groups are obvious data products: comparative studies will reveal systematic differences with galaxy properties, and help to fine tune the rungs of the distance ladder. Dwarf galaxies within 10Mpc that are too faint to find from surface brightness enhancements will be revealed via over-densities of their red giants: this systematic census will extend the luminosity function of galaxies to the faint limit. Novae discovered by LSST time sampling will trace intergalactic stars out to the Virgo and Fornax clusters.

Four faint T dwarfs from the UKIRT Infrared Deep Sky Survey (UKIDSS) Southern Stripe

NASA Astrophysics Data System (ADS)

Chiu, Kuenley; Liu, Michael C.; Jiang, Linhua; Allers, Katelyn N.; Stark, Daniel P.; Bunker, Andrew; Fan, Xiaohui; Glazebrook, Karl; Dupuy, Trent J.

2008-03-01

We present the optical and near-infrared photometry and spectroscopy of four faint T dwarfs newly discovered from the UKIDSS first data release. The sample, drawn from an imaged area of ~136 deg2 to a depth of Y = 19.9 (5σ, Vega), is located in the Sloan Digital Sky Survey (SDSS) Southern Equatorial Stripe, a region of significant future deep imaging potential. We detail the selection and followup of these objects, three of which are spectroscopically confirmed brown dwarfs ranging from type T2.5 to T7.5, and one is photometrically identified as early T. Their magnitudes range from Y = 19.01 to 19.88 with derived distances from 34 to 98 pc, making these among the coldest and faintest brown dwarfs known. The T7.5 dwarf appears to be single based on 0.05-arcsec images from Keck laser guide star adaptive optics. The sample brings the total number of T dwarfs found or confirmed by UKIDSS data in this region to nine, and we discuss the projected numbers of dwarfs in the future survey data. We estimate that ~240 early and late T dwarfs are discoverable in the UKIDSS Large Area Survey (LAS) data, falling significantly short of published model projections and suggesting that initial mass functions and/or birth rates may be at the low end of possible models. Thus, deeper optical data have good potential to exploit the UKIDSS survey depth more fully, but may still find the potential Y dwarf sample to be extremely rare.

A Search for Optically Faint GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Lederer, Susan M.; Barker, Edwin S.; Cowardin, Heather; Abercromby, Kira J.; ilha, Jiri

2011-01-01

Existing optical surveys for debris at geosynchronous orbit (GEO) have been conducted with meter class telescopes, which have detection limits in the range of 18th-19th magnitude. We report on a new search for optically faint debris at GEO using the 6.5-m Magellan 1 telescope Walter Baade at Las Campanas Observatory in Chile. Our goal is to go as faint as possible and characterize the brightness distribution of debris fainter than R = 20th magnitude, corresponding to a size smaller than 10 cm assuming an albedo of 0.175. We wish to compare the inferred size distribution for GEO debris with that for LEO debris. We describe results obtained during 9.4 hours of observing time during 25-27 March 2011. We used the IMACS f/2 instrument, which has a mosaic of 8 CCDs, and a field of view of 30 arc-minutes in diameter. This is the widest field of view of any instrument on either Magellan telescope. All observations were obtained through a Sloan r filter. The limiting magnitude for 5 second exposures is estimated to be fainter than 22. With this small field of view and the limited observing time, our objective was to search for optically faint objects from the Titan 3C Transtage (1968-081) fragmentation in 1992. Eight debris pieces and the parent rocket body are in the Space Surveillance Network public catalog. We successfully tracked two cataloged pieces of Titan debris (SSN # 25001 and 33519) with the 6.5-m telescope, followed by a survey for objects on similar orbits but with a spread in mean anomaly. To detect bright objects over a wider field of view (1.6x1.6 degrees), we observed the same field centers at the same time through a similar filter with the 0.6-m MODEST (Michigan Orbital DEbris Survey Telescope), located 100 km to the south of Magellan at Cerro Tololo Inter-American Observatory, Chile. We will describe our experiences using Magellan, a telescope never used previously for orbital debris research, and our initial results.

Map of Pluto Surface

NASA Image and Video Library

1998-03-28

This image-based surface map of Pluto was assembled by computer image processing software from four separate images of Pluto disk taken with the European Space Agency Faint Object Camera aboard NASA Hubble Space Telescope.

Deep imaging of high redshift QSO fields below the Lyman limit. II - Number counts and colors of field galaxies

NASA Technical Reports Server (NTRS)

Steidel, Charles C.; Hamilton, Donald

1993-01-01

We present an analysis of the number counts and colors of faint galaxies to about 26.5 mag in the fields of two high Galactic latitude, very-high-redshift QSOs. We concentrate on the general properties of the field galaxies at faint magnitudes. In particular, we readdress the faint galaxy number counts and colors as a function of apparent magnitude and we reexamine the possible contribution of very-high-redshift galaxies to the faint samples. We find that the number counts to R = 26 are well fitted by the relation log N(m) = 0.31R + C. The G-band counts for the same galaxies are consistent with the same slope fainter than G about 23.5, but exhibit a much steeper slope at brighter magnitudes. At R = 25.5, the differential number counts have reached about 1.2 x 10 exp 5/sq deg; the same surface density of galaxies is reached at G = 26.5. We confirm the existence of a gradual 'blueing' trend of the field galaxies toward fainter apparent magnitude; however, the blueing trend appears to extend only as faint as G about 24, fainter than which both the (G-R) and (U sub n-G) colors appear to level off. The mean colors of faint galaxies are considerably redder than flat spectrum. There are essentially no objects to R = 26 which have spectral energy distributions which are bluer than flat spectrum. The potential contribution of very-high-redshift galaxies may have been underestimated in previous analyses; the current data are consistent with the same population of relatively luminous galaxies at z about 3 as exist at z about 0.7.

Clearing the Cosmic Fog - The Most Distant Galaxy Ever Measured

NASA Astrophysics Data System (ADS)

2010-10-01

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

Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Spitler, L. R.; Leipski, C.; Parker, Q. A.

2015-08-01

Context. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims: This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods: A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results: All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any redshift; and (d) scaled and dust-obscured radio-loud quasars or compact steep spectrum sources. We estimated upper limits on the infrared luminosity, the black hole accretion rate, and the star formation rate of IFRS, which all agreed with corresponding numbers of HzRGs. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Astronomical data analysis software and systems I; Proceedings of the 1st Annual Conference, Tucson, AZ, Nov. 6-8, 1991

NASA Technical Reports Server (NTRS)

Worrall, Diana M. (Editor); Biemesderfer, Chris (Editor); Barnes, Jeannette (Editor)

1992-01-01

Consideration is given to a definition of a distribution format for X-ray data, the Einstein on-line system, the NASA/IPAC extragalactic database, COBE astronomical databases, Cosmic Background Explorer astronomical databases, the ADAM software environment, the Groningen Image Processing System, search for a common data model for astronomical data analysis systems, deconvolution for real and synthetic apertures, pitfalls in image reconstruction, a direct method for spectral and image restoration, and a discription of a Poisson imagery super resolution algorithm. Also discussed are multivariate statistics on HI and IRAS images, a faint object classification using neural networks, a matched filter for improving SNR of radio maps, automated aperture photometry of CCD images, interactive graphics interpreter, the ROSAT extreme ultra-violet sky survey, a quantitative study of optimal extraction, an automated analysis of spectra, applications of synthetic photometry, an algorithm for extra-solar planet system detection and data reduction facilities for the William Herschel telescope.

Cometary ephemerides - needs and concerns

NASA Technical Reports Server (NTRS)

Yeomans, D. K.

1981-01-01

With the use of narrow field-of-view instrumentation on faint comets, the accuracy requirements upon computed ephemerides are increasing. It is not uncommon for instruments with a one arc minute field-of-view to be tracking a faint comet that is not visible without a substantial integration time. As with all ephemerides of solar syste objects, the computed motion and reduction of these observations, the computed motion of a comet is further depenent upon effects related to the comet's activity. Thus, the ephemeris of an active comet is corrupted by both observational errors and errors due to the comet's activity.

CXB and CIB joint fluctuations in COSMOS, EGS, UDS and HDFN

NASA Astrophysics Data System (ADS)

Cappelluti, Nico; Li, Yanxia; Cooper, Rachel Ann; Guo, Joyce; Urry, C. Megan; Hasinger, Guenther; Arendt, Richard G.; Kashlinsky, Alexander

2017-01-01

I will present new results on the joint CIB and CXB joint fluctuations in the COSMOS, EGS, UDS and HDFN surveys. We used the deepest wide Chandra, XMM and Spitzer data available so far and cross-correlate with known optical galaxies. We demonstrate that the these joint fluctuations are produced by extremely faint sources mAB>28. We tested the hypothesis that early supermassive black holes could produce the observed signal

The first VLBI image of an infrared-faint radio source

NASA Astrophysics Data System (ADS)

Middelberg, E.; Norris, R. P.; Tingay, S.; Mao, M. Y.; Phillips, C. J.; Hotan, A. W.

2008-11-01

Context: We investigate the joint evolution of active galactic nuclei and star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia Telescope Compact Array of the Chandra Deep Field South and the European Large Area ISO Survey - S1 we have identified a class of objects which are strong in the radio but have no detectable infrared and optical counterparts. This class has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002 have been classified as IFRS. It is not known what these objects are. Methods: To address the many possible explanations as to what the nature of these objects is we have observed four sources with the Australian Long Baseline Array. Results: We have detected and imaged one of the four sources observed. Assuming that the source is at a high redshift, we find its properties in agreement with properties of Compact Steep Spectrum sources. However, due to the lack of optical and infrared data the constraints are not particularly strong.

Hubble Portrait of the Double

NASA Image and Video Library

1998-03-28

This is the clearest view yet of the distant planet Pluto and its moon, Charon, as revealed by NASA Hubble Space Telescope. The image was taken by the European Space Agency Faint Object Camera on February 21, 1994.

SELFI: an object-based, Bayesian method for faint emission line source detection in MUSE deep field data cubes

NASA Astrophysics Data System (ADS)

Meillier, Céline; Chatelain, Florent; Michel, Olivier; Bacon, Roland; Piqueras, Laure; Bacher, Raphael; Ayasso, Hacheme

2016-04-01

We present SELFI, the Source Emission Line FInder, a new Bayesian method optimized for detection of faint galaxies in Multi Unit Spectroscopic Explorer (MUSE) deep fields. MUSE is the new panoramic integral field spectrograph at the Very Large Telescope (VLT) that has unique capabilities for spectroscopic investigation of the deep sky. It has provided data cubes with 324 million voxels over a single 1 arcmin2 field of view. To address the challenge of faint-galaxy detection in these large data cubes, we developed a new method that processes 3D data either for modeling or for estimation and extraction of source configurations. This object-based approach yields a natural sparse representation of the sources in massive data fields, such as MUSE data cubes. In the Bayesian framework, the parameters that describe the observed sources are considered random variables. The Bayesian model leads to a general and robust algorithm where the parameters are estimated in a fully data-driven way. This detection algorithm was applied to the MUSE observation of Hubble Deep Field-South. With 27 h total integration time, these observations provide a catalog of 189 sources of various categories and with secured redshift. The algorithm retrieved 91% of the galaxies with only 9% false detection. This method also allowed the discovery of three new Lyα emitters and one [OII] emitter, all without any Hubble Space Telescope counterpart. We analyzed the reasons for failure for some targets, and found that the most important limitation of the method is when faint sources are located in the vicinity of bright spatially resolved galaxies that cannot be approximated by the Sérsic elliptical profile. The software and its documentation are available on the MUSE science web service (muse-vlt.eu/science).

Calibration and operation of the Faint Object Spectrograph

NASA Technical Reports Server (NTRS)

Harms, R.; Beaver, E.; Burbidge, E.; Hier, R.; Allen, R.; Angel, R.; Bartko, F.; Bohlin, R.; Ford, H.; Davidson, A.

1984-01-01

The design and basic performance characteristics of the Faint Object Spectrograph (FOS), one of five instruments built for use on the Space Telescope observatory, is summarized briefly. The results of the recently completed instrument-level calibration are presented with special emphasis on issues affecting plans for FOS astronomical observations. Examples include such fundamental characteristics as: limiting magnitudes (system sensitivity and noise figures), spectral coverage and resolution, scattered light properties, and instrumental polarization and modulation efficiencies. Also gated toward intended users, a rather detailed description of FOS operating modes is given. The discussion begins with the difficulties anticipated during target acquisition and their hoped-for resolution. Both the 'normal' spectroscopic operating modes of the FOS and its 'exotic' features (e.g. spectropolarimetric, time-tagged, and time-resolved modes) are presented. The paper concludes with an overview of the activities to assure proper alignment and operation of the FOS within the entire Space Telescope system (orbital and ground-based).

Nod-shuffle 3D spectroscopy with PMAS

NASA Astrophysics Data System (ADS)

Roth, Martin M.; Fechner, Thomas; Becker, Thomas; Kelz, Andreas

2004-09-01

PMAS is a versatile integral field spectrograph based on the principle of a fiber-coupled lens array type of IFU. The instrument was commissioned at the Calar Alto 3.5m Telescope in May 2001. PMAS is offered as a common user instrument at Calar Alto since 2002. However, it has remained flexible enough to be used as a testbed for new observing techniques. Since the instrument is sensitive in the wavelength range from 0.35 to 1 μm, it is being used to experiment with faint object 3D spectroscopy for a variety of objects in stellar and extragalactic astronomy. Among these experiments, we have implemented a nod-shuffle mode of operation, which is a beam switching technique to achieve a high degree of sky subtraction accuracy. We describe the technical details of the special solution found for PMAS and first results obtained in test observations of faint haloes of planetary nebulae.

Spectroscopic Results of Gravitational Microlenses: Are These Dark Objects or Faint Stars?

NASA Astrophysics Data System (ADS)

Joseph, C. L.; Gallagher, J.; Phillips, M.

1994-12-01

We report on the spectroscopic results obtained in October 1994 with the 4-meter telescope on Cerro Tololo Interamerican Observatory (CTIO). Spectra of 2 recent microlens candidates toward the Galactic bulge reported by the Optical Gravitational Lens Experiment (OGLE) as well as one caught in the early phases of brightening toward the LMC reported by the MAssive Compact Halo Object (MACHO) Project have been obtained. The spectral coverage is from 6500 to 9800 Angstroms at a resolution of 6 Angstroms. The long-term goal of this spectroscopic study is to obtain censored statistical evidence on the luminosity of the microlenses, constraining the nature of these lenses. Several models of composite spectra of a bulge or LMC star plus a cool lensing star of different spectral types are presented to demonstrate the ranges in the product of luminosity times distance that the faint star could be detected in a composite spectrum.

Sky Subtraction with Fiber-Fed Spectrograph

NASA Astrophysics Data System (ADS)

Rodrigues, Myriam

2017-09-01

"Historically, fiber-fed spectrographs had been deemed inadequate for the observation of faint targets, mainly because of the difficulty to achieve high accuracy on the sky subtraction. The impossibility to sample the sky in the immediate vicinity of the target in fiber instruments has led to a commonly held view that a multi-object fibre spectrograph cannot achieve an accurate sky subtraction under 1% contrary to their slit counterpart. The next generation of multi-objects spectrograph at the VLT (MOONS) and the planed MOS for the E-ELT (MOSAIC) are fiber-fed instruments, and are aimed to observed targets fainter than the sky continuum level. In this talk, I will present the state-of-art on sky subtraction strategies and data reduction algorithm specifically developed for fiber-fed spectrographs. I will also present the main results of an observational campaign to better characterise the sky spatial and temporal variations ( in particular the continuum and faint sky lines)."

Serendipitous discovery of a faint dwarf galaxy near a Local Volume dwarf

NASA Astrophysics Data System (ADS)

Makarova, L. N.; Makarov, D. I.; Antipova, A. V.; Karachentsev, I. D.; Tully, R. B.

2018-03-01

A faint dwarf irregular galaxy has been discovered in the HST/ACS field of LV J1157+5638. The galaxy is resolved into individual stars, including the brightest magnitude of the red giant branch. The dwarf is very likely a physical satellite of LV J1157+5638. The distance modulus of LV J1157+5638 using the tip of the red giant branch (TRGB) distance indicator is 29.82 ± 0.09 mag (D = 9.22 ± 0.38 Mpc). The TRGB distance modulus of LV J1157+5638 sat is 29.76 ± 0.11 mag (D = 8.95 ± 0.42 Mpc). The distances to the two galaxies are consistent within the uncertainties. The projected separation between them is only 3.9 kpc. LV J1157+5638 has a total absolute V magnitude of -13.26 ± 0.10 and linear Holmberg diameter of 1.36 kpc, whereas its faint satellite LV J1157+5638 sat has MV = -9.38 ± 0.13 mag and Holmberg diameter of 0.37 kpc. Such a faint dwarf was discovered for the first time beyond the nearest 4 Mpc from us. The presence of main-sequence stars in both galaxies unambiguously indicates the classification of the objects as dwarf irregulars with recent or ongoing star formation events in both galaxies.

Strongly lensed gravitational waves from intrinsically faint double compact binaries—prediction for the Einstein Telescope

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

Ding, Xuheng; Biesiada, Marek; Zhu, Zong-Hong, E-mail: dingxuheng@mail.bnu.edu.cn, E-mail: marek.biesiada@us.edu.pl, E-mail: zhuzh@bnu.edu.cn

With a fantastic sensitivity improving significantly over the advanced GW detectors, Einstein Telescope (ET) will be able to observe hundreds of thousand inspiralling double compact objects per year. By virtue of gravitational lensing effect, intrinsically unobservable faint sources can be observed by ET due to the magnification by intervening galaxies. We explore the possibility of observing such faint sources amplified by strong gravitational lensing. Following our previous work, we use the merger rates of DCO (NS-NS,BH-NS,BH-BH systems) as calculated by Dominik et al.(2013). It turns out that tens to hundreds of such (lensed) extra events will be registered by ET.more » This will strongly broaden the ET's distance reach for signals from such coalescences to the redshift range z = 2 − 8. However, with respect to the full inspiral event catalog this magnification bias is at the level of 0.001 and should not affect much cosmological inferences.« less

280 one-opposition near-Earth asteroids recovered by the EURONEAR with the Isaac Newton Telescope

NASA Astrophysics Data System (ADS)

Vaduvescu, O.; Hudin, L.; Mocnik, T.; Char, F.; Sonka, A.; Tudor, V.; Ordonez-Etxeberria, I.; Díaz Alfaro, M.; Ashley, R.; Errmann, R.; Short, P.; Moloceniuc, A.; Cornea, R.; Inceu, V.; Zavoianu, D.; Popescu, M.; Curelaru, L.; Mihalea, S.; Stoian, A.-M.; Boldea, A.; Toma, R.; Fields, L.; Grigore, V.; Stoev, H.; Lopez-Martinez, F.; Humphries, N.; Sowicka, P.; Ramanjooloo, Y.; Manilla-Robles, A.; Riddick, F. C.; Jimenez-Lujan, F.; Mendez, J.; Aceituno, F.; Sota, A.; Jones, D.; Hidalgo, S.; Murabito, S.; Oteo, I.; Bongiovanni, A.; Zamora, O.; Pyrzas, S.; Génova-Santos, R.; Font, J.; Bereciartua, A.; Perez-Fournon, I.; Martínez-Vázquez, C. E.; Monelli, M.; Cicuendez, L.; Monteagudo, L.; Agulli, I.; Bouy, H.; Huélamo, N.; Monguió, M.; Gänsicke, B. T.; Steeghs, D.; Gentile-Fusillo, N. P.; Hollands, M. A.; Toloza, O.; Manser, C. J.; Dhillon, V.; Sahman, D.; Fitzsimmons, A.; McNeill, A.; Thompson, A.; Tabor, M.; Murphy, D. N. A.; Davies, J.; Snodgrass, C.; Triaud, A. H. M. J.; Groot, P. J.; Macfarlane, S.; Peletier, R.; Sen, S.; İkiz, T.; Hoekstra, H.; Herbonnet, R.; Köhlinger, F.; Greimel, R.; Afonso, A.; Parker, Q. A.; Kong, A. K. H.; Bassa, C.; Pleunis, Z.

2018-01-01

Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions. Aims: We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets). Methods: Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS. Results: Most targets and recovered objects had apparent magnitudes centered around V 22.8 mag, with some becoming as faint as V 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O-C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015. Conclusions: Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys. Table 2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A105

An r-process enhanced star in the dwarf galaxy Tucana III

DOE PAGES

Hansen, T. T.; Simon, J. D.; Marshall, J. L.; ...

2017-03-20

Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66–593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-Imore » star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. Furthermore, we explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.« less

An r-process enhanced star in the dwarf galaxy Tucana III

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

Hansen, T. T.; Simon, J. D.; Marshall, J. L.

Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66–593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-Imore » star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. Furthermore, we explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.« less

Hubble Space Telescope, Faint Object Spectrograph

NASA Technical Reports Server (NTRS)

1981-01-01

This drawing illustrates the Hubble Space Telescope's (HST's), Faint Object Spectrograph (FOS). The HST's two spectrographs, the Goddard High-Resolution Spectrograph and the FOS, can detect a broader range of wavelengths than is possible from the Earth because there is no atmosphere to absorb certain wavelengths. Scientists can determine the chemical composition, temperature, pressure, and turbulence of the stellar atmosphere producing the light, all from spectral data. The FOC can detect detail in very faint objects, such as those at great distances, and light ranging from ultraviolet to red spectral bands. Both spectrographs operate in essentially the same way. The incoming light passes through a small entrance aperture, then passes through filters and diffraction gratings, that work like prisms. The filter or grating used determines what range of wavelength will be examined and in what detail. Then the spectrograph detectors record the strength of each wavelength band and sends it back to Earth. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST views galaxies, stars, planets, comets, possibly other solar systems, and even unusual phenomena such as quasars, with 10 times the clarity of ground-based telescopes. The HST was deployed from the Space Shuttle Discovery (STS-31 mission) into Earth orbit in April 1990. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

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

NASA Astrophysics Data System (ADS)

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

2007-05-01

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

Near-Infrared Photon-Counting Camera for High-Sensitivity Observations

NASA Technical Reports Server (NTRS)

Jurkovic, Michael

2012-01-01

The dark current of a transferred-electron photocathode with an InGaAs absorber, responsive over the 0.9-to-1.7- micron range, must be reduced to an ultralow level suitable for low signal spectral astrophysical measurements by lowering the temperature of the sensor incorporating the cathode. However, photocathode quantum efficiency (QE) is known to reduce to zero at such low temperatures. Moreover, it has not been demonstrated that the target dark current can be reached at any temperature using existing photocathodes. Changes in the transferred-electron photocathode epistructure (with an In- GaAs absorber lattice-matched to InP and exhibiting responsivity over the 0.9- to-1.7- m range) and fabrication processes were developed and implemented that resulted in a demonstrated >13x reduction in dark current at -40 C while retaining >95% of the approximately equal to 25% saturated room-temperature QE. Further testing at lower temperature is needed to confirm a >25 C predicted reduction in cooling required to achieve an ultralow dark-current target suitable for faint spectral astronomical observations that are not otherwise possible. This reduction in dark current makes it possible to increase the integration time of the imaging sensor, thus enabling a much higher near-infrared (NIR) sensitivity than is possible with current technology. As a result, extremely faint phenomena and NIR signals emitted from distant celestial objects can be now observed and imaged (such as the dynamics of redshifting galaxies, and spectral measurements on extra-solar planets in search of water and bio-markers) that were not previously possible. In addition, the enhanced NIR sensitivity also directly benefits other NIR imaging applications, including drug and bomb detection, stand-off detection of improvised explosive devices (IED's), Raman spectroscopy and microscopy for life/physical science applications, and semiconductor product defect detection.

Tidal stripping and the structure of dwarf galaxies in the Local Group

NASA Astrophysics Data System (ADS)

Fattahi, Azadeh; Navarro, Julio F.; Frenk, Carlos S.; Oman, Kyle A.; Sawala, Till; Schaller, Matthieu

2018-05-01

The shallow faint-end slope of the galaxy mass function is usually reproduced in Λ cold dark matter (ΛCDM) galaxy formation models by assuming that the fraction of baryons that turn into stars drops steeply with decreasing halo mass and essentially vanishes in haloes with maximum circular velocities Vmax < 20-30 km s-1. Dark-matter-dominated dwarfs should therefore have characteristic velocities of about that value, unless they are small enough to probe only the rising part of the halo circular velocity curve (i.e. half-mass radii, r1/2 ≪ 1 kpc). Many dwarfs have properties in disagreement with this prediction: they are large enough to probe their halo Vmax but their characteristic velocities are well below 20 km s-1. These `cold faint giants' (an extreme example is the recently discovered Crater 2 Milky Way satellite) can only be reconciled with our ΛCDM models if they are the remnants of once massive objects heavily affected by tidal stripping. We examine this possibility using the APOSTLE cosmological hydrodynamical simulations of the Local Group. Assuming that low-velocity-dispersion satellites have been affected by stripping, we infer their progenitor masses, radii, and velocity dispersions, and find them in remarkable agreement with those of isolated dwarfs. Tidal stripping also explains the large scatter in the mass discrepancy-acceleration relation in the dwarf galaxy regime: tides remove preferentially dark matter from satellite galaxies, lowering their accelerations below the amin ˜ 10-11 m s-2 minimum expected for isolated dwarfs. In many cases, the resulting velocity dispersions are inconsistent with the predictions from Modified Newtonian Dynamics, a result that poses a possibly insurmountable challenge to that scenario.

Lateral Cutoff Analysis and Results from NASA's Farfield Investigation of No-Boom Thresholds

NASA Technical Reports Server (NTRS)

Cliatt, Larry J., II; Haering, Edward A., Jr.; Arnac, Sarah R.; Hill, Michael A.

2016-01-01

In support of the ongoing effort by the National Aeronautics and Space Administration (NASA) to bring supersonic commercial travel to the public, the NASA Armstrong Flight Research Center (AFRC) and the NASA Langley Research Center (LaRC), in partnership with other industry organizations and academia, conducted a flight research experiment to analyze acoustic propagation at the lateral edge of the sonic boom carpet. The name of the effort was the Farfield Investigation of No-boom Thresholds (FaINT). The test helped to build a dataset that will go toward further understanding of the unique acoustic propagation characteristics near the sonic boom carpet extremity. The FaINT was an effort that collected finely-space sonic boom data across the entire lateral cutoff transition region. A major objective of the effort was to investigate the acoustic phenomena that occur at the audible edge of a sonic boom carpet, including the transition and shadow zones. A NASA F-18B aircraft made supersonic passes such that its sonic boom carpet transition zone would intersect a linear 60-microphone, 7500-ft long array. A TG-14 motor glider equipped with a microphone on its wing also attempted to capture the same sonic boom rays that were measured on the ground, at altitudes of 3000 - 6000 ft above ground level. This paper determined an appropriate metric for sonic boom waveforms in the transition and shadow zones called Perceived Sound Exposure Level, and established a value of 65 dB as a limit for the acoustic levels defining the lateral extent of a sonic boom's noise region; analyzed the change in sonic boom levels as a function of distance from flight path both on the ground and 4500 ft above the ground; and compared between sonic boom measurements and numerical predictions.

The contribution of faint AGNs to the ionizing background at z 4

NASA Astrophysics Data System (ADS)

Grazian, A.; Giallongo, E.; Boutsia, K.; Cristiani, S.; Vanzella, E.; Scarlata, C.; Santini, P.; Pentericci, L.; Merlin, E.; Menci, N.; Fontanot, F.; Fontana, A.; Fiore, F.; Civano, F.; Castellano, M.; Brusa, M.; Bonchi, A.; Carini, R.; Cusano, F.; Faccini, M.; Garilli, B.; Marchetti, A.; Rossi, A.; Speziali, R.

2018-05-01

Context. Finding the sources responsible for the hydrogen reionization is one of the most pressing issues in observational cosmology. Bright quasi-stellar objects (QSOs) are known to ionize their surrounding neighborhood, but they are too few to ensure the required HI ionizing background. A significant contribution by faint active galactic nuclei (AGNs), however, could solve the problem, as recently advocated on the basis of a relatively large space density of faint active nuclei at z > 4. Aims: This work is part of a long-term project aimed at measuring the Lyman Continuum escape fraction for a large sample of AGNs at z 4 down to an absolute magnitude of M1450 -23. We have carried out an exploratory spectroscopic program to measure the HI ionizing emission of 16 faint AGNs spanning a broad U - I color interval, with I 21-23, and 3.6 < z < 4.2. These AGNs are three magnitudes fainter than the typical SDSS QSOs (M1450 ≲-26) which are known to ionize their surrounding IGM at z ≳ 4. Methods: We acquired deep spectra of these faint AGNs with spectrographs available at the VLT, LBT, and Magellan telescopes, that is, FORS2, MODS1-2, and LDSS3, respectively. The emission in the Lyman Continuum region, close to 900 Å rest frame, has been detected with a signal to noise ratio of 10-120 for all 16 AGNs. The flux ratio between the 900 Å rest-frame region and 930 Å provides a robust estimate of the escape fraction of HI ionizing photons. Results: We have found that the Lyman Continuum escape fraction is between 44 and 100% for all the observed faint AGNs, with a mean value of 74% at 3.6 < z < 4.2 and - 25.1 ≲ M1450 ≲-23.3, in agreement with the value found in the literature for much brighter QSOs (M1450 ≲-26) at the same redshifts. The Lyman Continuum escape fraction of our faint AGNs does not show any dependence on the absolute luminosities or on the observed U - I colors of the objects. Assuming that the Lyman Continuum escape fraction remains close to 75% down to M1450 - 18, we find that the AGN population can provide between 16 and 73% (depending on the adopted luminosity function) of the whole ionizing UV background at z 4, measured through the Lyman forest. This contribution increases to 25-100% if other determinations of the ionizing UV background are adopted from the recent literature. Conclusions: Extrapolating these results to z 5-7, there are possible indications that bright QSOs and faint AGNs can provide a significant contribution to the reionization of the Universe, if their space density is high at M1450 -23. Based on observations made at the Large Binocular Telescope (LBT) at Mt. Graham (Arizona, USA). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 098.A-0862. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Faint blue objects at high Galactic latitude. V - Palomar Schmidt field centered on selected area 71

NASA Technical Reports Server (NTRS)

Usher, Peter D.; Mitchell, Kenneth J.; Warnock, Archibald, III

1988-01-01

Starlike objects with both blue and ultraviolet excess have been selected from a Palomar 1.2 m Schmidt field centered on Kapteyn selected area 71. The method of selection is that used in the previous papers of this series, but modified to account for the differential reddening that occurs across the field. The color classes, color subclasses, positions, and magnitudes of the selected objects are listed.

Investigation of small solar system objects with the space telescope

NASA Technical Reports Server (NTRS)

Morrison, D.

1979-01-01

The application of the space telescope (ST) to study small objects in the solar system in order to understand the birth and the early evolution of the solar system is discussed. The upper size limit of the small bodies is defined as approximately 5000 km and includes planetary satellites, planetary rings, asteroids, and comets.The use of the astronomical instruments aboard the ST, such as the faint object camera, ultraviolet and infrared spectrometers, and spectrophotometers, to study the small solar system objects is discussed.

New Image of Comet Halley in the Cold

NASA Astrophysics Data System (ADS)

2003-09-01

VLT Observes Famous Traveller at Record Distance Summary Seventeen years after the last passage of Comet Halley , the ESO Very Large Telescope at Paranal (Chile) has captured a unique image of this famous object as it cruises through the outer solar system. It is completely inactive in this cold environment. No other comet has ever been observed this far - 4200 million km from the Sun - or that faint - nearly 1000 million times fainter than what can be perceived with the unaided eye. This observation is a byproduct of a dedicated search [1] for small Trans-Neptunian Objects, a population of icy bodies of which more than 600 have been found during the past decade. PR Photo 27a/03 : VLT image (cleaned) of Comet Halley PR Photo 27b/03 : Sky field in which Comet Halley was observed PR Photo 27c/03 : Combined VLT image with star trails and Comet Halley The Halley image ESO PR Photo 27a/03 ESO PR Photo 27a/03 [Preview - JPEG: 546 x 400 pix - 207k] [Normal - JPEG: 1092 x 800 pix - 614k] [FullRes - JPEG: 1502 x 1100 pix - 1.1M] Caption : PR Photo 27a/03 shows the faint, star-like image of Comet Halley (centre), observed with the ESO Very Large Telescope (VLT) at the Paranal Observatory on March 6-8, 2003. 81 individual exposures from three of the four 8.2-m VLT telescopes with a total exposure time of about 9 hours were combined to show the magnitude 28.2 object. At this time, Comet Halley was about 4200 million km from the Sun (28.06 AU) and 4080 million km (27.26 AU) from the Earth. All images of stars and galaxies in the field were removed during the extensive image processing needed to produce this unique image. Due to the remaining, unavoidable "background noise", it is best to view the comet image from some distance. The field measures 60 x 40 arcsec 2 ; North is up and East is left. Remember Comet Halley - the famous "haired star" that has been observed with great regularity - about once every 76 years - during more than two millennia? Which was visited by an international spacecraft armada when it last passed through the inner solar system in 1986? And which put on a fine display in the sky at that time? Now, 17 years after that passage, this cosmic traveller has again been observed at the European Southern Observatory. Moving outward along its elongated orbit into the deep-freeze outer regions of the solar system, it is now almost as far away as Neptune, the most distant giant planet in our system. At 4,200 million km from the Sun, Comet Halley has now completed four-fifths of its travel towards the most distant point of this orbit. As the motion is getting ever slower, it will reach that turning point in December 2023, after which it begins its long return towards the next passage through the inner solar system in 2062. The new image of Halley was taken with the Very Large Telescope (VLT) at Paranal (Chile); a "cleaned" version is shown in PR Photo 27a/03 . It was obtained as a byproduct of an observing program aimed at studying the population of icy bodies at the rim of the solar system. The image shows the raven-black, 10-km cometary nucleus of ice and dust as an unresolved faint point of light, without any signs of activity. A cold and inactive "dirty snowball" The brightness of the comet was measured as visual magnitude V = 28.2, or nearly 1000 million times fainter than the faintest objects that can be perceived in a dark sky with the unaided eye. The pitch black nucleus of Halley reflects about 4% of the sunlight; it is a very "dirty" snowball indeed. We know from the images obtained by the ESA Giotto spacecraft in 1986 that it is avocado-shaped and on the average measures about 10 km diameter across. The VLT observation is therefore equivalent to seeing a 5-cm piece of coal at a distance of 20,500 km (about the distance between the Earth's poles) and to do so in the evening twilight. This is because at the large distance of Comet Halley, the infalling sunlight is 800 times fainter than here on Earth. The measured brightness of the cometary image perfectly matches that expected for the nucleus alone, taking into account the distance, the solar illumination and the reflectivity of the surface. This shows that all cometary activity has now ceased. The nucleus is now an inert ball of ice and dust, and is likely to remain so until it again returns to the solar neighbourhood, more than half a century from now. A record observation At 28.06 AU heliocentric distance (1 AU = 149,600,000 km - the mean distance between the Earth and the Sun), this is by far the most distant observation ever made of a comet [2]. It is also the faintest comet ever detected (by a factor of about 5); the previous record, magnitude 26.5, was co-held by comet Halley at 18.8 AU (with the ESO New Technology Telescope in 1994) and Comet Sanguin at 8.5 AU (with the Keck II telescope in 1997). Interestingly, when Comet Halley reaches its largest distance from the Sun in December 2023, about 35 AU, it will only be 2.5 times fainter than it is now. The comet would still have been detected within the present exposure time. This means that with the VLT, for the first time in the long history of this comet, the astronomers now possess the means to observe it at any point in its 76-year orbit! A census of faint Transneptunian Objects The image of Halley was obtained by combining a series of exposures obtained simultaneously with three of the 8.2-m telescopes (ANTU, MELIPAL and YEPUN) during 3 consecutive nights with the main goal to count the number of small icy bodies orbiting the Sun beyond Neptune, known as Transneptunian Objects (TNOs). Since the discovery of the first TNO in 1992, more than 600 have been found, most of these measuring several hundred km across. The VLT observations aim at a census of smaller TNOs - the incorporation of the sky field with Comet Halley allows verification of the associated, extensive data processing. Similar TNO-surveys have been performed before, but this is the first time that several very large telescopes are used simultaneously in order to observe extremely faint, hitherto inaccessible objects. The VLT observations will provide very useful information about the frequency of (smaller) TNOs of different sizes and thereby, indirectly, about the rate of collisions they have suffered since their formation. This study will also cast more light on the mystery of the apparent "emptiness" of the very distant solar system. Why are so few objects found beyond 45 AU? It is not known whether this is because there are no objects out there or if they are simply too small or too dark, or both, to have been detected so far. How to extract a very faint comet image ESO PR Photo 27b/03 ESO PR Photo 27b/03 [Preview - JPEG: 546 x 400 pix - 211k] [Normal - JPEG: 1092 x 800 pix - 649k] [FullRes - JPEG: 1502 x 1100 pix - 1.1M] ESO PR Photo 27c/03 ESO PR Photo 27c/03 [Preview - JPEG: 530 x 400 pix - 184k] [Normal - JPEG: 1059 x 800 pix - 573k] [FullRes - JPEG: 1515 x 1145 pix - 983k] Caption : PR Photo 27b/03 shows the sky field in which Comet Halley was observed with the ESO Very Large Telescope (VLT) at the Paranal Observatory on March 6-8, 2003. 81 individual exposures with a total exposure time of 32284 sec (almost 9 hours) from three of the four 8.2-m telescopes were cleaned and combined to produce this composite photo, displaying numerous faint stars and galaxies in the field. The predicted motion of Comet Halley during the three nights is indicated by short red lines. The long straight lines at the top and to the right were caused by artificial satellites in orbit around the Earth that passed through the field during the exposure. The field measures 300 x 180 arcsec 2. PR Photo 27c/03 was produced by adding the same frames, however, while shifting their positions according to the motion of the comet. The faint, star-like image of Comet Halley is now visible (in circle, at centre); all other objects (stars, galaxies) in the field are "trailed". A satellite trail is visible at the very top. The field measures 60 x 40 arcsec 2 ; North is up and East is left in both photos. The combination of the images from three 8.2-m telescopes obtained during three consecutive nights is not straightforward. The individual characteristics of the imaging instruments (FORS1 on ANTU, VIMOS on MELIPAL and FORS2 on YEPUN) must be taken into account and corrected. Moreover, the motion of the very faint moving objects has to be compensated for, even though they are too faint to be seen on individual exposures; they only reveal themselves when several (many!) frames are combined during the final steps of the process. It is for this reason that the presence of a known, faint object like Comet Halley in the field-of-view provides a powerful control of the data processing. If Halley is visible at the end, it has been done properly. The extensive data processing is now under way and the intensive search for new Transneptunian objects has started. The field with Comet Halley was observed with the giant telescopes during each of three consecutive nights, yielding 81 individual exposures with a total exposure time of almost 9 hours. The faint comet is completely invisible on the individual images. On PR Photo 27b/03 , these frames have been added directly, showing very faint stars and galaxies. Also this photo does not show the moving comet, but by shifting the frames before they are added in such a way that the comet remains fixed, a faint image does emerge among the stellar trails, cf. PR Photo 27c/03 . A better, but much more cumbersome method is to "subtract" the images of all stars and galaxies from the individual exposures, before they are added. PR Photo 27a/03 has been produced in this way and shows the image of Comet Halley more clearly. In total, about 20,000 photons were detected from the comet, i.e. about one photon per 8.2-m telescope every 1.6 second. However, during the same time, the telescopes collected about one thousand times more photons from molecular emission in the Earth's atmosphere within the sky area covered by the comet's image. The presence of this considerable "noise" calls for very careful image processing in order to detect the faint comet signal. The identity of the comet is beyond doubt: the image is faintly visible on composite photos obtained during a single night, demonstrating that the direction and rate of motion of the detected object perfectly matches that predicted for Comet Halley from its well-known orbit. Moreover, the image is located within 1 arcsec from the predicted position in the sky. Outlook After its passage in 1910, Comet Halley was again seen in 1982, when David Jewitt first observed its faint image with the 5-m Palomar telescope at a time when it was 11 AU from the Sun, a little further than planet Saturn. It was observed from La Silla two months later. As the comet approached, the ice in the nucleus began to evaporate (sublimate), and the comet soon became surrounded by a cloud of dust and gas (the "coma"). It developed the tail that is typical of comets and was extensively observed, also from several spacecraft passing close to its nucleus in early 1986. Observations have since been made of Comet Halley as it moves away from the Sun, documenting a steady decrease of activity. When it reached the distance of Saturn, the tail and coma had disappeared completely, leaving only the 5 x 5 x 15 km avocado-shaped "dirty snowball" nucleus. However, Halley was still good for a major surprise: in 1991, a gigantic explosion happened, providing it with an expanding, extensive cloud of dust for several months. It is not known whether this event was caused by a collision with an unknown piece of rock or by internal processes (a last "sigh" on the way out). Until now, the most recent observation of Comet Halley was done in 1994 with the New Technology Telescope (NTT) at La Silla, at that time the most powerful ESO telescope. It showed the comet to be completely inactive. Nine years later, so does the present VLT observation. It is unlikely that any activity will be seen until this famous object again approaches the Sun, more than 50 years from now.

COBE looks back to the Big Bang

NASA Technical Reports Server (NTRS)

Mather, John C.

1993-01-01

An overview is presented of NASA-Goddard's Cosmic Background Explorer (COBE), the first NASA satellite designed to observe the primeval explosion of the universe. The spacecraft carries three extremely sensitive IR and microwave instruments designed to measure the faint residual radiation from the Big Bang and to search for the formation of the first galaxies. COBE's far IR absolute spectrophotometer has shown that the Big Bang radiation has a blackbody spectrum, proving that there was no large energy release after the explosion.

A study of ultraviolet absorption lines through the complete Galactic halo by the analysis of HST faint object spectrograph spectra of active Galactic nuclei, 1

NASA Technical Reports Server (NTRS)

Burks, Geoffrey S.; Bartko, Frank; Shull, J. Michael; Stocke, John T.; Sachs, Elise R.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Harms, Richard J.; Massa, Derck

1994-01-01

The ultraviolet (1150 - 2850 A) spectra of a number of active galactic nuclei (AGNs) observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) have been used to study the properties of the Galactic halo. The objects that served as probes are 3C 273, PKS 0454-220, Pg 1211+143, CSO 251, Ton 951, and PG 1351+640. The equivalent widths of certain interstellar ions have been measured, with special attention paid to the C IV/C II and Si IV/Si II ratios. These ratios have been intercompared, and the highest values are found in the direction of 3C 273, where C IV/C II = 1.2 and Si IV/Si II greater than 1. These high ratios may be due to a nearby supernova remnant, rather than to ionized gas higher up in the Galactic halo. Our data give some support to the notion that QSO metal-line systems may arise from intervening galaxies which contain high supernova rates, galactic fountains, and turbulent mixing layers.

Discovery of Associated Absorption Lines in an X-Ray Warm Absorber: Hubble Space Telescope Faint Object Spectrograph Observations of MR 2251-178

NASA Technical Reports Server (NTRS)

Monier, Eric M.; Mathur, Smita; Wilkes, Belinda; Elvis, Martin

2001-01-01

The presence of a 'warm absorber' was first suggested to explain spectral variability in an X-ray spectrum of the radio-quiet quasi-stellar object (QSO) MR 2251-178. A unified picture, in which X-ray warm absorbers and 'intrinsic' UV absorbers are the same, offers the opportunity to probe the nuclear environment of active galactic nuclei. To test this scenario and understand the physical properties of the absorber, we obtained a UV spectrum of MR 2251-178 with the Faint Object Spectrograph on board the Hubble Space Telescope (HST). The HST spectrum clearly shows absorption due to Lyalpha, N v, and C IV, blueshifted by 300 km s(exp -1) from the emission redshift of the QSO. The rarity of both X-ray and UV absorbers in radio-quiet QSOs suggests these absorbers are physically related, if not identical. Assuming the unified scenario, we place constraints on the physical parameters of the absorber and conclude the mass outflow rate is essentially the same as the accretion rate in MR 2251-178.

Solar System Research with the Spacewatch 1.8-m Telescope

NASA Technical Reports Server (NTRS)

McMillan, Robert S.

2001-01-01

During this grant period, the 1.8-m Spacewatch telescope was put into routine operation to search for asteroids and comets ranging in location from near-Earth space to regions beyond the orbit of Neptune. All of these classes of objects can be detected simultaneously with our uniform scanning procedures. We are studying near Earth objects (NEOs), main belt asteroids, comets, Centaurs, and trans-Neptunian objects (TNOs), as well as the interrelationships of these classes and their bearing on the origin and evolution of the solar system. The Spacewatch 1.8-meter telescope is sensitive to V(mag) < 22.6 in sidereal scanning mode and is able to reach even fainter in longer 'staring' exposures, with a field of view 0.5 degrees square. These faint limits make the operation of the Spacewatch 1.8-m telescope complementary to asteroid surveys being done by other groups. Specifically, EAs smaller than 100 m in diameter and small main belt asteroids can be found, as well as more distant objects such as Centaurs/Scattered Disk Objects (SDOs) and TNOs. The 1.8-m telescope is also being used to do recoveries and astrometry of recently-discovered asteroids that subsequently become too faint for the other groups before good orbits are established.

The Extremely Low Activity Comet 209P/LINEAR During Its Extraordinary Close Approach in 2014

NASA Astrophysics Data System (ADS)

Schleicher, David G.; knight, Matthew m.

2016-10-01

We present results from our observing campaign of Comet 209P/LINEAR during its exceptionally close approach to Earth during 2014 May, the third smallest perigee of any comet in two centuries. These circumstances permitted us to pursue several studies of this intrinsically faint object, including measurements of gas and dust production rates, searching for coma morphology, and direct detection of the nucleus to measure its properties. Indeed, we successfully measured the lowest water production rates of an intact comet in over 35 years and a corresponding smallest active area, ∼0.007 km2. When combined with the nucleus size found from radar, this also yields the smallest active fraction for any comet, ∼0.024%. In all, this strongly suggests that 209P/LINEAR is on its way to becoming an inert object. The nucleus was detected but could not easily be disentangled from the inner coma due to seeing variations and changing spatial scales. Even so, we were able to measure a double-peaked lightcurve consistent with the shorter of two viable rotational periods found by Hergenrother. Radial profiles of the dust coma are quite steep, similar to that observed for some other very anemic comets, and suggest that vaporizing icy grains are present.

The Subaru/XMM-Newton Deep Survey (SXDS). V. Optically Faint Variable Object Survey

NASA Astrophysics Data System (ADS)

Morokuma, Tomoki; Doi, Mamoru; Yasuda, Naoki; Akiyama, Masayuki; Sekiguchi, Kazuhiro; Furusawa, Hisanori; Ueda, Yoshihiro; Totani, Tomonori; Oda, Takeshi; Nagao, Tohru; Kashikawa, Nobunari; Murayama, Takashi; Ouchi, Masami; Watson, Mike G.; Richmond, Michael W.; Lidman, Christopher; Perlmutter, Saul; Spadafora, Anthony L.; Aldering, Greg; Wang, Lifan; Hook, Isobel M.; Knop, Rob A.

2008-03-01

We present our survey for optically faint variable objects using multiepoch (8-10 epochs over 2-4 years) i'-band imaging data obtained with Subaru Suprime-Cam over 0.918 deg2 in the Subaru/XMM-Newton Deep Field (SXDF). We found 1040 optically variable objects by image subtraction for all the combinations of images at different epochs. This is the first statistical sample of variable objects at depths achieved with 8-10 m class telescopes or the Hubble Space Telescope. The detection limit for variable components is i'vari ~ 25.5 mag. These variable objects were classified into variable stars, supernovae (SNe), and active galactic nuclei (AGNs), based on the optical morphologies, magnitudes, colors, and optical-mid-infrared colors of the host objects, spatial offsets of variable components from the host objects, and light curves. Detection completeness was examined by simulating light curves for periodic and irregular variability. We detected optical variability for 36% +/- 2% (51% +/- 3% for a bright sample with i' < 24.4 mag) of X-ray sources in the field. Number densities of variable objects as functions of time intervals Δ t and variable component magnitudes i'vari are obtained. Number densities of variable stars, SNe, and AGNs are 120, 489, and 579 objects deg-2, respectively. Bimodal distributions of variable stars in the color-magnitude diagrams indicate that the variable star sample consists of bright (V ~ 22 mag) blue variable stars of the halo population and faint (V ~ 23.5 mag) red variable stars of the disk population. There are a few candidates of RR Lyrae providing a possible number density of ~10-2 kpc-3 at a distance of >150 kpc from the Galactic center. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based on observations (program GN-2002B-Q-30) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (US), the Particle Physics and Astronomy Research Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina).

Luminosity function of faint galaxies with ultraviolet continuum

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

Stepanyan, D.A.

1985-05-01

The spatial density of faint galaxies with ultraviolet continuum in the Second Survey of the Byurakan Astrophysical Observatory is determined. The luminosity function of galaxies with ultraviolet continuum can be extended to objects fainter by 1-1.5 magnitudes. The spatial density of such galaxies in the interval of luminosities -16 /sup m/ .5 to -21 /sup m/ .5 is on the average 0.08 of the total density of field galaxies in the same interval of absolute magnitudes. The spatial density of low-luminosity galaxies with ultraviolet continuum is very high. In the interval from -12 /sup m/ .5 to -15 /sup m/more » .5 it is 0.23 Mpc/sup -3/.« less

A faint field-galaxy redshift survey in quasar fields

NASA Technical Reports Server (NTRS)

Yee, Howard K. C.; Ellingson, Erica

1993-01-01

Quasars serve as excellent markers for the identification of high-redshift galaxies and galaxy clusters. In past surveys, nearly 20 clusters of Abell richness class 1 or richer associated with quasars in the redshift range 0.2 less than z less than 0.8 were identified. In order to study these galaxy clusters in detail, a major redshift survey of faint galaxies in these fields using the CFHT LAMA/MARLIN multi-object spectroscopy system was carried out. An equally important product in such a survey is the redshifts of the field galaxies not associated with the quasars. Some preliminary results on field galaxies from an interim set of data from our redshift survey in quasar fields are presented.

Faint Object Detection in Multi-Epoch Observations via Catalog Data Fusion

NASA Astrophysics Data System (ADS)

Budavári, Tamás; Szalay, Alexander S.; Loredo, Thomas J.

2017-03-01

Astronomy in the time-domain era faces several new challenges. One of them is the efficient use of observations obtained at multiple epochs. The work presented here addresses faint object detection and describes an incremental strategy for separating real objects from artifacts in ongoing surveys. The idea is to produce low-threshold single-epoch catalogs and to accumulate information across epochs. This is in contrast to more conventional strategies based on co-added or stacked images. We adopt a Bayesian approach, addressing object detection by calculating the marginal likelihoods for hypotheses asserting that there is no object or one object in a small image patch containing at most one cataloged source at each epoch. The object-present hypothesis interprets the sources in a patch at different epochs as arising from a genuine object; the no-object hypothesis interprets candidate sources as spurious, arising from noise peaks. We study the detection probability for constant-flux objects in a Gaussian noise setting, comparing results based on single and stacked exposures to results based on a series of single-epoch catalog summaries. Our procedure amounts to generalized cross-matching: it is the product of a factor accounting for the matching of the estimated fluxes of the candidate sources and a factor accounting for the matching of their estimated directions. We find that probabilistic fusion of multi-epoch catalogs can detect sources with similar sensitivity and selectivity compared to stacking. The probabilistic cross-matching framework underlying our approach plays an important role in maintaining detection sensitivity and points toward generalizations that could accommodate variability and complex object structure.

THE MULTI-WAVELENGTH EXTREME STARBURST SAMPLE OF LUMINOUS GALAXIES. I. SAMPLE CHARACTERISTICS

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

Laag, Edward; Croft, Steve; Canalizo, Gabriela

2010-12-15

This paper introduces the Multi-wavelength Extreme Starburst Sample (MESS), a new catalog of 138 star-forming galaxies (0.1 < z < 0.3) optically selected from the Sloan Digital Sky Survey using emission line strength diagnostics to have a high absolute star formation rate (SFR; minimum 11 M{sub sun} yr{sup -1} with median SFR {approx} 61 M{sub sun} yr{sup -1} based on a Kroupa initial mass function). The MESS was designed to complement samples of nearby star-forming galaxies such as the luminous infrared galaxies (LIRGs) and ultraviolet luminous galaxies (UVLGs). Observations using the Multi-band Imaging Photometer (24, 70, and 160 {mu}m channels)more » on the Spitzer Space Telescope indicate that the MESS galaxies have IR luminosities similar to those of LIRGs, with an estimated median L{sub TIR} {approx} 3 x 10{sup 11} L{sub sun}. The selection criteria for the MESS objects suggest they may be less obscured than typical far-IR-selected galaxies with similar estimated SFRs. Twenty out of 70 of the MESS objects detected in the Galaxy Evolution Explorer FUV band also appear to be UVLGs. We estimate the SFRs based directly on luminosities to determine the agreement for these methods in the MESS. We compare these estimates to the emission line strength technique, since the effective measurement of dust attenuation plays a central role in these methods. We apply an image stacking technique to the Very Large Array FIRST survey radio data to retrieve 1.4 GHz luminosity information for 3/4 of the sample covered by FIRST including sources too faint, and at too high a redshift, to be detected in FIRST. We also discuss the relationship between the MESS objects and samples selected through alternative criteria. Morphologies will be the subject of a forthcoming paper.« less

Discovery of the candidate Kuiper belt object 1992 QB1

NASA Astrophysics Data System (ADS)

Jewitt, D.; Luu, J.

1993-04-01

The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).

Fainting

MedlinePlus

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A PECULIAR FAINT SATELLITE IN THE REMOTE OUTER HALO OF M31

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

Mackey, A. D.; Dotter, A.; Huxor, A. P.

2013-06-20

We present Hubble Space Telescope imaging of a newly discovered faint stellar system, PAndAS-48, in the outskirts of the M31 halo. Our photometry reveals this object to be comprised of an ancient and very metal-poor stellar population with age {approx}> 10 Gyr and [Fe/H] {approx}< -2.3. Our inferred distance modulus (m - M){sub 0} = 24.57 {+-} 0.11 confirms that PAndAS-48 is most likely a remote M31 satellite with a three-dimensional galactocentric radius of 149{sup +19}{sub -8} kpc. We observe an apparent spread in color on the upper red giant branch that is larger than the photometric uncertainties should allow,more » and briefly explore the implications of this. Structurally, PAndAS-48 is diffuse, faint, and moderately flattened, with a half-light radius r{sub h}=26{sup +4}{sub -3} pc, integrated luminosity M{sub V} = -4.8 {+-} 0.5, and ellipticity {epsilon}=0.30{sup +0.08}{sub -0.15}. On the size-luminosity plane it falls between the extended globular clusters seen in several nearby galaxies and the recently discovered faint dwarf satellites of the Milky Way; however, its characteristics do not allow us to unambiguously classify it as either type of system. If PAndAS-48 is a globular cluster then it is among the most elliptical, isolated, and metal-poor of any seen in the Local Group, extended or otherwise. Conversely, while its properties are generally consistent with those observed for the faint Milky Way dwarfs, it would be a factor of {approx}2-3 smaller in spatial extent than any known counterpart of comparable luminosity.« less

Searching for Optically Faint GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Lederer, Susan M.; Abercromby, Kira J.; Barker, Edwin S.; Burkhardt, Andrew; Cowardin, Heather; Krisko, Paula; Silha, Jiri

2012-01-01

We report on results from a search for optically faint debris (defined as R > 20th magnitude, or smaller than 10 cm assuming an albedo of 0.175)) at geosynchronous orbit (GEO) using the 6.5-m Magellan telescope "Walter Baade" at Las Campanas Observatory in Chile. Our goal is to characterize the brightness distribution of debris to the faintest limiting magnitude possible. Our data was obtained during 6 hours of observing time during the photometric nights of 26 and 27 March 2011 with the IMACS f/2 instrument, which has a field of view (fov) of 0.5 degrees in diameter. All observations were obtained through a Sloan r filter, and calibrated by observations of Landolt standard stars. Our primary objective was to search for optically faint objects from one of the few known fragmentations at GEO: the Titan 3C Transtage (1968-081) fragmentation in 1992. Eight debris pieces and the parent rocket body are in the Space Surveillance Network public catalog. We successfully tracked two cataloged pieces of Titan debris with the 6.5-m telescope, followed by a survey for unknown objects on similar orbits but with different mean anomalies. To establish the bright end of the debris population, calibrated observations were acquired on the same field centers, telescope rates, and time period with a similar filter on the 0.6-m MODEST (Michigan Orbital DEbris Survey Telescope), located 100 km to the south of Magellan at Cerro Tololo Inter-American Observatory, Chile. We will show the calibrated brightness distributions from both telescopes, and compare the observed brightness distributions with that predicted for various population models of debris of different sizes.

The contribution of dissolving star clusters to the population of ultra faint objects in the outer halo of the Milky Way

NASA Astrophysics Data System (ADS)

Contenta, Filippo; Gieles, Mark; Balbinot, Eduardo; Collins, Michelle L. M.

2017-04-01

In the last decade, several ultra faint objects (UFOs, MV ≳ -3.5) have been discovered in the outer halo of the Milky Way. For some of these objects, it is not clear whether they are star clusters or (ultra faint) dwarf galaxies. In this work, we quantify the contribution of star clusters to the population of UFOs. We extrapolated the mass and Galactocentric radius distribution of the globular clusters using a population model, finding that the Milky Way contains about 3.3^{+7.3}_{-1.6} star clusters with MV ≳ -3.5 and Galactocentric radius ≥20 kpc. To understand whether dissolving clusters can appear as UFOs, we run a suite of direct N-body models, varying the orbit, the Galactic potential, the binary fraction and the black hole (BH) natal kick velocities. In the analyses, we consider observational biases such as luminosity limit, field stars and line-of-sight projection. We find that star clusters contribute to both the compact and the extended population of UFOs: clusters without BHs appear compact with radii ˜5 pc, while clusters that retain their BHs after formation have radii ≳ 20 pc. The properties of the extended clusters are remarkably similar to those of dwarf galaxies: high-inferred mass-to-light ratios due to binaries, binary properties mildly affected by dynamical evolution, no observable mass segregation and flattened stellar mass function. We conclude that the slope of the stellar mass function as a function of Galactocentric radius and the presence/absence of cold streams can discriminate between dark matter-free and dark matter-dominated UFOs.

Spacelab

NASA Image and Video Library

1990-12-05

This image shows a part of the Cygnus loop supernova remnant, taken by the Ultraviolet Imaging Telescope (UIT) on the Astro Observatory during the Astro-1 mission (STS-35) on December 5, 1990. Pictured is a portion of the huge Cygnus loop, an array of interstellar gas clouds that have been blasted by a 900,000 mile per hour shock wave from a prehistoric stellar explosion, which occurred about 20,000 years ago, known as supernova. With ultraviolet and x-rays, astronomers can see emissions from extremely hot gases, intense magnetic fields, and other high-energy phenomena that more faintly appear in visible and infrared light or in radio waves that are crucial to deepening the understanding of the universe. The Astro Observatory was designed to explore the universe by observing and measuring the ultraviolet radiation from celestial objects. Three instruments make up the Astro Observatory: The Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE). The Marshall Space Flight Center had managment responsibilities for the Astro-1 mission. The Astro-1 Observatory was launched aboard the Space Shuttle Orbiter Columbia (STS-35) on December 2, 1990.

Galaxy Formation At Extreme Redshifts: Semi-Analytic Model Predictions And Challenges For Observations

NASA Astrophysics Data System (ADS)

Yung, L. Y. Aaron; Somerville, Rachel S.

2017-06-01

The well-established Santa Cruz semi-analytic galaxy formation framework has been shown to be quite successful at explaining observations in the local Universe, as well as making predictions for low-redshift observations. Recently, metallicity-based gas partitioning and H2-based star formation recipes have been implemented in our model, replacing the legacy cold-gas based recipe. We then use our revised model to explore the high-redshift Universe and make predictions up to z = 15. Although our model is only calibrated to observations from the local universe, our predictions seem to match incredibly well with mid- to high-redshift observational constraints available-to-date, including rest-frame UV luminosity functions and the reionization history as constrained by CMB and IGM observations. We provide predictions for individual and statistical galaxy properties at a wide range of redshifts (z = 4 - 15), including objects that are too far or too faint to be detected with current facilities. And using our model predictions, we also provide forecasted luminosity functions and other observables for upcoming studies with JWST.

The UV Spectrum of the Ultracool Dwarf LSR J1835+3259 Observed with the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Saur, Joachim; Fischer, Christian; Wennmacher, Alexandre; Feldman, Paul D.; Roth, Lorenz; Strobel, Darrell F.; Reiners, Ansgar

2018-05-01

An interesting question about ultracool dwarfs recently raised in the literature is whether their emission is purely internally driven or partially powered by external processes similar to planetary aurora known from the solar system. In this work, we present Hubble Space Telescope observations of the energy fluxes of the M8.5 ultracool dwarf LSR J1835+3259 throughout the ultraviolet (UV). The obtained spectra reveal that the object is generally UV-fainter compared with other earlier-type dwarfs. We detect the Mg II doublet at 2800 Å and constrain an average flux throughout the near-UV. In the far-UV without Lyα, the ultracool dwarf is extremely faint with an energy output at least a factor of 250 smaller as expected from auroral emission physically similar to that on Jupiter. We also detect the red wing of the Lyα emission. Our overall finding is that the observed UV spectrum of LSR J1835+3259 resembles the spectrum of mid/late-type M-dwarf stars relatively well, but it is distinct from a spectrum expected from Jupiter-like auroral processes.

Simulated low-intensity optical pulsar observation with single-photon detector

NASA Astrophysics Data System (ADS)

Leeb, W. R.; Alves, J.; Meingast, S.; Brunner, M.

2015-02-01

Context. Optical radiation of pulsars offers valuable clues to the physics of neutron stars, which are our only probes of the most extreme states of matter in the present-day universe. Still, only about 1% of all cataloged pulsars have known optical counterparts. Aims: The goal of this work is to develop an observational method optimized for discovering faint optical pulsars. Methods: A single-photon detector transforms the signal received by the telescope into a pulse sequence. The events obtained are time tagged and transformed into a histogram of event time differences. The histogram envelope presents the autocorrelation of the recorded optical signal and thus displays any periodicity of the input signal. Results: Simulations show that faint pulsars radiating in the optical regime can be detected in a straightforward way. As an example, a fictitious pulsar with a V-magnitude of 24.6 mag and a signature like the Crab pulsar can be discovered within one minute using an 8-m class telescope. At the detector's peak sensitivity the average optical flux density would then amount to Fν = 0.63 μJy. With a 40-m class telescope, such as the forthcoming European ELT, the detection of optical pulsars with magnitudes V< 30 mag is within reach for a measurement time of one minute. A two-hour "blind search" with the ELT could reach V ~ 31.3 mag. Conclusions: This method allows detecting faint periodic optical radiation with simple equipment and easy signal processing.

Deep SOAR follow-up photometry of two Milky Way outer-halo companions discovered with Dark Energy Survey

NASA Astrophysics Data System (ADS)

Luque, E.; Santiago, B.; Pieres, A.; Marshall, J. L.; Pace, A. B.; Kron, R.; Drlica-Wagner, A.; Queiroz, A.; Balbinot, E.; Ponte, M. dal; Neto, A. Fausti; da Costa, L. N.; Maia, M. A. G.; Walker, A. R.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Davis, C.; Doel, P.; Eifler, T. F.; Flaugher, B.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Miquel, R.; Nichol, R. C.; Plazas, A. A.; Sanchez, E.; Scarpine, V.; Schindler, R.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.

2018-04-01

We report the discovery of a new star cluster, DES 3, in the constellation of Indus, and deeper observations of the previously identified satellite DES J0222.7-5217 (Eridanus III). DES 3 was detected as a stellar overdensity in first-year Dark Energy Survey data, and confirmed with deeper photometry from the 4.1 metre Southern Astrophysical Research (SOAR) telescope. The new system was detected with a relatively high significance and appears in the DES images as a compact concentration of faint blue point sources. We determine that DES 3 is located at a heliocentric distance of ≃ 76.2 kpc and it is dominated by an old (≃ 9.8 Gyr) and metal-poor ([Fe/H] ≃ -1.84) population. While the age and metallicity values of DES 3 are comparable to typical globular clusters (objects with a high stellar density, stellar mass of ˜105M⊙ and luminosity MV ˜ -7.3), its half-light radius (rh ˜ 6.87 pc) and luminosity (MV ˜ -1.7) are more indicative of faint star cluster. Based on the angular size, DES 3, with a value of rh ˜ 0{^'.}31, is among the smallest faint star clusters known to date. Furthermore, using deeper imaging of DES J0222.7-5217 taken with the SOAR telescope, we update structural parameters and perform the first isochrone modeling. Our analysis yields the first age (≃ 12.6 Gyr) and metallicity ([Fe/H] ≃ -2.01) estimates for this object. The half-light radius (rh ≃ 11.24 pc) and luminosity (MV ≃ -2.4) of DES J0222.7-5217 suggest that it is likely a faint star cluster. The discovery of DES 3 indicates that the census of stellar systems in the Milky Way is still far from complete, and demonstrates the power of modern wide-field imaging surveys to improve our knowledge of the Galaxy's satellite population.

Faint Object Camera observations of M87 - The jet and nucleus

NASA Technical Reports Server (NTRS)

Boksenberg, A.; Macchetto, F.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.

1992-01-01

UV and optical images of the central region and jet of the nearby elliptical galaxy M87 have been obtained with about 0.1 arcsec resolution in several spectral bands with the Faint Object Camera (FOC) on the HST, including polarization images. Deconvolution enhances the contrast of the complex structure and filamentary patterns in the jet already evident in the aberrated images. Morphologically there is close similarity between the FOC images of the extended jet and the best 2-cm radio maps obtained at similar resolution, and the magnetic field vectors from the UV and radio polarimetric data also correspond well. We observe structure in the inner jet within a few tenths arcsec of the nucleus which also has been well studied at radio wavelengths. Our UV and optical photometry of regions along the jet shows little variation in spectral index from the value 1.0 between markedly different regions and no trend to a steepening spectrum with distance along the jet.

BEASTS OF THE SOUTHERN WILD: DISCOVERY OF NINE ULTRA FAINT SATELLITES IN THE VICINITY OF THE MAGELLANIC CLOUDS

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

Koposov, Sergey E.; Belokurov, Vasily; Torrealba, Gabriel

2015-06-01

We have used the publicly released Dark Energy Survey (DES) data to hunt for new satellites of the Milky Way (MW) in the southern hemisphere. Our search yielded a large number of promising candidates. In this paper, we announce the discovery of nine new unambiguous ultra-faint objects, whose authenticity can be established with the DES data alone. Based on the morphological properties, three of the new satellites are dwarf galaxies, one of which is located at the very outskirts of the MW, at a distance of 380 kpc. The remaining six objects have sizes and luminosities comparable to the Seguemore » 1 satellite and cannot be classified straightforwardly without follow-up spectroscopic observations. The satellites we have discovered cluster around the LMC and the SMC. We show that such spatial distribution is unlikely under the assumption of isotropy, and, therefore, conclude that at least some of the new satellites must have been associated with the Magellanic Clouds in the past.« less

Observing Comet Halley with Space Telescope

NASA Technical Reports Server (NTRS)

Caldwell, J.

1983-01-01

The NASA Space Telescope (ST) to be launched into LEO by STS in late 1985 is characterized, and its potential use for observations of Comet Halley shortly after the perihelion passage in February, 1986, is discussed. The ST comprises a 2.4-m MgF2-coated primary reflector (with maximum field of view 2.7 x 2.7 arcmin, wavelength coverage 120-1100 nm, and maximum tracking rate 0.21 arcsec/sec) and five first-generation scientific instruments (wide-field planetary camera, faint-object camera, high-resolution and faint-object spectrographs, and high-speed photometer). Planned ST observations of Halley include periods of continuous observation much longer than can be obtained from the ground, provision of supplementary data and navigation information to Giotto and other deep-space missions, emission spectroscopy, UV polarimetry, and possible detection of 124-nm H2O absorption. Before March 11, 1986, earth occultation or similar procedures will be required to observe Halley because it will be within the ST 50-deg solar-elongation-distance limit.

Uncovering extreme AGN variability in serendipitous X-ray source surveys

NASA Astrophysics Data System (ADS)

Moran, Edward C.; Garcia Soto, Aylin; LaMassa, Stephanie; Urry, Meg

2018-01-01

Constraints on the duty cycle and duration of accretion episodes in active galactic nuclei (AGNs) are vital for establishing how most AGNs are fueled, which is essential for a complete picture of black hole/galaxy co-evolution. Perhaps the best handle we have on these activity parameters is provided by AGNs that have displayed dramatic changes in their bolometric luminosities and, in some cases, spectroscopic classifications. Given that X-ray emission is directly linked to black-hole accretion, X-ray surveys should provide a straightforward means of identifying AGNs that have undergone dramatic changes in their accretion states. However, it appears that such events are very rare, so wide-area surveys separated in time by many years are needed to maximize discovery rates. We have cross-correlated the Einstein IPC Two-Sigma Catalog with the ROSAT All-Sky Survey Faint Source Catalog to identify a sample of soft X-ray sources that varied by factors ranging from 7 to more than 100 over a ten year timescale. When possible, we have constructed long-term X-ray light curves for the sources by combining the Einstein and RASS fluxes with those obtained from serendipitous pointed observations by ROSAT, Chandra,XMM, and Swift. Optical follow-up observations indicate that many of the extremely variable sources in our sample are indeed radio-quiet AGNs. Interestingly, the majority of objects that dimmed between ~1980 and ~1990 are still (or are again) broad-line AGNs rather than“changing-look” candidates that have more subtle AGN signatures in their spectra — despite the fact that none of the sources examined thus far has returned to its highest observed luminosity. Future X-ray observations will provide the opportunity to characterize the X-ray behavior of these anonymous, extreme AGNs over a four decade span.

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

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

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

2015-02-10

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

Characterizing Sky Spectra Using SDSS BOSS Data

NASA Astrophysics Data System (ADS)

Florez, Lina Maria; Strauss, Michael A.

2018-01-01

In the optical/near-infrared spectra gathered by a ground-based telescope observing very faint sources, the strengths of the emission lines due to the Earth’s atmosphere can be many times larger than the fluxes of the sources we are interested in. Thus the limiting factor in faint-object spectroscopy is the degree to which systematics in the sky subtraction can be minimized. Longwards of 6000 Angstroms, the night-sky spectrum is dominated by multiple vibrational/rotational transitions of the OH radical from our upper atmosphere. While the wavelengths of these lines are the same in each sky spectrum, their relative strengths vary considerably as a function of time and position on the sky. The better we can model their strengths, the better we can hope to subtract them off. We expect that the strength of lines from common upper energy levels will be correlated with one another. We used flux-calibrated sky spectra from the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey (SDSS BOSS) to explore these correlations. Our aim is to use these correlations for creating improved sky subtraction algorithms for the Prime Focus Spectrograph (PFS) on the 8.2-meter Subaru Telescope. When PFS starts gathering data in 2019, it will be the most powerful multi-object spectrograph in the world. Since PFS will be gathering data on sources as faint as 24th magnitude and fainter, it's of upmost importance to be able to accurately measure and subtract sky spectra from the data that we receive.

Astrophysics on the Edge: New Instrumental Developments at the ING

NASA Astrophysics Data System (ADS)

Santander-García, M.; Rodríguez-Gil, P.; Tulloch, S.; Rutten, R. G. M.

Present and future key instruments at the Isaac Newton Group of Telescopes (ING) are introduced, and their corresponding latest scientific highlights are presented. GLAS (Ground-layer Laser Adaptive optics System): The recently installed 515 nm laser, mounted on the WHT (William Herschel Telescope), produces a bright artificial star at a height of 15 km. This enables almost full-sky access to Adaptive Optics observations. Recent commissioning observations with the NAOMI+GLAS system showed that very significant improvement in image quality can be obtained, e.g. down to 0.16 arcsec in the H band. QUCAM2 and QUCAM3: Two Low Light Level (L3) CCD cameras for fast or faint-object spectroscopy with the twin-armed ISIS spectrograph at the WHT. Their use opens a new window of high time-frequency observations, as well as access to fainter objects. They are powerful instruments for research on compact objects such as white dwarfs, neutron stars or black holes, stellar pulsations, and compact binaries.HARPS-NEF (High-Accuracy Radial-velocity Planet Searcher of the New Earths Facility): An extremely stable, high-resolution (R ˜ 120, 000) spectrograph for the WHT which is being constructed for commissioning in 2009-2010. Its radial velocity stability of < 1 m s- 1 may in the future be even further improved by using a Fabry-Perot laser-comb, a wavelength calibration unit capable of achieving an accuracy of 1 cm s- 1. This instrument will effectively allow to search for earth-like exoplanets.

Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

2004-01-01

Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

Deep CCD Photometry of the Rich Galaxy Cluster Abel 1656 Characteristics of the Dwarf Elliptical Galaxy Population in the Cluster Core

NASA Astrophysics Data System (ADS)

Secker, Jeffrey Alan

1995-01-01

We have developed a statistically rigorous and automated method to implement the detection, photometry and classification of faint objects on digital images. We use these methods to analyze deep R- and B-band CCD images of the central ~ 700 arcmin ^2 of the Coma cluster core, and an associated control field. We have detected and measured total R magnitudes and (B-R) colors for a sample of 3741 objects on the galaxy cluster fields, and 1164 objects on a remote control field, complete to a limiting magnitude of R = 22.5 mag. The typical uncertainties are +/- 0.06 and +/-0.12 mag in total magnitude and color respectively. The dwarf elliptical (dE) galaxies are confined to a well-defined sequence in the color range given by 0.7<= (B-R)<= 1.9 mag: within this interval there are 2535 dE candidates on our fields in the cluster core, and 694 objects on the control field. With an image scale of 0.53 arcsec/pixel and seeing near 1.2 arcsec, a large fraction of the dE galaxy candidates are resolved. We find a significant metallicity gradient in the radial distribution of the dwarf elliptical galaxies, which goes as Z~ R^{-0.32 } outwards from the cluster center at NGC 4874. As well, there is a strong color-luminosity correlation, in the sense that more luminous dE galaxies are redder in the mean. These effects give rise to a radial variation in the cluster luminosity function. The spatial distribution of the faint dE galaxies is well fit by a standard King model with a central surface density of Sigma _0 = 1.44 dEs arcmin^{ -2}, a core radius R_{ rm c} = 18.7 arcmin (~eq 0.44 Mpc), and a tidal radius of 1.44 deg ( ~eq 2.05 Mpc). This core is significantly larger than R_{rm c} = 12.3 arcmin (~eq 0.29 Mpc) found for the bright cluster galaxies. The composite luminosity function for Coma galaxies is modeled as the sum of a log -normal distribution for the giant galaxies and a Schechter function for the dwarf elliptical galaxies, with a faint -end slope of alpha = -1.41, consistent with known faint-end slopes for the Virgo and Fornax clusters. The early-type dwarf-to-giant ratio for the Coma cluster core is consistent with that of the Virgo cluster, and thus with the rich Coma cluster being formed as the merger of multiple less-rich galaxy clusters.

Infrared Astronomy at Extremely Faint Light Levels in Support of the LAIRTS Program.

DTIC Science & Technology

1987-09-01

Elliptical and Irregular Galaxies (T. X. Thuan), Ap. J., 299, 881-895 (1985). 2. IC 3475: A Stripped Dwarf Galaxy in the Virgo Cluster (L. Vigroux, T. X...imply a metallicity range for BCDs and dis between 1/30 and 1/3 of the sun’s metallicity, while the near-IR colors of the dEs (in the Virgo cluster of... clusters . A paper is in preparation which will study the stellar populations in these first brightest galaxies, as a function of the cluster

Treatment of rabies in the 21st century: curing the incurable?

PubMed

Franka, Richard; Rupprecht, Charles E

2011-10-01

Despite the extreme case fatality attributable to rabies, reports of survivors provide a faint glimpse of a possibility of overcoming this deadly disease, even after clinical symptoms manifest. At present, no existing approach fulfills modern medical criteria for the optimal therapy of rabies. Until new efficacious antiviral compounds and optimized treatment protocols are developed, animal population management and vaccination of major reservoirs and vectors, minimization of the risk of viral exposures, and appropriate and early postexposure prophylaxis, remain the hallmarks of modern public health intervention.

Vasovagal syncope in medical students and their first-degree relatives.

PubMed

Serletis, Anna; Rose, Sarah; Sheldon, Aaron G; Sheldon, Robert S

2006-08-01

To determine the effect of family history on the likelihood of vasovagal syncope. Sixty-two medical students and 228 first-degree relatives were studied. Vasovagal syncope was ascertained with the Calgary syncope symptom score. The effects of the sex of the subject and parental syncope history on the likelihood of offspring fainting were described using Kaplan-Meier estimates and analysed using proportional hazards regression. The prevalence of vasovagal syncope was 32% and the median age of first faint in those who fainted was 14 years. More females than males fainted [42 vs. 31%; P=0.02; hazard ratio (HR) 1.34 (95% CI 1.07-1.68)]. An individual with two fainting parents was more likely to faint than one with no fainting parents [P<0.0001; HR 3.4 (95% CI 1.7-7.03)]. In the proportional hazards model, offspring of either sex whose mother faints are more likely to faint than those whose mother does not faint [HR 2.86 (95% CI 1.54-5.31)]. Having a father who faints significantly increases the risk of syncope in sons [HR 4.12 (95%CI 1.39-12.31)], but not in daughters [HR 1.18 (95% CI 0.56-3.34)]. Family history and sex of subject are important predictors of vasovagal syncope in offspring.

Detection of Optically Faint GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, P.; Lederer, S.; Barker, E.; Cowardin, H.; Abercromby, K.; Silha, J.; Burkhardt, A.

2014-01-01

There have been extensive optical surveys for debris at geosynchronous orbit (GEO) conducted with meter-class telescopes, such as those conducted with MODEST (the Michigan Orbital DEbris Survey Telescope, a 0.6-m telescope located at Cerro Tololo in Chile), and the European Space Agency's 1.0-m space debris telescope (SDT) in the Canary Islands. These surveys have detection limits in the range of 18th or 19th magnitude, which corresponds to sizes larger than 10 cm assuming an albedo of 0.175. All of these surveys reveal a substantial population of objects fainter than R = 15th magnitude that are not in the public U.S. Satellite Catalog. To detect objects fainter than 20th magnitude (and presumably smaller than 10 cm) in the visible requires a larger telescope and excellent imaging conditions. This combination is available in Chile. NASA's Orbital Debris Program Office has begun collecting orbital debris observations with the 6.5-m (21.3-ft diameter) "Walter Baade" Magellan telescope at Las Campanas Observatory. The goal is to detect objects as faint as possible from a ground-based observatory and begin to understand the brightness distribution of GEO debris fainter than R = 20th magnitude.

ARACHNID: A prototype object-oriented database tool for distributed systems

NASA Technical Reports Server (NTRS)

Younger, Herbert; Oreilly, John; Frogner, Bjorn

1994-01-01

This paper discusses the results of a Phase 2 SBIR project sponsored by NASA and performed by MIMD Systems, Inc. A major objective of this project was to develop specific concepts for improved performance in accessing large databases. An object-oriented and distributed approach was used for the general design, while a geographical decomposition was used as a specific solution. The resulting software framework is called ARACHNID. The Faint Source Catalog developed by NASA was the initial database testbed. This is a database of many giga-bytes, where an order of magnitude improvement in query speed is being sought. This database contains faint infrared point sources obtained from telescope measurements of the sky. A geographical decomposition of this database is an attractive approach to dividing it into pieces. Each piece can then be searched on individual processors with only a weak data linkage between the processors being required. As a further demonstration of the concepts implemented in ARACHNID, a tourist information system is discussed. This version of ARACHNID is the commercial result of the project. It is a distributed, networked, database application where speed, maintenance, and reliability are important considerations. This paper focuses on the design concepts and technologies that form the basis for ARACHNID.

Faint Object Detection in Multi-Epoch Observations via Catalog Data Fusion

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

Budavári, Tamás; Szalay, Alexander S.; Loredo, Thomas J.

Astronomy in the time-domain era faces several new challenges. One of them is the efficient use of observations obtained at multiple epochs. The work presented here addresses faint object detection and describes an incremental strategy for separating real objects from artifacts in ongoing surveys. The idea is to produce low-threshold single-epoch catalogs and to accumulate information across epochs. This is in contrast to more conventional strategies based on co-added or stacked images. We adopt a Bayesian approach, addressing object detection by calculating the marginal likelihoods for hypotheses asserting that there is no object or one object in a small imagemore » patch containing at most one cataloged source at each epoch. The object-present hypothesis interprets the sources in a patch at different epochs as arising from a genuine object; the no-object hypothesis interprets candidate sources as spurious, arising from noise peaks. We study the detection probability for constant-flux objects in a Gaussian noise setting, comparing results based on single and stacked exposures to results based on a series of single-epoch catalog summaries. Our procedure amounts to generalized cross-matching: it is the product of a factor accounting for the matching of the estimated fluxes of the candidate sources and a factor accounting for the matching of their estimated directions. We find that probabilistic fusion of multi-epoch catalogs can detect sources with similar sensitivity and selectivity compared to stacking. The probabilistic cross-matching framework underlying our approach plays an important role in maintaining detection sensitivity and points toward generalizations that could accommodate variability and complex object structure.« less

The Origin of the EUV Emission in Her X-1

NASA Technical Reports Server (NTRS)

Leahy, D. A.; Marshall, H.

1999-01-01

Her X-1 exhibits a strong orbital modulation of its EUV flux with a large decrease around time of eclipse of the neutron star, and a significant dip which appears at different orbital phases at different 35-day phases. We consider observations of Her X-1 in the EUVE by the Extreme Ultraviolet Explorer (EUVE), which includes data from 1995 near the end of the Short High state, and date from 1997 at the start of the Short High state. The observed EUV lightcurve has bright and faint phases. The bright phase can be explained as the low energy tail of the soft x-ray pulse. The faint phase emission has been modeled to understand its origin. We find: the x-ray heated surface of HZ Her is too cool to produce enough emission; the accretion disk does not explain the orbital modulation; however, reflection of x-rays off of HZ Her can produce the observed lightcurve with orbital eclipses. The dip can be explained by shadowing of the companion by the accretion disk. We discuss the constraints on the accretion disk geometry derived from the observed shadowing.

A catalogue of faint local radio AGN and the properties of their host galaxies

NASA Astrophysics Data System (ADS)

Lofthouse, E. K.; Kaviraj, S.; Smith, D. JB; Hardcastle, M. J.

2018-05-01

We present a catalogue of local (z < 0.1) galaxies that contain faint AGN. We select these objects by identifying galaxies that exhibit a significant excess in their radio luminosities, compared to what is expected from the observed levels of star-formation activity in these systems. This is achieved by comparing the optical (spectroscopic) star formation rate (SFR) to the 1.4 GHz luminosity measured from the FIRST survey. The majority of the AGN identified in this study are fainter than those in previous work, such as in the Best and Heckman (2012) catalogue. We show that these faint AGN make a non-negligible contribution to the radio luminosity function at low luminosities (below 1022.5 W Hz-1), and host ˜13 per cent of the local radio luminosity budget. Their host galaxies are predominantly high stellar-mass systems (with a median stellar mass of 1011M⊙), are found across a range of environments (but typically in denser environments than star-forming galaxies) and have early-type morphologies. This study demonstrates a general technique to identify AGN in galaxy populations where reliable optical SFRs can be extracted using spectro-photometry and where radio data are also available so that a radio excess can be measured. Our results also demonstrate that it is unsafe to infer SFRs from radio emission alone, even if bright AGN have been excluded from a sample, since there is a significant population of faint radio AGN which may contaminate the radio-derived SFRs.

NASA's Webb Telescope "chilling out" in Houston for the summer

NASA Image and Video Library

2017-12-08

NASA’s James Webb Space Telescope was placed in Johnson Space Center’s historic Chamber A on June 20, 2017, to prepare for its final three months of testing in a cryogenic vacuum that mimics temperatures in space. Engineers will perform the test to prove that the telescope can operate in space at these temperatures. Chamber A will simulate an environment where the telescope will experience extreme cold -- around 37 Kelvin (minus 236 degrees Celsius or minus 393 degrees Fahrenheit). In space, the telescope must be kept extremely cold, in order to be able to detect the infrared light from very faint, distant objects. To protect the telescope from external sources of light and heat (like the sun, Earth, and moon), as well as from heat emitted by the observatory, a five-layer, tennis court-sized sunshield acts like a parasol that provides shade. The sunshield separates the observatory into a warm, sun-facing side (reaching temperatures close to 400 degrees Fahrenheit) and a cold side (185 degrees below zero). The sunshield blocks sunlight from interfering with the sensitive telescope instruments. Read more: go.nasa.gov/2sZAilS 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

Survival analysis, or what to do with upper limits in astronomical surveys

NASA Technical Reports Server (NTRS)

Isobe, Takashi; Feigelson, Eric D.

1986-01-01

A field of applied statistics called survival analysis has been developed over several decades to deal with censored data, which occur in astronomical surveys when objects are too faint to be detected. How these methods can assist in the statistical interpretation of astronomical data are reviewed.

Statistical Track-Before-Detect Methods Applied to Faint Optical Observations of Resident Space Objects

NASA Astrophysics Data System (ADS)

Fujimoto, K.; Yanagisawa, T.; Uetsuhara, M.

Automated detection and tracking of faint objects in optical, or bearing-only, sensor imagery is a topic of immense interest in space surveillance. Robust methods in this realm will lead to better space situational awareness (SSA) while reducing the cost of sensors and optics. They are especially relevant in the search for high area-to-mass ratio (HAMR) objects, as their apparent brightness can change significantly over time. A track-before-detect (TBD) approach has been shown to be suitable for faint, low signal-to-noise ratio (SNR) images of resident space objects (RSOs). TBD does not rely upon the extraction of feature points within the image based on some thresholding criteria, but rather directly takes as input the intensity information from the image file. Not only is all of the available information from the image used, TBD avoids the computational intractability of the conventional feature-based line detection (i.e., "string of pearls") approach to track detection for low SNR data. Implementation of TBD rooted in finite set statistics (FISST) theory has been proposed recently by Vo, et al. Compared to other TBD methods applied so far to SSA, such as the stacking method or multi-pass multi-period denoising, the FISST approach is statistically rigorous and has been shown to be more computationally efficient, thus paving the path toward on-line processing. In this paper, we intend to apply a multi-Bernoulli filter to actual CCD imagery of RSOs. The multi-Bernoulli filter can explicitly account for the birth and death of multiple targets in a measurement arc. TBD is achieved via a sequential Monte Carlo implementation. Preliminary results with simulated single-target data indicate that a Bernoulli filter can successfully track and detect objects with measurement SNR as low as 2.4. Although the advent of fast-cadence scientific CMOS sensors have made the automation of faint object detection a realistic goal, it is nonetheless a difficult goal, as measurements arcs in space surveillance are often both short and sparse. FISST methodologies have been applied to the general problem of SSA by many authors, but they generally focus on tracking scenarios with long arcs or assume that line detection is tractable. We will instead focus this work on estimating sensor-level kinematics of RSOs for low SNR too-short arc observations. Once said estimate is made available, track association and simultaneous initial orbit determination may be achieved via any number of proposed solutions to the too-short arc problem, such as those incorporating the admissible region. We show that the benefit of combining FISST-based TBD with too-short arc association goes both ways; i.e., the former provides consistent statistics regarding bearing-only measurements, whereas the latter makes better use of the precise dynamical models nominally applicable to RSOs in orbit determination.

The U.S. survey for faint blue objects

NASA Technical Reports Server (NTRS)

Mitchell, K. J.; Howell, S. B.; Usher, P. D.

1987-01-01

A spectrophotometric study of the blue and UV-excess starlike objects in the U.S. survey (Usher, 1981) has been conducted. Observations were obtained with a resolution of about 20 A over the 3500-7000-A wavelength range. Considered within the sample are 42 DA white dwarfs, 4 DB/DO white dwarfs, 13 subdwarf B stars, 12 subdwarf O stars, and 13 horizontal branch stars. The sample is analyzed using numerical convolution photometry.

Enhancing Ground Based Telescope Performance with Image Processing

DTIC Science & Technology

2013-11-13

driven by the need to detect small faint objects with relatively short integration times to avoid streaking of the satellite image across multiple...the time right before the eclipse. The orbital elements of the satellite were entered into the SST’s tracking system, so that the SST could be...short integration times , thereby avoiding streaking of the satellite image across multiple CCD pixels so that the objects are suitably modeled as point

Optical Observations of GEO Debris with Two Telescopes

NASA Technical Reports Server (NTRS)

Seitzer, P.; Abercromby, K.; Rodriguez, H.; Barker, E.

2007-01-01

For several years, the Michigan Orbital DEbris Survey Telescope (MODEST), the University of Michigan s 0.6/0.9-m Schmidt telescope on Cerro Tololo Inter-American Observatory in Chile has been used to survey the debris population at GEO in the visible regime. Magnitudes, positions, and angular rates are determined for GEO objects as they move across the telescope s field-of-view (FOV) during a 5-minute window. This short window of time is not long enough to determine a full six parameter orbit so usually a circular orbit is assumed. A longer arc of time is necessary to determine eccentricity and to look for changes in the orbit with time. MODEST can follow objects in real-time, but only at the price of stopping survey operations. A second telescope would allow for longer arcs of orbit to obtain the full six orbital parameters, as well as assess the changes over time. An additional benefit of having a second telescope is the capability of obtaining BVRI colors of the faint targets, aiding efforts to determine the material type of faint debris. For 14 nights in March 2007, two telescopes were used simultaneously to observe the GEO debris field. MODEST was used exclusively in survey mode. As objects were detected, they were handed off in near real-time to the Cerro Tololo 0.9-m telescope for follow-up observations. The goal was to determine orbits and colors for all objects fainter than R = 15th magnitude (corresponds to 1 meter in size assuming a 0.2 albedo) detected by MODEST. The hand-off process was completely functional during the final eight nights and follow-ups for objects from night-to-night were possible. The cutoff magnitude level of 15th was selected on the basis of an abrupt change in the observed angular rate distribution in the MODEST surveys. Objects brighter than 15th magnitude tend to lie on a well defined locus in the angular rate plane (and have orbits in the catalog), while fainter objects fill the plane almost uniformly. We need to determine full six-parameter orbits to investigate what causes this change in observed angular rates. Are these faint objects either the same population of high area-to-mass (A/M) objects on eccentric orbits as discovered by the ESA Space Debris Telescope (Schildknecht, et al. 2004), or are they just normal debris from breakups in GEO?

Astrometric satellites

NASA Astrophysics Data System (ADS)

Lindegren, Lennart

2012-01-01

The launch of the Hipparcos satellite in 1989 and the Hubble Space Telescope in 1990 revolutionized astrometry. By no means does this imply that not much progress was made in the ground-based techniques used exclusively until then. On the contrary, the 1960s to 1980s saw an intense development of new or highly improved instruments, including photoelectric meridian circles, automated plate measuring machines, and the use of chargecoupled device (CCD) detectors for small-field differential astrometry (for a review of optical astrometry at the time, see Monet 1988). In the radio domain, very long baseline interferometry (VLBI) astrometry already provided an extragalactic reference frame accurate to about 1 milliarcsecond (mas) (Ma et al. 1990). Spectacular improvements were made in terms of accuracy, the faintness of the observed objects, and their numbers. However, there was a widening gulf between small-angle astrometry, where differential techniques could overcome atmospheric effects down to below 1 mas, and large-angle astrometry, where conventional instruments such as meridian circles seemed to have hit a barrier in the underlying systematic errors at about 100 mas. Though very precise, the small-angle measurements were of limited use for the determination of positions and proper motions, due to the lack of suitable reference objects in the small fields, and even for parallaxes the necessary correction for the mean parallax of background stars was highly non-trivial. Linking the optical observations to the accurate VLBI frame also proved extremely difficult.

Understanding r-process nucleosynthesis with dwarf galaxies

NASA Astrophysics Data System (ADS)

Ji, Alexander P.

2018-06-01

The Milky Way's faintest dwarf galaxy satellites each sample short, independent bursts of star formation from the first 1-2 Gyr of the universe. Their simple formation history makes them ideal systems to understand how rare events like neutron star mergers contribute to early enrichment of r-process elements. I will focus on the ultra-faint galaxy Reticulum II, which experienced a single prolific r-process event that left ~80% of its stars extremely enriched in r-process elements. I will present abundances of ~40 elements derived from the highest signal-to-noise high-resolution spectrum ever taken for an ultra-faint dwarf galaxy star. Precise measurements of elements from all three r-process peaks reaffirm the universal nature of the r-process abundance pattern from Ba to Ir. The first r-process peak is significantly lower than solar but matches other r-process enhanced stars. This constrains the neutron-richness of r-process ejecta in neutron star mergers. The radioactive element thorium is detected with a somewhat low abundance. Naive application of currently predicted initial production ratios could imply an age >20 Gyr, but more likely indicates that the initial production ratios require revision. The abundance of lighter elements up to Zn are consistent with extremely metal-poor Milky Way halo stars. These elements may eventually provide a way to test for other hypothesized r-process sites, but only after a more detailed understanding of the chemical evolution in this galaxy. Reticulum II provides a clean view of early r-process enrichment that can be used to understand the increasing number of r-process measurements in other dwarf galaxies.

Globular clusters in high-redshift dwarf galaxies: a case study from the Local Group

NASA Astrophysics Data System (ADS)

Zick, Tom O.; Weisz, Daniel R.; Boylan-Kolchin, Michael

2018-06-01

We present the reconstructed evolution of rest-frame ultraviolet (UV) luminosities of the most massive Milky Way dwarf spheroidal satellite galaxy, Fornax, and its five globular clusters (GCs) across redshift, based on analysis of the stellar fossil record and stellar population synthesis modelling. We find that (1) Fornax's (proto-)GCs can generate 10-100 times more UV flux than the field population, despite comprising <˜{5} per cent of the stellar mass at the relevant redshifts; (2) due to their respective surface brightnesses, it is more likely that faint, compact sources in the Hubble Frontier Fields (HFFs) are GCs hosted by faint galaxies, than faint galaxies themselves. This may significantly complicate the construction of a galaxy UV luminosity function at z > 3. (3) GC formation can introduce order-of-magnitude errors in abundance matching. We also find that some compact HFF objects are consistent with the reconstructed properties of Fornax's GCs at the same redshifts (e.g. surface brightness, star formation rate), suggesting we may have already detected proto-GCs in the early Universe. Finally, we discuss the prospects for improving the connections between local GCs and proto-GCs detected in the early Universe.

Teaching the Thrill of Discovery: Student Exploration of Ultra-Faint Dwarf Galaxies with the NOAO Data Lab

NASA Astrophysics Data System (ADS)

Olsen, Knut; Walker, Constance E.; Smith, Blake; NOAO Data Lab Team

2018-01-01

We describe an activity aimed at teaching students how ultra-faint Milky Way dwarf galaxies are typically discovered: through filtering of optical photometric catalogs and cross-examination with deep images. The activity, which was developed as part of the Teen Astronomy Café program (https://teensciencecafe.org/cafes/az-teen-astronomy-cafe-tucson/), uses the NOAO Data Lab (http://datalab.noao.edu) and other professional-grade tools to lead high school students through exploration of the object catalog and images from the Survey of the Magellanic Stellar History (SMASH). The students are taught how to use images and color-magnitude diagrams to analyze and interpret stellar populations of increasing complexity, including those of star clusters and the Magellanic Clouds, and culminating with the discovery of the Hydra II ultra-faint dwarf galaxy. The tools and datasets presented allow the students to explore and discover other known stellar systems, as well as unknown candidate star clusters and dwarf galaxies. The ultimate goal of the activity is to give students insight into the methods of modern astronomical research and to allow them to participate in the thrill of discovery.

A LARGE AND FAINT PHOTOMETRIC CATALOG ON THE ECLIPTIC

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

Buie, Marc W.; Trilling, David E.; Wasserman, Lawrence H.

2011-06-01

A photometric catalog, developed for the calibration of the Deep Ecliptic Survey, is presented. The catalog contains 213,272 unique sources that were measured in V and R filters and transformed to the Johnson-Cousins systems using the Landolt standard catalog. All of the sources lie within 6{sup 0} of the ecliptic and cover all longitudes except for the densest stellar regions nearest the galactic center. Seventeen percent of the sources in the catalog are derived from three or more nights of observation. The catalog contains sources as faint as R {approx}19 but the largest fraction fall in the R {approx}15-16 (Vmore » {approx}16-17) mag range. All magnitude bins down to R = 19 have a significant fraction of objects with uncertainties {<=}0.1 mag.« less

Quantifying the abundance of faint, low-redshift satellite galaxies in the COSMOS survey

NASA Astrophysics Data System (ADS)

Xi, ChengYu; Taylor, James E.; Massey, Richard J.; Rhodes, Jason; Koekemoer, Anton; Salvato, Mara

2018-06-01

Faint dwarf satellite galaxies are important as tracers of small-scale structure, but remain poorly characterized outside the Local Group, due to the difficulty of identifying them consistently at larger distances. We review a recently proposed method for estimating the average satellite population around a given sample of nearby bright galaxies, using a combination of size and magnitude cuts (to select low-redshift dwarf galaxies preferentially) and clustering measurements (to estimate the fraction of true satellites in the cut sample). We test this method using the high-precision photometric redshift catalog of the COSMOS survey, exploring the effect of specific cuts on the clustering signal. The most effective of the size-magnitude cuts considered recover the clustering signal around low-redshift primaries (z < 0.15) with about two-thirds of the signal and 80% of the signal-to-noise ratio obtainable using the full COSMOS photometric redshifts. These cuts are also fairly efficient, with more than one third of the selected objects being clustered satellites. We conclude that structural selection represents a useful tool in characterizing dwarf populations to fainter magnitudes and/or over larger areas than are feasible with spectroscopic surveys. In reviewing the low-redshift content of the COSMOS field, we also note the existence of several dozen objects that appear resolved or partially resolved in the HST imaging, and are confirmed to be local (at distances of ˜250 Mpc or less) by their photometric or spectroscopic redshifts. This underlines the potential for future space-based surveys to reveal local populations of intrinsically faint galaxies through imaging alone.

Foreground effect on the J-factor estimation of ultra-faint dwarf spheroidal galaxies

NASA Astrophysics Data System (ADS)

Ichikawa, Koji; Horigome, Shun-ichi; Ishigaki, Miho N.; Matsumoto, Shigeki; Ibe, Masahiro; Sugai, Hajime; Hayashi, Kohei

2018-05-01

Dwarf spheroidal galaxies (dSphs) are promising targets for the gamma-ray dark matter (DM) search. In particular, DM annihilation signal is expected to be strong in some of the recently discovered nearby ultra-faint dSphs, which potentially give stringent constraints on the O(1) TeV WIMP DM. However, various non-negligible systematic uncertainties complicate the estimation of the astrophysical factors relevant for the DM search in these objects. Among them, the effects of foreground stars particularly attract attention because the contamination is unavoidable even for the future kinematical survey. In this article, we assess the effects of the foreground contamination on the astrophysical J-factor estimation by generating mock samples of stars in the four ultra-faint dSphs and using a model of future spectrographs. We investigate various data cuts to optimize the quality of the data and apply a likelihood analysis which takes member and foreground stellar distributions into account. We show that the foreground star contaminations in the signal region (the region of interest) and their statistical uncertainty can be estimated by interpolating the foreground star distribution in the control region where the foreground stars dominate the member stars. Such regions can be secured at future spectroscopic observations utilizing a multiple object spectrograph with a large field of view; e.g. the Prime Focus Spectrograph mounted on Subaru Telescope. The above estimation has several advantages: The data-driven estimation of the contamination makes the analysis of the astrophysical factor stable against the complicated foreground distribution. Besides, foreground contamination effect is considered in the likelihood analysis.

A Hubble Space Telescope survey for Novae in M87. II. Snuffing out the maximum magnitude–rate of decline relation for novae as a non-standard candle, and a prediction of the existence of ultrafast novae

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

Shara, Michael M.; Doyle, Trisha; Lauer, Tod R.

The extensive grid of numerical simulations of nova eruptions first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are inmore » the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10 –7–10 –8 M ⊙, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. As a result, these same models predict the existence of ultrafast novae that display decline times, t 2, to be as short as five hours. We outline a strategy for their future detection.« less

A Hubble Space Telescope Survey for Novae in M87. II. Snuffing out the Maximum Magnitude–Rate of Decline Relation for Novae as a Non-standard Candle, and a Prediction of the Existence of Ultrafast Novae

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

Shara, Michael M.; Doyle, Trisha; Zurek, David

The extensive grid of numerical simulations of nova eruptions from the work of Yaron et al. first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giantmore » elliptical galaxy M87 as they are in the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10{sup −7}–10{sup −8} M {sub ⊙}, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. These same models predict the existence of ultrafast novae that display decline times, t {sub 2,} to be as short as five hours. We outline a strategy for their future detection.« less

A Hubble Space Telescope survey for Novae in M87. II. Snuffing out the maximum magnitude–rate of decline relation for novae as a non-standard candle, and a prediction of the existence of ultrafast novae

DOE PAGES

Shara, Michael M.; Doyle, Trisha; Lauer, Tod R.; ...

2017-04-20

The extensive grid of numerical simulations of nova eruptions first predicted that some classical novae might significantly deviate from the Maximum Magnitude–Rate of Decline (MMRD) relation, which purports to characterize novae as standard candles. Kasliwal et al. have announced the observational detection of a new class of faint, fast classical novae in the Andromeda galaxy. These objects deviate strongly from the MMRD relationship, as predicted by Yaron et al. Recently, Shara et al. reported the first detections of faint, fast novae in M87. These previously overlooked objects are as common in the giant elliptical galaxy M87 as they are inmore » the giant spiral M31; they comprise about 40% of all classical nova eruptions and greatly increase the observational scatter in the MMRD relation. We use the extensive grid of the nova simulations of Yaron et al. to identify the underlying causes of the existence of faint, fast novae. These are systems that have accreted, and can thus eject, only very low-mass envelopes, of the order of 10 –7–10 –8 M ⊙, on massive white dwarfs. Such binaries include, but are not limited to, the recurrent novae. As a result, these same models predict the existence of ultrafast novae that display decline times, t 2, to be as short as five hours. We outline a strategy for their future detection.« less

A Peculiar Faint Satellite in the Remote Outer Halo of M31

NASA Astrophysics Data System (ADS)

Mackey, A. D.; Huxor, A. P.; Martin, N. F.; Ferguson, A. M. N.; Dotter, A.; McConnachie, A. W.; Ibata, R. A.; Irwin, M. J.; Lewis, G. F.; Sakari, C. M.; Tanvir, N. R.; Venn, K. A.

2013-06-01

We present Hubble Space Telescope imaging of a newly discovered faint stellar system, PAndAS-48, in the outskirts of the M31 halo. Our photometry reveals this object to be comprised of an ancient and very metal-poor stellar population with age >~ 10 Gyr and [Fe/H] lsim -2.3. Our inferred distance modulus (m - M)0 = 24.57 ± 0.11 confirms that PAndAS-48 is most likely a remote M31 satellite with a three-dimensional galactocentric radius of 149^{+19}_{-8} kpc. We observe an apparent spread in color on the upper red giant branch that is larger than the photometric uncertainties should allow, and briefly explore the implications of this. Structurally, PAndAS-48 is diffuse, faint, and moderately flattened, with a half-light radius r_h=26^{+4}_{-3} pc, integrated luminosity MV = -4.8 ± 0.5, and ellipticity \\epsilon =0.30^{+0.08}_{-0.15}. On the size-luminosity plane it falls between the extended globular clusters seen in several nearby galaxies and the recently discovered faint dwarf satellites of the Milky Way; however, its characteristics do not allow us to unambiguously classify it as either type of system. If PAndAS-48 is a globular cluster then it is among the most elliptical, isolated, and metal-poor of any seen in the Local Group, extended or otherwise. Conversely, while its properties are generally consistent with those observed for the faint Milky Way dwarfs, it would be a factor of ~2-3 smaller in spatial extent than any known counterpart of comparable luminosity. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program GO 12515.

Galaxy modelling. II. Multi-wavelength faint counts from a semi-analytic model of galaxy formation

NASA Astrophysics Data System (ADS)

Devriendt, J. E. G.; Guiderdoni, B.

2000-11-01

This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The stardust spectral energy distributions described in Devriendt et al. \\citeparyear{DGS99} (Paper I) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We begin with a description of the non-dissipative and dissipative collapses of primordial perturbations, and plug in standard recipes for star formation, stellar evolution and feedback. We also model the absorption of starlight by dust and its re-processing in the IR and submm. We then build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of Omega_0 , or a flat universe with a non-zero cosmological constant. We confirm the suggestion of Guiderdoni et al. \\citeparyear{GHBM98} that matching the current multi-wavelength data requires a population of heavily-extinguished, massive galaxies with large star formation rates ( ~ 500 M_sun yr-1) at intermediate and high redshift (z >= 1.5). Such a population of objects probably is the consequence of an increase of interaction and merging activity at high redshift, but a realistic quantitative description can only be obtained through more detailed modelling of such processes. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux levels.

The correlation between malaria RDT (Paracheck pf.®) faint test bands and microscopy in the diagnosis of malaria in Malawi.

PubMed

Makuuchi, Ryoko; Jere, Sandy; Hasejima, Nobuchika; Chigeda, Thoms; Gausi, January

2017-05-02

Faint test bands of Paracheck Pf.® are interpreted as malaria positive according to world health organization (WHO) guideline. However if there are conspicuous number of faint test bands, a performance of Paracheck Pf.® could be influenced depending on whether interpreting faint test bands as malaria positive or negative. Finding out the frequency and accurate interpretation of faint test bands are important to prevent the overdiagnosis and drug resistance. A cross-sectional, descriptive study was conducted to find out the frequency of faint test bands and evaluate the performance of Paracheck Pf.® by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy of diagnosis of Paracheck Pf.® using microscopy as the gold standard. 388 suspected patients with malaria in Malawi were recruited in this study. Malaria rapid diagnostic tests (RDTs) and microscopy were used and patients' information which includes age, sex, body temperature and signs or symptoms of malaria were recorded. Among all patients involved in the study, 29.1% (113/388) were found malaria positive by RDT. Overall 5.4% (21/388) of all Paracheck Pf.® tests resulted in a "faint test band" and 85.7% (18/21) corresponded with malaria negative by microscopy. Faint test bands which corresponded with malaria positive by microscopy were lower parasite density and there are no patients who showed definitive symptom of malaria, such as fever. When Paracheck Pf.® "faint test bands" were classified as positive, accuracy of diagnosis was 76.5% (95% CI 72%-80.7%) as compared to 80.4% (95% CI 76.1%-84.2%) when Paracheck Pf.® "faint test bands" were classified as negative. This study shows that frequency of faint test bands is 5.4% in all malaria RDTs. The accuracy of diagnosis was improved when faint test bands were interpreted as malaria negative. However information and data obtained in this study may not be enough and more intensive research including a frequency and property of faint test bands is needed for significant interpretation of faint test bands.

X-Ray Astronomy--A New View of the Sky From Space

ERIC Educational Resources Information Center

Gursky, Herbert

1973-01-01

Objects and energy sources are detected whose existence was only hinted at a few years ago. The X-Ray sky has a large number of sources along the Milky Way, most of which lie within 30 degrees of the galactic center, plus a number of faint sources associated with external galaxies. (DF)

Fireball multi object spectrograph: as-built optic performances

NASA Astrophysics Data System (ADS)

Grange, R.; Milliard, B.; Lemaitre, G.; Quiret, S.; Pascal, S.; Origné, A.; Hamden, E.; Schiminovich, D.

2016-07-01

Fireball (Faint Intergalactic Redshifted Emission Balloon) is a NASA/CNES balloon-borne experiment to study the faint diffuse circumgalactic medium from the line emissions in the ultraviolet (200 nm) above 37 km flight altitude. Fireball relies on a Multi Object Spectrograph (MOS) that takes full advantage of the new high QE, low noise 13 μm pixels UV EMCCD. The MOS is fed by a 1 meter diameter parabola with an extended field (1000 arcmin2) using a highly aspherized two mirror corrector. All the optical train is working at F/2.5 to maintain a high signal to noise ratio. The spectrograph (R 2200 and 1.5 arcsec FWHM) is based on two identical Schmidt systems acting as collimator and camera sharing a 2400 g/mm aspherized reflective Schmidt grating. This grating is manufactured from active optics methods by double replication technique of a metal deformable matrix whose active clear aperture is built-in to a rigid elliptical contour. The payload and gondola are presently under integration at LAM. We will present the alignment procedure and the as-built optic performances of the Fireball instrument.

VLBI observations of Infrared-Faint Radio Sources

NASA Astrophysics Data System (ADS)

Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

2006-10-01

We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

A search for AGN activity in Infrared-Faint Radio Sources (IFRS)

NASA Astrophysics Data System (ADS)

Lenc, Emil; Middelberg, Enno; Norris, Ray; Mao, Minnie

2009-04-01

We propose to observe a large sample of radio sources from the ATLAS (Australia Telescope Large Area Survey) source catalogue with the LBA, to determine their compactness. The sample consists of 36 sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubber Infrared-Faint Radio Sources (IFRS), is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations. We will measure the flux densities on long baselines to determine their compactness. Only five IFRS have been previously targeted with VLBI observations (resulting in two detections). We propose using single baseline (Parkes-ATCA) eVLBI observations with the LBA at 1 Gbps to maximise sensitivity. With the observations proposed here we will increase the number of VLBI-observed IFRS from 5 to 36, allowing us to draw statistical conclusions about this intriguing new class of objects.

A search for AGN activity in Infrared-Faint Radio Sources (IFRS)

NASA Astrophysics Data System (ADS)

Lenc, Emil; Middelberg, Enno; Norris, Ray; Mao, Minnie

2010-04-01

We propose to observe a large sample of radio sources from the ATLAS (Australia Telescope Large Area Survey) source catalogue with the LBA, to determine their compactness. The sample consists of 36 sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubber Infrared-Faint Radio Sources (IFRS), is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations. We will measure the flux densities on long baselines to determine their compactness. Only five IFRS have been previously targeted with VLBI observations (resulting in two detections). We propose using single baseline (Parkes-ATCA) eVLBI observations with the LBA at 1 Gbps to maximise sensitivity. With the observations proposed here we will increase the number of VLBI-observed IFRS from 5 to 36, allowing us to draw statistical conclusions about this intriguing new class of objects.

Eight new Milky Way companions discovered in first-year Dark Energy Survey data

DOE PAGES

Bechtol, K.

2015-06-30

We report the discovery of eight new Milky Way companions inmore » $$\\sim 1800\\;{\\mathrm{deg}}^{2}$$ of optical imaging data collected during the first year of the Dark Energy Survey (DES). Each system is identified as a statistically significant over-density of individual stars consistent with the expected isochrone and luminosity function of an old and metal-poor stellar population. The objects span a wide range of absolute magnitudes (MV from $-2.2$ to $$-7.4\\;\\mathrm{mag}$$), physical sizes ($$10-170\\;\\mathrm{pc}$$), and heliocentric distances ($$30-330\\;\\mathrm{kpc}$$). Based on the low surface brightnesses, large physical sizes, and/or large Galactocentric distances of these objects, several are likely to be new ultra-faint satellite galaxies of the Milky Way and/or Magellanic Clouds. We introduce a likelihood-based algorithm to search for and characterize stellar over-densities, as well as identify stars with high satellite membership probabilities. As a result, we also present completeness estimates for detecting ultra-faint galaxies of varying luminosities, sizes, and heliocentric distances in the first-year DES data.« less

The Hunt for Missing Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-11-01

Theories of galaxy formation and evolution predict that there should be significantly more dwarf galaxies than have been observed. Are our theories wrong? Or are dwarf galaxies just difficult to detect? Recent results from a survey of a galaxy cluster 62 million light-years away suggest there may be lots of undiscovered dwarf galaxies hiding throughout the universe!Hiding in FaintnessThe missing dwarf problem has had hints of a resolution with the recent discovery of Ultra-Diffuse Galaxies (UDGs) in the Coma and Virgo galaxy clusters. UDGs have low masses and large radii, resulting in a very low surface brightness that makes them extremely difficult to detect. If many dwarfs are UDGs, this could well explain why weve been missing them!But the Coma and Virgo galaxy clusters are similar in that theyre both very massive. Are there UDGs in other galaxy clusters as well? To answer this question, an international team of scientists is running the Next Generation Fornax Survey (NGFS), a survey searching for faint dwarf galaxies in the central 30 square degrees of the Fornax galaxy cluster.The NGFS uses near-UV and optical observations from the Dark Energy Camera mounted on the 4m Blanco Telescope in Chile. The survey is still underway, but in a recent publication led by Roberto P. Muoz (Institute of Astrophysics at the Pontifical Catholic University of Chile), the team has released an overview of the first results from only the central 3 square degrees of the NGFS field.Surprising DetectionGalaxy radii vs. their absolute i-band magnitudes, for the dwarfs found in NGFS as well as other stellar systems in the nearby universe. The NGFS dwarfs are similar to the ultra-diffuse dwarfs found in the Virgo and Coma clusters, but are several orders of magnitude fainter. [Muoz et al. 2015]In just this small central field, the team has found an astounding 284 low-surface-brightness dwarf galaxy candidates 158 of them previously undetected. At the bright end of this sample are dwarf galaxies that resemble the UDGs found in Virgo and Coma clusters, verifying that such objects exist in environments beyond only massive clusters.And at the faint end of the sample, the authors find additional extremely low-surface-brightness dwarfs that are several orders of magnitude fainter even than classical UDGs.The authors describe the properties of these galaxies and compare them to systems like classical UDGs and dwarf spheroidal galaxies in our own Local Cluster. The next step is to determine which of the differences between the sample of NGFS dwarfs and previously known systems are explained by the environmental factors of their host cluster, and which are simply due to sample biases.With much more data from the NGFS still to come, it seems likely that we will soon be able to examine an even larger sample of no-longer-missing dwarfs!CitationRoberto P. Muoz et al 2015 ApJ 813 L15. doi:10.1088/2041-8205/813/1/L15

Variable Stars in the Field of the Hydra II Ultra-faint Dwarf Galaxy

NASA Astrophysics Data System (ADS)

Vivas, A. Katherina; Olsen, Knut; Blum, Robert; Nidever, David L.; Walker, Alistair R.; Martin, Nicolas F.; Besla, Gurtina; Gallart, Carme; van der Marel, Roeland P.; Majewski, Steven R.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Saha, Abhijit; Conn, Blair C.; Jin, Shoko

2016-05-01

We report the discovery of one RR Lyrae star in the ultra-faint satellite galaxy Hydra II based on time series photometry in the g, r and I bands obtained with the Dark Energy Camera at Cerro Tololo Inter-American Observatory, Chile. The association of the RR Lyrae star discovered here with Hydra II is clear because is located at 42\\prime\\prime from the center of the dwarf, well within its half-light radius of 102\\prime\\prime . The RR Lyrae star has a mean magnitude of I=21.30+/- 0.04 which is too faint to be a field halo star. This magnitude translates to a heliocentric distance of 151 ± 8 kpc for Hydra II; this value is ˜ 13% larger than the estimate from the discovery paper based on the average magnitude of several blue horizontal branch star candidates. The new distance implies a slightly larger half-light radius of {76}-10+12 pc and a brighter absolute magnitude of {M}V=-5.1+/- 0.3, which keeps this object within the realm of the dwarf galaxies. A comparison with other RR Lyrae stars in ultra-faint systems indicates similar pulsational properties among them, which are different to those found among halo field stars and those in the largest of the Milky Way satellites. We also report the discovery of 31 additional short period variables in the field of view (RR Lyrae, SX Phe, eclipsing binaries, and a likely anomalous cepheid) which are likely not related with Hydra II.

Improving space debris detection in GEO ring using image deconvolution

NASA Astrophysics Data System (ADS)

Núñez, Jorge; Núñez, Anna; Montojo, Francisco Javier; Condominas, Marta

2015-07-01

In this paper we present a method based on image deconvolution to improve the detection of space debris, mainly in the geostationary ring. Among the deconvolution methods we chose the iterative Richardson-Lucy (R-L), as the method that achieves better goals with a reasonable amount of computation. For this work, we used two sets of real 4096 × 4096 pixel test images obtained with the Telescope Fabra-ROA at Montsec (TFRM). Using the first set of data, we establish the optimal number of iterations in 7, and applying the R-L method with 7 iterations to the images, we show that the astrometric accuracy does not vary significantly while the limiting magnitude of the deconvolved images increases significantly compared to the original ones. The increase is in average about 1.0 magnitude, which means that objects up to 2.5 times fainter can be detected after deconvolution. The application of the method to the second set of test images, which includes several faint objects, shows that, after deconvolution, up to four previously undetected faint objects are detected in a single frame. Finally, we carried out a study of some economic aspects of applying the deconvolution method, showing that an important economic impact can be envisaged.

An optical survey for space debris on highly eccentric and inclined MEO orbits

NASA Astrophysics Data System (ADS)

Schildknecht, Thomas; Flohrer, Tim; Hinze, Andreas; Vananti, Alessandro; Silha, Jiri

Optical surveys for space debris in high-altitude orbits have been conducted since more than fifteen years. Originally these efforts concentrated mainly on the geostationary ring (GEO) and its close region. Corresponding observation strategies, processing techniques and cataloguing approaches have been developed and successfully applied. The ESA GEO surveys, e.g., resulted in the detection of a significant population of small-size debris and later in the discovery of high area-to-mass ratio objects in GEO-like orbits. The observation scenarios were successively adapted to survey the geostationary transfer orbit (GTO) region; and surveys to search for debris in the medium Earth orbit (MEO) region of the global navigation satellite constellations were successfully conducted. Comparably less experience (both, in terms of practical observation and strategy definition) is available for eccentric orbits that (at least partly) are in the MEO region, in particular for the Molniya-type orbits. Several breakup events and deliberate fragmentations are known to have taken place in such orbits. Survey and follow-up strategies for searching space debris objects in highly-eccentric MEO orbits, and to acquire orbits which are sufficiently accurate to catalogue such objects and to maintain their orbits over longer time spans were developed and, eventually, optical observations were conducted in the framework of an ESA study using ESA' Space Debris Telescope (ESASDT) the 1-m Zeiss telescope located at the Optical Ground Station (OGS) at the Teide Observatory at Tenerife, Spain. Thirteen nights of surveys of Molniya-type orbits was performed between January and August 2013. A basic survey consisted of observing a single geocentric field for 10 minutes. If a faint object was found, follow-up observations were performed during the same night to ensure a save rediscovery of the object during the next nights. Additional follow-up observations to maintain the orbits of these newly discovered faint objects were also acquired with AIUB's 1 m ZIMLAT telescope in Zimmerwald, Switzerland. Eventually, 255 basic surveys were performed during these thirteen nights corresponding to about 47 hours of observations. In total 30 uncorrelated faint objects were discovered. On average one uncorrelated object was found every 100 minutes. Some of these objects show a considerable brightness variation and have a high area-to-mass ratio as determined in the orbit estimation process. We also investigated the detection efficiency of our surveys by comparing the observation results with the TLE population by means of ESA's PROOF tool. Furthermore a comparison of the real detections with the statistical population of the ESA MASTER-2009 model was performed. The result shows that the fragment population of objects in Molniya-type orbits is underestimated in the MASTER model.

The effect of recognizability on figure-ground processing: does it affect parsing or only figure selection?

PubMed

Navon, David

2011-03-01

Though figure-ground assignment has been shown to be probably affected by recognizability, it appears sensible that object recognition must follow at least the earlier process of figure-ground segregation. To examine whether or not rudimentary object recognition could, counterintuitively, start even before the completion of the stage of parsing in which figure-ground segregation is done, participants were asked to respond, in a go/no-go fashion, whenever any out of 16 alternative connected patterns (that constituted familiar stimuli in the upright orientation) appeared. The white figure of the to-be-attended stimulus-target or foil-could be segregated from the white ambient ground only by means of a frame surrounding it. Such a frame was absent until the onset of target display. Then, to manipulate organizational quality, the greyness of the frame was either gradually increased from zero (in Experiment 1) or changed abruptly to a stationary level whose greyness was varied between trials (in Experiments 2 and 3). Stimulus recognizability was manipulated by orientation angle. In all three experiments the effect of recognizability was found to be considerably larger when organizational quality was minimal due to an extremely faint frame. This result is argued to be incompatible with any version of a serial thesis suggesting that processing aimed at object recognition starts only with a good enough level of organizational quality. The experiments rather provide some support to the claim, termed here "early interaction hypothesis", positing interaction between early recognition processing and preassignment parsing processes.

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.

Astro-1 Image Taken by Ultraviolet Imaging Telescope

NASA Technical Reports Server (NTRS)

1990-01-01

This image shows a part of the Cygnus loop supernova remnant, taken by the Ultraviolet Imaging Telescope (UIT) on the Astro Observatory during the Astro-1 mission (STS-35) on December 5, 1990. Pictured is a portion of the huge Cygnus loop, an array of interstellar gas clouds that have been blasted by a 900,000 mile per hour shock wave from a prehistoric stellar explosion, which occurred about 20,000 years ago, known as supernova. With ultraviolet and x-rays, astronomers can see emissions from extremely hot gases, intense magnetic fields, and other high-energy phenomena that more faintly appear in visible and infrared light or in radio waves that are crucial to deepening the understanding of the universe. The Astro Observatory was designed to explore the universe by observing and measuring the ultraviolet radiation from celestial objects. Three instruments make up the Astro Observatory: The Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE). The Marshall Space Flight Center had managment responsibilities for the Astro-1 mission. The Astro-1 Observatory was launched aboard the Space Shuttle Orbiter Columbia (STS-35) on December 2, 1990.

Blue stragglers in the core of the globular cluster 47 Tucanae

NASA Technical Reports Server (NTRS)

Paresce, F.; Meylan, G.; Shara, M.; Baxter, D.; Greenfield, P.

1991-01-01

High-resolution observations of the core of the globular cluster 47 Tucanae with the Faint Object Camera on the Hubble Space Telescope reveal a high density of 'blue straggler' stars, occupying the upper end of the main sequence from which all stars in the cluster should have long since evolved. Their presence in the dense core supports the hypothesis that they formed by stellar collision and coalescence, and, as the heaviest objects in the cluster, have drifted to the core.

High resolution imaging of galaxy cores

NASA Technical Reports Server (NTRS)

Crane, P.; Stiavelli, M.; King, I. R.; Deharveng, J. M.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Disney, M. J.; Jakobsen, P.

1993-01-01

Surface photometry data obtained with the Faint Object Camera of the Hubble Space Telescope in the cores of ten galaxies is presented. The major results are: (1) none of the galaxies show truly 'isothermal' cores, (2) galaxies with nuclear activity show very similar light profiles, (3) all objects show central mass densities above 10 exp 3 solar masses/cu pc3, and (4) four of the galaxies (M87, NGC 3862, NGC 4594, NGC 6251) show evidence for exceptional nuclear mass concentrations.

ARC-1986-AC86-7015

NASA Image and Video Library

1986-01-21

4.17 million miles (2.59 million miles) Resolution : 40 km. (25mi.) P-29498C This false color, Voyager 2 composite view of all nine of Uranian rings was made from six 15 second exposures through the narrow angle camera. The special computer processing used to extract color information from the extremely dark and faint rings, causing the even fainter, pastel lines seen between the rings. Two images, each in the green, clear, & violet filters, were added together and averaged to find the proper color difference between the rings. the final image was made from these three color averages and represents an enhanced, false color view. The image shows that the brightest, or Epsilon ring, at top ,is neutral in color, with the fainter eight other rings showing color differences between them. moving down, toward, Uranus, we see the Delta, Gamma, & Eta rings in shades of blue and green; the Beta & Alpha rings in somewhat lighter tones; and then finally, a set of three, known simply as 4, 5, & 6 rings, in faint off-white tones. Scientists will use this color information to try to understand the nature and origin of the ring material.

One- and two-mode squeezed light in correlated interferometry

NASA Astrophysics Data System (ADS)

Ruo-Berchera, I.; Degiovanni, I. P.; Olivares, S.; Samantaray, N.; Traina, P.; Genovese, M.

2015-11-01

We study in detail a system of two interferometers aimed at detecting extremely faint phase fluctuations. This system can represent a breakthrough for detecting a faint correlated signal that would remain otherwise undetectable even using the most sensitive individual interferometric devices, as in the case of so-called holographic noise. The signature of this kind of noise emerges as a correlation between the output signals of the interferometers. On the other hand, when holographic noise is absent one expects uncorrelated signals since the time-averaged fluctuations due to shot noise and other independent contributions vanish (though limiting the overall sensitivity). We show how injecting quantum light in the free ports of the interferometers can reduce the photon noise of the system beyond the shot noise, enhancing the resolution in the phase-correlation estimation. We analyze the use of both the two-mode squeezed vacuum and two independent squeezed states. Our results confirm the benefit of using squeezed beams together with strong coherent beams in interferometry. We also investigate the possible use of the two-mode squeezed vacuum, discovering interesting and unexplored areas of application of bipartite entanglement, in particular the possibility of reaching in principle a surprising uncertainty reduction.

The Distribution of Fixation Durations during Reading: Effects of Stimulus Quality

ERIC Educational Resources Information Center

White, Sarah J.; Staub, Adrian

2012-01-01

Participants' eye movements were recorded as they read single sentences presented normally, presented entirely in faint text, or presented normally except for a single faint word. Fixations were longer when the entire sentence was faint than when the sentence was presented normally. In addition, fixations were much longer on a single faint word…

Get Ready for Gaia: Cool White Dwarfs in Common Proper Motion with Tycho Stars

NASA Astrophysics Data System (ADS)

Hambly, N.; Rowell, N.; Lam, M.

2017-03-01

We discuss the Gaia Data Release 1 (September 2016) and preliminary work on maximising the benefit for cool white dwarf (WD) science in advance of the full parallax catalogue which will appear around one year later in DR2. The Tycho catalogue is used in conjunction with the all-sky ground based astrometric/ photometric SuperCOSMOS Sky Survey in order to identify candidate faint common proper motion objects to the Tycho stars. Gaia DR1 is supplemented by the Tycho-Gaia Astrometric Solution catalogue containing some 2 million parallaxes with Hipparcos-like precision for Tycho stars. While hotter, brighter WDs are present in Tycho, cooler examples are much rarer (if present at all) and CPM offers one method to infer precision distances for a statistically useful sample of these very faint WDs.

Fainting

MedlinePlus

... in older people. Some causes of fainting include Heat or dehydration Emotional distress Standing up too quickly Certain medicines Drop in blood sugar Heart problems When someone faints, make sure that the ...

The LST scientific instruments

NASA Technical Reports Server (NTRS)

Levin, G. M.

1975-01-01

Seven scientific instruments are presently being studied for use with the Large Space Telescope (LST). These instruments are the F/24 Field Camera, the F/48-F/96 Planetary Camera, the High Resolution Spectrograph, the Faint Object Spectrograph, the Infrared Photometer, and the Astrometer. These instruments are being designed as facility instruments to be replaceable during the life of the Observatory.

High Energy Astronomy Observatory (HEAO)

NASA Image and Video Library

1959-01-01

This image is of the Crab Nebula in visible light photographed by the Hale Observatory optical telescope in 1959. The faint object at the center had been identified as a pulsar and is thought to be the remains of the original star. It had been observed as a pulsar in visible light, radio wave, x-rays, and gamma-rays.

Clasificación de asterismos utilizando datos astrométricos

NASA Astrophysics Data System (ADS)

de Biasi, M. S.; Orellana, R. B.

Based on accurate positions and proper motion data up to faint magnitudes, we have studied the regions of twenty three objects known in the literature as asterisms. A parametric method was applied to confirm the nature of these objects. The following objects have been classified: Alessi 11, Alessi 17, Brosch 1, Collinder 21, Dol-Dzim 1, Dolidze 31, Dolidze 43, Dolidze 50, Dolidze 51, NGC 272, NGC2063, NGC 2413, NGC 2664, NGC 5155, NGC 5284, NGC 6222, NGC 6360, NGC 6447, NGC 6476, NGC 6480, NGC 6605, NGC 6659, NGC 6728. FULL TEXT IN SPANISH

VizieR Online Data Catalog: Faint blue objects at high galactic latitude (Mitchell+, 2004)

NASA Astrophysics Data System (ADS)

Mitchell, K. J.; Usher, P. D.

2006-11-01

The US (UV-excess Starlike) survey has cataloged 3987 objects in 7 high Galactic latitude fields according to their optical colors, magnitudes, and morphologies using photographic techniques. This paper analyzes the effectiveness of the survey at producing finding lists for complete samples of hot stars and quasars that exhibit blue and/or ultraviolet excess (B-UVX) relative to the colors of halo F and G subdwarf stars. A table of 599 spectroscopic identifications summarizes the spectroscopic coverage of the US objects that has been accomplished to date. (6 data files).

Near-Earth Object (NEO) Hazard Background

NASA Technical Reports Server (NTRS)

Mazanek, Daniel D.

2005-01-01

The fundamental problem regarding NEO hazards is that the Earth and other planets, as well as their moons, share the solar system with a vast number of small planetary bodies and orbiting debris. Objects of substantial size are typically classified as either comets or asteroids. Although the solar system is quite expansive, the planets and moons (as well as the Sun) are occasionally impacted by these objects. We live in a cosmic shooting gallery where collisions with Earth occur on a regular basis. Because the number of smaller comets and asteroids is believed to be much greater than larger objects, the frequency of impacts is significantly higher. Fortunately, the smaller objects, which are much more numerous, are usually neutralized by the Earth's protective atmosphere. It is estimated that between 1000 and 10,000 tons of debris fall to Earth each year, most of it in the form of dust particles and extremely small meteorites. With no atmosphere, the Moon's surface is continuously impacted with dust and small debris. On November 17 and 18, 1999, during the annual Leonid meteor shower, several lunar surface impacts were observed by amateur astronomers in North America. The Leonids result from the Earth's passage each year through the debris ejected from Comet Tempel-Tuttle. These annual showers provide a periodic reminder of the possibility of a much more consequential cosmic collision, and the heavily cratered lunar surface acts a constant testimony to the impact threat. The impact problem and those planetary bodies that are a threat have been discussed in great depth in a wide range of publications and books, such as The Spaceguard Survey , Hazards Due to Comets and Asteroids, and Cosmic Catastrophes. This paper gives a brief overview on the background of this problem and address some limitations of ground-based surveys for detection of small and/or faint near-Earth objects.

Detection and Characterization of Exoplanets using Projections on Karhunen-Loeve Eigenimages: Forward Modeling

NASA Astrophysics Data System (ADS)

Pueyo, Laurent

2016-01-01

A new class of high-contrast image analysis algorithms, that empirically fit and subtract systematic noise has lead to recent discoveries of faint exoplanet /substellar companions and scattered light images of circumstellar disks. The consensus emerging in the community is that these methods are extremely efficient at enhancing the detectability of faint astrophysical signal, but do generally create systematic biases in their observed properties. This poster provides a solution this outstanding problem. We present an analytical derivation of a linear expansion that captures the impact of astrophysical over/self-subtraction in current image analysis techniques. We examine the general case for which the reference images of the astrophysical scene moves azimuthally and/or radially across the field of view as a result of the observation strategy. Our new method method is based on perturbing the covariance matrix underlying any least-squares speckles problem and propagating this perturbation through the data analysis algorithm. This work is presented in the framework of Karhunen-Loeve Image Processing (KLIP) but it can be easily generalized to methods relying on linear combination of images (instead of eigen-modes). Based on this linear expansion, obtained in the most general case, we then demonstrate practical applications of this new algorithm. We first consider the case of the spectral extraction of faint point sources in IFS data and illustrate, using public Gemini Planet Imager commissioning data, that our novel perturbation based Forward Modeling (which we named KLIP-FM) can indeed alleviate algorithmic biases. We then apply KLIP-FM to the detection of point sources and show how it decreases the rate of false negatives while keeping the rate of false positives unchanged when compared to classical KLIP. This can potentially have important consequences on the design of follow-up strategies of ongoing direct imaging surveys.

The Properties of Faint Field Galaxies

NASA Astrophysics Data System (ADS)

Driver, Simon. P.

1994-12-01

One of the current drawbacks of Charge Coupled Devices (CCDs) is their restrictive fields of view. The Hitchhiker CCD camera overcomes this limitation by operating in parallel with existing instrumentation and is able to cover a large area as well as large volumes. Hitchhiker is mounted on the 4.2m William Herschel Telescope and has been operating for two years. The first use of the Hitchhiker data set has been to study the general properties of faint galaxies. The observed trend of how the differential numbers of galaxies vary with magnitude agrees extremely well with those of other groups and covers, for the first time, all four major optical bandpasses. This multi-band capability has also allowed the study of how the colors of galaxies change with magnitude and how the correlation of galaxies on the sky varies between the optical bandpasses. A dwarf dominated model has been developed to explain these observations and challenges our knowledge of the space-density of dwarf galaxies. The model demonstrates that a simple upward turn in the luminosity distribution of galaxies, similar to that observed in clusters, would remain undetected by the field surveys yet can explain many of the observations without recourse to non-passive galaxy evolution. The conclusion is that the field luminosity distribution is not constrained at faint absolute magnitudes. A combination of a high density of dwarf galaxies and mild evolution could explain all the observations. Continuing work with HST and the Medium Deep Survey Team now reveals the morphological mix of galaxies down to mI ~ 24.0. The results confirm that ellipticals and early-type spirals are well fitted by standard no-evolution models whilst the late-type spirals can only be fitted by strong evolution and/or a significant turn-up in the local field LF.

Kinematic, Photometric, and Spectroscopic Properties of Faint White Dwarf Stars Discovered in the HALO7D Survey of the Milky Way Galaxy

NASA Astrophysics Data System (ADS)

Harris, Madison; Cunningham, Emily; Guhathakurta, Puragra; Cheshire, Ishani; Gupta, Nandita

2018-01-01

White dwarf (WD) stars represent the final phase in the life of solar-mass stars. The extreme low luminosity of WDs means that most detailed measurements of such stars are limited to samples in the immediate neighborhood of the Sun in the thin disk of the Milky Way galaxy. We present spectra, line-of-sight (LOS) velocities, and proper motions (PMs) of a sample of faint (m_V ~ 19.0–24.5) white dwarfs (WDs) from the HALO7D survey. HALO7D is a Keck II/DEIMOS spectroscopic survey of unprecedented depth (8–24 hour integrations) in the CANDELS fields of main sequence turnoff stars in the Milky Way's outer halo. Faint WD stars are rare but useful by-products of this survey. We identify the sample of WDs based on their characteristic broad spectral Balmer absorption features, and present a Bayesian method for measuring their LOS velocities. Using their broadband colors, LOS velocities and PMs measured with the Hubble Space Telescope, we identify candidate halo members among the WDs based on the predicted velocity distributions from the Besançon numerical model of stellar populations in the Milky Way galaxy. The WDs found in the HALO7D survey will yield new insights on the old stellar population associated with the Milky Way's thick disk and halo. Funding for this research was provided by the National Science Foundation and NASA/STScI. NG and IC's participation in this research was under the auspices of the Science Internship Program at the University of California Santa Cruz.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2013-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs {WDs}. A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: {1} Procyon {P = 40.83 yr}, containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. {2} Sirius {P = 50.14 yr}, an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. {3} Mu Cas {P = 21.08 yr}, a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: {1} G 107-70 {P = 18.84 yr}, and {2} WD 1818+126 {P = 12.19 yr}. Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2015-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs (WDs). A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: (1) Procyon (P = 40.83 yr), containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. (2) Sirius (P = 50.14 yr), an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. (3) Mu Cas (P = 21.08 yr), a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: (1) G 107-70 (P = 18.84 yr), and (2) WD 1818+126 (P = 12.19 yr). Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

HST Observations of Astrophysically Important Visual Binaries

NASA Astrophysics Data System (ADS)

Bond, Howard

2014-10-01

We propose to continue our long-term program of astrometry of close visual binaries, with the primary goal of determining purely dynamical masses for 3 important main-sequence stars and 9 white dwarfs (WDs). A secondary aim is to set limits on third bodies in the systems down to planetary mass. Three of our targets are naked-eye stars with much fainter companions that are extremely difficult to image from the ground. Our other 2 targets are double WDs, whose small separations and faintness likewise make them difficult to measure using ground-based techniques. Observations have been completed for a 3rd double WD.The bright stars, to be imaged with WFC3, are: (1) Procyon (P = 40.83 yr), containing a bright F star and a much fainter WD companion. With the continued monitoring proposed here, we will obtain masses to an accuracy of better than 1%, providing a testbed for theories of both Sun-like stars and WDs. (2) Sirius (P = 50.14 yr), an A-type star also having a faint WD companion, Sirius B, the nearest and brightest of all WDs. (3) Mu Cas (P = 21.08 yr), a nearby metal-deficient G dwarf for which accurate masses will lead to the stars' helium contents, with cosmological implications. The faint double WDs, to be observed with FGS, are: (1) G 107-70 (P = 18.84 yr), and (2) WD 1818+126 (P = 12.19 yr). Our astrometry of these systems will add 4 accurate masses to the handful of WD masses that are directly known from dynamical measurements. The FGS measurements will also provide precise parallaxes for the systems, a necessary ingredient in the mass determinations.

A spectroscopic search for faint secondaries in cataclysmic variables

NASA Astrophysics Data System (ADS)

Vande Putte, D.; Smith, Robert Connon; Hawkins, N. A.; Martin, J. S.

2003-06-01

The secondary in cataclysmic variables (CVs) is usually detected by cross-correlation of the CV spectrum with that of a K or M dwarf template, to produce a radial velocity curve. Although this method has demonstrated its power, it has its limits in the case of noisy spectra, such as are found when the secondary is faint. A method of coadding spectra, called skew mapping, has been proposed in the past. Gradually, examples of its application are being published; none the less, so far no journal article has described the technique in detail. To answer this need, this paper explores in detail the capabilities of skew mapping when determining the amplitude of the radial velocity for faint secondaries. It demonstrates the power of the method over techniques that are more conventional, when the signal-to-noise ratio is poor. The paper suggests an approach to assessing the quality of results. This leads in the case of the investigated objects to a first tier of results, where we find K2= 127 +/- 23 km s-1 for SY Cnc, K2= 144 +/- 18 km s-1 for RW Sex and K2= 262 +/- 14 km s-1 for UX UMa. These we believe to be the first direct determinations of K2 for these objects. Furthermore, we also obtain K2= 263 +/- 30 km s-1 for RW Tri, close to a skew mapping result obtained elsewhere. In the first three cases, we use these results to derive the mass of the white dwarf companion. A second tier of results includes UU Aqr, EX Hya and LX Ser, for which we propose more tentative values of K2. Clear failures of the method are also discussed (EF Eri, VV Pup and SW Sex).

DEEP IMAGING OF M51: A NEW VIEW OF THE WHIRLPOOL’S EXTENDED TIDAL DEBRIS

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

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

We present deep, wide-field imaging of the M51 system using CWRU’s Burrell Schmidt Telescope at KPNO to study the faint tidal features that constrain its interaction history. Our images trace M51's tidal morphology down to a limiting surface brightness of μ{sub B,lim} ∼ 30 mag arcsec{sup −2} and provide accurate colors (σ{sub B−V}<0.1) down to μ{sub B} ∼ 28. We identify two new tidal streams in the system (the south and northeast plumes) with surface brightnesses of μ{sub B} = 29 and luminosities of ∼10{sup 6}L{sub ⊙,B}. While the northeast plume may be a faint outer extension of the tidalmore » “crown” north of NGC 5195 (M51b), the south plume has no analog in any existing M51 simulation and may represent a distinct tidal stream or disrupted dwarf galaxy. We also trace the extremely diffuse northwest plume out to a total extent of 20′ (43 kpc) from NGC 5194 (M51a) and show it to be physically distinct from the overlapping bright tidal streams from M51b. The northwest plume’s morphology and red color (B−V=0.8) instead argue that it originated from tidal stripping of M51a’s extreme outer disk. Finally, we confirm the strong segregation of gas and stars in the southeast tail and do not detect any diffuse stellar component in the H i portion of the tail. Extant simulations of M51 have difficulty matching both the wealth of tidal structure in the system and the lack of stars in the H i tail, motivating new modeling campaigns to study the dynamical evolution of this classic interacting system.« less

Hubble Sees a “Behemoth” Bleeding Atmosphere Around a Warm Exoplanet

NASA Image and Video Library

2015-06-24

Astronomers using NASA’s Hubble Space Telescope have discovered an immense cloud of hydrogen dubbed “The Behemoth” bleeding from a planet orbiting a nearby star. The enormous, comet-like feature is about 50 times the size of the parent star. The hydrogen is evaporating from a warm, Neptune-sized planet, due to extreme radiation from the star. This phenomenon has never been seen around an exoplanet so small. It may offer clues to how other planets with hydrogen-enveloped atmospheres could have their outer layers evaporated by their parent star, leaving behind solid, rocky cores. Hot, rocky planets such as these that roughly the size of Earth are known as Hot-Super Earths. “This cloud is very spectacular, though the evaporation rate does not threaten the planet right now,” explains the study’s leader, David Ehrenreich of the Observatory of the University of Geneva in Switzerland. “But we know that in the past, the star, which is a faint red dwarf, was more active. This means that the planet evaporated faster during its first billion years of existence because of the strong radiation from the young star. Overall, we estimate that it may have lost up to 10 percent of its atmosphere over the past several billion years.” Caption: This artist's concept shows "The Behemoth," an enormous comet-like cloud of hydrogen bleeding off of a warm, Neptune-sized planet just 30 light-years from Earth. Also depicted is the parent star, which is a faint red dwarf named GJ 436. The hydrogen is evaporating from the planet due to extreme radiation from the star. A phenomenon this large has never before been seen around any exoplanet. Credits: NASA, ESA, and G. Bacon (STScI)

Faint blue counts from formation of dwarf galaxies at z approximately equals 1

NASA Technical Reports Server (NTRS)

Babul, Arif; Rees, Martin J.

1993-01-01

The nature of faint blue objects (FBO's) has been a source of much speculation since their detection in deep CCD images of the sky. Their high surface density argues against them being progenitors of present-day bright galaxies and since they are only weakly clustered on small scales, they cannot be entities that merged together to form present-day galaxies. Babul & Rees (1992) have suggested that the observed faint blue counts may be due to dwarf elliptical galaxies undergoing their initial starburst at z is approximately equal to 1. In generic hierarchical clustering scenarios, however, dwarf galaxy halos (M is approximately 10(exp 9) solar mass) are expected to form at an earlier epoch; for example, typical 10(exp 9) solar mass halos will virialize at z is approximately equal to 2.3 if the power-spectrum for the density fluctuations is that of the standard b = 2 cold dark matter (CDM) model. Under 'ordinary conditions' the gas would rapidly cool, collect in the cores, and undergo star-formation. Conditions at high redshifts are far from 'ordinary'. The intense UV background will prevent the gas in the dwarf halos from cooling, the halos being released from their suspended state only when the UV flux has diminished sufficiently.

The Enigmatic (Almost) Dark Galaxy Coma P: The Atomic Interstellar Medium

NASA Astrophysics Data System (ADS)

Ball, Catherine; Cannon, John M.; Leisman, Lukas; Adams, Elizabeth A. K.; Haynes, Martha P.; Józsa, Gyula I. G.; McQuinn, Kristen B. W.; Salzer, John J.; Brunker, Samantha; Giovanelli, Riccardo; Hallenbeck, Gregory; Janesh, William; Janowiecki, Steven; Jones, Michael G.; Rhode, Katherine L.

2018-02-01

We present new high-resolution H I spectral line imaging of Coma P, the brightest H I source in the system HI 1232+20. This galaxy with extremely low surface brightness was first identified in the ALFALFA survey as an “(Almost) Dark” object: a clearly extragalactic H I source with no obvious optical counterpart in existing optical survey data (although faint ultraviolet emission was detected in archival GALEX imaging). Using a combination of data from the Westerbork Synthesis Radio Telescope and the Karl G. Jansky Very Large Array, we investigate the H I morphology and kinematics at a variety of physical scales. The H I morphology is irregular, reaching only moderate maxima in mass surface density (peak {σ }{{H}{{I}}}∼ 10 {M}ȯ pc‑2). Gas of lower surface brightness extends to large radial distances, with the H I diameter measured at 4.0 ± 0.2 kpc inside the 1 {M}ȯ pc‑2 level. We quantify the relationships between mass surface density of H I gas and star formation on timescales of ∼100–200 Myr as traced by GALEX far-ultraviolet emission. While Coma P has regions of dense H I gas reaching the {N}{{H}{{I}}}={10}21 cm‑2 level typically associated with ongoing star formation, it lacks massive star formation as traced by Hα emission. The H I kinematics are extremely complex: a simple model of a rotating disk cannot describe the H I gas in Coma P. Using spatially resolved position–velocity analysis we identify two nearly perpendicular axes of projected rotation that we interpret as either the collision of two H I disks or a significant infall event. Similarly, three-dimensional modeling of the H I dynamics provides a best fit with two H I components. Coma P is just consistent (within 3σ) with the known {M}{{H}{{I}}}{--}{D}{{H}{{I}}} scaling relation. It is either too large for its H I mass, has too low an H I mass for its H I size, or the two H I components artificially extend its H I size. Coma P lies within the empirical scatter at the faint end of the baryonic Tully–Fisher relation, although the complexity of the H I dynamics complicates the interpretation. Along with its large ratio of H I to stellar mass, the collective H I characteristics of Coma P make it unusual among known galaxies in the nearby universe.

Optical Observations of Space Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Abercromby, Kira; Rodriquez, Heather; Barker, Edwin S.; Kelecy, Thomas

2008-01-01

This viewgraph presentation reviews the use of optical telescopes to observe space debris. .It will present a brief review of how the survey is conducted, and what some of the significant results encompass. The goal is to characterize the population of debris objects at GEO, with emphasis on the faint object population. Because the survey observations extend over a very short arc (5 minutes), a full six parameter orbit can not be determined. Recently we have begun to use a second telescope, the 0.9-m at CTIO, as a chase telescope to do follow-up observations of potential GEO debris candidates found by MODEST. With a long enough sequence of observations, a full six-parameter orbit including eccentricity can be determined. The project has used STK since inception for planning observing sessions based on the distribution of bright cataloged objects and the anti-solar point (to avoid eclipse). Recently, AGI's Orbit Determination Tool Kit (ODTK) has been used to determine orbits, including the effects of solar radiation pressure. Since an unknown fraction of the faint debris at GEO has a high area-to-mass ratio (A/M), the orbits are perturbed significantly by solar radiation. The ODTK analysis results indicate that temporal variations in the solar perturbations, possibly due to debris orientation dynamics, can be estimated in the OD process. Additionally, the best results appear to be achieved when solar forces orthogonal to the object-Sun line are considered. Determining the A/M of individual objects and the distribution of A/M values of a large sample of debris is important to understanding the total population of debris at GEO

THE PRISM MULTI-OBJECT SURVEY (PRIMUS). I. SURVEY OVERVIEW AND CHARACTERISTICS

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

Coil, Alison L.; Moustakas, John; Aird, James

2011-11-01

We present the PRIsm MUlti-object Survey (PRIMUS), a spectroscopic faint galaxy redshift survey to z {approx} 1. PRIMUS uses a low-dispersion prism and slitmasks to observe {approx}2500 objects at once in a 0.18 deg{sup 2} field of view, using the Inamori Magellan Areal Camera and Spectrograph camera on the Magellan I Baade 6.5 m telescope at Las Campanas Observatory. PRIMUS covers a total of 9.1 deg{sup 2} of sky to a depth of i{sub AB} {approx} 23.5 in seven different deep, multi-wavelength fields that have coverage from the Galaxy Evolution Explorer, Spitzer, and either XMM or Chandra, as well asmore » multiple-band optical and near-IR coverage. PRIMUS includes {approx}130,000 robust redshifts of unique objects with a redshift precision of {sigma}{sub z}/(1 + z) {approx} 0.005. The redshift distribution peaks at z {approx} 0.6 and extends to z = 1.2 for galaxies and z = 5 for broad-line active galactic nuclei. The motivation, observational techniques, fields, target selection, slitmask design, and observations are presented here, with a brief summary of the redshift precision; a forthcoming paper presents the data reduction, redshift fitting, redshift confidence, and survey completeness. PRIMUS is the largest faint galaxy survey undertaken to date. The high targeting fraction ({approx}80%) and large survey size will allow for precise measures of galaxy properties and large-scale structure to z {approx} 1.« less

Optical Observation, Image-processing, and Detection of Space Debris in Geosynchronous Earth Orbit

NASA Astrophysics Data System (ADS)

Oda, H.; Yanagisawa, T.; Kurosaki, H.; Tagawa, M.

2014-09-01

We report on optical observations and an efficient detection method of space debris in the geosynchronous Earth orbit (GEO). We operate our new Australia Remote Observatory (ARO) where an 18 cm optical telescope with a charged-coupled device (CCD) camera covering a 3.14-degree field of view is used for GEO debris survey, and analyse datasets of successive CCD images using the line detection method (Yanagisawa and Nakajima 2005). In our operation, the exposure time of each CCD image is set to be 3 seconds (or 5 seconds), and the time interval of CCD shutter open is about 4.7 seconds (or 6.7 seconds). In the line detection method, a sufficient number of sample objects are taken from each image based on their shape and intensity, which includes not only faint signals but also background noise (we take 500 sample objects from each image in this paper). Then we search a sequence of sample objects aligning in a straight line in the successive images to exclude the noise sample. We succeed in detecting faint signals (down to about 1.8 sigma of background noise) by applying the line detection method to 18 CCD images. As a result, we detected about 300 GEO objects up to magnitude of 15.5 among 5 nights data. We also calculate orbits of objects detected using the Simplified General Perturbations Satellite Orbit Model 4(SGP4), and identify the objects listed in the two-line-element (TLE) data catalogue publicly provided by the U.S. Strategic Command (USSTRATCOM). We found that a certain amount of our detections are new objects that are not contained in the catalogue. We conclude that our ARO and detection method posse a high efficiency detection of GEO objects despite the use of comparatively-inexpensive observation and analysis system. We also describe the image-processing specialized for the detection of GEO objects (not for usual astronomical objects like stars) in this paper.

Optical Properties of High Area-to-Mass Objects at GEO

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Schildknecht, Thomas; Musci, Reto; Flohrer, Tim; Barker, Ed; Stansbery, Eugene; Agapov, Vladimir; Rumyantsev, Vasilij; Biryukov, Vadym; Abercromby, Kira;

A normal abundance of faint satellites in the fossil group NGC 6482

NASA Astrophysics Data System (ADS)

Lieder, S.; Mieske, S.; Sánchez-Janssen, R.; Hilker, M.; Lisker, T.; Tanaka, M.

2013-11-01

A fossil group is considered the end product in a galaxy group's evolution. It is a massive central galaxy that dominates the luminosity budget of the group, and is the outcome of efficient merging between intermediate-luminosity members. Little is known, however, about the faint satellite systems of fossil groups. Here we present a Subaru/Suprime-Cam wide-field, deep imaging study in the B - and R -bands of the nearest fossil group NGC 6482 (Mtot ~ 4 × 1012M⊙), covering the virial radius out to 310 kpc. We performed detailed completeness estimations and selected group member candidates by a combination of automated object detection and visual inspection. A fiducial sample of 48 member candidates down to MR ~ -10.5 mag is detected, making this study the deepest of a fossil group to now. We investigate the photometric scaling relations, the color-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The color-magnitude relation is comparable to that of nearby galaxy clusters, and it exhibits significant scatter at the faintest luminosities. The completeness-corrected luminosity function is dominated by early-type dwarfs and is characterized by a faint end slope α = -1.32 ± 0.05. We conclude that the NGC 6482 fossil group shows photometric properties consistent with those of regular galaxy clusters and groups, including a normal abundance of faint satellites. Appendix A is available in electronic form at http://www.aanda.orgThe reduced data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/559/A76

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)

New Observational Evidence of Active Asteroid P/2010 A2: Slow Rotation of the Largest Fragment

NASA Astrophysics Data System (ADS)

Kim, Yoonyoung; Ishiguro, Masateru; Lee, Myung Gyoon

2017-06-01

We report new observations of the active asteroid P/2010 A2 taken when it made its closest approach to Earth (1.06 au in 2017 January) after its first discovery in 2010. Despite a crucial role of the rotational period in clarifying its ejection mechanism, the rotational property of P/2010 A2 has not yet been studied due to the extreme faintness of this tiny object (∼120 m in diameter). Taking advantage of the best observing geometry since the discovery, we succeed in obtaining the rotational light curve of the largest fragment with Gemini/GMOS-N. We find that (1) the largest fragment has a double-peaked period of 11.36 ± 0.02 hr spinning much slower than its critical spin period; (2) the largest fragment is a highly elongated object (a/b ≥ 1.94) with an effective radius of {61.9}-9.2+16.8 m; (3) the size distribution of the ejecta follows a broken power law (the power indices of the cumulative size distributions of the dust and fragments are 2.5 ± 0.1 and 5.2 ± 0.1, respectively); (4) the mass ratio of the largest fragment to the total ejecta is around 0.8; and (5) the dust cloud morphology is in agreement with the anisotropic ejection model in Kim et al. These new characteristics of the ejecta obtained in this work are favorable to the impact shattering hypothesis.

Near-ultraviolet imaging of Jupiter's satellite Io with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Paresce, F.; Sartoretti, P.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.

1992-01-01

The surface of Jupiter's Galilean satellite Io has been resolved for the first time in the near ultraviolet at 2850 A by the Faint Object Camera (FOC) on the Hubble Space Telescope (HST). The restored images reveal significant surface structure down to the resolution limit of the optical system corresponding to approximately 250 km at the sub-earth point.

Imaging of four planetary nebulae in the Magellanic Clouds using the Hubble Space Telescope Faint Object Camera

NASA Technical Reports Server (NTRS)

Blades, J. C.; Barlow, M. J.; Albrecht, R.; Barbieri, C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.

1992-01-01

Using the Faint Object Camera on-board the Hubble Space Telescope, we have obtained images of four planetary nebulae (PNe) in the Magellanic Clouds, namely N2 and N5 in the SMC and N66 and N201 in the LMC. Each nebula was imaged through two narrow-band filters isolating forbidden O III 5007 and H-beta, for a nominal exposure time of 1000 s in each filter. In forbidden O III, SMC N5 shows a circular ring structure, with a peak-to-peak diameter of 0.26 arcsec and a FWHM of 0.35 arcsec while SMC N2 shows an elliptical ring structure with a peak-to-peak diameter of 0.26 x 0.21. The expansion ages corresponding to the observed structures in SMC N2 and N5 are of the order of 3000 yr. LMC N201 is very compact, with a FWHM of 0.2 arcsec in H-beta. The Type I PN LMC N66 is a multipolar nebula, with the brightest part having an extent of about 2 arcsec and with fainter structures extending over 4 arcsec.

Aging jets from low-mass stars

NASA Technical Reports Server (NTRS)

Graham, J. A.; Chen, W. P.

1994-01-01

An extended faint optical jet is associated with the compact emission region plus faint star known as HH 55. HH 55 is located in the Lupus 2 cloud 2 min SW of the well studied T Tauri star RU Lupi. The HH 55 jet extends 55 sec N and 35 sec S in PA 160 deg. The HH 55 star is an emission line star of spectral type M3.5. Its image in the emission lines of H-alpha and (S II) is slightly elongated by 2 sec - 3 sec to the S but in continuum light is symmetrical and pointlike ((full width at half maximum) (FWHM) = 1.7 sec). The star and jet have several features in common with the star and jet known as Sz 102 = Th 28 in the nearby Lupus 3 cloud. We suggest that these objects are representative of the late evolutionary stage of the HH jet-outflow phenomenon and point out that such objects may be quite common although difficult to detect. With L(sub bol) approximately = 0.005 solar luminosity, and log T(sub e) approximately = 3.5, the HH 55 star is close to the main sequence and evolutionary tracks suggest an age of 3 x 10(exp 7) yr.

New astrometry and photometry for the companion candidates of CT Cha

NASA Astrophysics Data System (ADS)

Schmidt, Tobias O. B.; Neuhäuser, Ralph; Mugrauer, Markus; Bedalov, Ana; Vogt, Nikolaus

2009-02-01

In our ongoing search for close and faint companions around T Tauri stars in the Chamaeleon star-forming region, we recently (Schmidt et al. 2008 b) presented direct observations and integral field spectroscopy of a new common proper motion companion to the young T-Tauri star and Chamaeleon member CT Cha and discussed its properties in comparison to other young, low-mass objects and to synthetic model spectra from different origins. We now obtained for the first time direct H-Band observations of the companion CT Cha b and of another faint companion candidate (cc2) approximately 1.9 arcsec northeast of CT Cha using the Adaptive Optics (AO) instrument Naos-Conica (NACO) at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in February 2008. From these data we can now exclude by 4.4 & 4.8 σ that CT Cha b is a non-moving background object and find cc2 to be most likely a background star of spectral type <=K4 with a proper motion of μα cos δ = -8.5+/-5.7 mas/yr and μδ = 12.0+/-5.6 mas/yr, not consistent with being a member of the Cha I star-forming region.

Data mining of near-Earth asteroids in the Subaru Suprime-Cam archive

NASA Astrophysics Data System (ADS)

Vaduvescu, O.; Conovici, M.; Popescu, M.; Sonka, A.; Paraschiv, A.; Lacatus, D.; Tudorica, A.; Hudin, L.; Curelaru, L.; Inceu, V.; Zavoianu, D.; Cornea, R.; Toma, R.; Asher, D. J.; Hadnett, J.; Cheallaigh, L. Ó.

2017-06-01

As part of the EURONEAR project, almost 70,000 mosaic Suprime-Cam images taken between 1999 and 2013 were data mined for about 9,800 near Earth asteroids (NEAs) known by 2013 May. Using our PRECOVERY server and the "Find Subaru CCD" tool, we scrutinized 4,186 candidate CCD images possibly holding 518 NEAs. We found 113 NEAs as faint as V<25 magnitude, their positions being measured in 589 images using Astrometrica, then reported to the Minor Planet Center. Among them, 18 objects represent encounters of previously single opposition NEAs, their orbital arcs being extended by up to 10 years. In the second part of this work we searched for unknown NEAs in 78 sequences (780 CCD fields) of 4-5 mosaic images selected from the same Suprime-Cam archive and totaling 16.6 sq.deg, with the aim to assess the faint NEA distribution observable with an 8-m class survey. A total of 2,018 moving objects were measured, from which we identified 18 better NEA candidates. Using the R_c filter in good weather conditions, mostly dark time and sky directions slightly biased towards the ecliptic, at least one NEA could be discovered in every 1 sq.deg surveyed.

Searching for Planet Nine and Other Nearby Worlds with WISE and NEOWISE

NASA Astrophysics Data System (ADS)

Meisner, Aaron Michael; Bromley, Benjamin; Nugent, Peter; Schlegel, David; Kenyon, Scott; Schlafly, Eddie; Dawson, Kyle; Anderson, Teddy

2018-01-01

Launched nearly eight years ago, NASA's WISE satellite continues to collect millions of infrared images at 3-5 microns as part of its asteroid-hunting NEOWISE mission. We have repurposed these NEOWISE exposures for science beyond the main belt by generating a novel full-sky set of time-resolved coadded images. This reprocessing allows for moving object searches reaching ~1.3 magnitudes fainter than previous studies while also providing a factor of ten increase in time baseline. This creates an exciting opportunity for motion-based discovery of very cold and faint objects which may have thus far eluded detection despite residing close to the Sun. We present the results of our latest WISE/NEOWISE search for 'Planet Nine', a giant planet hypothesized to orbit the Sun at hundreds of astronomical units. Our search incorporates over four years of WISE W1 observations spanning a seven year time period, and covers more than 75% of the sky. Variants of the WISE/NEOWISE Planet Nine search methodology we have developed should enable motion-based discoveries of large numbers of cold, faint brown dwarfs, especially those which are not detectable with Gaia.

Cryogenic Photogrammetry and Radiometry for the James Webb Space Telescope Microshutters

NASA Technical Reports Server (NTRS)

Chambers, Victor J.; Morey, Peter A.; Zukowski, Barbara J.; Kutyrev, Alexander S.; Collins, Nicholas R.

2012-01-01

The James Webb Space Telescope (JWST) relies on several innovations to complete its five year mission. One vital technology is microshutters, the programmable field selectors that enable the Near Infrared Spectrometer (NIRSpec) to perform multi-object spectroscopy. Mission success depends on acquiring spectra from large numbers of galaxies by positioning shutter slits over faint targets. Precise selection of faint targets requires field selectors that are both high in contrast and stable in position. We have developed test facilities to evaluate microshutter contrast and alignment stability at their 35K operating temperature. These facilities used a novel application of image registration algorithms to obtain non-contact, sub-micron measurements in cryogenic conditions. The cryogenic motion of the shutters was successfully characterized. Optical results also demonstrated that shutter contrast far exceeds the NIRSpec requirements. Our test program has concluded with the delivery of a flight-qualified field selection subsystem to the NIRSpec bench.

The distant red galaxy neighbour population of 1

NASA Astrophysics Data System (ADS)

Bornancini, C.; García Lambas, D.

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

Faint warm debris disks around nearby bright stars explored by AKARI and IRSF

NASA Astrophysics Data System (ADS)

Ishihara, Daisuke; Takeuchi, Nami; Kobayashi, Hiroshi; Nagayama, Takahiro; Kaneda, Hidehiro; Inutsuka, Shu-ichiro; Fujiwara, Hideaki; Onaka, Takashi

2017-05-01

Context. Debris disks are important observational clues for understanding planetary-system formation process. In particular, faint warm debris disks may be related to late planet formation near 1 au. A systematic search of faint warm debris disks is necessary to reveal terrestrial planet formation. Aims: Faint warm debris disks show excess emission that peaks at mid-IR wavelengths. Thus we explore debris disks using the AKARI mid-IR all-sky point source catalog (PSC), a product of the second generation unbiased IR all-sky survey. Methods: We investigate IR excess emission for 678 isolated main-sequence stars for which there are 18 μm detections in the AKARI mid-IR all-sky catalog by comparing their fluxes with the predicted fluxes of the photospheres based on optical to near-IR fluxes and model spectra. The near-IR fluxes are first taken from the 2MASS PSC. However, 286 stars with Ks < 4.5 in our sample have large flux errors in the 2MASS photometry due to saturation. Thus we have measured accurate J, H, and Ks band fluxes, applying neutral density (ND) filters for Simultaneous InfraRed Imager for Unbiased Survey (SIRIUS) on IRSF, the φ1.4 m near-IR telescope in South Africa, and improved the flux accuracy from 14% to 1.8% on average. Results: We identified 53 debris-disk candidates including eight new detections from our sample of 678 main-sequence stars. The detection rate of debris disks for this work is 8%, which is comparable with those in previous works by Spitzer and Herschel. Conclusions: The importance of this study is the detection of faint warm debris disks around nearby field stars. At least nine objects have a large amount of dust for their ages, which cannot be explained by the conventional steady-state collisional cascade model. The full version of Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A72

OzDES multifibre spectroscopy for the Dark Energy Survey: First-year operation and results

DOE PAGES

Yuan, Fang

2015-07-29

The Australian Dark Energy Survey (OzDES) is a five-year, 100-night, spectroscopic survey on the Anglo-Australian Telescope, whose primary aim is to measure redshifts of approximately 2500 Type Ia supernovae host galaxies over the redshift range 0.1 < z < 1.2, and derive reverberation-mapped black hole masses for approximately 500 active galactic nuclei and quasars over 0.3 < z < 4.5. This treasure trove of data forms a major part of the spectroscopic follow-up for the Dark Energy Survey for which we are also targeting cluster galaxies, radio galaxies, strong lenses, and unidentified transients, as well as measuring luminous red galaxiesmore » and emission line galaxies to help calibrate photometric redshifts. Here, we present an overview of the OzDES programme and our first-year results. Between 2012 December and 2013 December, we observed over 10 000 objects and measured more than 6 000 redshifts. Our strategy of retargeting faint objects across many observing runs has allowed us to measure redshifts for galaxies as faint as m r = 25 mag. We outline our target selection and observing strategy, quantify the redshift success rate for different types of targets, and discuss the implications for our main science goals. In conclusion, we highlight a few interesting objects as examples of the fortuitous yet not totally unexpected discoveries that can come from such a large spectroscopic survey.« less

OzDES multifibre spectroscopy for the Dark Energy Survey: first-year operation and results

NASA Astrophysics Data System (ADS)

Yuan, Fang; Lidman, C.; Davis, T. M.; Childress, M.; Abdalla, F. B.; Banerji, M.; Buckley-Geer, E.; Carnero Rosell, A.; Carollo, D.; Castander, F. J.; D'Andrea, C. B.; Diehl, H. T.; Cunha, C. E.; Foley, R. J.; Frieman, J.; Glazebrook, K.; Gschwend, J.; Hinton, S.; Jouvel, S.; Kessler, R.; Kim, A. G.; King, A. L.; Kuehn, K.; Kuhlmann, S.; Lewis, G. F.; Lin, H.; Martini, P.; McMahon, R. G.; Mould, J.; Nichol, R. C.; Norris, R. P.; O'Neill, C. R.; Ostrovski, F.; Papadopoulos, A.; Parkinson, D.; Reed, S.; Romer, A. K.; Rooney, P. J.; Rozo, E.; Rykoff, E. S.; Sako, M.; Scalzo, R.; Schmidt, B. P.; Scolnic, D.; Seymour, N.; Sharp, R.; Sobreira, F.; Sullivan, M.; Thomas, R. C.; Tucker, D.; Uddin, S. A.; Wechsler, R. H.; Wester, W.; Wilcox, H.; Zhang, B.; Abbott, T.; Allam, S.; Bauer, A. H.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Carrasco Kind, M.; Covarrubias, R.; Crocce, M.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; Fosalba, P.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Maia, M. A. G.; Makler, M.; Marshall, J.; Miller, C. J.; Miquel, R.; Ogando, R.; Plazas, A. A.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Walker, A. R.

2015-09-01

The Australian Dark Energy Survey (OzDES) is a five-year, 100-night, spectroscopic survey on the Anglo-Australian Telescope, whose primary aim is to measure redshifts of approximately 2500 Type Ia supernovae host galaxies over the redshift range 0.1 < z < 1.2, and derive reverberation-mapped black hole masses for approximately 500 active galactic nuclei and quasars over 0.3 < z < 4.5. This treasure trove of data forms a major part of the spectroscopic follow-up for the Dark Energy Survey for which we are also targeting cluster galaxies, radio galaxies, strong lenses, and unidentified transients, as well as measuring luminous red galaxies and emission line galaxies to help calibrate photometric redshifts. Here, we present an overview of the OzDES programme and our first-year results. Between 2012 December and 2013 December, we observed over 10 000 objects and measured more than 6 000 redshifts. Our strategy of retargeting faint objects across many observing runs has allowed us to measure redshifts for galaxies as faint as mr = 25 mag. We outline our target selection and observing strategy, quantify the redshift success rate for different types of targets, and discuss the implications for our main science goals. Finally, we highlight a few interesting objects as examples of the fortuitous yet not totally unexpected discoveries that can come from such a large spectroscopic survey.

Spitzer DDT observations of the interstellar comet A/2017 U1

NASA Astrophysics Data System (ADS)

Trilling, David; Hora, Joe; Mommert, Michael; Carey, Sean; Lisse, Carey; Werner, Mike; Chesley, Steve; Emery, Josh; Fazio, Giovanni; Fernandez, Yan; Harris, Alan; Marengo, Massimo; Mueller, Migo; Roegge, Alissa; Smith, Howard; Smith, Nathan; Weaver, Hal

2017-11-01

We propose to observe the newly discovered interstellar comet A/2017 U1 to measure its diameter and albedo. Little is known about this object, which presumably formed in another planetary system. This is the only opportunity *ever* to determine the albedo of this object, which will help us understand how planetary system formation in other systems compares to what occurred in our Solar System. The proposed observations -- requiring 32.6 hours in late November -- are the last telescopic observations that will ever be made of this object. The return from these proposed observations would be tremendous -- characterizing the first ever known object from beyond our Solar System. Because the object is faint and fading, these observations must be made as soon as possible.

Fainting

MedlinePlus

... fainted one time and you are otherwise in good health. Fainting is common and usually not serious. However, if you have serious health problems, you probably should see your doctor. This is ... your overall, good health. It helps maintain your temperature, remove waste ...

Rocket ultraviolet observations of Comet Halley

NASA Technical Reports Server (NTRS)

Carruthers, George R.; Mccoy, Robert P.; Woods, Thomas N.; Feldman, Paul D.; Opal, Chet B.

1987-01-01

Ultraviolet observations of Comet Halley have been obtained in February and March, 1986 with two instrument payloads, one with the Faint Object Telescope and one with a direct imaging electrographic Schmidt camera and an objective grating spectrograph. The observations include spectroscopic imagery in the 1200-200 A wavelength range and imagery of the comet in hydrogen Lyman-alpha (1216 A) radiation. The present observations have been reduced to intensity contour plots in the different emission wavelengths, and production rates are given for the emitting species H, C, O, S, and CO.

Meeting contribution: Low mass stars, brown dwarfs and hot Jupiters

NASA Astrophysics Data System (ADS)

Viti, S.

2007-02-01

Dr Viti opened with an apology that hers was not a field which could yet produce nice images; the objects she would be describing were too faint to be meaningfully imaged. Yet she would be arguing that even without images, a tremendous amount had been learnt from such objects in the past decade, and that there were exciting prospects for the future. The primary subject of this talk would be low mass stars (LMSs), defined as those stars of around half the mass of the Sun or less.

Optical Studies of Space Debris at GEO: Survey and Follow-up with Two Telescopes

NASA Technical Reports Server (NTRS)

Seitzer, P.; Abercomby, K. J.; Rodriquez, H. M.; Barker, E. S.

2007-01-01

For 14 nights in March 2007, we used two telescopes at the Cerro Tololo Inter-American Observatory (CTIO) in Chile to study the nature of space debris at Geosynchronous Earth Orbit (GEO). In this project one telescope was dedicated to survey operations, while a second telescope was used for follow-up observations for orbits and colors. The goal was to obtain orbital and photometric information on every faint object found with the survey telescope. Thus we concentrate on objects fainter than R = 15th magnitude.

VizieR Online Data Catalog: SN2009ip UBVRI, UVOT and JHK light curves (Fraser+, 2013)

NASA Astrophysics Data System (ADS)

Fraser, M.; Inserra, C.; Jerkstrand, A.; Kotak, R.; Pignata, G.; Benetti, S.; Botticella, M.-T.; Bufano, F.; Childress, M.; Mattila, S.; Pastorello, A.; Smartt, S. J.; Turatto, M.; Yuan, F.; Anderson, J. P.; Bayliss, D. D. R.; Bauer, F. E.; Chen, T.-W.; Forster Buron, F.; Gal-Yam, A.; Haislip, J. B.; Knapic, C.; Le Guillou, L.; Marchi, S.; Mazzali, P.; Molinaro, M.; Moore, J. P.; Reichart, D.; Smareglia, R.; Smith, K. W.; Sternberg, A.; Sullivan, M.; Takats, K.; Tucker, B. E.; Valenti, S.; Yaron, O.; Young, D. R.; Zhou, G.

2014-11-01

Optical spectroscopic follow-up of SN 2009ip was chiefly obtained with the New Technology Telescope (NTT) + ESO Faint Object Spectrograph and Camera 2 (EFOSC2), as part of the Public European Southern Observatory (ESO) Spectroscopic Survey of Transient Objects (PESSTO). The PESSTO data were supplemented with data from the Telescopio Nazionale Galileo (TNG) + Device Optimized for the LOw RESolution (DOLORES), and the Australian National University (ANU) 2.3m telescope + Wide Field Spectrograph (WiFeS). (3 data files).

Study of galaxies in the Lynx-Cancer void - VII. New oxygen abundances

NASA Astrophysics Data System (ADS)

Pustilnik, S. A.; Perepelitsyna, Y. A.; Kniazev, A. Y.

2016-11-01

We present new or improved oxygen abundances (O/H) for the nearby Lynx-Cancer void updated galaxy sample. They are obtained via the SAO 6-m telescope spectroscopy (25 objects), or derived from the Sloan Digital Sky Survey spectra (14 galaxies, of which for seven objects O/H values were unknown). For eight galaxies with detected [O III] λ4363 line, O/H values are derived via the direct (Te) method. For the remaining objects, O/H was estimated via semi-empirical and empirical methods. For all accumulated O/H data for 81 galaxies of this void (with 40 of them derived via Te method), their relation `O/H versus MB' is compared with that for similar late-type galaxies from denser environments (the Local Volume `reference sample'). We confirm our previous conclusion derived for a subsample of 48 objects: void galaxies show systematically reduced O/H for the same luminosity with respect to the reference sample, in average by 0.2 dex, or by a factor of ˜1.6. Moreover, we confirm the fraction of ˜20 per cent of strong outliers, with O/H of two to four times lower than the typical values for the `reference' sample. The new data are consistent with the conclusion on the slower evolution of the main void galaxy population. We obtained Hα velocity for the faint optical counterpart of the most gas-rich (M(H I)/LB = 25) void object J0723+3624, confirming its connection with the respective H I blob. For similar extremely gas-rich dwarf J0706+3020, we give a tentative O/H ˜(O/H)⊙/45. In Appendix A, we present the results of calibration of semi-empirical method by Izotov & Thuan and of empirical calibrators by Pilyugin & Thuan and Yin et al. on the sample of ˜150 galaxies from the literature with O/H measured by Te method.

Using Spatial Correlations of SPDC Sources for Increasing the Signal to Noise Ratio in Images

NASA Astrophysics Data System (ADS)

Ruíz, A. I.; Caudillo, R.; Velázquez, V. M.; Barrios, E.

2017-05-01

We experimentally show that, by using spatial correlations of photon pairs produced by Spontaneous Parametric Down-Conversion, it is possible to increase the Signal to Noise Ratio in images of objects illuminated with those photons; in comparison, objects illuminated with light from a laser present a minor ratio. Our simple experimental set-up was capable to produce an average improvement in signal to noise ratio of 11dB of Parametric Down-Converted light over laser light. This simple method can be easily implemented for obtaining high contrast images of faint objects and for transmitting information with low noise.

New Candidate Supernova Remnants in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Winkler, P. F.; Lewinter, R.

1992-12-01

We have surveyed six 30(') times 30(') fields in the Small Magellanic Cloud, using the Curtis Schmidt telescope at CTIO with a Thomson CCD, to search for previously undetected supernova remnants (SNRs). Narrow-band images are obtained in lines of [S II] (lambda lambda \\ 6716,31), Hα , and a nearby continuum band. The ratio of [S II]/Hα \\ emission discriminates well between shock-heated material charcteristic of SNRs and photo-ionized material such as H II regions. This technique has proved highly effective in surveys of other galaxies (e.g. Long et al., Ap J Supp, 72, 61). Deep emission-line images and a continuum band closely matched in wavelength enable us to subtract virtually the entire stellar contribution and thus achieve high sensitivity to faint, diffuse emission. We have identified 13 objects, all of which have [S II]/Hα \\ ratios > 0.4\\ and a full or partial shell-like morphology, making them extremely strong SNR candidates. Several other diffuse objects have high [S II]/Hα \\ ratios, and many of these may also be SNRs. Compared with the 12 previously known remnants of Mathewson et al., (Ap J Supp 51, 345; 55, 189), the new candidates are generally larger and have lower surface brightness. An investigation of the cumulative number vs diameter relation for our larger sample indicates a slope significantly steeper than the value near unity originally found by Mathewson et al., and is more consistent with standard models for SNR evolution. Selection effects may well have led to an excess of small, bright objects in the earlier samples. This work was supported in part by NSF grant AST-9114935 and by the W.M. Keck Foundation through the Keck Northeast Astronomy Consortium.

Analysis of Faint Glints from Stabilized GEO Satellites

DTIC Science & Technology

2013-09-01

this regard temporal photometry (i.e., measurements of whole-object brightness as a function of time ) can be very valuable. For instance, GEO satellite ...INTRODUCTION Ground-based optical and radar sites routinely acquire resolved images of satellites , yielding a great deal of knowledge about orbiting...spacecraft. However, the important population of GEO satellites often cannot be resolved , and must be characterized using methods other than imagery. In

HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

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

Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.

2016-01-20

We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Itsmore » variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.« less

Young, metal-enriched cores in early-type dwarf galaxies in the Virgo cluster based on colour gradients

NASA Astrophysics Data System (ADS)

Urich, Linda; Lisker, Thorsten; Janz, Joachim; van de Ven, Glenn; Leaman, Ryan; Boselli, Alessandro; Paudel, Sanjaya; Sybilska, Agnieszka; Peletier, Reynier F.; den Brok, Mark; Hensler, Gerhard; Toloba, Elisa; Falcón-Barroso, Jesús; Niemi, Sami-Matias

2017-10-01

Early-type dwarf galaxies are not simply featureless, old objects, but were found to be much more diverse, hosting substructures and a variety of stellar population properties. To explore the stellar content of faint early-type galaxies, and to investigate in particular those with recent central star formation, we study colours and colour gradients within one effective radius in optical (g - r) and near-infrared (I - H) bands for 120 Virgo cluster early-type galaxies with - 19 mag

a Faint and Lonely Brown Dwarf in the Solar Vicinity

NASA Astrophysics Data System (ADS)

1997-04-01

Discovery of KELU-1 Promises New Insights into Strange Objects Brown Dwarfs are star-like objects which are too small to become real stars, yet too large to be real planets. Their mass is too small to ignite those nuclear processes which are responsible for the large energies and high temperatures of stars, but it is much larger than that of the planets we know in our solar system. Until now, very few Brown Dwarfs have been securely identified as such. Two are members of double-star systems, and a few more are located deep within the Pleiades star cluster. Now, however, Maria Teresa Ruiz of the Astronomy Department at Universidad de Chile (Santiago de Chile), using telescopes at the ESO La Silla observatory, has just discovered one that is all alone and apparently quite near to us. Contrary to the others which are influenced by other objects in their immediate surroundings, this new Brown Dwarf is unaffected and will thus be a perfect object for further investigations that may finally allow us to better understand these very interesting celestial bodies. It has been suggested that Brown Dwarfs may constitute a substantial part of the unseen dark matter in our Galaxy. This discovery may therefore also have important implications for this highly relevant research area. Searching for nearby faint stars The story of this discovery goes back to 1987 when Maria Teresa Ruiz decided to embark upon a long-term search (known as the Calan-ESO proper-motion survey ) for another type of unusual object, the so-called White Dwarfs , i.e. highly evolved, small and rather faint stars. Although they have masses similar to that of the Sun, such stars are no larger than the Earth and are therefore extremely compact. They are particularly interesting, because they most probably represent the future end point of evolution of our Sun, some billions of years from now. For this project, the Chilean astronomer obtained large-field photographic exposures with the 1-m ESO Schmidt telescope at La Silla, each covering a sky area of 5 o.5 x 5 o.5. When comparing plates of the same sky field obtained at time intervals of several years [1] , she was able to detect, among the hundreds of thousands of stellar images on the plates, a few faint ones whose positions had changed a little in the meantime. The search technique is based on the fact that such a shift is a good indicator of the object being relatively nearby. It must therefore also be intrinsically faint, i.e. a potential White Dwarf candidate. On every pair of plates, approximately twenty faint moving objects were detected with proper motions [2] of more than 0.25 arcsec per year. Indeed, follow-up spectroscopic observations showed that about 20 percent of these or about four per plate were White Dwarfs. Until now, a total of forty new White Dwarfs have been discovered during this very successful project, i.e. over ten times more than originally expected. And then - a Brown Dwarf! Caption to ESO PR Photo 11/97 [JPEG, 144k] ESO Press Photo 11/97 When checking two plates with a time inverval of 11 years, Maria Teresa Ruiz earlier this year discovered a very faint object in the southern constellation of Hydra (The Water-Snake), moving at 0.35 arcsec per year (cf. ESO Press Photo 11/97). In order to establish its true nature, she obtained its spectrum (in the visual to near-infrared region from wavelengths 450-1000 nm) on March 15 using the ESO 3.6-m telescope and the EFOSC1 spectrograph. Caption to ESO PR Photo 12/97 [GIF, 35k] ESO Press Photo 12/97 To her great surprise, the spectrum was of a type never seen before and certainly not that of a White Dwarf or any other easily identifiable type of star (cf. ESO Press Photo 12/97). In particular, there were no signs of spectral bands of titanium oxide (TiO) or vanadium oxide (VO) which are common in very cool stars, nor of the spectral lines seen in White Dwarfs. On the other hand, an absorption line of the short-lived element lithium was identified, as well as a hydrogen line in emission. However, when the colour of this mysterious object was measured in different wavebands, it was found to be very red and quite similar to that of one of the two known Brown Dwarfs in double star systems. The presence of the lithium line in the spectrum is also an indication that it might be of that type. The astronomer now decided to give the new object the name KELU-1 ; this word means `red' in the language of the Mapuche people, the ancient population in the central part of Chile. Its visual magnitude is 22.3, i.e. more than 3 million times fainter than what can be seen with the unaided eye. In early April, additional infrared observations with the UKIRT (UK Infrared Telescope) on Mauna Kea (Hawaii) by Sandra K. Leggett (Joint Astrophysical Centre, Hilo, Hawaii, USA) confirmed the Brown Dwarf nature of KELU-1, in particular through the unambiguous detection of Methane (CH 4 ) bands in its spectrum. The nature of Brown Dwarfs Brown Dwarfs are first of all characterised by their low mass. When a body of such a small mass is formed in an interstellar cloud and subsequently begins to contract, its temperature at the centre will rise, but it will never reach a level that is sufficient to ignite the nuclear burning of hydrogen to helium, the process that it is main source of energy in the Sun and most other stars. The Brown Dwarf will just continue to contract, more and more slowly, and it will eventually fade from view. This is also the reason that some astronomers consider Brown Dwarfs in the Milky Way and other galaxies as an important component of the `dark matter' whose presence is infered from other indirect measurements but has never been directly observed. It is assumed that the mass limit that separates nuclear-burning stars and slowly contracting Brown Dwarfs is at about 90 times the mass of the giant planet Jupiter, or 8 percent of that of the Sun. KELU-1: a great opportunity for Brown Dwarf studies Assuming that KELU-1 is identical to other known Brown Dwarfs, its measured characteristics indicate that it must be located at a distance of only 10 parsecs, that is about 33 light-years, from the solar system. Its temperature is obviously below 1700 degrees C (where TiO and VO condense as dust grains [3] so that the spectral lines of these molecules are no longer seen). Its mass can be no more than 75 times that of Jupiter, or 6 percent of that of the Sun. During recent years, several Brown Dwarf candidates have been de-masked as low-mass stars and only recently a few Brown Dwarfs were identified in the Pleiades star cluster. Those Brown Dwarfs are quite young and therefore comparatively hotter and brighter. Contrarily, KELU-1 is most probably somewhat older and its unique location so close to us greatly facilitates future investigations. Moreover, it is not at all `disturbed' by the presence of other objects in its immediate surroundings, as this is the case for all other known objects of this type. It will now be important to obtain accurate measurements of KELU-1's parallax , that is, the small annual change of its position in the sky that is caused by the Earth's motion around the Sun and thus the viewing angle of an Earth-based observer. This should be possible within the next year. Moreover, high resolution spectral investigations with large telescope facilities, soon to include the ESO Very Large Telescope at the Paranal observatory in northern Chile, will now for the first time enable us to investigate the processes that take place in the relatively cold upper layers of Brown Dwarfs. For instance, the observed presence of lithium shows that its atmosphere must be different from that of low-mass stars. KELU-1 and the `Dark Matter' From the fact that KELU-1 is so faint that it was barely detectable on the ESO Schmidt plates, it is possible to estimate that the total volume so far surveyed for this type of objects by this research programme is rather small, only about 23 cubic parsecs (800 cubic light-years). A further consideration of the search statistics indicates that less than 10 percent of the Brown Dwarfs present in the surveyed volume would have been found. This translates into a local density of about 0.4 such objects per cubic parsec. Although the mass density of Brown Dwarfs derived from this estimate is insufficient to constitute all the `dark matter' in the Milky Way Galaxy, it is consistent with the most recent estimates of the local mass density, both observed and as infered from dynamical considerations of the motions of stars in the solar neighborhood. Notes: [1] This is done by means of a so-called blink-comparator , an optical device in which the two plates are placed. A tilting mirror allows to view the same sky field alternately on the two plates. Any celestial object that has changed its position will appear to `jump' back and forth and can thus be identified. [2] A proper motion in the sky of 0.25 arcsec/year corresponds to a transversal speed of about 12 km/sec if the object is located at a distance of 10 parsec, or 32.6 light-years. The largest known proper motion of an object outside the solar system is that of Barnard's Star at about 10 arcsec/year. [3] For instance, as the mineral perovskite . How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Photometric monitoring of three BL Lacertae objects in 1993-1998

NASA Astrophysics Data System (ADS)

Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.

1999-05-01

The results of optical photometric (BVRI) monitoring of three BL Lac objects over a time interval of about four years are presented. The sources are three classical radio-selected BL Lac objects, BL Lac, OJ 287 and PKS 0735+178. During our observation OJ 287 was in the stage of a large periodic outburst which consisted of at least two peaks. Almost all the observations obtained over consecutive nights detected intranight variations. In 1995 and 1996 BL Lac kept in faint states, with fewer and smaller rapid flares and fluctuations. On the contrary, in late 1997 BL Lac was at the stage of a large outburst, accompanied with much more large amplitude rapid flares and fluctuations. PKS 0735+178 was almost at its faint end from 1994 to early 1998. Over this time interval, the intraday variations and microvariations in PKS 0735+178 were rare and the amplitude was very small, except a rapid darkening of ~ 0.4 mag on 24 January 1995. Previous work by \\cite[Webb et al. (1988);]{web88} \\cite[Wagner et al. (1996);]{wag96} \\cite[Pian et al. (1997)]{pia97} also showed the same behaviour of variability as BL Lac and PKS 0735+178 in BL Lac, S5 0716+714, PKS 2155-304, respectively. We propose that the motion of orientation of the relativistic jet in a BL Lac object be responsible for these variability behaviours. Table~1 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/Abstract.html

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

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

Huang, Xingxing; Wang, Junxian; Shu, Xinwen

2015-03-01

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

Constraining Accretion Signatures of Exoplanets in the TW Hya Transitional Disk

NASA Astrophysics Data System (ADS)

Uyama, Taichi; Tanigawa, Takayuki; Hashimoto, Jun; Tamura, Motohide; Aoyama, Yuhiko; Brandt, Timothy D.; Ishizuka, Masato

2017-09-01

We present a near-infrared direct imaging search for accretion signatures of possible protoplanets around the young stellar object (YSO) TW Hya, a multi-ring disk exhibiting evidence of planet formation. The Paβ line (1.282 μm) is an indication of accretion onto a protoplanet, and its intensity is much higher than that of blackbody radiation from the protoplanet. We focused on the Paβ line and performed Keck/OSIRIS spectroscopic observations. Although spectral differential imaging (SDI) reduction detected no accretion signatures, the results of the present study allowed us to set 5σ detection limits for Paβ emission of 5.8 × 10-18 and 1.5 × 10-18 erg-1 s-1 cm-2 at 0.″4 and 1.″6, respectively. We considered the mass of potential planets using theoretical simulations of circumplanetary disks and hydrogen emission. The resulting masses were 1.45 ± 0.04 M J and {2.29}-0.04+0.03 {M}{{J}} at 25 and 95 au, respectively, which agree with the detection limits obtained from previous broadband imaging. The detection limits should allow for the identification of protoplanets as small as ˜1 M J, which may assist in direct imaging searches around faint YSOs for which extreme adaptive optics instruments are unavailable.

Confirmation of Small Dynamical and Stellar Masses for Extreme Emission Line Galaxies at z Approx. 2

NASA Technical Reports Server (NTRS)

Maseda, Michael V.; van Der Wel, Arjen; da Cunha, Elisabete; Rix, Hans-Walter; Pacifici, Camilla; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; van Dokkum, Pieter; Bell, Eric F.;

Parallel object-oriented data mining system

DOEpatents

Kamath, Chandrika; Cantu-Paz, Erick

2004-01-06

A data mining system uncovers patterns, associations, anomalies and other statistically significant structures in data. Data files are read and displayed. Objects in the data files are identified. Relevant features for the objects are extracted. Patterns among the objects are recognized based upon the features. Data from the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) sky survey was used to search for bent doubles. This test was conducted on data from the Very Large Array in New Mexico which seeks to locate a special type of quasar (radio-emitting stellar object) called bent doubles. The FIRST survey has generated more than 32,000 images of the sky to date. Each image is 7.1 megabytes, yielding more than 100 gigabytes of image data in the entire data set.

Breaking the Habit: The Peculiar 2016 Eruption of the Unique Recurrent Nova M31N 2008-12a

NASA Astrophysics Data System (ADS)

Henze, M.; Darnley, M. J.; Williams, S. C.; Kato, M.; Hachisu, I.; Anupama, G. C.; Arai, A.; Boyd, D.; Burke, D.; Ciardullo, R.; Chinetti, K.; Cook, L. M.; Cook, M. J.; Erdman, P.; Gao, X.; Harris, B.; Hartmann, D. H.; Hornoch, K.; Horst, J. Chuck; Hounsell, R.; Husar, D.; Itagaki, K.; Kabashima, F.; Kafka, S.; Kaur, A.; Kiyota, S.; Kojiguchi, N.; Kučáková, H.; Kuramoto, K.; Maehara, H.; Mantero, A.; Masci, F. J.; Matsumoto, K.; Naito, H.; Ness, J.-U.; Nishiyama, K.; Oksanen, A.; Osborne, J. P.; Page, K. L.; Paunzen, E.; Pavana, M.; Pickard, R.; Prieto-Arranz, J.; Rodríguez-Gil, P.; Sala, G.; Sano, Y.; Shafter, A. W.; Sugiura, Y.; Tan, H.; Tordai, T.; Vraštil, J.; Wagner, R. M.; Watanabe, F.; Williams, B. F.; Bode, M. F.; Bruno, A.; Buchheim, B.; Crawford, T.; Goff, B.; Hernanz, M.; Igarashi, A. S.; José, J.; Motta, M.; O’Brien, T. J.; Oswalt, T.; Poyner, G.; Ribeiro, V. A. R. M.; Sabo, R.; Shara, M. M.; Shears, J.; Starkey, D.; Starrfield, S.; Woodward, C. E.

2018-04-01

Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every single year. This unprecedented frequency indicates an extreme object, with a massive white dwarf and a high accretion rate, which is the most promising candidate for the single-degenerate progenitor of a Type Ia supernova known to date. The previous three eruptions of M31N 2008-12a have displayed remarkably homogeneous multiwavelength properties: (i) from a faint peak, the optical light curve declined rapidly by two magnitudes in less than two days, (ii) early spectra showed initial high velocities that slowed down significantly within days and displayed clear He/N lines throughout, and (iii) the supersoft X-ray source (SSS) phase of the nova began extremely early, six days after eruption, and only lasted for about two weeks. In contrast, the peculiar 2016 eruption was clearly different. Here we report (i) the considerable delay in the 2016 eruption date, (ii) the significantly shorter SSS phase, and (iii) the brighter optical peak magnitude (with a hitherto unobserved cusp shape). Early theoretical models suggest that these three different effects can be consistently understood as caused by a lower quiescence mass accretion rate. The corresponding higher ignition mass caused a brighter peak in the free–free emission model. The less massive accretion disk experienced greater disruption, consequently delaying the re-establishment of effective accretion. Without the early refueling, the SSS phase was shortened. Observing the next few eruptions will determine whether the properties of the 2016 outburst make it a genuine outlier in the evolution of M31N 2008-12a.

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

Very high energy observations of the Galactic Centre: recent results and perspectives with CTA

NASA Astrophysics Data System (ADS)

Terrier, Regis

2016-07-01

The central 300 pc of our Galaxy are a major laboratory for high energy astrophysics. They harbor the closest supermassive black hole (SMBH) and are the site of a sustained star formation activity. The energy released by the supernovae on the ambient medium must be very strong. Similarly, albeit extremely faint nowadays, the SMBH must have experienced episodes of intense activity in the past which can influence significantly the central regions and beyond, e.g. powering the Fermi bubbles. I review observational results at very high energies from the central region and discuss their implications and the questions they leave open. I discuss the perspectives CTA offers for Galactic Centre astrophysics.

EMISSION-LINE OBJECTS PROJECTED UPON THE GALACTIC BULGE*

PubMed Central

Herbig, G. H.

1969-01-01

Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Hα line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean Mv ≈ -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae. Images PMID:16578699

Emission-line objects projected upon the galactic bulge.

PubMed

Herbig, G H

1969-08-01

Low-dispersion slit spectrograms have been obtained of 34 faint objects that lie in the direction of the galactic bulge and have the Halpha line in emission upon a detectable continuum. Eleven of these are certain or probable symbiotic stars. A rough comparison with R CrB stars in the same area suggests that these brightest symbiotics in the bulge have in the mean M(v) approximately -3 to -4, which suggest Population II red giants rather than conventional Population I M-type objects. The sample also contains a number of hot stars having H and [O II] or [O III] in emission, as well as four conventional Be stars, and six certain or possible planetary nebulae.

Spectroscopy of asteroids in unusual orbits

NASA Technical Reports Server (NTRS)

Cochran, W. D.; Cochran, A. L.; Barker, E. S.

1986-01-01

Medium-resolution spectroscopy of a collection of nonmain-belt asteroids has been obtained in order to search for possible cometlike spectral features. The asteroids include nine earth approachers, two Trojans, and the unusual object 2060 Chiron. All spectra were obtained and reduced in the same manner as comet data in the McDonald Observatory Faint Comet Survey. No indication of cometary activity was found in any of the asteroids observed.

Direct Observation of Hot Jupiters and Other Faint Companions with the VLTI

NASA Astrophysics Data System (ADS)

Coudé du Foresto, Vincent

The existence of Jupiter-size planets very close to their parent stars (two examples of which are 51 Peg and τ Boo) creates a challenge for theories of planetary formation and structure. Only a direct measurement of their mass and luminosity (not accessible via the current radial velocity techniques) can help discriminate between the different models that have been proposed for this class of objects.

What's Going on Around BN

NASA Technical Reports Server (NTRS)

Erickson, Edwin; Colgan, S. W. J.; Schultz, A. S. B.; Simpson, J. P.; Burton, M. G.; Kaufman, M. J.; Young, E. T.; Stolovy, S.

2005-01-01

The Becklin-Neugebauer object, discovered in observations made by Eric Becklin as a graduate student, is the brightest mid-infrared source outside the solar system, and a beacon in the nearest region of massive star formation. Using NICMOS on HST, we have obtained near infrared photometric, spectroscopic, and polarimetric images of the region immediately around BN. These images, with resolutions < -0.2", reveal remarkable morphologies, shock details, new young stellar objects, faint stars with variable intensities, and outflow features. We will summarize these results and inferences regarding the shock properties, illuminating sources of the nebulosity, and IRc sources near BN.

Speckle imaging for planetary research

NASA Technical Reports Server (NTRS)

Nisenson, P.; Goody, R.; Apt, J.; Papaliolios, C.

1983-01-01

The present study of speckle imaging technique effectiveness encompasses image reconstruction by means of a division algorithm for Fourier amplitudes, and the Knox-Thompson (1974) algorithm for Fourier phases. Results which have been obtained for Io, Titan, Pallas, Jupiter and Uranus indicate that spatial resolutions lower than the seeing limit by a factor of four are obtainable for objects brighter than Uranus. The resolutions obtained are well above the diffraction limit, due to inadequacies of the video camera employed. A photon-counting camera has been developed to overcome these difficulties, making possible the diffraction-limited resolution of objects as faint as Charon.

Global astrometry with the space interferometry mission

NASA Technical Reports Server (NTRS)

Boden, A.; Unwin, S.; Shao, M.

1997-01-01

The prospects for global astrometric measurements with the space interferometry mission (SIM) are discussed. The SIM mission will perform four microarcsec astrometric measurements on objects as faint as 20 mag using the optical interferometry technique with a 10 m baseline. The SIM satellite will perform narrow angle astrometry and global astrometry by means of an astrometric grid. The sensitivities of the SIM global astrometric performance and the grid accuracy versus instrumental parameters and sky coverage schemes are reported on. The problems in finding suitable astrometric grid objects to support microarcsec astrometry, and related ground-based observation programs are discussed.

Near Infrared Imaging of the Hubble Deep Field with Keck Telescope

NASA Technical Reports Server (NTRS)

Hogg, David W.; Neugebauer, G.; Armus, Lee; Matthews, K.; Pahre, Michael A.; Soifer, B. T.; Weinberger, A. J.

1997-01-01

Two deep K-band (2.2 micrometer) images, with point-source detection limits of K=25.2 mag (one sigma), taken with the Keck Telescope in subfields of the Hubble Deep Field, are presented and analyzed. A sample of objects to K=24 mag is constructed and V(sub 606)- I(sub 814) and I(sub 814)-K colors are measured. By stacking visually selected objects, mean I(sub 814)-K colors can be measured to very faint levels, the mean I(sub 814)-K color is constant with apparent magnitude down to V(sub 606)=28 mag.

Clustering of High-Redshift Quasars

NASA Astrophysics Data System (ADS)

Timlin, John D., III

In this work, we investigate the clustering of faint quasars in the early Universe and use the clustering strength to gain a better understanding of quasar feedback mechanisms and the growth of central supermassive black holes at early times in the history of the Universe. It has long been understood (e.g., Hopkins et al. 2007a) that the clustering of distant quasars can be used as a probe of different feedback models; however, until now, there was no sample of faint, high-redshift quasars with sufficient density to accurately measure the clustering strength. Therefore we conducted a new survey to increase the number density of these objects. Here, we describe the Spitzer -IRAC Equatorial Survey (SpIES) which is a moderately deep, large-area Spitzer survey which was designed to discover faint, high-redshift (2.9 ≤ z ≤ 5.1) quasars. SpIES spans 115 deg 2 in the equatorial "Stripe 82" region of the Sloan Digital Sky Survey (SDSS) and probes to 5sigma depths of 6.13 microJy (21.93 AB magnitude) and 5.75 microJy (22.0 AB magnitude) at 3.6 and 4.5 microns. At these depths, SpIES is able to observe faint quasars, and we show that SpIES recovers 94% of the high-redshift (z ≥ 3.5), spectroscopically-confirmed quasars that lie within its footprint. SpIES is also ideally located on Stripe 82 for two reasons: It surrounds existing infrared data from the Spitzer-HETDEX Exploratory Large-area (SHELA) survey which increases the area of infrared coverage, and there is a wide range of multi-wavelength, multi-epoch ancillary data on Stripe 82 which we can use together to select high-redshift quasar candidates. To photometrically identify quasar candidates, we combined the optical data from the Sloan Digital Sky Survey and the infrared data from SpIES and SHELA and employed three machine learning algorithms. These algorithms were trained on the optical/infrared colors of known, high-redshift quasars. Using this method, we generate a sample of 1378 objects that are both faint (i ≥ 20.2) and high-redshift (2.9 ≤ z ≤ 5.1) which we use to compute the angular two-point correlation function. We fit a single power-law model with an index of delta = 1.39 +/- 0.618 and amplitude of theta0 = 0.71 +/- 0.546 arcmin to the correlation function, as well as a dark matter model with a bias of b = 6.78 +/- 1.79. The bias in our investigation suggests a model of quasar feedback that considers quasar activity as an intermittent phase in galaxy evolution. If this model is correct, quasar feedback is strong enough to periodically halt the accretion of gas onto the central supermassive black hole of the quasar, which shuts down quasar activity and causes the black hole to stop growing, however it is not strong enough to completely shut down the quasar in the early Universe.

First Results from the ISO-IRAS Faint Galaxy Survey

NASA Technical Reports Server (NTRS)

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

1997-01-01

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

VizieR Online Data Catalog: CoRoT observation log (N2-4.4) (CoRoT, 2009-2016)

NASA Astrophysics Data System (ADS)

COROT Team

2014-03-01

CoRoT is a space astronomy mission devoted to the study of the variability with time of stars brightness, with an extremely high accuracy (100 times better than from the ground), on very long durations (up to 150 days) and a very high duty cycle (more than 90%). The mission was led by CNES in association with four french laboratories, and 7 participating countries and agencies (Austria, Belgium, Brazil, Germany, Spain, and the ESA Science Programme). The satellite is composed of a PROTEUS platform (the 3rd in the serie), and a unique instrument: a stellar photometer. It has been launched on December 27th 2006 by a Soyuz Rocket, from Baikonour. The mission has lasted almost 6 years (the nominal 3 years duration and a 3 years extension) and has observed more than 160 000 stars. It stopped to send data suddenly on November 2nd 2012. CoRoT is performing Ultra High Precision Photomery of Stars to detect and characterise the variability of their luminosity with two main directions: - variability of the object itself: oscillations, rotation, magnetic activity - variability due to external causes as bodies in orbit around the star: planets and stars The original scientific objectives were focussed on the study of stellar pulsations (asteroseismology) to probe the internal structure of stars, and the detection of small exoplanets through their "transit in front of their host star, and the measurement of their size. This lead to introduce two modes of observations, working simultaneously: - The bright star mode dedicated to very precise seismology of a small sample of bright and closeby stars (data presented in file momentarily named "astero.dat", but should change in the near future to to "bright star.dat") - The faint star mode, observing a very large number of stars at the same time, to detect transits, which are rare events, as they imply the alignment of the star, the planet and the observer (data presented in momentarily named "exo.dat" but should change in the near future to "faint star.dat"). The large amount of data gathered in this mode mode turned out to be extremely fruitful for many topics of stellar physics. Due to project constraints, two regions of the sky were accessible (circles of 10 degrees centered on the equator around alpha=06:50 and alpha=18:50). They are called the CoRoT eyes: the fisrt one is called the "anticenter" eye, whereas the second one is called the "center eye". Each pointing covers 1.4x2.8 square degrees The CoRoT project is still processing the data, aiming at at removing instrumental artifacts and defects. Therefore the format and content of the catalog is still somehow evolving. More details on the data can be found in the "CoRoTN2versions_30sept2014.pdf" document available on the vizier ftp as well as project websites listed in the "See also" field below. (3 data files).

Optical Studies of Orbital Debris at GEO Using Two Telescopes

NASA Technical Reports Server (NTRS)

Seitzer, P.; Abercromby, K. J.; Rodriquez,H. M.; Barker, E.

2008-01-01

Beginning in March, 2007, optical observations of debris at geosynchronous orbit (GEO) were commenced using two telescopes simultaneously at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. The University of Michigan's 0.6/0.9-m Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope) was used in survey mode to find objects that potentially could be at GEO. Because GEO objects only appear in this telescope's field of view for an average of 5 minutes, a full six-parameter orbit can not be determined. Interrupting the survey for follow-up observations leads to incompleteness in the survey results. Instead, as objects are detected on MODEST, initial predictions assuming a circular orbit are done for where the object will be for the next hour, and the objects are reacquired as quickly as possible on the CTIO 0.9-m telescope. This second telescope then follows-up during the first night and, if possible, over several more nights to obtain the maximum time arc possible, and the best six parameter orbit. Our goal is to obtain an initial orbit for all detected objects fainter than R = 15th in order to estimate the orbital distribution of objects selected on the basis of two observational criteria: magnitude and angular rate. Objects fainter than 15th are largely uncataloged and have a completely different angular rate distribution than brighter objects. Combining the information obtained for both faint and bright objects yields a more complete picture of the debris environment rather than just concentrating on the faint debris. One objective is to estimate what fraction of objects selected on the basis of angular rate are not at GEO. A second objective is to obtain magnitudes and colors in standard astronomical filters (BVRI) for comparison with reflectance spectra of likely spacecraft materials. This paper reports on results from two 14 night runs with both telescopes: in March and November 2007: (1) A significant fraction of objects fainter than R = 15th have eccentric orbits (e > 0.1) (2) Virtually all objects selected on the basis of angular rate are in the GEO and GTO regimes. (3) Calibrated magnitudes and colors in BVRI were obtained for many objects fainter than R = 15th magnitude. This work is supported by NASA's Orbital Debris Program Office, Johnson Space Center, Houston, Texas, USA.

Star formation rate and extinction in faint z ∼ 4 Lyman break galaxies

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

To, Chun-Hao; Wang, Wei-Hao; Owen, Frazer N.

We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ∼ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images in the GOODS-N. We select a large sample of 1771 z ∼ 4 LBGs from the ACS catalog using B {sub F435W}-dropout color criteria. Our LBG samples have I {sub F775W} ∼ 25-28 (AB), ∼0-3 mag fainter than M{sub UV}{sup ⋆} at zmore » ∼ 4. In our stacked radio images, we find the LBGs to be point-like under our 2'' angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of S {sub 1.5} {sub GHz} = 0.210 ± 0.075 μJy at ∼3σ for the first time on such a faint LBG population at z ∼ 4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an obscured SFR of 16.0 ± 5.7 M {sub ☉} yr{sup –1}, and implies a rest-frame UV extinction correction factor of 3.8. This extinction correction is in excellent agreement with that derived from the observed UV continuum spectral slope, using the local calibration of Meurer et al. This result supports the use of the local calibration on high-redshift LBGs to derive the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.« less

Active galactic nuclei cores in infrared-faint radio sources. Very long baseline interferometry observations using the Very Long Baseline Array

NASA Astrophysics Data System (ADS)

Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

2015-06-01

Context. Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z ≳ 2). Aims: Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. Methods: We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Results: Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginally higher VLBI detection fraction than randomly selected sources with mJy flux densities at arcsec-scales. Moreover, our data provide a positive correlation between compactness - defined as the ratio of milliarcsec- to arcsec-scale flux density - and redshift for IFRS, but suggest a decreasing mean compactness with increasing arcsec-scale radio flux density. Based on these findings, we suggest that IFRS tend to contain young AGNs whose jets have not formed yet or have not expanded, equivalent to very compact objects. We found two IFRS that are resolved into two components. The two components are spatially separated by a few hundred milliarcseconds in both cases. They might be components of one AGN, a binary black hole, or the result of gravitational lensing.

Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

NASA Astrophysics Data System (ADS)

Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

2016-12-01

Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

Improving the astrometric performance of VLTI-PRIMA

NASA Astrophysics Data System (ADS)

Woillez, J.; Abuter, R.; Andolfato, L.; Berger, J.-P.; Bonnet, H.; Delplancke, F.; Derie, F.; Di Lieto, N.; Guniat, S.; Mérand, A.; Duc, T. Phan; Schmid, C.; Schuhler, N.; Henning, T.; Launhardt, R.; Pepe, F.; Queloz, D.; Quirrenbach, A.; Reffert, S.; Sahlmann, J.; Segransan, D.

2014-07-01

In the summer of 2011, the first on-sky astrometric commissioning of PRIMA-Astrometry delivered a performance of 3 m″ for a 10 ″ separation on bright objects, orders of magnitude away from its exoplanet requirement of 50 μ″ ~ 20 μ″ on objects as faint as 11 mag ~ 13 mag in K band. This contribution focuses on upgrades and characterizations carried out since then. The astrometric metrology was extended from the Coudé focus of the Auxillary Telescopes to their secondary mirror, in order to reduce the baseline instabilities and improve the astrometric performance. While carrying out this extension, it was realized that the polarization retardance of the star separator derotator had a major impact on both the astrometric metrology and the fringe sensors. A local compensation of this retardance and the operation on a symmetric baseline allowed a new astrometric commissioning. In October 2013, an improved astrometric performance of 160 μ″ was demonstrated, still short of the requirements. Instabilities in the astrometric baseline still appear to be the dominating factor. In preparation to a review held in January 2014, a plan was developed to further improve the astrometric and faint target performance of PRIMA Astrometry. On the astrometric aspect, it involved the extension of the internal longitudinal metrology to primary space, the design and implementation of an external baseline metrology, and the development of an astrometric internal fringes mode. On the faint target aspect, investigations of the performance of the fringe sensor units and the development of an AO system (NAOMI) were in the plan. Following this review, ESO decided to take a proposal to the April 2014 STC that PRIMA be cancelled, and that ESO resources be concentrated on ensuring that Gravity and Matisse are a success. This proposal was recommended by the STC in May 2014, and endorsed by ESO.

The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

2011-02-01

We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

A Spectroscopic Survey of Lensed Dwarf Galaxies at 1

NASA Astrophysics Data System (ADS)

Alavi, Anahita; Siana, Brian; gburek, Timothy; Richard, Johan; Teplitz, Harry; Rafelski, Marc; Stark, Daniel P.; Anahita Alavi

2018-01-01

High-redshift dwarf galaxies (M<109 M⊙) are one of the primary targets of the James Web Space Telescope. Recent studies have suggested that these galaxies are different than their bright counterparts, as they follow a divergent evolutionary history of star formation. In our previous study, utilizing the magnification from massive clusters of galaxies (Hubble Frontier Fields), we found a large sample of dwarf star-forming galaxies at the peak epoch of star formation (1

An Improved Technique for the Photometry and Astrometry of Faint Companions

NASA Astrophysics Data System (ADS)

Burke, Daniel; Gladysz, Szymon; Roberts, Lewis; Devaney, Nicholas; Dainty, Chris

2009-07-01

We propose a new approach to differential astrometry and photometry of faint companions in adaptive optics images. It is based on a prewhitening matched filter, also referred to in the literature as the Hotelling observer. We focus on cases where the signal of the companion is located within the bright halo of the parent star. Using real adaptive optics data from the 3 m Shane telescope at the Lick Observatory, we compare the performance of the Hotelling algorithm with other estimation algorithms currently used for the same problem. The real single-star data are used to generate artificial binary objects with a range of magnitude ratios. In most cases, the Hotelling observer gives significantly lower astrometric and photometric errors. In the case of high Strehl ratio (SR) data (SR ≈ 0.5), the differential photometry of a binary star with a Δm = 4.5 and a separation of 0.6″ is better than 0.1 mag a factor of 2 lower than the other algorithms considered.

THE DETECTION OF ULTRA-FAINT LOW SURFACE BRIGHTNESS DWARF GALAXIES IN THE VIRGO CLUSTER: A PROBE OF DARK MATTER AND BARYONIC PHYSICS

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

Giallongo, E.; Menci, N.; Grazian, A.

2015-11-01

We have discovered 11 ultra-faint (r ≲ 22.1) low surface brightness (LSB, central surface brightness 23 ≲ μ{sub r} ≲ 26) dwarf galaxy candidates in one deep Virgo field of just 576 arcmin{sup 2} obtained by the Large Binocular Camera at the Large Binocular Telescope. Their association with the Virgo cluster is supported by their distinct position in the central surface brightness—total magnitude plane with respect to the background galaxies of similar total magnitude. They have typical absolute magnitudes and scale sizes, if at the distance of Virgo, in the range −13 ≲ M{sub r} ≲ −9 and 250 ≲more » r{sub s} ≲ 850 pc, respectively. Their colors are consistent with a gradually declining star formation history with a specific star formation rate of the order of 10{sup −11} yr{sup −1}, i.e., 10 times lower than that of main sequence star-forming galaxies. They are older than the cluster formation age and appear to be regular in morphology. They represent the faintest extremes of the population of low luminosity LSB dwarfs that has recently been detected in wider surveys of the Virgo cluster. Thanks to the depth of our observations, we are able to extend the Virgo luminosity function down to M{sub r} ∼ −9.3 (corresponding to total masses M ∼ 10{sup 7} M{sub ⊙}), finding an average faint-end slope α ≃ −1.4. This relatively steep slope puts interesting constraints on the nature of the dark matter and, in particular, on warm dark matter (WDM) often invoked to solve the overprediction of the dwarf number density by the standard cold dark matter scenario. We derive a lower limit on the WDM particle mass >1.5 keV.« less

Minor Contribution of Quasars to Ionizing Photon Budget at z ˜ 6: Update on Quasar Luminosity Function at the Faint End with Subaru/Suprime-Cam

NASA Astrophysics Data System (ADS)

Onoue, Masafusa; Kashikawa, Nobunari; Willott, Chris J.; Hibon, Pascale; Im, Myungshin; Furusawa, Hisanori; Harikane, Yuichi; Imanishi, Masatoshi; Ishikawa, Shogo; Kikuta, Satoshi; Matsuoka, Yoshiki; Nagao, Tohru; Niino, Yuu; Ono, Yoshiaki; Ouchi, Masami; Tanaka, Masayuki; Tang, Ji-Jia; Toshikawa, Jun; Uchiyama, Hisakazu

2017-10-01

We constrain the quasar contribution to the cosmic reionization based on our deep optical survey of z ˜ 6 quasars down to z R = 24.15 using Subaru/Suprime-Cam in three UKIDSS-DXS fields covering 6.5 deg2. In Kashikawa et al. (2015), we select 17 quasar candidates and report our initial discovery of two low-luminosity quasars ({M}1450˜ -23) from seven targets, one of which might be a Lyα-emitting galaxy. From an additional optical spectroscopy, none of the four candidates out of the remaining 10 turn out to be genuine quasars. Moreover, the deeper optical photometry provided by the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) shows that, unlike the two already-known quasars, the I - z and z - y colors of the last six candidates are consistent with M- or L-type brown dwarfs. Therefore, the quasar luminosity function (QLF) measurement in the previous paper is confirmed. Compiling the QLF measurements from the literature over a wide magnitude range, including an extremely faint AGN candidate from Parsa et al. (2017), to fit them with a double power law, we find that the best-fit faint-end slope is α =-{2.04}-0.18+0.33 (-{1.98}-0.21+0.48) and characteristic magnitude is {M}1450* =-{25.8}-1.9+1.1 (-{25.7}-1.8+1.0) in the case of two (one) quasar detection. Our result suggests that, if the QLF is integrated down to {M}1450=-18, quasars produce ˜1%-12% of the ionizing photons required to fully ionize the universe at z ˜ 6 with a 2σ confidence level, assuming that the escape fraction is {f}{esc}=1 and the intergalactic medium clumpy factor is C = 3. Even when the systematic uncertainties are taken into account, our result supports the scenario that quasars are the minor contributors of the reionization.

GRB 080503: IMPLICATIONS OF A NAKED SHORT GAMMA-RAY BURST DOMINATED BY EXTENDED EMISSION

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

Perley, D. A.; Metzger, B. D.; Butler, N. R.

We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at {approx}1 hr after the Burst Alert Telescope (BAT) trigger. The optical brightness peaks at {approx}1 day and then falls sharply in a manner similar to the predictions of Li and Paczynski (1998) for supernova-like emission following compact binary mergers. However,more » a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low density medium surrounding the burst (a 'naked' GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep Hubble Space Telescope imaging. The late optical and X-ray peak could be explained by a slightly off-axis jet or by a refreshed shock. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. This extended emission is not the onset of an afterglow, and its relative brightness is probably either a viewing-angle effect or intrinsic to the central engine itself. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature.« less

Lyman Break Galaxies in the Hubble Ultra Deep Field through Deep U-Band Imaging

NASA Astrophysics Data System (ADS)

Rafelski, Marc; Wolfe, A. M.; Cooke, J.; Chen, H. W.; Armandroff, T. E.; Wirth, G. D.

2009-12-01

We introduce an extremely deep U-band image taken of the Hubble Ultra Deep Field (HUDF), with a one sigma depth of 30.7 mag arcsec-2 and a detection limiting magnitude of 28 mag arcsec-2. The observations were carried out on the Keck I telescope using the LRIS-B detector. The U-band image substantially improves the accuracy of photometric redshift measurements of faint galaxies in the HUDF at z=[2.5,3.5]. The U-band for these galaxies is attenuated by lyman limit absorption, allowing for more reliable selections of candidate Lyman Break Galaxies (LBGs) than from photometric redshifts without U-band. We present a reliable sample of 300 LBGs at z=[2.5,3.5] in the HUDF. Accurate redshifts of faint galaxies at z=[2.5,3.5] are needed to obtain empirical constraints on the star formation efficiency of neutral gas at high redshift. Wolfe & Chen (2006) showed that the star formation rate (SFR) density in damped Ly-alpha absorption systems (DLAs) at z=[2.5,3.5] is significantly lower than predicted by the Kennicutt-Schmidt law for nearby galaxies. One caveat to this result that we wish to test is whether LBGs are embedded in DLAs. If in-situ star formation is occurring in DLAs, we would see it as extended low surface brightness emission around LBGs. We shall use the more accurate photometric redshifts to create a sample of LBGs around which we will look for extended emission in the more sensitive and higher resolution HUDF images. The absence of extended emission would put limits on the SFR density of DLAs associated with LBGs at high redshift. On the other hand, detection of faint emission on scales large compared to the bright LBG cores would indicate the presence of in situ star formation in those DLAs. Such gas would presumably fuel the higher star formation rates present in the LBG cores.

Sakurai's Object Continues to Brighten and Expand

NASA Astrophysics Data System (ADS)

Hinkle, Kenneth H.; Joyce, Richard R.; Matheson, Thomas

2017-01-01

Sakurai's Object (V4334 Sgr), the prototype final flash object discovered in the mid-1990s, was observed to undergo rapid cooling becoming as faint as 25th magnitude at K during the first decade of the 21st century. A review of imaging data suggests the minimum K magnitude occurred about 2006. Sakuarai's Object was re-acquired at K in 2010. Between 2010 Sep and 2013 Apr Sakurai's object brightened more than 2 magnitudes to K=14.2. Here we report on a Gemini-NIRI K band AO image obtained in 2016 July. The Ks magnitude was 13.35. The AO image also records the continuing expansion of the debris cloud. The central star remains obscured. Spectro-spatial NIFS images of the spectral region around He I 1.0830 micron and a GMOS optical spectrum, both observed in 2015, will also be displayed.

The Orion Nebula Cluster as a Paradigm of Star Formation

NASA Astrophysics Data System (ADS)

Robberto, Massimo

2014-10-01

We propose a 52-orbit Treasury Program to investigate two fundamental questions of star formation: a) the low-mass tail of the IMF, down to a few Jupiter masses; b) the dynamical evolution of clusters, as revealed by stellar proper motions. We target the Orion Nebula Cluster (ONC) using WFC3 and ACS in coordinated parallel mode to perform a synoptic survey in the 1.345micron H2O feature and Ic broad-band. Our main objectives are: 1) to discover and classify ~500 brown dwarfs and planetary-mass objects in the field, extending the IMF down to lowest masses formed by gravitational collapse. Using the latest generation of high contrast image processing we will also search for faint companions, reaching down to sub-arcsecond separations and 1E-4 flux ratios. 2) to derive high precision (~0.2km/s) relative proper motions of low-mass stars and substellar objects (about 1000 sources total), leveraging on first epoch data obtained by our previous HST Treasury Program about 10 years ago. These data will unveil the cluster dynamics: velocity dispersion vs. mass, substructures, and the fraction of escaping sources. Only HST can access the IR H2O absorption feature sensitive to the effective temperature of substellar objects, while providing the exceptionally stable PSF needed for the detection of faint companions, and the identical ACS platform for our second epoch proper-motion survey. This program will provide the definitive HST legacy dataset on the ONC. Our High-Level Science Products will be mined by the community, both statistically to constrain competing theories of star formation, and to study in depth the multitude of exotic sources harboured by the cluster.

A Large Asymmetry in the Distribution of Faint Stars in the Inner Galaxy

NASA Astrophysics Data System (ADS)

Parker, J. E.; Humphreys, R. M.; Larsen, J. A.

2002-12-01

We present a star count analysis of the faint stars on either side of the Sun-Center line, from l=±20 deg -- ±75 deg and b=+20 deg -- +50 deg with data from 40 POSS I fields. Larsen & Humphreys (1996) found a significant asymmetry in the number of faint blue stars on either side of the line to the Galactic center with significantly more stars observed in the first quadrant. Using a galactic model, we chose color ranges to distinguish between halo/thick disk and old disk stellar populations. Our results indicate that the stellar excess is comprised of mainly halo/thick disk stars and that it increases with fainter magnitudes. In addition, we analyzed the star counts for 40 fields above the plane compared to their 40 complementary fields below the plane (b=±20 deg -- ±50 deg). We find that the excess is also present in quadrant I below the plane. It is possible that the excess in star counts may be due to a bar--induced ``wake", an interaction of the disk by a merger, or a result of a triaxial thick disk/inner halo. Spectroscopic observations have been made using both the CTIO 4 meter and the KPNO WIYN 3.5 meter telescopes with HYDRA to measure the radial velocities and classify nearly 1000 stars. The objective is to determine the extent of the asymmetry and the nature and kinematics of the stars responsible.

A New Milky Way Satellite Discovered in the Subaru/Hyper Suprime-Cam Survey

NASA Astrophysics Data System (ADS)

Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Akiyama, Masayuki; Arimoto, Nobuo; Garmilla, José A.; Lupton, Robert H.; Strauss, Michael A.; Furusawa, Hisanori; Miyazaki, Satoshi; Murayama, Hitoshi; Nishizawa, Atsushi J.; Takada, Masahiro; Usuda, Tomonori; Wang, Shiang-Yu

2016-11-01

We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way (MW) based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5σ) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in the color-magnitude diagram. The significance of this overdensity increases to 10.8σ when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main-sequence turnoff at r ˜ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M V = -0.8 ± 0.9 mag. This stellar system has an extended spatial distribution with a half-light radius of {38}-11+12 pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of Virgo I is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the MW.

Searching for Faint Companions to Nearby Stars with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Schroeder, Daniel J.; Golimowski, David A.

1996-01-01

A search for faint companions (FC's) to selected stars within 5 pc of the Sun using the Hubble Space Telescope's Planetary Camera (PC) has been initiated. To assess the PC's ability to detect FCs, we have constructed both model and laboratory-simulated images and compared them to actual PC images. We find that the PC's point-spread function (PSF) is 3-4 times brighter over the angular range 2-5 sec than the PSF expected for a perfect optical system. Azimuthal variations of the PC's PSF are 10-20 times larger than expected for a perfect PSF. These variations suggest that light is scattered nonuniformly from the surface of the detector. Because the anomalies in the PC's PSF cannot be precisely simulated, subtracting a reference PSF from the PC image is problematic. We have developed a computer algorithm that identifies local brightness anomalies within the PSF as potential FCs. We find that this search algorithm will successfully locate FCs anywhere within the circumstellar field provided that the average pixel signal from the FC is at least 10 sigma above the local background. This detection limit suggests that a comprehensive search for extrasolar Jovian planets with the PC is impractical. However, the PC is useful for detecting other types of substellar objects. With a stellar signal of 10(exp 9) e(-), for example, we may detect brown dwarfs as faint as M(sub I) = 16.7 separated by 1 sec from alpha Cen A.

The International Ultraviolet Explorer: Case study in spacecraft design

NASA Technical Reports Server (NTRS)

Freeman, H. R.; Longanecker, G. W.

1979-01-01

The International Ultraviolet Explorer (IUE) is a geosynchronous scientific satellite that was conceived as an international space observatory capable of measuring UV spectra of faint celestial bodies. Simple operational procedures allow the astronomers to joystick the spaceborne telescope about the sky, using familiar ground-based observatory techniques. The present paper deals with the IUE project objectives, the technical problems, constraints, trade-offs, and the problem solving techniques used in the IUE program.

VizieR Online Data Catalog: Texas-Oxford NVSS (TONS) radio galaxies (Brand+, 2005)

NASA Astrophysics Data System (ADS)

Brand, K.; Rawlings, S.; Hill, G. J.; Tufts, J. R.

2005-10-01

Optical spectra were obtained during the period 2000 October-2003 May on the 2.6-m Nordic Optical Telescope (NOT) using the Andalucia faint object spectrograph, the 4.2-m William Herschel telescope (WHT) using ISIS, the 2.7-m Smith reflector at McDonald with the Imaging Grism Instrument (IGI), and the Hobby-Eberly Telescope (HET) using the Marcario low-resolution spectrograph (LRS). (3 data files).

Weighing the Smallest Stars

NASA Astrophysics Data System (ADS)

2005-01-01

VLT Finds Young, Very Low Mass Objects Are Twice As Heavy As Predicted Summary Thanks to the powerful new high-contrast camera installed at the Very Large Telescope, photos have been obtained of a low-mass companion very close to a star. This has allowed astronomers to measure directly the mass of a young, very low mass object for the first time. The object, more than 100 times fainter than its host star, is still 93 times as massive as Jupiter. And it appears to be almost twice as heavy as theory predicts it to be. This discovery therefore suggests that, due to errors in the models, astronomers may have overestimated the number of young "brown dwarfs" and "free floating" extrasolar planets. PR Photo 03/05: Near-infrared image of AB Doradus A and its companion (NACO SDI/VLT) A winning combination A star can be characterised by many parameters. But one is of uttermost importance: its mass. It is the mass of a star that will decide its fate. It is thus no surprise that astronomers are keen to obtain a precise measure of this parameter. This is however not an easy task, especially for the least massive ones, those at the border between stars and brown dwarf objects. Brown dwarfs, or "failed stars", are objects which are up to 75 times more massive than Jupiter, too small for major nuclear fusion processes to have ignited in its interior. To determine the mass of a star, astronomers generally look at the motion of stars in a binary system. And then apply the same method that allows determining the mass of the Earth, knowing the distance of the Moon and the time it takes for its satellite to complete one full orbit (the so-called "Kepler's Third Law"). In the same way, they have also measured the mass of the Sun by knowing the Earth-Sun distance and the time - one year - it takes our planet to make a tour around the Sun. The problem with low-mass objects is that they are very faint and will often be hidden in the glare of the brighter star they orbit, also when viewed in large telescopes. Astronomers have however found ways to overcome this difficulty. For this, they rely on a combination of a well-considered observational strategy with state-of-the-art instruments. High contrast camera First, astronomers searching for very low mass objects look at young nearby stars because low-mass companion objects will be brightest while they are young, before they contract and cool off. In this particular case, an international team of astronomers [1] led by Laird Close (Steward Observatory, University of Arizona), studied the star AB Doradus A (AB Dor A). This star is located about 48 light-years away and is "only" 50 million years old. Because the position in the sky of AB Dor A "wobbles", due to the gravitational pull of a star-like object, it was believed since the early 1990s that AB Dor A must have a low-mass companion. To photograph this companion and obtain a comprehensive set of data about it, Close and his colleagues used a novel instrument on the European Southern Observatory's Very Large Telescope. This new high-contrast adaptive optics camera, the NACO Simultaneous Differential Imager, or NACO SDI [2], was specifically developed by Laird Close and Rainer Lenzen (Max-Planck-Institute for Astronomy in Heidelberg, Germany) for hunting extrasolar planets. The SDI camera enhances the ability of the VLT and its adaptive optics system to detect faint companions that would normally be lost in the glare of the primary star. A world premiere ESO PR Photo 03/05 ESO PR Photo 03/05 Infrared image of AB Doradus A and its companion [Preview - JPEG: 400 x 406 pix - 99k] [Normal - JPEG: 800 x 812 pix - 235k] Caption: ESO PR Photo 03/05 is an enhanced, false-colour near-infrared image of AB Dor A and C. The faint companion "AB Dor C" - seen as the pink dot at 8 o'clock - is 120 times fainter than its primary star. The tiny separation between A and C, only 0.156 arcsec, is smaller than a one Euro coin seen at 20 km distance. Nevertheless, the new NACO SDI camera was able to distinguish it as a "redder" dot surrounded by the "bluer" light from AB Dor A. The orbit of AB Dor C around AB Dor A is shown as a yellow ellipse. It takes 11.75 years for the 93 Jupiter-mass companion to complete this orbit. Turning this camera towards AB Dor A in February 2004, they were able for the first time to image a companion so faint - 120 times fainter than its star - and so near its star. Says Markus Hartung (ESO), member of the team: "This world premiere was only possible because of the unique capabilities of the NACO SDI instrument on the VLT. In fact, the Hubble Space Telescope tried but failed to detect the companion, as it was too faint and too close to the glare of the primary star." The tiny distance between the star and the faint companion (0.156 arcsec) is the same as the width of a one Euro coin (2.3 cm) when seen 20 km away. The companion, called AB Dor C, was seen at a distance of 2.3 times the mean distance between the Earth and the Sun. It completes a cycle around its host star in 11.75 years on a rather eccentric orbit. Using the companion's exact location, along with the star's known 'wobble', the astronomers could then accurately determine the companion's mass. The object, more than 100 times fainter than its close primary star, has one tenth of the mass of its host star, i.e., it is 93 times more massive than Jupiter. It is thus slightly above the brown dwarf limit. Using NACO on the VLT, the astronomers further observed AB Dor C at near infrared wavelengths to measure its temperature and luminosity. "We were surprised to find that the companion was 400 degrees (Celsius) cooler and 2.5 times fainter than the most recent models predict for an object of this mass," Close said. "Theory predicts that this low-mass, cool object would be about 50 Jupiter masses. But theory is incorrect: this object is indeed between 88 to 98 Jupiter masses." These new findings therefore challenge current ideas about the brown dwarf population and the possible existence of widely publicized "free-floating" extrasolar planets. Indeed, if young objects hitherto identified as brown dwarfs are twice as massive as was thought, many must rather be low-mass stars. And objects recently identified as "free-floating" planets are in turn likely to be low-mass brown dwarfs. For Close and his colleagues, "this discovery will force astronomers to rethink what masses of the smallest objects produced in nature really are."

Uranus Rings in False Color

NASA Technical Reports Server (NTRS)

1986-01-01

This false-color view of the rings of Uranus was made from images taken by Voyager 2 on Jan. 21, 1986, from a distance of 4.17 million kilometers (2.59 million miles). All nine known rings are visible here; the somewhat fainter, pastel lines seen between them are contributed by the computer enhancement. Six 15-second narrow-angle images were used to extract color information from the extremely dark and faint rings. Two images each in the green, clear and violet filters were added together and averaged to find the proper color differences between the rings. The final image was made from these three color averages and represents an enhanced, false-color view. The image shows that the brightest, or epsilon, ring at top is neutral in color, with the fainter eight other rings showing color differences between them. Moving down, toward Uranus, we see the delta, gamma and eta rings in shades of blue and green; the beta and alpha rings in somewhat lighter tones; and then a final set of three, known simply as the 4, 5 and 6 rings, in faint off-white tones. Scientists will use this color information to try to understand the nature and origin of the ring material. The resolution of this image is approximately 40 km (25 mi). The Voyager project is managed for NASA by the Jet Propulsion Laboratory.

Breaking the Habit - The peculiar 2016 eruption of the remarkable recurrent nova M31N 2008-12a

NASA Astrophysics Data System (ADS)

Henze, Martin; M31N 2008-12a Monitoring Collaboration

2018-01-01

Since its discovery in 2008, the Andromeda galaxy nova M31N 2008-12a has been observed in eruption every year. This makes it the most extreme member of the new class of Rapidly Recurring Novae (RRN) which show repeated eruptions within a time span of a decade or less. Such frequent outbursts indicate a high mass accretion rate onto a white dwarf that is extremely close to the Chandrasekhar limit, thereby making RRN the most promising observable candidates for the progenitors of type-Ia supernovae currently known.The previous three eruptions of M31N 2008-12a have displayed remarkably homogeneous multi-wavelength properties. From a relatively faint peak brightness the optical light curve declined rapidly by two magnitudes in less than two days. Early spectra showed high velocities that declined significantly within days and displayed clear helium and nitrogen lines throughout. The supersoft X-ray source phase of the nova began extremely early, around day six after eruption, and only lasted for about two weeks.In contrast, the delayed 2016 eruption showed significant deviations from the established pattern. In this talk, I will discuss the observational results and their impact on our understanding of the physics and evolution of this unique nova.

Outreach syncope clinic managed by a nurse practitioner: Outcome and cost effectiveness.

PubMed

Hamdan, Mohamed H; Walsh, Kathleen E; Brignole, Michele; Key, Jamie

2017-01-01

Introduction The purpose of this study was to assess the clinical and financial outcomes of a novel outreach syncope clinic. Methods We compared the clinical outcome of the Faint and Fall Clinic at the American Center (January-June 2016) with that of the University of Wisconsin Health and Clinics Faint and Fall Clinic (January 2013-December 2014). The American Center-Faint and Fall Clinic is run solely by a nurse practitioner, assisted by online faint-decision software and consultancy of a faint specialist through video-conferencing. Results Five hundred and twenty-eight consecutive patients were seen at the University of Wisconsin Hospital and Clinics-Faint and Fall Clinic and 68 patients at the American Center-Faint and Fall Clinic. The patients' clinical characteristics were similar except for a lower age in the American Center patients (45 ± 18 vs 51 ± 22, p = 0.03). Overall, a diagnosis was made within 45 days in 70% (95% confidence interval 66-74%) of the University of Wisconsin Hospital and Clinics patients and 69% (95% confidence interval 58-80%) of the American Center patients, ( p = 0.9). A mean of 3.0 ± 1.6 tests per patient was used in the University of Wisconsin Hospital and Clinics group compared to 1.5 ± 0.8 tests per patient in the American Center group, p = 0.001. Over the six-month study period, the total revenue at the American Center was US$152,597 (contribution margin of US$122,393 plus professional revenue of US$30,204). The total cost of the nurse practitioner including benefits was US$66,662 ((US$98,466 salary/year + 35.4% benefits)/2). Total revenue minus expenses resulted in a net profit of US$85,935. Discussion A nurse practitioner-run outreach syncope-clinic equipped with online faint-decision software and consultancy of a faint specialist through vedio-conferencing is feasible and financially self-sustainable. It allows the dissemination of standardized high-quality syncope care to patients who have no immediate access to a tertiary teaching hospital.

Depth Perception in Space (Artist's Concept)

NASA Technical Reports Server (NTRS)

2007-01-01

This artist's concept shows how astronomers use the unique orbit of NASA's Spitzer Space Telescope and a depth-perceiving trick called parallax to determine the distance of dark planets, black holes and failed stars that lurk invisibly among us. These objects do not produce light, and are too faint to detect from Earth. However, astronomers can deduce their presence from the way they affect the light from background objects. When such a dark body passes in front of a bright star, its gravity warps the path of the star's light and causes it to brighten -- this process is called gravitational microlensing.

By comparing the 'peak brightness' of the microlensing event from two perspectives -- Earth and Spitzer -- scientists can determine how far away the dark object is. Peak brightness is the moment when the observer, the dark object and background star are most closely aligned.

Humans naturally use parallax to determine distance -- this is commonly referred to as depth perception. In the case of humans, each eye sees the position of an object differently. The brain takes each eye's perspective, and instantaneously calculates how far away the object is. In space, astronomers can use the same trick to determine the distance of an invisible dark object.

In this illustration, the dark object is the moving black ball between Earth, Spitzer and our neighboring galaxy the Small Magellanic Cloud (SMC; bottom right).

To determine the object's distance, astronomers observe the microlensing event at its 'peak brightness' from Earth when the dark object crosses our line-of-sight (dashed line) to a given star in the SMC. This represents one perspective, like looking at an object with only your left eye.

To get the other 'right eye' perspective, astronomers also observe the peak brightness with Spitzer when the object later moves through its line-of-sight. Because astronomers know the exact distance between Earth and Spitzer, they can determine the dark body's speed by timing how long it took for Spitzer to see peak brightness after astronomers observed the event on Earth. Using trigonometric equations and graphs to do the 'brain's' job, scientists can infer the dark body's distance.

The scales in this diagram are greatly exaggerated for clarity. The distance between Spitzer and the Earth is miniscule in comparison to the distance to the dark object and SMC. Since microlensing events require extremely precise alignments, even such a tiny separation is enough to measure these objects out to tremendous distances.

An algorithm for determining the rotation count of pulsars

NASA Astrophysics Data System (ADS)

Freire, Paulo C. C.; Ridolfi, Alessandro

2018-06-01

We present here a simple, systematic method for determining the correct global rotation count of a radio pulsar; an essential step for the derivation of an accurate phase-coherent ephemeris. We then build on this method by developing a new algorithm for determining the global rotational count for pulsars with sparse timing data sets. This makes it possible to obtain phase-coherent ephemerides for pulsars for which this has been impossible until now. As an example, we do this for PSR J0024-7205aa, an extremely faint Millisecond pulsar (MSP) recently discovered in the globular cluster 47 Tucanae. This algorithm has the potential to significantly reduce the number of observations and the amount of telescope time needed to follow up on new pulsar discoveries.

The Extreme Ultraviolet Flux of Very Low Mass Stars

NASA Astrophysics Data System (ADS)

Drake, Jeremy

2017-09-01

The X-ray and EUV emission of stars is vital for understanding the atmospheres and evolution of their planets. The coronae of dwarf stars later than M6 behave differently to those of earlier spectral types and are more X-ray dim and radio bright. Too faint to have been observed by EUVE, their EUV behavior is currently highly uncertain. We propose to observe a small sample of late M dwarfs using the off-axis HRC-S thin Al" filter that is sensitive to EUV emission in the 50-200 A range. The measured fluxes will be used to understand the amount of cooler coronal plasma present, and extend X-ray-EUV flux relations to the latest stellar types.

[Changes in mammographic features of breast cancer--comparison with previous films].

PubMed

Matsunaga, T; Hagiwara, K; Kimura, K; Kusama, M

1992-11-25

Mammographic features of 87 breast cancer patients were studied in comparison with their previous survey films. Changes in the mammographic features included microcalicification (28 cases), tumor shadow (35 cases) and intratumorous microcalicifications (6 cases). Seven cases had several extremely faint calcifications on the previous films, and three of six cases with clustered and scattered microcalcifications that extended over an entire breast quadrant had increased in number, density and extent. Eight cases in which clustered microcalcifications had increased in number, density and extent suggested a relationship between the increase in the extent of microcalcifications and length of time between visits. In most cases with tumor shadow, a slight localized increase in mammary gland density, irregular margins and straightened trabeculae were overlooked because of breast density.

The superiority of L3-CCDs in the high-flux and wide dynamic range regimes

NASA Astrophysics Data System (ADS)

Butler, Raymond F.; Sheehan, Brendan J.

2008-02-01

Low Light Level CCD (L3-CCD) cameras have received much attention for high cadence astronomical imaging applications. Efforts to date have concentrated on exploiting them for two scenarios: post-exposure image sharpening and ``lucky imaging'', and rapid variability in astrophysically interesting sources. We demonstrate their marked superiority in a third distinct scenario: observing in the high-flux and wide dynamic range regimes. We realized that the unique features of L3-CCDs would make them ideal for maximizing signal-to-noise in observations of bright objects (whether variable or not), and for high dynamic range scenarios such as faint targets embedded in a crowded field of bright objects. Conventional CCDs have drawbacks in such regimes, due to a poor duty cycle-the combination of short exposure times (for time-series sampling or to avoid saturation) and extended readout times (for minimizing readout noise). For different telescope sizes, we use detailed models to show that a range of conventional imaging systems are photometrically out-performed across a wide range of object brightness, once the operational parameters of the L3-CCD are carefully set. The cross-over fluxes, above which the L3-CCD is operationally superior, are surprisingly faint-even for modest telescope apertures. We also show that the use of L3-CCDs is the optimum strategy for minimizing atmospheric scintillation noise in photometric observations employing a given telescope aperture. This is particularly significant, since scintillation can be the largest source of error in timeseries photometry. These results should prompt a new direction in developing imaging instrumentation solutions for observatories.

The intraday variability in the radio-selected and X-ray-selected BL Lacertae objects

NASA Astrophysics Data System (ADS)

Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.

1998-10-01

Seven BL Lac objects have been photometrically observed in an effort to study the difference of optical intraday variability between the radio-selected BL Lac objects (RBLs) and X-ray-selected BL Lac objects (XBLs). The objects we observed are selected arbitrarily. They are four RBLs, PKS 0735+178, PKS 0754+101, OJ 287 and BL Lac, and three XBLs, H 0323+022, H 0548-322 and H 2154-304. During the observation all of them exhibited microvariation, and H 0323+022 and H 0548-322 sometimes showed brightness oscillation. PKS 0735+178 and BL Lac were in their faint states and not very active. It seems that RBLs do not show microvariability more frequently than XBLs. Table 2 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)

Stress and the Senior Leader: A Proposed Stress Reduction Program for the Military.

DTIC Science & Technology

1988-03-30

operations except when he is frozen , or faint from heat and thirst, or depressed from privation and fatigue, objective and accurate views would be...perception of things or events is probably the most important factor in causing unhealthy reactions to a stressor. The key to a discussion on stress is...regularly ingested in the diet as a constituent of protein foods . L-tryptophan shows a diurnal blood plasma pattern and may be a physiological

Astronomical Data Center Bulletin, volume 1, number 3

NASA Technical Reports Server (NTRS)

Mead, J. M.; Warren, W. H., Jr.; Nagy, T. A.

1983-01-01

A catalog of galactic O-type stars, a machine-readable version of the bright star catalog, a two-micron sky survey, sky survey sources with problematical Durchmusterung identifications, data retrieval for visual binary stars, faint blue objects, the sixth catalog of galactic Wolf-Rayet stars, declination versus magnitude distribution, the SAO-HD-GC-DM cross index catalog, star cross-identification tables, astronomical sources, bibliographical star index search updates, DO-HD and HD-DO cross indices, and catalogs, are reviewed.

The Detection of Faint Space Objects Using Solid State Imaging Detectors.

DTIC Science & Technology

1983-12-31

are con.iposed of baryonic matter . New arguments were presented against halos being composed of planets or asteroids. D. Hegyi was also invited to...being made up of baryonic matter . 5.0 THE CHARGE-COUPLED DEVICE IMAGING SYSTEM Our major hardware improvement during the past year is a stainless steel...Hegyi Department of Physics University of Michigan Ann Arbor, Michigan ABSIR:CT The problems with massive halos being composed of baryonic matter are

Search for Gravitational Wave Counterparts with Fermi GBM

NASA Technical Reports Server (NTRS)

Hui, C. M.

2017-01-01

The progenitor of short gamma-ray bursts (GRBs) is believed to be the merger of two compact objects. This type of events will also produce gravitational waves. Since the gravitational waves discovery by LIGO, the search for a joint detection with an electromagnetic counterpart has been ongoing. Fermi GBM detects approximately 40 short GRBs per year, and we have been expanding our search looking for faint events in the GBM data that did not trigger onboard.

A Study of Planetary Nebulae using the Faint Object Infrared Camera for the SOFIA Telescope

NASA Technical Reports Server (NTRS)

Davis, Jessica

2012-01-01

A planetary nebula is formed following an intermediate-mass (1-8 solar M) star's evolution off of the main sequence; it undergoes a phase of mass loss whereby the stellar envelope is ejected and the core is converted into a white dwarf. Planetary nebulae often display complex morphologies such as waists or torii, rings, collimated jet-like outflows, and bipolar symmetry, but exactly how these features form is unclear. To study how the distribution of dust in the interstellar medium affects their morphology, we utilize the Faint Object InfraRed CAmera for the SOFIA Telescope (FORCAST) to obtain well-resolved images of four planetary nebulae--NGC 7027, NGC 6543, M2-9, and the Frosty Leo Nebula--at wavelengths where they radiate most of their energy. We retrieve mid infrared images at wavelengths ranging from 6.3 to 37.1 micron for each of our targets. IDL (Interactive Data Language) is used to perform basic analysis. We select M2-9 to investigate further; analyzing cross sections of the southern lobe reveals a slight limb brightening effect. Modeling the dust distribution within the lobes reveals that the thickness of the lobe walls is higher than anticipated, or rather than surrounding a vacuum surrounds a low density region of tenuous dust. Further analysis of this and other planetary nebulae is needed before drawing more specific conclusions.

On the possibility of ground-based direct imaging detection of extra-solar planets: the case of TWA-7

NASA Astrophysics Data System (ADS)

Neuhäuser, R.; Brandner, W.; Eckart, A.; Guenther, E.; Alves, J.; Ott, T.; Huélamo, N.; Fernández, M.

2000-02-01

We show that ground-based direct imaging detection of extra-solar planets is possible with current technology. As an example, we present evidence for a possible planetary companion to the young T Tauri star 1RXSJ104230.3-334014 (=TWA-7), discovered by ROSAT as a member of the nearby TW Hya association. In an HST NICMOS F160W image, an object is detected that is more than 9 mag fainter than TWA-7, located 2.445 +/- 0.035'' south-east at a position angle of 142.24 +/- 1.34deg. One year later using the ESO-NTT with the SHARP speckle camera, we obtained H- and K-band detections of this faint object at a separation of 2.536 +/- 0.077'' and a position angle of 139.3 +/- 2.1deg. Given the known proper motion of TWA-7, the pair may form a proper motion pair. If the faint object orbits TWA-7, then its apparent magnitudes of H=16.42 +/- 0.11 and K=16.34 +/- 0.15 mag yield absolute magnitudes consistent with a ~ 106.5 yr old ~ 3 M_jup mass object according to the non-gray theory by Burrows et al. (1997). At ~ 55 pc, the angular separation of ~ 2.5'' corresponds to ~ 138 AU, clearly within typical disk sizes. However, position angles and separations are slightly more consistent with a background object than with a companion. Based on observations obtained at the European Southern Observatory, La Silla (ESO Proposals 62.I-0418 and 63.N-0178), and on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555.

The Universe Going Green: Extraordinarily Strong [OIII]5007 in Typical Dwarf Galaxies at z~3

NASA Astrophysics Data System (ADS)

Malkan, Matthew Arnold; Cohen, Daniel

2017-01-01

We constructed the average SEDs of U-dropout galaxies in the Subaru Deep Field. This sample contains more than 5000 Lyman-break galaxies at z~3. Their average near- and mid-IR colors were obtained by stacking JHK and IRAC imaging, in bins of stellar mass. At the lowest mass bins an increasingly strong excess flux is seen in the K filter. This excess can reach 1 magnitude in the broadband filter, and we attribute it to strong \\OIII $\\lambda{5007}$ line emission. The equivalent width is extraordinarily high, reaching almost 1000\\Ang\\ for the average z=3 galaxy at an i magnitude of 27. Such extreme [OIII] emission is very rare in the current epoch, only seen in a handful of metal-deficient dwarf starbursts sometimes referred to as ''Green Peas". In contrast, extreme [OIII]--strong enough to dominate the entire broad-band SED--was evidently the norm for faint galaxies at high redshift. We present evidence that these small but numerous galaxies were primarily responsible for the reionization of the Universe.

Direct evidence of a sub-stellar companion around CT Chamaeleontis

NASA Astrophysics Data System (ADS)

Schmidt, T. O. B.; Neuhäuser, R.; Seifahrt, A.; Vogt, N.; Bedalov, A.; Helling, Ch.; Witte, S.; Hauschildt, P. H.

2008-11-01

Aims: In our ongoing search for close and faint companions around T Tauri stars in the Chamaeleon star-forming region, we here present observations of a new common proper motion companion to the young T-Tauri star and Chamaeleon member CT Cha and discuss its properties in comparison to other young, low-mass objects and to synthetic model spectra from different origins. Methods: Common proper motion of the companion and CT Cha was confirmed by direct Ks-band imaging data taken with the VLT Adaptive Optics (AO) instrument NACO in February 2006 and March 2007, together with a Hipparcos binary for astrometric calibration. An additional J-band image was taken in March 2007 to obtain color information for a first classification of the companion. Moreover, AO integral field spectroscopy with SINFONI in J, and H+K bands was obtained to deduce physical parameters of the companion, such as temperature and extinction. Relative flux calibration of the bands was achieved using photometry from the NACO imaging data. Results: We found a very faint (Ks = 14.9 mag, Ks0 = 14.4 mag) object, just ~2.67´´ northwest of CT Cha corresponding to a projected separation of ~440 AU at 165 ± 30 pc. We show that CT Cha A and this faint object form a common proper motion pair and that the companion is by ≥4σ significance not a stationary background object. The near-infrared spectroscopy yields a temperature of 2600 ± 250 K for the companion and an optical extinction of AV = 5.2 ± 0.8 mag, when compared to spectra calculated from Drift-Phoenix model atmospheres. We demonstrate the validity of the model fits by comparison to several other well-known young sub-stellar objects. Conclusions: We conclude that the CT Cha companion is a very low-mass member of Chamaeleon and very likely a physical companion to CT Cha, as the probability for a by chance alignment is ≤0.01. Due to a prominent Pa-β emission in the J-band, accretion is probably still ongoing onto the CT Cha companion. From temperature and luminosity (log(L_bol/L⊙) = -2.68 ± 0.21), we derive a radius of R = 2.20_-0.60+0.81 RJup. We find a consistent mass of M = 17 ± 6 MJup for the CT Cha companion from both its luminosity and temperature when placed on evolutionary tracks. Hence, the CT Cha companion is most likely a wide brown dwarf companion or possibly even a planetary mass object. Based on observations made with ESO telescopes at the Paranal Observatory under program IDs 076.C-0292(A), 078.C-0535(A), & 279.C-5010(A). Color versions of Figs. 4, 6, 8 and 11 are only available in electronic form at http://www.aanda.org

The SDSS-XDQSO quasar targeting catalog

NASA Astrophysics Data System (ADS)

Bovy, Jo; Hennawi, J. F.; Hogg, D. W.; Myers, A. D.; Ross, N. P.

2011-01-01

We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the SDSS catalog, even at medium redshifts (2.5 < z < 3). We build models of the distributions of stars and quasars in flux space down to the flux limit by applying the extreme-deconvolution method (XD) to estimate the underlying density. We properly convolve this density with the flux uncertainties when evaluating the probability that an object is a quasar. This results in a targeting algorithm that is more principled, more efficient, and faster than other similar methods. We apply the algorithm to derive low- (z < 2.2), medium- (2.2 <= z 3.5) quasar probabilities for all 160,904,060 point-sources with dereddened i-and magnitude between 17.75 and 22.45 mag in SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar selection technique at low redshift, and out-performs all other flux-based methods for selecting the medium-redshift quasars of our primary interest. Research supported by NASA (grant NNX08AJ48G) and the NSF (grant AST-0908357).

mocca-SURVEY database I. Accreting white dwarf binary systems in globular clusters - III. Cataclysmic variables - implications of model assumptions

NASA Astrophysics Data System (ADS)

Belloni, Diogo; Zorotovic, Mónica; Schreiber, Matthias R.; Leigh, Nathan W. C.; Giersz, Mirek; Askar, Abbas

2017-06-01

In this third of a series of papers related to cataclysmic variables (CVs) and related objects, we analyse the population of CVs in a set of 12 globular cluster models evolved with the MOCCA Monte Carlo code, for two initial binary populations (IBPs), two choices of common-envelope phase (CEP) parameters, and three different models for the evolution of CVs and the treatment of angular momentum loss. When more realistic models and parameters are considered, we find that present-day cluster CV duty cycles are extremely low (≲0.1 per cent) that makes their detection during outbursts rather difficult. Additionally, the IBP plays a significant role in shaping the CV population properties, and models that follow the Kroupa IBP are less affected by enhanced angular momentum loss. We also predict from our simulations that CVs formed dynamically in the past few Gyr (massive CVs) correspond to bright CVs (as expected) and that faint CVs formed several Gyr ago (dynamically or not) represent the overwhelming majority. Regarding the CV formation rate, we rule out the notion that it is similar irrespective of the cluster properties. Finally, we discuss the differences in the present-day CV properties related to the IBPs, the initial cluster conditions, the CEP parameters, formation channels, the CV evolution models and the angular momentum loss treatments.

The Search for RR Lyrae Variables in the Dark Energy Survey

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

The Rest-frame Optical Spectroscopic Properties of Lyalpha-emitters at Z~2.5: The Physical Origins of Strong Lyalpha Emission

NASA Astrophysics Data System (ADS)

Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.; Rudie, Gwen C.

2016-12-01

We present the rest-frame optical spectroscopic properties of 60 faint (R AB ˜ 27; L ˜ 0.1 L *) Lyα-selected galaxies (LAEs) at z ≈ 2.56. These LAEs also have rest-UV spectra of their Lyα emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Lyα photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z ≈ 2-3. In particular, the LAEs have extremely high [O III] λ5008/Hβ ratios (log([O III]/Hβ) ˜ 0.8) and low [N II] λ6585/Hα ratios (log([N II]/Hα) < 1.15). Coupled with a detection of the [O III] λ4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T e ≈ 1.8 × 104 K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z neb ≈ 0.22Z ⊙), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9-7.4 (Z neb ≈ 0.02-0.05Z ⊙). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Lyα emission across the largest current sample of combined Lyα and rest-optical galaxy spectroscopy, including both the 60 KBSS-Lyα LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Lyα emissivity (parameterized by the Lyα equivalent width) is strongly correlated with nebular excitation and ionization properties and weakly correlated with dust attenuation, suggesting that metallicity plays a strong role in determining the observed properties of these galaxies by modulating their stellar spectra, nebular excitation, and dust content. Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.

THE REST-FRAME OPTICAL SPECTROSCOPIC PROPERTIES OF LY α -EMITTERS AT z  ∼ 2.5: THE PHYSICAL ORIGINS OF STRONG LY α EMISSION

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

Trainor, Ryan F.; Strom, Allison L.; Steidel, Charles C.

We present the rest-frame optical spectroscopic properties of 60 faint ( R {sub AB} ∼ 27; L ∼ 0.1 L {sub *}) Ly α -selected galaxies (LAEs) at z  ≈ 2.56. These LAEs also have rest-UV spectra of their Ly α emission line morphologies, which trace the effects of interstellar and circumgalactic gas on the escape of Ly α photons. We find that the LAEs have diverse rest-optical spectra, but their average spectroscopic properties are broadly consistent with the extreme low-metallicity end of the populations of continuum-selected galaxies selected at z  ≈ 2–3. In particular, the LAEs have extremely high [O iii]more » λ 5008/H β ratios (log([O iii]/H β ) ∼ 0.8) and low [N ii] λ 6585/H α ratios (log([N ii]/H α ) < 1.15). Coupled with a detection of the [O iii] λ 4364 auroral line, these measurements indicate that the star-forming regions in faint LAEs are characterized by high electron temperatures (T{sub e} ≈ 1.8 × 10{sup 4} K), low oxygen abundances (12 + log(O/H) ≈ 8.04, Z{sub neb} ≈ 0.22 Z {sub ⊙}), and high excitations with respect to their more luminous continuum-selected analogs. Several of our faintest LAEs have line ratios consistent with even lower metallicities, including six with 12 + log(O/H) ≈ 6.9–7.4 (Z {sub neb} ≈ 0.02–0.05 Z{sub ⊙}). We interpret these observations in light of new models of stellar evolution (including binary interactions) that have been shown to produce long-lived populations of hot, massive stars at low metallicities. We find that strong, hard ionizing continua are required to reproduce our observed line ratios, suggesting that faint galaxies are efficient producers of ionizing photons and important analogs of reionization-era galaxies. Furthermore, we investigate the physical trends accompanying Ly α emission across the largest current sample of combined Ly α and rest-optical galaxy spectroscopy, including both the 60 KBSS-Ly α LAEs and 368 more luminous galaxies at similar redshifts. We find that the net Ly α emissivity (parameterized by the Ly α equivalent width) is strongly correlated with nebular excitation and ionization properties and weakly correlated with dust attenuation, suggesting that metallicity plays a strong role in determining the observed properties of these galaxies by modulating their stellar spectra, nebular excitation, and dust content.« less

Polarimeter Arrays for Cosmic Microwave Background Measurements

NASA Technical Reports Server (NTRS)

Stevenson, Thomas; Cao, Nga; Chuss, David; Fixsen, Dale; Hsieh, Wen-Ting; Kogut, Alan; Limon, Michele; Moseley, S. Harvey; Phillips, Nicholas; Schneider, Gideon

2006-01-01

We discuss general system architectures and specific work towards precision measurements of Cosmic Microwave Background (CMB) polarization. The CMB and its polarization carry fundamental information on the origin, structure, and evolution of the universe. Detecting the imprint of primordial gravitational radiation on the faint polarization of the CMB will be difficult. The two primary challenges will be achieving both the required sensitivity and precise control over systematic errors. At anisotropy levels possibly as small as a few nanokelvin, the gravity-wave signal is faint compared to the fundamental sensitivity limit imposed by photon arrival statistics, and one must make simultaneous measurements with large numbers, hundreds to thousands, of independent background-limited direct detectors. Highly integrated focal plane architectures, and multiplexing of detector outputs, will be essential. Because the detectors, optics, and even the CMB itself are brighter than the faint gravity-wave signal by six to nine orders of magnitude, even a tiny leakage of polarized light reflected or diffracted from warm objects could overwhelm the primordial signal. Advanced methods of modulating only the polarized component of the incident radiation will play an essential role in measurements of CMB polarization. One promising general polarimeter concept that is under investigation by a number of institutions is to first use planar antennas to separate millimeter-wave radiation collected by a lens or horn into two polarization channels. Then the signals can be fed to a pair of direct detectors through a planar circuit consisting of superconducting niobium microstrip transmission lines, hybrid couplers, band-pass filters, and phase modulators to measure the Stokes parameters of the incoming radiation.

CFHT and VLT Identify Extremely Remote Galaxy

NASA Astrophysics Data System (ADS)

2003-05-01

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

The stellar wind of an O8.5 I(f) star in M 31

NASA Technical Reports Server (NTRS)

Haser, S. M.; Lennon, D. J.; Kudritzki, R.-P.; Puls, J.; Pauldrach, A. W. A.; Bianchi, L.; Hutchings, J. B.

1995-01-01

We rediscuss the UV spectrum of OB 78#231, an O8.5 I(f) star in the Andromeda galaxy M 31, which has been obtained with the Faint Object Spectrograph on the Hubble Space Telescope by Hutchings et al. (1992). The spectrum has been re-extracted with better knowledge of background, calibration, and scattered light. The empirical analysis of the stellar wind lines results in a terminal velocity and mass loss rate similar to those typically found in comparable galactic objects. Furthermore, a comparison with an FOS spectrum of an O7 supergiant in the Small Magellanic Cloud and IUE spectra of galactic objects implies a metallicity close to galactic counterparts. These results are confirmed quantitatively by spectrum synthesis calculations using a theoretical description of O-star winds.

The little Galaxies that could (reionize the universe): predicting faint end slopes & escape fractions at z>4

NASA Astrophysics Data System (ADS)

Anderson, Lauren; Governato, F.; Karcher, M.; Quinn, T.; Wadsley, J.

2017-07-01

The sources that reionized the universe are still unknown, but likely candidates are faint but numerous galaxies. In this paper, we present results from running a high-resolution, uniform volume simulation, the Vulcan, to predict the number densities of undetectable, faint galaxies and their escape fractions of ionizing radiation, fesc, during reionization. Our approach combines a high spatial resolution, a realistic treatment of feedback and hydroprocesses, a strict threshold for minimum number of resolution elements per galaxy, and a converged measurement of fesc. We calibrate our physical model using a novel approach to create realistic galaxies at z = 0, so the simulation is predictive at high redshifts. With this approach, we can (1) robustly predict the evolution of the galaxy UV luminosity function at faint magnitudes down to MUV ˜ -15, two magnitudes fainter than observations, and (2) estimate fesc over a large range of galaxy masses based on the detailed stellar and gas distributions in resolved galaxies. We find steep faint end slopes, implying high number densities of faint galaxies, and the dependence of fesc on the UV magnitude of a galaxy, given by the power law: log fesc = (0.51 ± 0.04)MUV + 7.3 ± 0.8, with the faint population having fesc ˜ 35 per cent. Convolving the UV luminosity function with fesc(MUV), we find an ionizing emissivity that is (1) dominated by the faintest galaxies and (2) reionizes the universe at the appropriate rate, consistent with observational constraints of the ionizing emissivity and the optical depth to the decoupling surface τes, without the need for additional sources of ionizing radiation.

The quenching of the ultra-faint dwarf galaxies in the reionization era

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

Brown, Thomas M.; Tumlinson, Jason; Kalirai, Jason S.

2014-12-01

We present new constraints on the star formation histories of six ultra-faint dwarf galaxies: Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I. Our analysis employs a combination of high-precision photometry obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, medium-resolution spectroscopy obtained with the DEep Imaging Multi-Object Spectrograph on the W. M. Keck Observatory, and updated Victoria-Regina isochrones tailored to the abundance patterns appropriate for these galaxies. The data for five of these Milky Way satellites are best fit by a star formation history where at least 75% of the starsmore » formed by z ∼ 10 (13.3 Gyr ago). All of the galaxies are consistent with 80% of the stars forming by z ∼ 6 (12.8 Gyr ago) and 100% of the stars forming by z ∼ 3 (11.6 Gyr ago). The similarly ancient populations of these galaxies support the hypothesis that star formation in the smallest dark-matter sub-halos was suppressed by a global outside influence, such as the reionization of the universe.« less

A Hero’s Dark Horse: Discovery of an Ultra-faint Milky Way Satellite in Pegasus

NASA Astrophysics Data System (ADS)

Kim, Dongwon; Jerjen, Helmut; Mackey, Dougal; Da Costa, Gary S.; Milone, Antonino P.

2015-05-01

We report the discovery of an ultra-faint Milky Way satellite galaxy in the constellation of Pegasus. The concentration of stars was detected by applying our overdensity detection algorithm to the SDSS-DR 10 and confirmed with deeper photometry from the Dark Energy Camera at the 4 m Blanco telescope. Fitting model isochrones indicates that this object, Pegasus III, features an old and metal-poor stellar population ([Fe/H] ˜ -2.1) at a heliocentric distance of 205 ± 20 kpc. The new stellar system has an estimated half-light radius of {{r}h}=78-24+30 pc and a total luminosity of {{M}V}˜ -4.1+/- 0.5 that places it into the domain of dwarf galaxies on the size-luminosity plane. Pegasus III is spatially close to the MW satellite Pisces II. It is possible that the two might be physically associated, similar to the Leo IV and Leo V pair. Pegasus III is also well aligned with the Vast Polar Structure, which suggests a possible physical association.

Is This Speck of Light an Exoplanet?

NASA Astrophysics Data System (ADS)

2004-09-01

VLT Images and Spectra of Intriguing Object near Young Brown Dwarf [1] Summary Is this newly discovered feeble point of light the long-sought bona-fide image of an exoplanet? A research paper by an international team of astronomers [2] provides sound arguments in favour, but the definitive answer is now awaiting further observations. On several occasions during the past years, astronomical images revealed faint objects, seen near much brighter stars. Some of these have been thought to be those of orbiting exoplanets, but after further study, none of them could stand up to the real test. Some turned out to be faint stellar companions, others were entirely unrelated background stars. This one may well be different. In April of this year, the team of European and American astronomers detected a faint and very red point of light very near (at 0.8 arcsec angular distance) a brown-dwarf object, designated 2MASSWJ1207334-393254. Also known as "2M1207", this is a "failed star", i.e. a body too small for major nuclear fusion processes to have ignited in its interior and now producing energy by contraction. It is a member of the TW Hydrae stellar association located at a distance of about 230 light-years. The discovery was made with the adaptive-optics supported NACO facility [3] at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory (Chile). The feeble object is more than 100 times fainter than 2M1207 and its near-infrared spectrum was obtained with great efforts in June 2004 by NACO, at the technical limit of the powerful facility. This spectrum shows the signatures of water molecules and confirms that the object must be comparatively small and light. None of the available observations contradict that it may be an exoplanet in orbit around 2M1207. Taking into account the infrared colours and the spectral data, evolutionary model calculations point to a 5 jupiter-mass planet in orbit around 2M1207. Still, they do not yet allow a clear-cut decision about the real nature of this intriguing object. Thus, the astronomers refer to it as a "Giant Planet Candidate Companion (GPCC)" [4]. Observations will now be made to ascertain whether the motion in the sky of GPCC is compatible with that of a planet orbiting 2M1207. This should become evident within 1-2 years at the most. PR Photo 26a/04: NACO image of the brown dwarf object 2M1207 and GPCC PR Photo 26b/04: Near-infrared spectrum of the brown dwarf object 2M1207 and GPCC PR Photo 26c/04: Comparison between the possible 2M1207 system and the solar system Just a speck of light ESO PR Photo 26a/04 ESO PR Photo 26a/04 The Brown Dwarf Object 2M1207 and GPCC [Preview - JPEG: 400 x 471 pix - 65k] [Normal - JPEG: 800 x 942 pix - 158k] Caption: ESO PR Photo 26a/04 is a composite image of the brown dwarf object 2M1207 (centre) and the fainter object seen near it, at an angular distance of 778 milliarcsec. Designated "Giant Planet Candidate Companion" by the discoverers, it may represent the first image of an exoplanet. Further observations, in particular of its motion in the sky relative to 2M1207 are needed to ascertain its true nature. The photo is based on three near-infrared exposures (in the H, K and L' wavebands) with the NACO adaptive-optics facility at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory. Since 1998, a team of European and American astronomers [2] is studying the environment of young, nearby "stellar associations", i.e., large conglomerates of mostly young stars and the dust and gas clouds from which they were recently formed. The stars in these associations are ideal targets for the direct imaging of sub-stellar companions (planets or brown dwarf objects). The leader of the team, ESO astronomer Gael Chauvin notes that "whatever their nature, sub-stellar objects are much hotter and brighter when young - tens of millions of years - and therefore can be more easily detected than older objects of similar mass". The team especially focused on the study of the TW Hydrae Association. It is located in the direction of the constellation Hydra (The Water-Snake) deep down in the southern sky, at a distance of about 230 light-years. For this, they used the NACO facility [3] at the 8.2-m VLT Yepun telescope, one of the four giant telescopes at the ESO Paranal Observatory in northern Chile. The instrument's adaptive optics (AO) overcome the distortion induced by atmospheric turbulence, producing extremely sharp near-infrared images. The infrared wavefront sensor was an essential component of the AO system for the success of these observations. This unique instrument senses the deformation of the near-infrared image, i.e. in a wavelength region where objects like 2M1207 (see below) are much brighter than in the visible range. The TW Hydrae Association contains a star with an orbiting brown dwarf companion, approximately 20 times the mass of Jupiter, and four stars surrounded by dusty proto-planetary disks. Brown dwarf objects are "failed stars", i.e. bodies too small for nuclear processes to have ignited in their interior and now producing energy by contraction. They emit almost no visible light. Like the Sun and the giant planets in the solar system, they are composed mainly of hydrogen gas, perhaps with swirling cloud belts. On a series of exposures made through different optical filters, the astronomers discovered a tiny red speck of light, only 0.8 arcsec from the TW Hydrae Association brown-dwarf object 2MASSWJ1207334-393254, or just "2M1207", cf. PR Photo 26a/04. The feeble image is more than 100 times fainter than that of 2M1207. "If these images had been obtained without adaptive optics, that object would not have been seen," says Gael Chauvin. Christophe Dumas, another member of the team, is enthusiastic: "The thrill of seeing this faint source of light in real-time on the instrument display was unbelievable. Although it is surely much bigger than a terrestrial-size object, it is a strange feeling that it may indeed be the first planetary system beyond our own ever imaged." Exoplanet or Brown Dwarf? ESO PR Photo 26b/04 ESO PR Photo 26b/04 The Brown Dwarf Object 2M1207 and GPCC [Preview - JPEG: 400 x 486 pix - 102k] [Normal - JPEG: 800 x 912 pix - 234k] Caption: ESO PR Photo 26b/04 shows near-infrared H-band spectra of the brown dwarf object 2M1207 and the fainter "GPCC" object seen near it, obtained with the NACO facility at the 8.2-m VLT Yepun telescope. In the upper part, the spectrum of 2M1207 (fully drawn blue curve) is compared with that of another substellar object (T513; dashed line); in the lower, the (somewhat noisy) spectrum of GPCC (fully drawn red curve) is compared with two substellar objects of different types (2M0301 and SDSS0539). The spectrum of GPCC is clearly very similar to these, confirming the substellar nature of this body. The broad dips at the left and the right are clear signatures of water in the (atmospheres of the) objects. What is the nature of this faint object [4]? Could it be an exoplanet in orbit around that young brown dwarf object at a projected distance of about 8,250 million km (about twice the distance between the Sun and Neptune)? "If the candidate companion of 2M1207 is really a planet, this would be the first time that a gravitationally bound exoplanet has been imaged around a star or a brown dwarf" says Benjamin Zuckerman of UCLA, a member of the team and also of NASA's Astrobiology Institute. Using high-angular-resolution spectroscopy with the NACO facility, the team has confirmed the substellar status of this object - now referred to as the "Giant Planet Candidate Companion (GPCC)" - by identifying broad water-band absorptions in its atmosphere, cf. PR Photo 26b/04. The spectrum of a young and hot planet - as the GPCC may well be - will have strong similarities with an older and more massive object such as a brown dwarf. However, when it cools down after a few tens of millions of years, such an object will show the spectral signatures of a giant gaseous planet like those in our own solar system. Although the spectrum of GPCC is quite "noisy" because of its faintness, the team was able to assign to it a spectral characterization that excludes a possible contamination by extra-galactic objects or late-type cool stars with abnormal infrared excess, located beyond the brown dwarf. After a very careful study of all options, the team found that, although this is statistically very improbable, the possibility that this object could be an older and more massive, foreground or background, cool brown dwarf cannot be completely excluded. The related detailed analysis is available in the resulting research paper that has been accepted for publication in the European journal Astronomy & Astrophysics (see below). Implications The brown dwarf 2M1207 has approximately 25 times the mass of Jupiter and is thus about 42 times lighter than the Sun. As a member of the TW Hydrae Association, it is about eight million years old. Because our solar system is 4,600 million years old, there is no way to directly measure how the Earth and other planets formed during the first tens of millions of years following the formation of the Sun. But, if astronomers can study the vicinity of young stars which are now only tens of millions of years old, then by witnessing a variety of planetary systems that are now forming, they will be able to understand much more accurately our own distant origins. Anne-Marie Lagrange, a member of the team from the Grenoble Observatory (France), looks towards the future: "Our discovery represents a first step towards opening a whole new field in astrophysics: the imaging and spectroscopic study of planetary systems. Such studies will enable astronomers to characterize the physical structure and chemical composition of giant and, eventually, terrestrial-like planets." Follow-up observations ESO PR Photo 26c/04 ESO PR Photo 26c/04 Comparison between the solar and 2M1207 systems [Preview - JPEG: 400 x 190 pix - 38k] [Normal - JPEG: 800 x 397 pix - 86k] [HiRes - JPEG: 2000 x 948 pix - 326k] Caption: ESO PR Photo 26c/04 shows for illustration a comparison between the solar system and the brown dwarf object 2M1207 system with its possible planet at 55 AU distance. The sizes of the objects are drawn to the same scale, but the distances have been strongly compressed. Taking into account the infrared colours and the spectral data available for GPCC, evolutionary model calculations point to a 5 jupiter-mass planet, about 55 times more distant from 2M1207 than the Earth is from the Sun (55 AU). The surface temperature appears to be about 10 times hotter than Jupiter, about 1000 °C; this is easily explained by the amount of energy that must be liberated during the current rate of contraction of this young object (indeed, the much older giant planet Jupiter is still producing energy in its interior). The astronomers will now continue their research to confirm or deny whether they have in fact discovered an exoplanet. Over the next few years, they expect to establish beyond doubt whether the object is indeed a planet in orbit around the brown dwarf 2M1207 by watching how the two objects move through space and to learn whether or not they move together. They will also measure the brightness of the GPCC at multiple wavelengths and more spectral observations may be attempted. There is no doubt that future programmes to image exoplanets around nearby stars, either from the ground with extremely large telescopes equipped with specially designed adaptive optics, or from space with special planet-finder telescopes, will greatly profit from current technological achievements. More information The results presented in this ESO Press Release are based on a research paper ("A Giant Planet Candidate near a Young Brown Dwarf" by G. Chauvin et al.) that has been accepted for publication and will appear in the leading research journal "Astronomy and Astrophysics" on September 23, 2004 (Vol. 425, Issue 2, page L29). A preprint is available here and also as astro-ph0409323. Notes [1]: This press release is issued simultaneously by ESO and CNRS (in French). [2]: The team consists of Gael Chauvin and Christophe Dumas (ESO-Chile), Anne-Marie Lagrange and Jean-Luc Beuzit (LAOG, Grenoble, France), Benjamin Zuckerman and Inseok Song (UCLA, Los Angeles, USA), David Mouillet (LAOMP, Tarbes, France) and Patrick Lowrance (IPAC, Pasadena, USA). The American members of the team acknowledge funding in part by NASA's Astrobiology Institute. [3]: The NACO facility (from NAOS/Nasmyth Adaptive Optics System and CONICA/Near-Infrared Imager and Spectrograph) at the 8.2-m VLT Yepun telescope on Paranal offers the capability to produce diffraction-limited near-infrared images of astronomical objects. It senses the radiation in this wavelength region with the N90C10 dichroic; 90 percent of the flux is transmitted to the wavefront sensor and 10 percent to the near-infrared camera CONICA. This mode is particularly useful for sharp imaging of red and very-low-mass stellar or substellar objects. The adaptive optics corrector (NAOS) was built, under an ESO contract, by Office National d'Etudes et de Recherches Aérospatiales (ONERA), Laboratoire d'Astrophysique de Grenoble (LAOG) and the LESIA and GEPI laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. [4]: What is the difference between a small brown dwarf and an exoplanet ? The border line between the two is still being investigated but it appears that a brown dwarf object is formed in the same way as stars, i.e. by contraction in an interstellar cloud while planets are formed within stable circumstellar disks via collision/accretion of planetesimals or disk instabilities. This implies that brown dwarfs are formed faster (less than 1 million years) than planets (~10 million years). Another way of separating the two kinds of objects is by mass (as this is also done between brown dwarfs and stars): (giant) planets are lighter than about 13 jupiter-masses (the critical mass needed to ignite deuterium fusion), brown dwarfs are heavier. Unfortunately, the first definition cannot be used in practice, e.g., when detecting a faint companion as in the present case, since the observations do not provide information about the way the object was formed. On the contrary, the above mass criterion is useful in the sense that spectroscopy and astrometry of a faint object, together with the appropriate evolutionary models, may reveal the mass and hence the nature of the object.

Valbenazine

MedlinePlus

... It works by changing the activity of certain natural substances in the brain. ... treatment: feeling faint fainting or loss of consciousness fast or ... the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting ...

A far-ultraviolet flare on a Pleiades G dwarf

NASA Technical Reports Server (NTRS)

Ayres, T. R.; Stauffer, J. R.; Simon, Theodore; Stern, R. A.; Antiochos, S. K.; Basri, G. S.; Bookbinder, J. A.; Brown, A.; Doschek, G. A.; Linsky, J. L.

1994-01-01

The Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) recorded a remarkable transient brightening in the C IV lambda lambda 1548,50 emissions of the rapidly rotating Pleiades G dwarf H II 314. On the one hand the 'flare' might be a rare event luckily observed; on the other hand it might be a bellwether of the coronal heating in very young solar-mass stars. If the latter, flaring provides a natural spin-down mechanism through associated sporadic magnetospheric mass loss.

AGN in the Swift/BAT and INTEGRAL Hard X-ray Surveys

NASA Technical Reports Server (NTRS)

Beckmann, Volker; Tueller, Jack; Baumgartner, Wayne; Markwardt, Craig; Mushotzky, Richard; Skinner, Gerry

2008-01-01

Two hard X-ray surveys are in progress at this time. They provide a unique new window on compact objects and black holes. I will discuss how these two surveys complement each other and the potential for improved coordination that could yield significant near term results in both sensitivity and time coverage. I will pay particular attention to the discovery of faint sources including new results from the 36 month survey from Swift/Burst Alert Telescope (BAT).

Extent of warm haloes around medium-redshift galaxies

NASA Technical Reports Server (NTRS)

Burbidge, E. M.; Barlow, T. A.; Cohen, R. D.; Junkkarinen, V. T.; Womble, D. S.

1989-01-01

The properties of low-to-medium ionization gaseous haloes around galaxies are briefly reviewed. New observations concerning such haloes are presented. For the galaxy-QSO pair in the field of the radio source 3C303, the higher-redshift QSO has been found to show Mg II absorption at the lower redshift of the faint nearby galaxy. Secondly, new data are presented on one of the galaxies in the environment of the well-known BL Lac object AO 0235 + 164.

Space telescopes planetary monitoring (PM) and Zvezdny (eng. star) patrol (ZP) for planetary science and exoplanets exploration

NASA Astrophysics Data System (ADS)

Tavrov, Alexander; Frolov, Pavel; Korablev, Oleg; Vedenkin, Nikolai; Barabanov, Sergey

2017-11-01

Solar System planetology requires a wide use of observing spectroscopy for surface geology to atmosphere climatology. A high-contrast imaging is required to study and to characterize extra-solar planetary systems among other faint astronomical targets observed in the vicinity of bright objects. Two middle class space telescopes projects aimed to observe Solar system planets by a long term monitoring via spectroscopy and polarimetry. Extra solar planets (exoplanets) engineering and scientific explorations are included in science program.

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

NASA Astrophysics Data System (ADS)

Wheeler, Coral Rose

2016-06-01

The high dark matter content and the shallow potential wells of low mass galaxies (10^3 Msun < Mstar < 10^9.5 Msun) make them excellent testbeds for differing theories of galaxy formation. Additionally, the recent up-tick in the number and detail of Local Group dwarf galaxy observations provides a rich dataset for comparison to simulations that attempt to answer important questions in near field cosmology: why are there so few observed dwarfs compared to the number predicted by simulations? What shuts down star formation in ultra-faint galaxies? Why do dwarfs have inverted age gradients and what does it take to convert a dwarf irregular (dIrrs) into a dwarf spheroidal (dSph) galaxy?We to attempt to answer these questions by running ultra-high resolution cosmological FIRE simulations of isolated dwarf galaxies. We predict that many ultra-faint dwarfs should exist as satellites of more massive isolated Local Group dwarfs. The ultra-faints (Mstar < 10^4 Msun) formed in these simulations have uniformly ancient stellar populations (> 10 Gyr), having had their star formation shut down by reionization. Additionally, we show that the kinematics and ellipticities of isolated simulated dwarf centrals are consistent with observed dSphs satellites without the need for harassment from a massive host. We further show that most (but not all) observed *isolated* dIrrs in the Local Volume also have dispersion-supported stellar populations, contradicting the previous view that these objects are rotating. Finally, we investigate the stellar age gradients in dwarfs — showing that early mergers and strong feedback can create an inverted gradient, with the older stars occupying larger galactocentric radii.These results offer an interesting direction in testing models that attempt to solve dark matter problems via explosive feedback episodes. Can the same models that create large cores in simulated dwarfs preserve the mild stellar rotation that is seen in a minority of isolated dIrrs? Can the bursty star formation that created a dark matter core also match observed stellar gradients in low mass galaxies? Comparisons between our simulations and observed dwarfs should provide an important benchmark for this question going forward.

First ISON observations for satellite conjunction analysis in the Western Hemisphere

NASA Astrophysics Data System (ADS)

Zalles, R.; Molotov, I.; Kokina, T.; Zolotov, V.; Condori, R.

2018-01-01

In this paper we report on observations of a pair of approaching space objects in the beginning of June 2016, observed jointly by the Tarija Observatory in Bolivia and the Mexican observatory of Sinaloa University in Cosala in the context of the ISON collaboration. These objects were the STAR ONE C1 (2007-056A) active satellite in GEO position 65\\ deg west, and the passive satellite LES 6 (1968-081D). The large number of measurements obtained in a few nights allowed a precise orbit reconstruction. The passive satellite LES 6 (with a brigtness amplitude variation of 3 magnitudes) was too faint for the small aperture of the Cosala telescope.

A search for N-type galaxies

NASA Technical Reports Server (NTRS)

Jefferies, J. T.

1971-01-01

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

KSC-01pp1802

NASA Image and Video Library

2001-12-01

KENNEDY SPACE CENTER, Fla. - STS-109 Mission Specialist Richard Lennehan (left) and Payload Commander John Grunsfeld get a feel for tools and equipment that will be used on the mission. The crew is at KSC to take part in Crew Equipment Interface Test activities that include familiarization with the orbiter and equipment. The goal of the mission is to service the HST, replacing Solar Array 2 with Solar Array 3, replacing the Power Control Unit, removing the Faint Object Camera and installing the Advanced Camera for Surveys, installing the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cooling System, and installing New Outer Blanket Layer insulation on bays 5 through 8. Mission STS-109 is scheduled for launch Feb. 14, 2002

1548C27 - An interesting new cometary nebula

NASA Technical Reports Server (NTRS)

Craine, E. R.; Byard, P. L.; Boeshaar, G. O.

1981-01-01

The object 1548C27, a faint cometary nebula of classical form, discovered by an examination of early Near Infrared Photographic Sky Survey (NIPSS) data (1979) is presented. Direct imaging and polarimetric, photometric, and spectroscopic observations are reported. Early survey test photographs show that the object lies at R.A. 19h40m48s, Decl. +23 deg 17 arcmin 09 arc sec (1950) in the Vulpecula constellation in the immediate vicinity of the complex H II region and galactic cluster NGC 6820/6823. From the photographs, the nebula was estimated to be 15 m visual and of color class one. The object was observed spectroscopically in the region 5700-6800 A using an Image Dissector Scanner with a 1.8 m reflector, and the spectral scan, obtained on November 4, 1978, is presented. New information on cometary nebulae may further illuminate the evolutionary importance of the objects.

Luminous Blue Compact Galaxies: Probes of galaxy assembly

NASA Astrophysics Data System (ADS)

Newton, Cassidy Louann

The life cycles of galaxies over cosmic time is yet to be fully understood. How did galaxies evolve from their formative stages to the structures we observe today? This dissertation details the identification and analysis of a sample of Luminous Blue Compact Galaxies (LBCGs), a class of galaxy in the local (z < 0.05) universe exhibiting blue colors, high surface brightness, and high star formation rates. These systems appear to be very similar in their global properties to the early evolutionary phases of most galaxies, however their locality permits detailed investigation over a broad range of the electromagnetic spectrum in contrast to the smaller angular sizes and extreme faintness of distant galaxies. We use a combination of optical, ultraviolet, and infrared data to investigate a sample of LBCGs utilizing space and ground-based data.

Faint submillimeter galaxies revealed by multifield deep ALMA observations: number counts, spatial clustering, and a dark submillimeter line emitter

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

Ono, Yoshiaki; Ouchi, Masami; Momose, Rieko

2014-11-01

We present the statistics of faint submillimeter/millimeter galaxies (SMGs) and serendipitous detections of a submillimeter/millimeter line emitter (SLE) with no multi-wavelength continuum counterpart revealed by the deep ALMA observations. We identify faint SMGs with flux densities of 0.1-1.0 mJy in the deep Band-6 and Band-7 maps of 10 independent fields that reduce cosmic variance effects. The differential number counts at 1.2 mm are found to increase with decreasing flux density down to 0.1 mJy. Our number counts indicate that the faint (0.1-1.0 mJy, or SFR{sub IR} ∼ 30-300 M {sub ☉} yr{sup –1}) SMGs contribute nearly a half of themore » extragalactic background light (EBL), while the remaining half of the EBL is mostly contributed by very faint sources with flux densities of <0.1 mJy (SFR{sub IR} ≲ 30 M {sub ☉} yr{sup –1}). We conduct counts-in-cells analysis with multifield ALMA data for the faint SMGs, and obtain a coarse estimate of galaxy bias, b {sub g} < 4. The galaxy bias suggests that the dark halo masses of the faint SMGs are ≲ 7 × 10{sup 12} M {sub ☉}, which is smaller than those of bright (>1 mJy) SMGs, but consistent with abundant high-z star-forming populations, such as sBzKs, LBGs, and LAEs. Finally, we report the serendipitous detection of SLE-1, which has no continuum counterparts in our 1.2 mm-band or multi-wavelength images, including ultra deep HST/WFC3 and Spitzer data. The SLE has a significant line at 249.9 GHz with a signal-to-noise ratio of 7.1. If the SLE is not a spurious source made by the unknown systematic noise of ALMA, the strong upper limits of our multi-wavelength data suggest that the SLE would be a faint galaxy at z ≳ 6.« less

The Evolution of Dwarf Galaxy Satellites with Different Dark Matter Density Profiles in the ErisMod Simulations. I. The Early Infalls

NASA Astrophysics Data System (ADS)

Tomozeiu, Mihai; Mayer, Lucio; Quinn, Thomas

2016-02-01

We present the first simulations of tidal stirring of dwarf galaxies in the Local Group carried out in a fully cosmological context. We use the ErisDARK cosmological simulation of a Milky Way (MW)-sized galaxy to identify some of the most massive subhalos (Mvir > 108 M⊙) that fall into the main host before z = 2. Subhalos are replaced before infall with extremely high-resolution models of dwarf galaxies comprising a faint stellar disk embedded in a dark matter halo. The set of models contains cuspy halos as well as halos with “cored” profiles (with the cusp coefficient γ = 0.6) consistent with recent results of hydrodynamical simulations of dwarf galaxy formation. The simulations are then run to z = 0 with as many as 54 million particles and resolutions as small as ∼4 pc using the new parallel N-body code ChaNGa. The stellar components of all satellites are significantly affected by tidal stirring, losing stellar mass, and undergoing a morphological transformation toward a pressure supported spheroidal system. However, while some remnants with cuspy halos maintain significant rotational flattening and disk-like features, all the shallow halo models achieve vrot/σ⋆ < 0.5 and round shapes typical of dSph satellites of the MW and M31. Mass loss is also enhanced in the latter, and remnants can reach luminosities and velocity dispersions as low as those of ultra-faint dwarfs.

Pervasive faint Fe XIX emission from a solar active region observed with EUNIS-13: Evidence for nanoflare heating

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

Brosius, Jeffrey W.; Daw, Adrian N.; Rabin, D. M., E-mail: Jeffrey.W.Brosius@nasa.gov

2014-08-01

We present spatially resolved EUV spectroscopic measurements of pervasive, faint Fe XIX 592.2 Å line emission in an active region observed during the 2013 April 23 flight of the Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS-13) sounding rocket instrument. With cooled detectors, high sensitivity, and high spectral resolution, EUNIS-13 resolves the lines of Fe XIX at 592.2 Å (formed at temperature T ≈ 8.9 MK) and Fe XII at 592.6 Å (T ≈ 1.6 MK). The Fe XIX line emission, observed over an area in excess of 4920 arcsec{sup 2} (2.58 × 10{sup 9} km{sup 2}, more than 60% of themore » active region), provides strong evidence for the nanoflare heating model of the solar corona. No GOES events occurred in the region less than 2 hr before the rocket flight, but a microflare was observed north and east of the region with RHESSI and EUNIS during the flight. The absence of significant upward velocities anywhere in the region, particularly the microflare, indicates that the pervasive Fe XIX emission is not propelled outward from the microflare site, but is most likely attributed to localized heating (not necessarily due to reconnection) consistent with the nanoflare heating model of the solar corona. Assuming ionization equilibrium we estimate Fe XIX/Fe XII emission measure ratios of ∼0.076 just outside the AR core and ∼0.59 in the core.« less

Variability of faint ROSAT field sources

NASA Astrophysics Data System (ADS)

Nicholson, K. L.; Mittaz, J. P. D.; Mason, K. O.

1997-03-01

We describe a technique to search for variability in faint X-ray sources, based on Poisson statistics. This is applied to data in the field of the detached white dwarf binary RE J1629+781 which has been observed repeatedly with the ROSAT Position Sensitive Proportional Counter (PSPC) over a period of 2.5yr as part of the calibration programme of the co-aligned extreme ultraviolet (EUV) sensitive Wide Field Camera. The field contains eight other identified sources comprising four active galactic nuclei (AGN), a LINER, a probable cluster of galaxies and two stars. Variability is detected in three of the AGN, which all have redshifts between 0.35 and 0.38. The amplitude of variability ranges between one and three times the mean count rate, but is only detected on time-scales of less than 3-5 months. No variability is found in the fourth AGN which is at a redshift of 1.1, nor in the LINER galaxy, Arp 185. The X-ray emission from Arp 185 is relatively bright, and the upper limit to flux variations is 27 per cent of the mean flux. This result is consistent with a non-AGN origin for the X-ray emission from this galaxy. Variability is detected from one of the identified stars in the field, of spectral type dM5.5e. No variations were seen in the flux of the other star (spectral type G) or from the probable cluster of galaxies.

46 CFR 160.041-4 - Contents.

Code of Federal Regulations, 2013 CFR

2013-10-01

... inhalants 10 do 1 Iodine applicators (1/2 ml swab type) 10 do 1 Aspirin, phenacetin and caffeine compound... Ammonia inhalants Break one and inhale for faintness, fainting, or collapse. Aspirin, phenacetin, caffeine...

46 CFR 160.041-4 - Contents.

Code of Federal Regulations, 2014 CFR

2014-10-01

... inhalants 10 do 1 Iodine applicators (1/2 ml swab type) 10 do 1 Aspirin, phenacetin and caffeine compound... Ammonia inhalants Break one and inhale for faintness, fainting, or collapse. Aspirin, phenacetin, caffeine...

A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies

NASA Astrophysics Data System (ADS)

Martin, N. F.; Ibata, R. A.; Chapman, S. C.; Irwin, M.; Lewis, G. F.

2007-09-01

We present the results of a spectroscopic survey of the recently discovered faint Milky Way satellites Boötes, Ursa Major I, Ursa Major II and Willman 1 (Wil1). Using the DEep Imaging Multi-Object Spectrograph mounted on the Keck II telescope, we have obtained samples that contain from ~15 to ~85 probable members of these satellites for which we derive radial velocities precise to a few kms-1 down to i ~ 21-22. About half of these stars are observed with a high enough signal-to-noise ratio to estimate their metallicity to within +/-0.2 dex. The characteristics of all the observed stars are made available, along with those of the Canes Venatici I dwarf galaxy that have been analysed in a companion paper. From this data set, we show that Ursa Major II is the only object that does not show a clear radial velocity peak. However, the measured systemic radial velocity (vr = 115 +/- 5kms-1) is in good agreement with simulations in which this object is the progenitor of the recently discovered Orphan Stream. The three other satellites show velocity dispersions that make them highly dark matter dominated systems (under the usual assumptions of symmetry and virial equilibrium). In particular, we show that despite its small size and faintness, the Wil1 object is not a globular cluster given its metallicity scatter over -2.0 <~ [Fe/H] <~ -1.0 and is therefore almost certainly a dwarf galaxy or dwarf galaxy remnant. We measure a radial velocity dispersion of only 4.3+2.3-1.3kms-1 around a systemic velocity of -12.3 +/- 2.3kms-1 which implies a mass-to-light ratio of ~700 and a total mass of ~5 × 105Msolar for this satellite, making it the least massive satellite galaxy known to date. Such a low mass could mean that the 107Msolar limit that had until now never been crossed for Milky Way and Andromeda satellite galaxies may only be an observational limit and that fainter, less massive systems exist within the Local Group. However, more modelling and an extended search for potential extratidal stars are required to rule out the possibility that these systems have not been significantly heated by tidal interaction. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation. E-mail: martin@mpia-hd.mpg.de ‡ Canadian Space Agency Fellow.

Does the chemical signature of TYC 8442-1036-1 originate from a rotating massive star that died in a faint explosion?

NASA Astrophysics Data System (ADS)

Cescutti, G.; Valentini, M.; François, P.; Chiappini, C.; Depagne, E.; Christlieb, N.; Cortés, C.

2016-11-01

Context. We have recently investigated the origin of chemical signatures observed in Galactic halo stars by means of a stochastic chemical evolution model. We found that rotating massive stars are a promising way to explain several signatures observed in these fossil stars. Aims: We discuss how the extremely metal-poor halo star TYC 8442-1036-1, for which we have now obtained detailed abundances from VLT-UVES spectra, fits into the framework of our previous work. Methods: We applied a standard one-dimensional (1D) LTE analysis to the spectrum of this star. We measured the abundances of 14 chemical elements; we computed the abundances for Na, Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, and Zn using equivalent widths; we obtained the abundances for C, Sr, and Ba by means of synthetic spectra generated by MOOG. Results: We find an abundance of [Fe/H] = -3.5 ±0.13 dex based on our high-resolution spectrum; this points to an iron content that is lower by a factor of three (0.5 dex) compared to that obtained by a low-resolution spectrum. The star has a [C/Fe] = 0.4 dex, and it is not carbon enhanced like most of the stars at this metallicity. Moreover, this star lies in the plane [Ba/Fe] versus [Fe/H] in a relatively unusual position, shared by a few other Galactic halo stars, which is only marginally explained by our past results. Conclusions: The comparison of the model results with the chemical abundance characteristics of this group of stars can be improved if we consider in our model the presence of faint supernovae coupled with rotating massive stars. These results seem to imply that rotating massive stars and faint supernovae scenarios are complementary to each other, and are both required in order to match the observed chemistry of the earliest phases of the chemical enrichment of the Universe. Based on observations made with the ESO Very Large Telescope at Paranal Observatory, Chile (ID 094.B-0781(A); P.I. G. Cescutti).

Fainting (Syncope)

MedlinePlus

... Attack Heart Valve Problems Join our e-newsletter! Aging & Health A to Z Fainting (Syncope) Basic Facts & ... November 2016 Posted: March 2012 © 2018 Health in Aging. All rights reserved. Feedback • Site Map • Privacy Policy • ...

Faint Ring, Bright Arc

NASA Image and Video Library

2010-01-12

In this image taken by NASA Cassini spacecraft, the bright arc in Saturn faint G ring contains a little something special. Although it cant be seen here, the tiny moonlet Aegaeon orbits within the bright arc.

The Demographics and Properties of Wide-Orbit, Planetary-Mass Companions from PSF Fitting of Spitzer/IRAC Images

NASA Astrophysics Data System (ADS)

Martinez, Raquel; Kraus, Adam L.

2017-06-01

Over the past decade, a growing population of planetary-mass companions (< 20 MJup PMCs) orbiting young stars have been discovered. These objects are at wide separations (> 100 AU) from their host stars, challenging existing models of both star and planet formation. It is unclear whether these systems represent the low-mass extreme of stellar binary formation or the high-mass and wide-orbit extreme of planet formation theories, as various proposed formation pathways inadequately explain the physical and orbital aspects of these systems. Even so, determining which scenario best reproduces the observed characteristics of the PMCs will come once a statistically robust sample of directly-imaged PMCs are found and studied.We are developing an automated pipeline to search for wide-orbit PMCs to young stars in Spitzer/IRAC images. A Markov Chain Monte Carlo (MCMC) algorithm is the backbone of our novel point spread function (PSF) subtraction routine that efficiently creates and subtracts χ2-minimizing instrumental PSFs, simultaneously measuring astrometry and infrared photometry of these systems across the four IRAC channels (3.6 μm, 4.5 μm, 5.8 μm, and 8 μm). In this work, we present the results of a Spitzer/IRAC archival imaging study of 11 young, low-mass (0.044-0.88 M⊙ K3.5-M7.5) stars known to have faint, low-mass companions in 3 nearby star-forming regions (Chameleon, Taurus, and Upper Scorpius). We characterize the systems found to have low-mass companions with non-zero [I1] - [I4] colors, potentially signifying the presence of a circum(sub?)stellar disk. Plans for future pipeline improvements and paths forward will also be discussed. Once this computational foundation is optimized, the stage is set to quickly scour the nearby star-forming regions already imaged by Spitzer, identify potential candidates for further characterization with ground- or space-based telescopes, and increase the number of widely-separated PMCs known.

Nascent starbursts: a missing link in galaxy evolution

NASA Astrophysics Data System (ADS)

Roussel, Helene; Beck, Rainer; Condon, Jim; Helou, George; Smith, John-David

2005-06-01

We have identified a rare category of galaxies characterized by an extreme deficiency in synchro- tron radiation, relative to dust emission, and very high dust temperatures. We studied in detail the most extreme such object, and concluded in favor of a starburst just breaking out, less than one megayear old, in a galaxy having undergone no major star formation episode in the last 100 Myr. Such systems offer a perfect setting to study the initial conditions and early dynamics of starbursts and understand better the regulation of the infrared-radio continuum correlation in galaxies. For the prototypical nascent starburst, the mid-infrared spectrum is quite peculiar, suggesting tran- sient dust species and high optical depth; tracers of dust and molecular gas are the only indicators of unusual activity, and the active regions are likely very compact and dust-bounded, suppressing ionization. Only Spitzer data can provide the needed physical diagnostics for such regions. A sample of 25 nascent starbursts was drawn from the cross-correlation of the IRAS Faint Source Catalog and the NVSS VLA radio survey, and carefully selected based on our multi-wavelength VLA maps to span a range of infrared to radio ratios and luminosities. This sample allows a first step beyond studying prototypes toward a statistical analysis addressing systematic physical pro- perties, classification and search for starburst development sequences. We propose imaging and spectroscopic observations from 3 to 160 microns to characterize the state of the interstellar medium and the gas and dust excitation origin. Our aim is to learn from these unique systems how a star formation burst may develop in its very earliest phases, how it affects the fueling material and the host galaxy. Acquired observations of the radio continuum, cold molecular gas and tracers of shocks and HII regions will help us interpret the rich Spitzer data set and extract a coherent picture of the interstellar medium in our targets.

Ultra-High Resolution Orbit Determination of (486958) 2014 MU69: Predicting an Occultation with 1% of an Orbit

NASA Astrophysics Data System (ADS)

Porter, Simon Bernard; Buie, Marc W.; Spencer, John R.; Folkner, William; Parker, Alex; Zangari, Amanda Marie; Verbiscer, Anne J.; Benecchi, Susan; Stern, S. Alan; Terrell, Dirk; Soto, Alejandro; Tamblyn, Peter; Wasserman, Lawrence H.; Young, Eliot F.; New Horizons MU69 Occultation Team

2017-10-01

In November 2015, the NASA New Horizons spacecraft burned its thrusters to intercept the cold classical Kuiper Belt Object (486958) 2014 MU69. Then, on July 17, 2017, five small telescopes in Chubut Province, Argentina recorded a solid body occultation of MU69. Both these events required an orbital solution of unprecedented accuracy, as will the January 1, 2019 flyby of MU69 by New Horizons. This was especially difficult because there were no precoveries of MU69 prior to July 2014, it is in an extremely crowded field near the galactic core, and it is faint enough to only be reliably detected by Hubble Space Telescope’s Wide Field Camera 3 (WFC3). To accomplish this, we performed an extremely detailed analysis of 237 WFC3 images, down to the subpixel distortion level, in order to produce individual probability distribution functions (PDFs) for the position of MU69 in each WFC3 image. We registered each WFC3 image against a pre-release version of the Gaia DR2 catalog, which produced even smaller residuals than the now-released DR1. We then combined these WFC3+Gaia PDFs with a high-precision few-body numerical integrator and a Monte Carlo Markov Chain (MCMC) sampler to produce a state vector PDF for MU69 at defined epoch. Propagating those state vectors from the epoch produces an instantaneous positional cloud for MU69 at any given time. This positional cloud was then directly translated into a shadow path uncertainty cloud in order to plan the MU69 occultation campaign. We will describe this process of fully propagating errors from WFC3 images to telescope sites on the ground, and also describe refinements for future guiding of New Horizons to its encounter with MU69. We thank NASA, Hubble, Gaia, CONAE, the city of Comodoro Rivadavia, and the government of Argentina for their assistance and support of the MU69 occultation campaign.

Ultraviolet to optical diffuse sky emission as seen by the Hubble Space Telescope Faint Object Spectrograph

NASA Astrophysics Data System (ADS)

Kawara, Kimiaki; Matsuoka, Yoshiki; Sano, Kei; Brandt, Timothy D.; Sameshima, Hiroaki; Tsumura, Kohji; Oyabu, Shinki; Ienaka, Nobuyuki

2017-04-01

We present an analysis of the blank-sky spectra observed with the Faint Object Spectrograph on board the Hubble Space Telescope. We study the diffuse sky emission from ultraviolet to optical wavelengths, which is composed of zodiacal light (ZL), diffuse Galactic light (DGL), and residual emission. The observations were performed towards 54 fields distributed widely over the sky, with spectral coverage from 0.2 to 0.7 μm. In order to avoid contaminating light from earthshine, we use the data collected only in orbital nighttime. The observed intensity is decomposed into the ZL, DGL, and residual emission, in eight photometric bands spanning our spectral coverage. We found that the derived ZL reflectance spectrum is flat in the optical, which indicates major contribution of C-type asteroids to the interplanetary dust (IPD). In addition, the ZL reflectance spectrum has an absorption feature at ∼0.3 μm. The shape of the DGL spectrum is consistent with those found in earlier measurements and model predictions. While the residual emission contains a contribution from the extragalactic background light, we found that the spectral shape of the residual looks similar to the ZL spectrum. Moreover, its optical intensity is much higher than that measured from beyond the IPD cloud by Pioneer 10/11, and also than that of the integrated galaxy light. These findings may indicate the presence of an isotropic ZL component, which is missed in the conventional ZL models.

Understanding the Milky Way Halo through Large Surveys

NASA Astrophysics Data System (ADS)

Koposov, Sergey

This thesis presents an extensive study of stellar substructure in the outskirts of the Milky Way(MW), combining data mining of SDSS with theoretical modeling. Such substructure, either bound star clusters and satellite galaxies, or tidally disrupted objects forming stellar streams are powerful diagnostics of the Milky Way's dynamics and formation history. I have developed an algorithmic technique of searching for stellar overdensities in the MW halo, based on SDSS catalogs. This led to the discovery of unusual ultra-faint ~ (1000Lsun) globular clusters with very compact sizes and relaxation times << t_Hubble. The detailed analysis of a known stellar stream (GD-1), allowed me to make the first 6-D phase space map for such an object along 60 degrees on the sky. By modeling the stream's orbit I could place strong constraints on the Galactic potential, e.g. Vcirc(R0)= 224+/-13 km/s. The application of the algorithmic search for stellar overdensities to the SDSS dataset and to mock datasets allowed me to quantify SDSS's severe radial incompleteness in its search for ultra-faint dwarf galaxies and to determine the luminosity function of MW satellites down to luminosities of M_V ~ -3. I used the semi-analytical model in order to compare the CDM model predictions for the MW satellite population with the observations; this comparison has shown that the recently increased census of MW satellites, better understanding of the radial incompleteness and the suppression of star formation after the reionization can fully solve the "Missing satellite problem".

KECK/LRIS SPECTROSCOPIC CONFIRMATION OF COMA CLUSTER DWARF GALAXY MEMBERSHIP ASSIGNMENTS

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

Chiboucas, Kristin; Tully, R. Brent; Marzke, Ronald O.

2010-11-01

Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of the lowest and highest surface brightness faint (19 < R < 22) dwarf galaxy candidates in the core region of the Coma Cluster. These spectra are used to measure redshifts and establish membership for these faint dwarf populations. The primary goal of the low surface brightness sample is to test our ability to use morphological and surface brightness criteria to distinguish between Coma Cluster members and background galaxies using high resolution Hubble Space Telescope/Advanced Camera for Surveys images. Candidates were rated as expected members, uncertain, or expected background.more » From 93 spectra, 51 dwarf galaxy members and 20 background galaxies are identified. Our morphological membership estimation success rate is {approx}100% for objects expected to be members and better than {approx}90% for galaxies expected to be in the background. We confirm that low surface brightness is a very good indicator of cluster membership. High surface brightness galaxies are almost always background with confusion arising only from the cases of the rare compact elliptical (cE) galaxies. The more problematic cases occur at intermediate surface brightness. Many of these galaxies are given uncertain membership ratings, and these were found to be members about half of the time. Including color information will improve membership determination but will fail for some of the same objects that are already misidentified when using only surface brightness and morphology criteria. cE galaxies with B-V colors {approx}0.2 mag redward of the red sequence in particular require spectroscopic follow up. In a sample of 47 high surface brightness, ultracompact dwarf candidates, 19 objects have redshifts which place them in the Coma Cluster, while another 6 have questionable redshift measurements but may also prove to be members. Redshift measurements are presented and the use of indirect means for establishing cluster membership is discussed.« less

RECONSTRUCTING REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS: TESTS AND AN OPTIMIZED RECIPE

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

Matthews, Daniel J.; Newman, Jeffrey A., E-mail: djm70@pitt.ed, E-mail: janewman@pitt.ed

2010-09-20

Many of the cosmological tests to be performed by planned dark energy experiments will require extremely well-characterized photometric redshift measurements. Current estimates for cosmic shear are that the true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1 + z), and the width of the bin must be known to {approx}0.003(1 + z) if errors in cosmological measurements are not to be degraded significantly. A conventional approach is to calibrate these photometric redshifts with large sets of spectroscopic redshifts. However, at the depths probed by Stage III surveys (such as DES), let alonemore » Stage IV (LSST, JDEM, and Euclid), existing large redshift samples have all been highly (25%-60%) incomplete, with a strong dependence of success rate on both redshift and galaxy properties. A powerful alternative approach is to exploit the clustering of galaxies to perform photometric redshift calibrations. Measuring the two-point angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete. We test this technique using mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium Simulation semi-analytic galaxy catalogs. From this realistic test, which incorporates the effects of galaxy bias evolution and cosmic variance, we find that the true redshift distribution of a photometric sample can, in fact, be determined accurately with cross-correlation techniques. We also compare the empirical error in the reconstruction of redshift distributions to previous analytic predictions, finding that additional components must be included in error budgets to match the simulation results. This extra error contribution is small for surveys that sample large areas of sky (>{approx}10{sup 0}-100{sup 0}), but dominant for {approx}1 deg{sup 2} fields. We conclude by presenting a step-by-step, optimized recipe for reconstructing redshift distributions from cross-correlation information using standard correlation measurements.« less

[Fainting in Greco-Roman medicine, especially in the traumatology and surgery fields].

PubMed

Salazar, C F

2001-01-01

Occurrences of fainting are very common in medical as well as non-medical literature; in order to restrict the field to a manageable size, this article focuses mainly on surgery and traumatology. An examination of the various passages suggests that there was considerable ambiguity associated with the concept of fainting. On the one hand it was seen as a common occurrence, to be expected in the context of wounds or surgery, but on the other it was also regarded as a life-threatening force in its own right.

Searches for new Milky Way satellites from the first two years of data of the Subaru/Hyper Suprime-Cam survey: Discovery of Cetus III

NASA Astrophysics Data System (ADS)

Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Hayashi, Kohei; Arimoto, Nobuo; Garmilla, José A.; Lupton, Robert H.; Strauss, Michael A.; Miyazaki, Satoshi; Wang, Shiang-Yu; Murayama, Hitoshi

2018-01-01

We present the results from a search for new Milky Way (MW) satellites from the first two years of data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) ˜300 deg2 and report the discovery of a highly compelling ultra-faint dwarf galaxy candidate in Cetus. This is the second ultra-faint dwarf we have discovered after Virgo I reported in our previous paper. This satellite, Cetus III, has been identified as a statistically significant (10.7 σ) spatial overdensity of star-like objects, which are selected from a relevant isochrone filter designed for a metal-poor and old stellar population. This stellar system is located at a heliocentric distance of 251^{+24}_{-11}kpc with a most likely absolute magnitude of MV = -2.4 ± 0.6 mag estimated from a Monte Carlo analysis. Cetus III is extended with a half-light radius of r_h = 90^{+42}_{-17}pc, suggesting that this is a faint dwarf satellite in the MW located beyond the detection limit of the Sloan Digital Sky Survey. Further spectroscopic studies are needed to assess the nature of this stellar system. We also revisit and update the parameters for Virgo I, finding M_V = -0.33^{+0.75}_{-0.87}mag and r_h = 47^{+19}_{-13}pc. Using simulations of Λ-dominated cold dark matter models, we predict that we should find one or two new MW satellites from ˜300 deg2 HSC-SSP data, in rough agreement with the discovery rate so far. The further survey and completion of HSC-SSP over ˜1400 deg2 will provide robust insights into the missing satellites problem.

EMS Activations for School-Aged Children From Public Buildings, Places of Recreation or Sport, and Health Care Facilities in Pennsylvania.

PubMed

Catherine, Andrew T; Olympia, Robert P

2016-06-01

To determine the etiology of emergency medical services (EMS) activations in 2011 to public buildings, places of recreation or sport, and health care facilities involving children aged 5 to 18 years in Pennsylvania. Electronic records documenting 2011 EMS activations as provided by the Pennsylvania Department of Health's Bureau of EMS were reviewed. Data elements (demographics, dispatch complaint, mechanism of injury, primary assessment) from patients aged 5 to 18 years involved in an EMS response call originating from either a public building, a place of recreation and sport, or health care facility were analyzed. A total of 12,289 records were available for analysis. The most common primary assessments from public buildings were traumatic injury, behavioral/psychiatric disorder, syncope/fainting, seizure, and poisoning. The most common primary assessments from places of recreation or sport were traumatic injury, syncope/fainting, altered level of consciousness, respiratory distress, and abdominal pain. The most common primary assessments from health care facilities were behavioral/psychiatric disorder, traumatic injury, abdominal pain, respiratory distress, and syncope/fainting. When examining the mechanism of injury for trauma-related primary assessments, falls were the most common mechanism at all 3 locations, followed by being struck by an object. Of the 1335 serious-incident calls (11% of the total EMS activations meeting inclusion criteria), 61.2% were from public buildings, 14.1% from places of recreation or sport, and 24.7% from health care facilities. Our identification of common EMS dispatch complaints, mechanisms of injury, and primary assessments can be used in the education of staff and preparation of facilities for medical emergencies and injuries where children spend time.

Deconvolution of post-adaptive optics images of faint circumstellar environments by means of the inexact Bregman procedure

NASA Astrophysics Data System (ADS)

Benfenati, A.; La Camera, A.; Carbillet, M.

2016-02-01

Aims: High-dynamic range images of astrophysical objects present some difficulties in their restoration because of the presence of very bright point-wise sources surrounded by faint and smooth structures. We propose a method that enables the restoration of this kind of images by taking these kinds of sources into account and, at the same time, improving the contrast enhancement in the final image. Moreover, the proposed approach can help to detect the position of the bright sources. Methods: The classical variational scheme in the presence of Poisson noise aims to find the minimum of a functional compound of the generalized Kullback-Leibler function and a regularization functional: the latter function is employed to preserve some characteristic in the restored image. The inexact Bregman procedure substitutes the regularization function with its inexact Bregman distance. This proposed scheme allows us to take under control the level of inexactness arising in the computed solution and permits us to employ an overestimation of the regularization parameter (which balances the trade-off between the Kullback-Leibler and the Bregman distance). This aspect is fundamental, since the estimation of this kind of parameter is very difficult in the presence of Poisson noise. Results: The inexact Bregman procedure is tested on a bright unresolved binary star with a faint circumstellar environment. When the sources' position is exactly known, this scheme provides us with very satisfactory results. In case of inexact knowledge of the sources' position, it can in addition give some useful information on the true positions. Finally, the inexact Bregman scheme can be also used when information about the binary star's position concerns a connected region instead of isolated pixels.

A common origin for globular clusters and ultra-faint dwarfs in simulations of the first galaxies

DOE PAGES

Ricotti, Massimo; Parry, Owen H.; Gnedin, Nickolay Y.

2016-11-09

In this study, the first in a series on galaxy formation before reionization, we focus on understanding what determines the size and morphology of stellar objects in the first low-mass galaxies, using parsec-scale cosmological simulations performed with an adaptive mesh hydrodynamics code. Although the dense gas in which stars are formed tends to have a disk structure, stars are found in spheroids with little rotation. Halos with masses betweenmore » $${10}^{6}\\,{M}_{\\odot }$$ and $$5\\times {10}^{8}\\,{M}_{\\odot }$$ form stars stochastically, with stellar masses in the range $${10}^{4}\\,{M}_{\\odot }$$ to $$2\\times {10}^{6}\\,{M}_{\\odot }$$. We observe, nearly independent of stellar mass, a large range of half-light radii for the stars, from a few parsecs to a few hundred parsecs and surface brightnesses and mass-to-light ratios ranging from those typical of globular clusters to ultra-faint dwarfs. In our simulations, stars form in dense stellar clusters with high gas-to-star conversion efficiencies and rather uniform metallicities. A fraction of these clusters remain bound after the gas is removed by feedback, but others are destroyed, and their stars, which typically have velocity dispersions of 20–40 km s –1, expand until they become bound by the dark matter halo. We thus speculate that the stars in ultra-faint dwarf galaxies may show kinematic and chemical signatures consistent with their origin in a few distinct stellar clusters. On the other hand, some globular clusters may form at the center of primordial dwarf galaxies and may contain dark matter, perhaps detectable in the outer parts.« less

The Chemical Evolution of the Bootes I Ultra-faint Dwarf Galaxy

NASA Astrophysics Data System (ADS)

Frebel, Anna; Norris, John E.; Gilmore, Gerard; Wyse, Rosemary F. G.

2016-08-01

We present chemical abundance measurements of two metal-poor red giant stars in the ultra-faint dwarf galaxy Boötes I, based on Magellan/MIKE high-resolution spectra. For Boo-980, with {{[Fe/H]}}=-3.1, we present the first elemental abundance measurements, while Boo-127, with {{[Fe/H]}}=-2.0, shows abundances in good agreement with previous measurements. Light and iron-peak element abundance ratios in the two Boötes I stars, as well as those of most other Boötes I members, collected from the literature, closely resemble those of regular metal-poor halo stars. Neutron-capture element abundances Sr and Ba are systematically lower than the main halo trend and also show a significant abundance spread. Overall, this is similar to what has been found for other ultra-faint dwarf galaxies. We apply corrections to the carbon abundances (commensurate with stellar evolutionary status) of the entire sample and find 21% of stars to be carbon-enhanced metal-poor (CEMP) stars, compared to 13% without using the carbon correction. We reassess the metallicity distribution functions for the CEMP stars and non-CEMP stars, and confirm earlier claims that CEMP stars might belong to a different, earlier population. Applying a set of abundance criteria to test to what extent Boötes I could be a surviving first galaxy suggests that it is one of the earliest assembled systems that perhaps received gas from accretion from other clouds in the system, or from swallowing a first galaxy or building block type object. This resulted in the two stellar populations observable today. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

A common origin for globular clusters and ultra-faint dwarfs in simulations of the first galaxies

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

Ricotti, Massimo; Parry, Owen H.; Gnedin, Nickolay Y.

In this study, the first in a series on galaxy formation before reionization, we focus on understanding what determines the size and morphology of stellar objects in the first low-mass galaxies, using parsec-scale cosmological simulations performed with an adaptive mesh hydrodynamics code. Although the dense gas in which stars are formed tends to have a disk structure, stars are found in spheroids with little rotation. Halos with masses betweenmore » $${10}^{6}\\,{M}_{\\odot }$$ and $$5\\times {10}^{8}\\,{M}_{\\odot }$$ form stars stochastically, with stellar masses in the range $${10}^{4}\\,{M}_{\\odot }$$ to $$2\\times {10}^{6}\\,{M}_{\\odot }$$. We observe, nearly independent of stellar mass, a large range of half-light radii for the stars, from a few parsecs to a few hundred parsecs and surface brightnesses and mass-to-light ratios ranging from those typical of globular clusters to ultra-faint dwarfs. In our simulations, stars form in dense stellar clusters with high gas-to-star conversion efficiencies and rather uniform metallicities. A fraction of these clusters remain bound after the gas is removed by feedback, but others are destroyed, and their stars, which typically have velocity dispersions of 20–40 km s –1, expand until they become bound by the dark matter halo. We thus speculate that the stars in ultra-faint dwarf galaxies may show kinematic and chemical signatures consistent with their origin in a few distinct stellar clusters. On the other hand, some globular clusters may form at the center of primordial dwarf galaxies and may contain dark matter, perhaps detectable in the outer parts.« less

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

Su, Yang; Fang, Min; Yang, Ji

We have carried out {sup 12}CO, {sup 13}CO, and C{sup 18}O observations toward the mixed morphology supernova remnant (SNR) IC 443. The observations cover a 1.°5 × 1.°5 area and allow us to investigate the overall molecular environment of the remnant. Some northern and northeastern partial shell structure of CO gas is around the remnant. One of the partial shells, about 5' extending beyond the northeastern border of the remnant's bright radio shell, seems to just confine the faint radio halo. On the other hand, some faint CO clumps can be discerned along the eastern boundary of the faint remnant'smore » radio halo. Connecting the eastern CO clumps, the northeastern partial shell structures, and the northern CO partial shell, we can see that a half molecular ring structure appears to surround the remnant. The LSR velocity of the half-ring structure is in the range of –5 km s{sup –1} to –2 km s{sup –1}, which is consistent with that of the –4 km s{sup –1} molecular clouds. We suggest that the half-ring structure of the CO emission at V {sub LSR} ∼ –4 km s{sup –1} is associated with the SNR. The structures are possibly swept up by the stellar winds of SNR IC 443's massive progenitor. Based on the Wide-field Infrared Survey Explorer and the Two Micron All Sky Survey near-IR database, 62 young stellar object (YSO) candidates are selected within the radio halo of the remnant. These YSO candidates concentrated along the boundary of the remnant's bright radio shell are likely to be triggered by the stellar winds from the massive progenitor of SNR IC 443.« less

Hubble Sees a “Behemoth” Bleeding Atmosphere Around a Warm Exoplanet

NASA Image and Video Library

2015-06-24

Astronomers using NASA’s Hubble Space Telescope have discovered an immense cloud of hydrogen dubbed “The Behemoth” bleeding from a planet orbiting a nearby star. The enormous, comet-like feature is about 50 times the size of the parent star. The hydrogen is evaporating from a warm, Neptune-sized planet, due to extreme radiation from the star. This phenomenon has never been seen around an exoplanet so small. It may offer clues to how other planets with hydrogen-enveloped atmospheres could have their outer layers evaporated by their parent star, leaving behind solid, rocky cores. Hot, rocky planets such as these that roughly the size of Earth are known as Hot-Super Earths. “This cloud is very spectacular, though the evaporation rate does not threaten the planet right now,” explains the study’s leader, David Ehrenreich of the Observatory of the University of Geneva in Switzerland. “But we know that in the past, the star, which is a faint red dwarf, was more active. This means that the planet evaporated faster during its first billion years of existence because of the strong radiation from the young star. Overall, we estimate that it may have lost up to 10 percent of its atmosphere over the past several billion years.” Read more: www.nasa.gov/feature/goddard/hubble-sees-a-behemoth-bleed... Caption: This artist's concept shows "The Behemoth," an enormous comet-like cloud of hydrogen bleeding off of a warm, Neptune-sized planet just 30 light-years from Earth. Also depicted is the parent star, which is a faint red dwarf named GJ 436. The hydrogen is evaporating from the planet due to extreme radiation from the star. A phenomenon this large has never before been seen around any exoplanet. Credits: NASA, ESA, and G. Bacon (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

Track-Before-Detect Algorithm for Faint Moving Objects based on Random Sampling and Consensus

NASA Astrophysics Data System (ADS)

Dao, P.; Rast, R.; Schlaegel, W.; Schmidt, V.; Dentamaro, A.

2014-09-01

There are many algorithms developed for tracking and detecting faint moving objects in congested backgrounds. One obvious application is detection of targets in images where each pixel corresponds to the received power in a particular location. In our application, a visible imager operated in stare mode observes geostationary objects as fixed, stars as moving and non-geostationary objects as drifting in the field of view. We would like to achieve high sensitivity detection of the drifters. The ability to improve SNR with track-before-detect (TBD) processing, where target information is collected and collated before the detection decision is made, allows respectable performance against dim moving objects. Generally, a TBD algorithm consists of a pre-processing stage that highlights potential targets and a temporal filtering stage. However, the algorithms that have been successfully demonstrated, e.g. Viterbi-based and Bayesian-based, demand formidable processing power and memory. We propose an algorithm that exploits the quasi constant velocity of objects, the predictability of the stellar clutter and the intrinsically low false alarm rate of detecting signature candidates in 3-D, based on an iterative method called "RANdom SAmple Consensus” and one that can run real-time on a typical PC. The technique is tailored for searching objects with small telescopes in stare mode. Our RANSAC-MT (Moving Target) algorithm estimates parameters of a mathematical model (e.g., linear motion) from a set of observed data which contains a significant number of outliers while identifying inliers. In the pre-processing phase, candidate blobs were selected based on morphology and an intensity threshold that would normally generate unacceptable level of false alarms. The RANSAC sampling rejects candidates that conform to the predictable motion of the stars. Data collected with a 17 inch telescope by AFRL/RH and a COTS lens/EM-CCD sensor by the AFRL/RD Satellite Assessment Center is used to assess the performance of the algorithm. In the second application, a visible imager operated in sidereal mode observes geostationary objects as moving, stars as fixed except for field rotation, and non-geostationary objects as drifting. RANSAC-MT is used to detect the drifter. In this set of data, the drifting space object was detected at a distance of 13800 km. The AFRL/RH set of data, collected in the stare mode, contained the signature of two geostationary satellites. The signature of a moving object was simulated and added to the sequence of frames to determine the sensitivity in magnitude. The performance compares well with the more intensive TBD algorithms reported in the literature.

VizieR Online Data Catalog: Spectroscopy of 104 objects in the ONC (Ingraham+, 2014)

NASA Astrophysics Data System (ADS)

Ingraham, P.; Albert, L.; Doyon, R.; Artigau, E.

2016-03-01

In 2003 December, we obtained six nights (on CFHT to perform MOS observations of faint objects in the central region of the Orion Trapezium cluster. The observations used the infrared imager and multi-object spectrograph SIMON (Spectrometre Infrarouge de Montreal). The optical design is fully achromatic between 0.8 and 2.5μm and features a HAWAII-I 1024*1024 HgCdTe detector with an image scale of 0.2'' on CFHT. SIMON utilizes a low-dispersion Amici prism enabling multi-object low-resolution (R~30) spectroscopy over the wavelength range of 0.9-2.4μm. The slit width, in the spectral direction, was chosen to be 0.6'' (3pixels) resulting in a spectral resolution of R~30. In total, spectra for 240 point sources were obtained. Here, we present only the 104 objects (see Table5) with low-extinction (AV<8) spectra having well constrained spectral types. (2 data files).

Wearable vital parameters monitoring system

NASA Astrophysics Data System (ADS)

Caramaliu, Radu Vadim; Vasile, Alexandru; Bacis, Irina

2015-02-01

The system we propose monitors body temperature, heart rate and beside this, it tracks if the person who wears it suffers a faint. It uses a digital temperature sensor, a pulse sensor and a gravitational acceleration sensor to monitor the eventual faint or small heights free falls. The system continuously tracks the GPS position when available and stores the last valid data. So, when measuring abnormal vital parameters the module will send an SMS, using the GSM cellular network , with the person's social security number, the last valid GPS position for that person, the heart rate, the body temperature and, where applicable, a valid fall alert or non-valid fall alert. Even though such systems exist, they contain only faint detection or heart rate detection. Usually there is a strong correlation between low/high heart rate and an eventual faint. Combining both features into one system results in a more reliable detection device.

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

NASA Astrophysics Data System (ADS)

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

2017-08-01

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

Extremely Red Objects in Two Quasar Fields at z ~ 1.4

NASA Astrophysics Data System (ADS)

Stockton, Alan; McGrath, Elizabeth; Canalizo, Gabriela

2006-10-01

We present an investigation of the properties and environments of bright extremely red objects (EROs) found in the fields of the quasars TXS 0145+386 and 4C 15.55, both at z~1.4. There is marginal evidence from Chandra Advanced CCD Imaging Spectrometer (ACIS) imaging for hot cluster gas with a luminosity of a few 1044 ergs s-1 in the field of 4C 15.55. The TXS 0145+386 field has an upper limit at a similar value, but it also clearly shows an overdensity of faint galaxies. None of the EROs are detected as X-ray sources. For two of the EROs that have spectral energy distributions and rest-frame near-UV spectra that show that they are strongly dominated by old stellar populations, we determine radial surface brightness profiles from adaptive optics images. Both of these galaxies are best fit by profiles close to exponentials, plus a compact nucleus comprising ~30% of the total light in one case and 8% in the other. Neither is well fit by an r1/4-law profile. This apparent evidence for the formation of massive ~2×1011 disks of old stars in the early universe indicates that at least some galaxies formed essentially monolithically, with high star formation rates sustained over a few 108 yr and without the aid of major mergers. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; on data obtained with the Chandra X-Ray Observatory, which is operated for NASA by the Smithsonian Astrophysical Observatory; on data obtained at the Canada-France-Hawaii Telescope, which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii; and on data obtained at the the United Kingdom Infrared Telescope, which is operated by the Joint Astronomy Centre on behalf of the UK. Particle Physics and Astronomy Research Council. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA. The Observatory was made possible by the financial support of the W. M. Keck Foundation.

Gravity and Extreme Magnetism SMEX

NASA Technical Reports Server (NTRS)

Swank, Jean; Kallman, Timothy R.; Jahoda, Keith M.

2008-01-01

Gas accreting ont,o black holes and neutron stars form a dynamic system generating X-rays with spectroscopic signatures and varying on time scales determined by the system. The radiation from various parts of these systems is surely polarized and compact sources have been calculated to give rise to net polarization from the unresolved sum of the radiation from the systems. Polarization has been looked to for some time as also bearing the imprint of strong gravity and providing complementary information that could resolve ambiguities between the physical models that can give rise to frequencies, time delays, and spectra. In the cases of both stellar black holes and supermassive black holes the net polarizations predicted for probable disk and corona models are less than 10 needed. This sensitivity can be achieved, even for sources as faint as 1 milliCrab, in the Gravity and Extreme Magnetism SMEX (GEMS) mission that uses foil mirrors and Time Projection Chamber detectors. Similarities have been pointed out between the timing and the spectral characteristics of low mass X-ray binaries and stellar black hole sources. Polarization measurements for these sources could play a role in determining the configuration of the disk and the neutron star.

EUV observation from the Earth-orbiting satellite, EXCEED

NASA Astrophysics Data System (ADS)

Yoshioka, K.; Murakami, G.; Yoshikawa, I.; Ueno, M.; Uemizu, K.; Yamazaki, A.

2010-01-01

An Earth-orbiting small satellite “EXtreme ultraviolet spectrosCope for ExosphEric Dynamics” (EXCEED) which will be launched in 2012 is under development. The mission will carry out spectroscopic and imaging observation of EUV (Extreme Ultraviolet: 60-145 nm) emissions from tenuous plasmas around the planets (Venus, Mars, Mercury, and Jupiter). It is essential for EUV observation to put on an observing site outside the Earth’s atmosphere to avoid the absorption. It is also essential that the detection efficiency must be very high in order to catch the faint signals from those targets. In this mission, we employ cesium iodide coated microchannel plate as a 2 dimensional photon counting devise which shows 1.5-50 times higher quantum detection efficiency comparing with the bared one. We coat the surface of the grating and entrance mirror with silicon carbides by the chemical vapor deposition method in order to archive the high diffraction efficiency and reflectivity. The whole spectrometer is shielded by the 2 mm thick stainless steel to prevent the contamination caused by the high energy electrons from the inner radiation belt. In this paper, we will introduce the mission overview, its instrument, and their performance.

Retainment of r-process material in dwarf galaxies

NASA Astrophysics Data System (ADS)

Beniamini, Paz; Dvorkin, Irina; Silk, Joe

2018-04-01

The synthesis of r-process elements is known to involve extremely energetic explosions. At the same time, recent observations find significant r-process enrichment even in extremely small ultra-faint dwarf (UFD) galaxies. This raises the question of retainment of those elements within their hosts. We estimate the retainment fraction and find that it is large ˜0.9, unless the r-process event is very energetic (≳ 1052erg) and / or the host has lost a large fraction of its gas prior to the event. We estimate the r-process mass per event and rate as implied by abundances in UFDs, taking into account imperfect retainment and different models of UFD evolution. The results are consistent with previous estimates (Beniamini et al. 2016b) and with the constraints from the recently detected macronova accompanying a neutron star merger (GW170817). We also estimate the distribution of abundances predicted by these models. We find that ˜0.07 of UFDs should have r-process enrichment. The results are consistent with both the mean values and the fluctuations of [Eu/Fe] in galactic metal poor stars, supporting the possibility that UFDs are the main 'building blocks' of the galactic halo population.

On the SW Sex-type eclipsing cataclysmic variable SDSS0756+0858

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

Tovmassian, Gagik; Hernandez, Mercedes Stephania; González-Buitrago, Diego

We conducted a spectroscopic and photometric study of SDSS J075653.11+085831. X-ray observations were also attempted. We determined the orbital period of this binary system to be 3.29 hr. It is a deep eclipsing system, whose spectra show mostly single-peaked, Balmer emission lines and a rather intense He II line. There is also the presence of faint (often double-peaked) He I emission lines as well as several absorption lines, Mg I being the most prominent. All of these features point toward the affiliation of this object with the growing number of SW Sex-type objects. We developed a phenomenological model of anmore » SW Sex system to reproduce the observed photometric and spectral features.« less

Evolution of X-ray astronomy

NASA Technical Reports Server (NTRS)

Rossj, B.

1981-01-01

The evolution of X-ray astronomy up to the launching of the Einstein observatory is presented. The evaluation proceeded through the following major steps: (1) discovery of an extrasolar X-ray source, Sco X-1, orders of magnitude stronger than astronomers believed might exist; (2) identification of a strong X-ray source with the Crab Nebula; (3) identification of Sco X-1 with a faint, peculiar optical object; (4) demonstration that X-ray stars are binary systems, each consisting of a collapsed object accreting matter from an ordinary star; (5) discovery of X-ray bursts; (6) discovery of exceedingly strong X-ray emission from active galaxies, quasars and clusters of galaxies; (7) demonstration that the principal X-ray source is a hot gas filling the space between galaxies.

HST image of Gravitational Lens G2237 + 305 or 'Einstein Cross'

NASA Technical Reports Server (NTRS)

1990-01-01

European Space Agency (ESA) Faint Object Camera (FOC) science image was taken from the Hubble Space Telescope (HST) of Gravitational Lens G2237 + 305 or 'Einstein Cross'. The gravitational lens G2237 + 305 or 'Einstein Cross' shows four images of a very distant quasar which has been multiple-imaged by a relatively nearby galaxy acting as a gravitational lens. The angular separation between the upper and lower images is 1.6 arc seconds. Photo was released from Goddard Space Flight Center (GSFC) 09-12-90.

Cluster analysis of the hot subdwarfs in the PG survey

NASA Technical Reports Server (NTRS)

Thejll, Peter; Charache, Darryl; Shipman, Harry L.

1989-01-01

Application of cluster analysis to the hot subdwarfs in the Palomar Green (PG) survey of faint blue high-Galactic-latitude objects is assessed, with emphasis on data noise and the number of clusters to subdivide the data into. The data used in the study are presented, and cluster analysis, using the CLUSTAN program, is applied to it. Distances are calculated using the Euclidean formula, and clustering is done by Ward's method. The results are discussed, and five groups representing natural divisions of the subdwarfs in the PG survey are presented.

Symbiotic Stars in X-rays. II. Faint Sources Detected with XMM-Newton and Chandra

NASA Technical Reports Server (NTRS)

Nunez, N. E.; Luna, G. J. M.; Pillitteri, I.; Mukai, K.

2014-01-01

We report the detection from four symbiotic stars that were not known to be X-ray sources. These four object show a ß-type X-ray spectrum, that is, their spectra can be modeled with an absorbed optically thin thermal emission with temperatures of a few million degrees. Photometric series obtained with the Optical Monitor on board XMM-Newton from V2416 Sgr and NSV 25735 support the proposed scenario where the X-ray emission is produced in a shock-heated region inside the symbiotic nebulae.

Possible new VY Scl-type variable 1RXS J075330.1+044606

NASA Astrophysics Data System (ADS)

Sokolovsky, K.; Denisenko, D.; Mescheryakov, A.; Tkachenko, A.; Korotkiy, S.; Gerke, V.

2012-02-01

We report the discovery of a possible new VY Scl-type cataclysmic variable associated with previously unidentified X-ray source 1RXS J075330.1+044606. The variable optical object USNO-B1.0 0947-0148659 (07:53:30.78 +04:45:56.3, J2000) located 15" from the X-ray source listed in the ROSAT All Sky Survey Faint Source Catalog (Voges et al., 2000, IAUC, 7432) was identified from information listed in the USNO-B1.0 catalog (Monet et al.

ZTF Bright Transient Survey classifications

NASA Astrophysics Data System (ADS)

Graham, M. L.; Bellm, E.; Bektesevic, D.; Eadie, G.; Huppenkothen, D.; Davenport, J. R. A.; Fremling, C.; Sharma, Y.; Kulkarni, S. R.; Walters, R.; Blagorodnova, N.; Neill, J.; Miller, A. A.; Taddia, F.; Lunnan, R.; Taggart, K.; Perley, D. A.; Goobar, A.

2018-06-01

The Zwicky Transient Facility (ZTF; ATel #11266) Bright Transient Survey (BTS; ATel #11688) reports classifications of the following targets. Spectra have been obtained with the Dual Imaging Spectrograph (range 340-1000nm, spectral resolution R 1000) mounted on the 3.5m telescope at Apache Point Observatory, the Spectral Energy Distribution Machine (SEDM) (range 350-950nm, spectral resolution R 100) mounted on the Palomar 60-inch (P60) telescope (Blagorodnova et. al. 2018, PASP, 130, 5003), or the Andalucia Faint Object Spectrograph and Camera (ALFOSC) on the 2.5m Nordic Optical Telescope (NOT).

Mid-Infrared Spectroscopy of Mercury from the Kuiper Airborne Observatory

NASA Astrophysics Data System (ADS)

Sprague, A. L.; Witteborn, F. C.; Kozlowski, R. W. H.; Wooden, D. H.

1996-03-01

We present mid-infrared (5 - 10mic) spectroscopic measurements of the planet Mercury obtained from the Kuiper Airborne Observatory (KAO) using the High Efficiency Infrared Faint Object Grating Spectrograph (HIFOGS). Spectra show features characteristic of plagioclase feldspar that was previously observed near 120 deg mercurian longitude. The spectra also show spectral features that could be interpreted indicative of the presence of pyrrhotite (pyrr). An analysis that fully accounts for the effects of large field of view (FOV), thermal gradients, rough surface and absolute calibration is still underway.

VizieR Online Data Catalog: Faint OB stars between Car and Cen (Lynga 1968)

NASA Astrophysics Data System (ADS)

Lynga, G.

2016-03-01

The instrument used is the 50/65/175cm Schmidt telescope of the Uppsala Southern Station at Mount Stromlo. The objective prism gives a dispersion of 470Angstrom/mm et Hγ. The emulsion has constantly been Kodak IIa-O, the exposure time 20min, and the width of the spectra 0.2mm. A 12 degree zone centered on the galactic equator has been scanned for OB stars. Accurate positions of the stars were added in 2016, using the results from B. Skiff (Lowell Obs.) (2 data files).

The White Dwarf Mass and the Accretion Rate of Recurrent Novae: An X-ray Perspective

NASA Technical Reports Server (NTRS)

Mukai, Koji; Sokoloski, Jennifer L.; Nelson, Thomas; Luna, Gerardo J. M.

2011-01-01

We present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RN candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

An Unusual Transient in the Extremely Metal-Poor Galaxy SDSS J094332.35+332657.6 (Leoncino Dwarf)

NASA Astrophysics Data System (ADS)

Filho, Mercedes E.; Sánchez Almeida, J.

2018-05-01

We have serendipitously discovered that Leoncino Dwarf, an ultra-faint, low-metallicity record-holder dwarf galaxy, may have hosted a transient source, and possibly exhibited a change in morphology, a shift in the center of brightness, and peak variability of the main (host) source in images taken approximately 40 yr apart; it is highly likely that these phenomena are related. Scenarios involving a Solar System object, a stellar cluster, dust enshrouding, and accretion variability have been considered, and discarded, as the origin of the transient. Although a combination of time-varying strong and weak lensing effects, induced by an intermediate mass black hole (104 - 5 × 105 M⊙) moving within the Milky Way halo (0.1 - 4 kpc), can conceivably explain all of the observed variable galaxy properties, it is statistically highly unlikely according to current theoretical predictions, and, therefore, also discarded. A cataclysmic event such as a supernova/hypernova could have occurred, as long as the event was observed towards the later/late-stage descent of the light curve, but this scenario fails to explain the absence of a post-explosion source and/or host HII region in recent optical images. An episode related to the giant eruption of a luminous blue variable star, a stellar merger or a nova, observed at, or near, peak magnitude may explain the transient source and possibly the change in morphology/center of brightness, but can not justify the main source peak variability, unless stellar variability is evoked.

Establishing Extreme Dynamic Range with JWST: Decoding Smoke Signals in the Glare of a Wolf-Rayet Binary

NASA Astrophysics Data System (ADS)

Lau, Ryan; Hankins, M.; Kasliwal, M.; Sivaramakrishnan, A.; Thatte, D.

2017-11-01

Dust is a key ingredient in the formation of stars and planets. However, the dominant channels of dust production throughout cosmic time are still unclear. With its unprecedented sensitivity and spatial resolution in the mid-IR, the James Webb Space Telescope (JWST) is the ideal platform to address this issue by investigating the dust abundance, composition, and production rates of various dusty sources. In particular, colliding-wind Wolf-Rayet (WR) binaries are efficient dust producers in the local Universe, and likely existed in the earliest galaxies. To study these interesting objects, we propose JWST observations of the archetypal colliding-wind binary WR 140 to study its dust composition, abundance, and formation mechanisms. We will utilize two key JWST observing modes with the medium resolution spectrometer (MRS) on the Mid-Infrared Instrument (MIRI) and the Aperture Masking Interferometry (AMI) mode with the Near Infrared Imager and Slitless Spectrograph (NIRISS). Our proposed observations will yield high impact scientific results on the dust forming properties WR binaries, and establish a benchmark for key observing modes for imaging bright sources with faint extended emission. This will be valuable in various astrophysical contexts including mass-loss from evolved stars, dusty tori around active galactic nuclei, and protoplanetary disks. We are committed to designing and delivering science-enabling products for the JWST community that address technical issues such as bright source artifacts that will limit the maximum achievable image contrast.

STRUCTURE AND DYNAMICS OF THE 2010 JULY 11 ECLIPSE WHITE-LIGHT CORONA

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

Pasachoff, J. M.; Rusin, V.; Saniga, M.

The white-light corona (WLC) during the total solar eclipse on 2010 July 11 was observed by several teams in the Moon's shadow stretching across the Pacific Ocean and a number of isolated islands. We present a comparison of the WLC as observed by eclipse teams located on the Tatakoto Atoll in French Polynesia and on Easter Island, 83 minutes later, combined with near-simultaneous space observations. The eclipse was observed at the beginning of the solar cycle, not long after solar minimum. Nevertheless, the solar corona shows a plethora of different features (coronal holes, helmet streamers, polar rays, very faint loopsmore » and radial-oriented thin streamers, a coronal mass ejection, and a puzzling 'curtain-like' object above the north pole). Comparing the observations from the two sites enables us to detect some dynamic phenomena. The eclipse observations are further compared with a hairy-ball model of the magnetic field and near-simultaneous images from the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory, the Extreme Ultraviolet Imager on NASA's Solar Terrestrial Relations Observatory, the Sun Watcher, using Active Pixel System Detector and Image Processing on ESA's PRoject for Onboard Autonomy, and the Naval Research Laboratory's Large Angle and Spectrometric Coronagraph on ESA's Solar and Heliospheric Observatory. The Ludendorff flattening coefficient is 0.156, matching the expected ellipticity of coronal isophotes at 2 Rs{sub un}, for this rising phase of the solar-activity cycle.« less

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

The Symbiotic System SS73 17 seen with Suzaku

NASA Technical Reports Server (NTRS)

Smith, Randall K.; Mushotzky, Richard; Kallman, Tim; Tueller, Jack; Mukai, Koji; Markwardt, Craig

2007-01-01

We observed with Suzaku the symbiotic star SS73 17, motivated by the discovery by the INTEGRAL satellite and the Swift BAT survey that it emits hard X-rays. Our observations showed a highly-absorbed X-ray spectrum with NH > loz3 emp2, equivalent to Av > 26, although the source has B magnitude 11.3 and is also bright in UV. The source also shows strong, narrow iron lines including fluorescent Fe K as well as Fe xxv and Fe XXVI. The X-ray spectrum can be fit with a thermal model including an absorption component that partially covers the source. Most of the equivalent width of the iron fluorescent line in this model can be explained as a combination of reprocessing in a dense absorber plus reflection off a white dwarf surface, but it is likely that the continuum is partially seen in reflection as well. Unlike other symbiotic systems that show hard X-ray emission (CH Cyg, RT Cru, T CrB, GX1+4), SS73 17 is not known to have shown nova-like optical variability, X-ray flashes, or pulsations, and has always shown faint soft X-ray emission. As a result, although it is likely a white dwarf, the nature of the compact object in SS73 17 is still uncertain. SS73 17 is probably an extreme example of the recently discovered and relatively small class of hard X-ray emitting symbiotic systems.

Optical Photometric Observations of GEO Debris

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Rodriquez-Cowardin, Heather M.; Barker, Edwin S.; Abercromby, Kira J.; Kelecy, Thomas M.; Horstman, Matt

2010-01-01

We report on a continuing program of optical photometric measurements of faint orbital debris at geosynchronous Earth orbit (GEO). These observations can be compared with laboratory studies of actual spacecraft materials in an effort to determine what the faint debris at GEO may be. We have optical observations from Cerro Tololo Inter-American Observatory (CTIO) in Chile of two samples of debris: 1. GEO objects discovered in a survey with the University of Michigan's 0.6-m aperture Curtis-Schmidt telescope MODEST (for Michigan Orbital DEbris Survey Telescope), and then followed up in real-time with the CTIO/SMARTS 0.9-m for orbits and photometry. Our goal is to determine 6 parameter orbits and measure colors for all objects fainter than R = 15 t11 magnitude that are discovered in the MODEST survey. 2. A smaller sample of high area to mass ratio (AMR) objects discovered independently, and acquired using predictions from orbits derived from independent tracking data collected days prior to the observations. Our optical observations in standard astronomical BVRI filters are done with either telescope, and with the telescope tracking the debris object at the object's angular rate. Observations in different filters are obtained sequentially. We have obtained 71 calibrated sequences of R-B-V-I-R magnitudes. A total of 66 of these sequences have 3 or more good measurements in all filters (not contaminated by star streaks or in Earth's shadow). Most of these sequences show brightness variations, but a small subset has observed brightness variations consistent with that expected from observational errors alone. The majority of these stable objects are redder than a solar color in both B-R and R-I. There is no dependence on color with brightness. For a smaller sample of objects we have observed with synchronized CCD cameras on the two telescopes. The CTIO 0.9-m observes in B, and MODEST in R. The CCD cameras are electronically linked together so that the start time and duration of observations are the same to better than 50 milliseconds. Thus, the B-R color is a true measure of the surface of the debris piece facing the telescopes for that observation. Any change in color reflects a real change in the debris surface. We will compare our observations with models and laboratory measurements of selected surfaces.

EoR Foregrounds: the Faint Extragalactic Radio Sky

NASA Astrophysics Data System (ADS)

Prandoni, Isabella

2018-05-01

A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and μJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population and on the modeling of its various components. In this paper I will provide a brief overview of the latest results in areas that are potentially important for an accurate treatment of extra-galactic foregrounds in experiments designed to probe the Epoch of Reionization.

Confirmation of Faint Dwarf Galaxies in the M81 Group

NASA Astrophysics Data System (ADS)

Chiboucas, Kristin; Jacobs, Bradley A.; Tully, R. Brent; Karachentsev, Igor D.

2013-11-01

We have followed up on the results of a 65 deg2 CFHT/MegaCam imaging survey of the nearby M81 Group searching for faint and ultra-faint dwarf galaxies. The original survey turned up 22 faint candidate dwarf members. Based on two-color HST ACS/WFC and WFPC2 photometry, we now confirm 14 of these as dwarf galaxy members of the group. Distances and stellar population characteristics are discussed for each. To a completeness limit of M_{r^{\\prime }} = -10, we find a galaxy luminosity function slope of -1.27 ± 0.04 for the M81 Group. In this region, there are now 36 M81 Group members known, including 4 blue compact dwarfs; 8 other late types including the interacting giants M81, NGC 3077, and M82; 19 early type dwarfs; and at least 5 potential tidal dwarf galaxies. We find that the dSph galaxies in M81 appear to lie in a flattened distribution, similar to that found for the Milky Way and M31. One of the newly discovered dSph galaxies has properties similar to the ultra-faint dwarfs being found in the Local Group with a size Re ~ 100 pc and total magnitude estimates M_{r^{\\prime }} = -6.8 and MI ~ -9.1.

The Chandra Deep Field-North Survey and the cosmic X-ray background.

PubMed

Brandt, W Nielsen; Alexander, David M; Bauer, Franz E; Hornschemeier, Ann E

2002-09-15

Chandra has performed a 1.4 Ms survey centred on the Hubble Deep Field-North (HDF-N), probing the X-ray Universe 55-550 times deeper than was possible with pre-Chandra missions. We describe the detected point and extended X-ray sources and discuss their overall multi-wavelength (optical, infrared, submillimetre and radio) properties. Special attention is paid to the HDF-N X-ray sources, luminous infrared starburst galaxies, optically faint X-ray sources and high-to-extreme redshift active galactic nuclei. We also describe how stacking analyses have been used to probe the average X-ray-emission properties of normal and starburst galaxies at cosmologically interesting distances. Finally, we discuss plans to extend the survey and argue that a 5-10 Ms Chandra survey would lay key groundwork for future missions such as XEUS and Generation-X.

Interior properties of the inner Saturnian moons from space astrometry data

NASA Astrophysics Data System (ADS)

Lainey, Valery; Noyelles, Benoît; Cooper, Nick; Murray, Carl; Park, Ryan; Rambaux, Nicolas

2018-04-01

During thirteen years in orbit around Saturn before its final plunge, the Cassini spacecraft provided more than ten thousand astrometric measurements. Such large amounts of accurate data enable the search for extremely faint signals in the orbital motion of the moons. Among those, the detection of the dynamical feedback of the rotation of the inner moons of Saturn on their respective orbits becomes possible. Using all the currently available astrometric data associated with Atlas, Prometheus, Pandora, Janus and Epimetheus, we provide a detailed analysis of the ISS data, with special emphasis on their statistical behavior and source of biases. Then, we try quantifying the physical librations of Prometheus, Pandora, Epimetheus and Janus from the monitoring of their orbits. Last, we show how introducing measurements directly derived from imaging can provide tighter constraints on these quantities.

Photometric Redshift Calibration Strategy for WFIRST Cosmology

NASA Astrophysics Data System (ADS)

Hemmati, Shoubaneh; WFIRST, WFIRST-HLS-COSMOLOGY

2018-01-01

In order for WFIRST and other Stage IV Dark energy experiments (e.g. LSST, Euclid) to infer cosmological parameters not limited by systematic errors, accurate redshift measurements are needed. This accuracy can only be met using spectroscopic subsamples to calibrate the full sample. In this poster, we employ the machine leaning, SOM based spectroscopic sampling technique developed in Masters et al. 2015, using the empirical color-redshift relation among galaxies to find the minimum spectra required for the WFIRST weak lensing calibration. We use galaxies from the CANDELS survey to build the LSST+WFIRST lensing analog sample of ~36k objects and train the LSST+WFIRST SOM. We show that 26% of the WFIRST lensing sample consists of sources fainter than the Euclid depth in the optical, 91% of which live in color cells already occupied by brighter galaxies. We demonstrate the similarity between faint and bright galaxies as well as the feasibility of redshift measurements at different brightness levels. 4% of SOM cells are however only occupied by faint galaxies for which we recommend extra spectroscopy of ~200 new sources. Acquiring the spectra of these sources will enable the comprehensive calibration of the WFIRST color-redshift relation.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1994-01-01

A comparison image of the M100 Galactic Nucleus, taken by the Hubble Space Telescope (HST) Wide Field Planetary Camera-1 (WF/PC1) and Wide Field Planetary Camera-2 (WF/PC2). The HST was placed in a low-Earth orbit by the Space Shuttle Discovery, STS-31 mission, in April 1990. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. During four spacewalks, the STS-61 crew replaced the solar panel with its flexing problems; the WF/PC1 with the WF/PC2, with built-in corrective optics; and the High-Speed Photometer with the Corrective Optics Space Telescope Axial Replacement (COSTAR), to correct the aberration for the remaining instruments. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1990-04-25

In this photograph, the Hubble Space Telescope (HST) was being deployed on April 25, 1990. The photograph was taken by the IMAX Cargo Bay Camera (ICBC) mounted in a container on the port side of the Space Shuttle orbiter Discovery (STS-31 mission). The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. A scheduled Space Service servicing mission (STS-61) in 1993 permitted scientists to correct the problem. During four spacewalks, new instruments were installed into the HST that had optical corrections. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors. Photo Credit: NASA/Smithsonian Institution/Lockheed Corporation.

Disks around Failed Stars - a Question of Age

NASA Astrophysics Data System (ADS)

2002-08-01

First Ground-Based Mid-Infrared Observations of Brown Dwarfs [1] Summary A team of European astronomers [2] have observed eight Brown Dwarfs, i.e., small and faint objects also known as "failed stars", with the TIMMI2 infrared sensitive instrument at the ESO 3.6-m telescope on La Silla. From two of these, mid-infrared radiation is detected - for the first time ever from such objects with a ground-based telescope . While the younger Brown Dwarf, aged a few million years, is found to be surrounded by a dusty disk, no warm dust is present around the older ones. The new observations support the following formation hypothesis for Brown Dwarfs: they are born in the same way as "real" stars, by contraction in interstellar clouds of gas and dust . During the later stages of this process, the infalling material is transferred onto the star via a gas and dust disk . This disk - in which planets may possibly form - then disperses with time. PR Photo 17a/02 : Image of Brown Dwarf LP 944-20 PR Photo 17b/02 : Models of the disk around Brown Dwarf Cha HA 2 Brown Dwarfs are faint and cool objects Astronomical objects known as "Brown Dwarfs" are "failed stars" . Their comparatively small mass, less than about 7% of that of our Sun (or about 75 times the mass of planet Jupiter), is too small to achieve sufficiently high pressure and temperature at their centre to ignite energy-producing nuclear processes. Some astronomers also refer to Brown Dwarfs as a "missing link" between planets and stars, being neither one nor the other, yet with similarities to both. They do not burn hydrogen to helium as "real" stars do, but continue to emit faint light as they slowly contract and cool during millions of years. They end their inglorious life with a whimper and finally fade into eternal insignificance. Although Brown Dwarfs were theoretically predicted already in 1963, astronomers had to wait until 1995 for the first one to be discovered. This was mainly due to their extreme faintness as compared to normal stars - even the most nearby Brown Dwarfs shine so faintly that they can only be observed with relatively large telescopes. As they are rather cool objects, they emit mostly in the infrared spectral region; hence they are best observed with astronomical instruments that operate at those wavelengths. With improved techniques, however, more and more Brown Dwarfs have been found and the count has now reached several hundred. Many of these are located in the well-known Orion Nebula. Others move through interstellar space, like the lonely KELU-1 first discovered in 1997 at the ESO La Silla Observatory by Chilean astronomers, cf. ESO PR 07/97.With a distance of only 33 light-years from the Sun, it was one of the closest Brown Dwarfs known at that time. Formation of Brown Dwarfs Astronomers are still doubtful about the way Brown Dwarfs form. Among the numerous suggestions are the star-like contraction from an interstellar cloud of gas and dust and also another based on "ejected stellar embryos" . This latter scenario says that very young stars that are still accreting material are "kicked out of the nest" by their more massive brothers in multiple stellar systems. In this dramatic process, the unlucky objects are stripped of their surrounding disks. This effectively halts their further growth by accretion and they end up as underweight Brown Dwarfs. Recent observations at ESO have shown that the Brown Dwarfs in the Orion Nebula most likely have formed as stars do, i.e. by contraction in a cloud of dust and gas, cf. ESO PR 14/01. The clue to this was the observation of an excess of near-infrared radiation from many of these objects, interpreted as the presence of dusty disks around them. The astronomers then argued that if the young Brown Dwarfs possess such disks exactly like real stars do, then they must also form in the same way. Infrared observations of Brown Dwarfs Those observations were carried out in the near-infrared spectral region (in the 1.2 - 2.2 µm wavelength interval) with the ESO 3.5-m New Technology Telescope (NTT) . However, dusty disks around young stars (and presumably, those around Brown Dwarfs) radiate mostly at longer wavelengths. A detailed study of those disks is therefore best done with instruments that are sensitive to even longer wavelengths, e.g., in the mid-infrared to the sub-millimetre spectral region (10 - 1000 µm). This is in fact the only spectral interval where emission emanating from solid particles can be directly observed and their (mineral) composition thus be analysed. Pioneering observations in this wavelength interval of some Brown Dwarfs were made in mid-1995 by the ESA Infrared Space Observatory. However, the ISO instruments provided comparatively low image sharpness and these observations were hampered by confusion with the radiation from other objects in the same sky field. And the ISO mission was over before Brown Dwarf objects were discovered in larger numbers. Astronomers have therefore long wanted to observe Brown Dwarfs with large ground-based telescopes in the mid-infrared spectral region. But these objects are faint and few suitable instruments that work at these wavelengths are available at the world's large astronomical telescopes. Long exposures are necessary to record the faint emissions and until now, it had not been possible to perform such highly demanding observations of Brown Dwarfs. TIMMI2 observes Brown Dwarfs ESO PR Photo 17a/02 ESO PR Photo 17a/02 [Preview - JPEG: 874 x 400 pix - 75k [Normal - JPEG: 1747 x 800 pix - 752k] ESO PR Photo 17b/02 ESO PR Photo 17b/02 [Preview - JPEG: 400 x 451 pix - 48k] [Normal - JPEG: 800 x 901 pix - 200k] Caption : PR Photo 17a/02 shows the sky field with the nearby Brown Dwarf LP 944-20 at the centre, as photographed in blue (B), red (R) and near-infrared (IR) light (reproduced from the Digital Sky Survey [STScI Digitized Sky Survey, (C) 1993, 1994, AURA, Inc. all rights reserved - cf. http://archive.eso.org/dss/dss]). The object (at the arrow) is obviously very red. Observations with the TIMMI2 instrument at the ESO 3.6-m telescope on La Silla have shown that this comparatively old object does not possess a surrounding disk of dust and gas. Another much younger Brown Dwarf, Cha HA 2 , has one. The new measurements show that this object has a flat, dense disk (lower diagramme in PR Photo 17b/02 ), unlike the hotter (solar-like), young stars, that harbour "flared" disks with a diluted, very hot top layer (upper diagramme). Now, however, the first ground-based detection of mid-infrared radiation from two Brown Dwarfs has been achieved by a team of European astronomers [2], using the Thermal Infrared Multimode Instrument (TIMMI2) on the ESO 3.6-m telescope at the La Silla Observatory (Chile). They pointed the telescope towards a total of eight Brown Dwarf objects and recorded the emission at three different mid-infrared wavelengths (5, 9.8 and 11.9 µm). "We were delighted" , says team leader Daniel Apai, "to detect radiation from two of these with TIMMI2. These are the first observations of their kind with a ground-based instrument. And although we could only establish upper limits for the radiation from the five other objects, these results are highly significant for our attempts to understand the formation and evolution of Brown Dwarfs." One of the objects, known as Cha HA 2 and located in the southern constellation Chamaeleon [3], had earlier been observed with ISO. It is a bona-fide Brown Dwarf object and an image obtained with the Hubble Space Telescope indicates that it may possibly be double. It is a relatively young Brown Dwarf and is a member of the very young Cha I star-forming region - the age has been estimated at 2 - 4.5 million years. The ISO observations hinted at the presence of a dust disk around this object - this is fully confirmed by the new TIMMI2 observations. Moreover, the mid-IR radiation measured with this instrument interestingly shows the absence of a strong emission feature from silicates (at about 10 µm wavelength). According to the astronomers, this indicates that the disk around Cha HA 2 is comparatively dense and flat, and without a heated outer layer, cf. PR Photo 17b/02 . The other Brown Dwarf from which TIMMI2 has now detected mid-infrared radiation is one of the closest of its type. Designated LP 944-20 , it is located in the southern constellation Fornax (The Oven) at a distance of only ~15 light-years. It is much older than Cha HA 2 , though, probably 500 - 650 million years. In this case, the age was determined by measuring the strengths of spectral lines of the element Lithium; the older the object, the less is the content of Lithium. The observations show that the radiation from LP 944-20 comes from the cool star itself - it does not possess a surrounding disk as does the much younger Cha HA 2 [4]. Evolution of Brown Dwarfs Daniel Apai explains: "This all fits very nicely into the current picture of the evolution of Brown Dwarfs. They are born like stars by contraction in an interstellar cloud of gas and dust. At least some of them acquire a surrounding disk during this process. But that disk disperses after some time and we therefore only find it around relatively young Brown Dwarfs, not around older ones." . Nobody knows yet whether planets form in those disks around young Brown Dwarfs (as this was the case in the disk around the young Sun and other stars), but it might happen. Only future observations with much more sensitive instruments will be able to cast more light on this intriguing question. Future observations ESO's Very Large Telescope (VLT) will soon be equipped with the VLT Mid Infrared Spectrometer/Imager (VISIR) , an extremely powerful mid-infrared sensitive instrument that is well suited for this kind of studies. Further into the future, the Atacama Large Millimeter Array (ALMA) will provide excellent opportunities for in-depth investigations of Brown Dwarfs. With unequalled sensitivity and very good image sharpness, ALMA will be able to image disks around the nearest Brown Dwarfs and possibly, to detect signs of (forming) planets in them. More information The information presented in this Press Release is based on a Letter to the Editor in the research journal "Astrophysical Journal" ("Probing Dust around Brown Dwarfs: The Naked LP 944-20 and the Disk of Chamaeleon H-alpha 2" by D. Apai and co-authors (Vol. 573, pp. L115-L117; July 10, 2002). It is available on the web at http://arXiv.org/abs/astro-ph/0206210. Notes [1]: This press release is issued in coordination between ESO and the Max-Planck-Institut für Astronomie (Heidelberg, Germany). A German version is available at the MPIA website ( http://www.mpia.de/Public/Aktuelles/index_de.html ). [2]: The team consists of Daniel Apai , Ilaria Pascucci and Thomas Henning (all at Astrophysikalisches Institut und Universitätssternwarte, Jena, Germany, and Max-Planck-Institut für Astronomie, Heidelberg, Germany), Michael Sterzik (ESO-Chile), Randolf Klein and Dimitri Semenov (Astrophysikalisches Institut und Universitätssternwarte, Jena, Germany), Eike Günther and Bringfried Stecklum (Thüringer Landessternwarte Tautenburg, Germany). [3]: Cha HA 2 stands for "H-alpha emitting object no. 2 in the Chamaeleon I Dark Cloud". [4]: The photosphere of the young Brown Dwarf Cha HA 2 also emits mid-IR radiation. However, it is quite far away - about 500 light-years, or more than 30 times more distant than LP 944-20 - and that radiation is too weak to be detected with TIMMI2.

1. Dyea Dock looking south. Note faint evenly spaced circular ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Dyea Dock looking south. Note faint evenly spaced circular dark pieces of grass up through the middle of the picture indicating posts making up the pier. Photograph made from park service cherry picker. - Dyea Dock & Association (Ruins), Skagway, Skagway, AK

ARE THE FAINT STRUCTURES AHEAD OF SOLAR CORONAL MASS EJECTIONS REAL SIGNATURES OF DRIVEN SHOCKS?

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

Lee, Jae-Ok; Moon, Y.-J.; Lee, Kangjin

2014-11-20

Recently, several studies have assumed that the faint structures ahead of coronal mass ejections (CMEs) are caused by CME-driven shocks. In this study, we have conducted a statistical investigation to determine whether or not the appearance of such faint structures depends on CME speeds. For this purpose, we use 127 Solar and Heliospheric Observatory/Large Angle Spectroscopic COronagraph (LASCO) front-side halo (partial and full) CMEs near the limb from 1997 to 2011. We classify these CMEs into two groups by visual inspection of CMEs in the LASCO-C2 field of view: Group 1 has the faint structure ahead of a CME andmore » Group 2 does not have such a structure. We find the following results. (1) Eighty-seven CMEs belong to Group 1 and 40 CMEs belong to Group 2. (2) Group 1 events have much higher speeds (average = 1230 km s{sup –1} and median = 1199 km s{sup –1}) than Group 2 events (average = 598 km s{sup –1} and median = 518 km s{sup –1}). (3) The fraction of CMEs with faint structures strongly depends on CME speeds (V): 0.93 (50/54) for fast CMEs with V ≥ 1000 km s{sup –1}, 0.65 (34/52) for intermediate CMEs with 500 km s{sup –1} ≤ V < 1000 km s{sup –1}, and 0.14 (3/21) for slow CMEs with V < 500 km s{sup –1}. We also find that the fraction of CMEs with deca-hecto metric type II radio bursts is consistent with the above tendency. Our results indicate that the observed faint structures ahead of fast CMEs are most likely an enhanced density manifestation of CME-driven shocks.« less

Preliminary analysis of an ultraviolet Hubble Space Telescope faint object camera image of the center of M31

NASA Technical Reports Server (NTRS)

King, I. R.; Deharveng, J. M.; Albrecht, R.; Barbieri, C.; Blades, J. C.; Boksenberg, A.; Crane, P.; Disney, M. J.; Jakobsen, P.; Kamperman, T. M.

1992-01-01

A 5161 s exposure was taken with the FOC on the central 44 arcsec of M31, through a filter centered at 1750 A. Much of the light is redleak from visible wavelengths, but nearly half of it is genuine UV. The image shows the same central peak found earlier by Stratoscope, with a somewhat steeper dropoff outside that peak. More than 100 individual objects are seen, some pointlike and some slightly extended. We identify them as post-asymptotic giant branch stars, some of them surrounded by a contribution from their accompanying planetary nebulae. These objects contribute almost a fifth of the total UV light, but fall far short of accounting for all of it. We suggest that the remainder may result from the corresponding evolutionary tracks in a population more metal-rich than solar.

A New Approach to Space Situational Awareness using Small Ground-Based Telescopes

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

Anheier, Norman C.; Chen, Cliff S.

This report discusses a new SSA approach evaluated by Pacific Northwest National Laboratory (PNNL) that may lead to highly scalable, small telescope observing stations designed to help manage the growing space surveillance burden. Using the methods and observing tools described in this report, the team was able to acquire and track very faint satellites (near Pluto’s apparent brightness). Photometric data was collected and used to correlate object orbital position as a function of atomic clock-derived time. Object apparent brightness was estimated by image analysis and nearby star calibration. The measurement performance was only limited by weather conditions, object brightness, andmore » the sky glow at the observation site. In the future, these new SSA technologies and techniques may be utilized to protect satellite assets, detect and monitor orbiting debris fields, and support Outer Space Treaty monitoring and transparency.« less

The Small Size Debris Population at GEO from Optical Observations

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Barker, Ed; Buckalew, Brent; Burkhardt, Andrew; Cowardin, Heather; Frith, James; Kaleida, Catherine; Lederer, Susan M.; Lee, Chris H.

2017-01-01

We have observed the geosynchronous orbit (GEO) debris population at sizes smaller than 10 cm using optical observations with the 6.5-m Magellan telescope 'Walter Baade' at the Las Campanas Observatory in Chile. The IMACS f/2 imaging camera with a 0.5-degree diameter field of view has been used in small area surveys of the GEO regime to study the population of optically faint GEO debris. The goal is to estimate the population of GEO debris that is fainter than can be studied with 1-meter class telescopes. A significant population of objects fainter than R = 19th magnitude has been found. These objects have observed with angular rates consistent with circular orbits and orbital inclinations up to 15 degrees at GEO. A sizeable number of these objects have significant brightness variations ("flashes") during the 5-second exposure, which suggest rapid changes in the albedo-projected size product.

Galaxias enanas: las voces de la mayoría

NASA Astrophysics Data System (ADS)

Cellone, S. A.

More than twenty years after photographic surveys of nearby clusters of galaxies revealed that low-luminosity, or ``dwarf'', galaxies (M_B ≳ -18 mag) are the numerically dominant population, research on these objects has been boosted by new instrumental and theoretical developments. Among several breakthroughs that have re-shaped our knowledge abut dwarf galaxies, we should point out: the detection of underlying spiral structure, disks/bars in dwarf ``elliptical'' galaxies; the possible evolutionary relation between (some?) dwarf ellipticals and spiral galaxies; the discoveries of ultra-compact and ultra-faint dwarfs; the universality of the color-luminosity relation extending along ˜ 10 mag. A brief review on these subjects is presented, with emphasis on early-type dwarfs and their possible evolutionary relations with other galaxy types. I will particularly address the controversy about which are the objects that extend the E sequence down to the lowest luminosities (if such objects really exist). FULL TEXT IN SPANISH

WHERE ARE THE FOSSILS OF THE FIRST GALAXIES? I. LOCAL VOLUME MAPS AND PROPERTIES OF THE UNDETECTED DWARFS

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

Bovill, Mia S.; Ricotti, Massimo, E-mail: msbovill@astro.umd.edu, E-mail: ricotti@astro.umd.edu

We present a new method for generating initial conditions for {Lambda}CDM N-body simulations which provides the dynamical range necessary to follow the evolution and distribution of the fossils of the first galaxies on Local Volume, 5-10 Mpc, scales. The initial distribution of particles represents the position, velocity, and mass distribution of the dark and luminous halos extracted from pre-reionization simulations. We confirm previous results that ultra-faint dwarfs have properties compatible with being well-preserved fossils of the first galaxies. However, because the brightest pre-reionization dwarfs form preferentially in biased regions, they most likely merge into non-fossil halos with circular velocities >20-30more » km s{sup -1}. Hence, we find that the maximum luminosity of true fossils in the Milky Way is L{sub V} < 10{sup 6} L{sub sun}, casting doubts on the interpretation that some classical dSphs are true fossils. In addition, we argue that most ultra-faints at small galactocentric distance, R < 50 kpc, had their stellar properties modified by tides, while a large population of fossils is still undetected due to their extremely low surface brightness log ({Sigma}{sub V}) < -1.4. We estimate that the region outside R{sub 50} ({approx}400 kpc) up to 1 Mpc from the Milky Way contains about a hundred true fossils of the first galaxies with V-band luminosity 10{sup 3}-10{sup 5} L{sub sun} and half-light radii, r{sub hl} {approx} 100-1000 pc.« less

View of southeast side, faint "141" sign, Cranes P76 and ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

View of southeast side, faint "141" sign, Cranes P-76 and P-71 are behind, view facing northwest - U.S. Naval Base, Pearl Harbor, Dry Dock No. 1, Latrine, Sixth Street, adjacent to Dry Dock No. 1, Pearl City, Honolulu County, HI

The faint galaxy contribution to the diffuse extragalactic background light

NASA Technical Reports Server (NTRS)

Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

1992-01-01

Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

Handling Technique Development of Live Carp, Cyprinus carpio, In Cold Dry Styrofoam Box

NASA Astrophysics Data System (ADS)

Ketut Suwetja, I.; Salindeho, Netty; Gede Prabawa Suwetja, I.

2017-10-01

The study focused on several following aspects: temperature and time optimation for fainting, holding media optimation, temperature and time optimation for recovery, and their correlation with mortality rate of carp, Cyprinus carpio. Fainting occurred at the optimum time of 11 minutes and 03 seconds, temperature of 8°C, and holding time of 6 hours. Holding medium was rice husk. The fastest consciousness of the fish was found in 6 volt-aerated water medium. The fish consciousness after 6 hours of storing in the rice husk at the fainting temperature of 8°C was found faster (p < 0.05), 11 minutes and 15 seconds, than that added with 0.02% of clove oil, 25 minutes and 16 seconds. The fish mortality rate after 6 hours of storage in the rice husk at fainting temperature of 8°C was lower (p < 0.05), 46%, than that with addition of 0.02% of clove oil, 75%.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1981-01-01

This drawing illustrates the Hubble Space Telescope's (HST's), Faint Object Spectrograph (FOS). The HST's two spectrographs, the Goddard High-Resolution Spectrograph and the FOS, can detect a broader range of wavelengths than is possible from the Earth because there is no atmosphere to absorb certain wavelengths. Scientists can determine the chemical composition, temperature, pressure, and turbulence of the stellar atmosphere producing the light, all from spectral data. The FOC can detect detail in very faint objects, such as those at great distances, and light ranging from ultraviolet to red spectral bands. Both spectrographs operate in essentially the same way. The incoming light passes through a small entrance aperture, then passes through filters and diffraction gratings, that work like prisms. The filter or grating used determines what range of wavelength will be examined and in what detail. Then the spectrograph detectors record the strength of each wavelength band and sends it back to Earth. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST views galaxies, stars, planets, comets, possibly other solar systems, and even unusual phenomena such as quasars, with 10 times the clarity of ground-based telescopes. The HST was deployed from the Space Shuttle Discovery (STS-31 mission) into Earth orbit in April 1990. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

Deep Stromvil Photometry for Star Formation in the Head of the Pelican Nebula

NASA Astrophysics Data System (ADS)

Boyle, Richard P.; J., S.; Stott, J.; J., S.; Janusz, R.; J., S.; Straizys, V.

2010-01-01

The North America and Pelican Nebulae, and specifically the dark cloud L935 contain regions of active star formation (Herbig, G. H. 1958, ApJ, 128,259). Previously we reported on Vatican telescope observations by Stromvil intermediate-band filters in a 12-arcmin field in the "Gulf of Mexico" region of L935. There we classify A, F, and G-type stars. However, the many faint K and M-type dwarf stars remain somewhat ambiguous in calibration and classification. But attaining reasonable progress, we turn to another part of L935 located near the Pelican head. This area includes the "bright rim" which is formed by dust and gas condensed by the light pressure of an unseen O-type star hidden behind the dense dark cloud. Straizys and Laugalys (2008 Baltic Astronomy, 17, 143 ) have identified this star to be one of the 2MASS objects with Av=23 mag. A few concentrations of faint stars, V 13 to 14 mag. are immersed in this dark region. Among these stars are a few known emission-line objects (T-Tauri or post T-Tauri stars). A half degree nearby are some photometric Vilnius standards we use to calibrate our new field. We call on 2MASS data for correlative information. Also the Stromvil photometry offers candidate stars for spectral observations. The aim of this study in the Vilnius and Stromvil photometric systems is to classify stars down to V = 18 mag., to confirm the existence of the young star clusters, and to determine the distance of the cloud covering the suspected hidden ionizing star.

Far-ultraviolet stellar photometry: A field in Orion

NASA Astrophysics Data System (ADS)

Schmidt, Edward G.; Carruthers, George R.

1993-12-01

Far-ultraviolet photometry for 625 objects in Orion is presented. These data were extracted from electrographic camera images obtained during sounding rocket flights in 1975 and 1982. The 1975 images were centered close to the belt of Orion while the 1982 images were centered approximately 9 deg further north. One hundred and fifty stars fell in the overlapping region and were observed with both cameras. Sixty-eight percent of the objects were tentatively identified with known stars using the SIMBAD database while another 24% are blends of objects too close together to separate with our resolution. As in previous studies, the majority of the identified ultraviolet sources are early-type stars. However, there are a significant number for which no such identification was possible, and we suggest that these are interesting objects which should be further investigated. Seven stars were found which were bright in the ultraviolet but faint in the visible. We suggest that some of these are nearby white dwarfs.

[Congenital hemihypertrophy associated with cutaneous pigmento-vascular, cerebral, visceral and bone abnormalities].

PubMed

Hidano, A; Arai, Y

1987-01-01

A case of hemihypertrophy associated with multiple anomalies of the skin, bone and visceral organs is presented. A 31-year-old female was admitted for evaluation of her skin conditions. Her family history is noncontributory, while her past history discloses operations for syndactyly of the right foot, tonsillar hypertrophy, anal prolapse and ovarial cyst. Erythemas of the face and the left upper extremity were noticed during the neonatal period and hypertrophy of the right side of the body started at age 2 months. On admission, hemihypertrophy was observed in the face, trunk and extremities. Multiple faint nevi flammei were seen on the right half of the face and on the left side of the trunk and extremities. Telangiectasis and nevus anemicus were seen in the upper chest. The left upper extremity showed diffuse brown patches that was histologically basal pigmentation with some giant melanosomes. Visceral anomalies consisted of fibromatous tumors of the tip of the tongue and mitral prolapse. Angiography and computed tomography revealed a possible arteriovenous malformation of the right occipital region, small hemangiomas around the patella, dilation of the lateral ventricle, and calcification of the choroid plexus. Tortuous superficial veins were noted in the right leg. She had no seizure, but her IQ was 68. The bone disorders consisted of scoliosis, short forth metacarpus, hypoplastic mandible and peroneal exostosis. Examination revealed a slight diminution of urinary corticosteroid, but no other endocrinological disorders were found. The hemihypertrophy in this case is at least partially due to an arteriovenous shunt, suggested by elevated oxygen saturation of the blood obtained from the internal saphenous vein.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of the discrepant QSO X-ray luminosity function from the HEAO-2 data archive

NASA Technical Reports Server (NTRS)

Margon, B.

1984-01-01

An in-progress investigation aimed at characterizing the X-ray luminosity of very faint QSOs is described. More than 100 faint, previously uncataloged QSOs which lie in areas imaged in X rays at very high sensitivity were discovered.

The possible nature of socket stars in H II regions

NASA Technical Reports Server (NTRS)

Castelaz, Michael W.

1990-01-01

Close inspection of faint stars (V of about 14 mag) in H II regions show that they appear to be surrounded by circumstellar envelopes of about 10 arcsecs in diameter (as reported by Feibelman in 1989). The present premise is that the sockets are envelopes of obscuring dust which should emit a measurable amount of infrared radiation based on a simple thermal equilibrium model. A search of literature shows that, of 36 socket stars listed by Feibelman, 17 have been measured in the infrared. Of the 17, 14 show excess IR emission. This is very strong evidence that the socket stars are really stars with circumstellar envelopes. Socket stars may be a new type of astronomical object or well-known astronomical objects in environments or evolutionary states not previously seen.

Studies of the Coldest Brown Dwarfs With The James Webb Space Telescope

NASA Astrophysics Data System (ADS)

Roellig, Thomas L.; Greene, Thomas P.; Beichman, Charles; Meyer, Michael; Rieke, Marcia

2016-07-01

The coolest T and Y-class Brown Dwarf objects are very faint and are therefore very poorly understood, since they are barely detectable with the current astronomical instrumentation. The upcoming James Webb Space Telescope now in development for a launch in the Fall of 2018 will have vastly increased sensitivity in the near and mid-infrared compared to any current facilities and will not be affected by telluric absorption over its entire wavelength range of operations. As a result it will be an ideal tool to obtain information about the composition and temperature-pressure structure in these objects' atmospheres. This presentation outlines the JWST guaranteed time observing plans for these studies. These plans comprise both spectro-photometric and spectroscopic observations of a selection of late T and Y-dwarf targets.

KSC-01pp1730

NASA Image and Video Library

2001-11-27

KENNEDY SPACE CENTER, Fla. -- In the Vertical Processing Facility, members of the STS-109 crew look over the Solar Array 3 panels that will be replacing Solar Array 2 panels on the Hubble Space Telescope (HST). Trainers, at left, point to the panels while Mission Specialist Nancy Currie (second from right) and Commander Scott Altman (far right) look on. Other crew members are Pilot Duane Carey, Payload Commander John Grunsfeld and Mission Specialists James Newman, Richard Linnehan and Michael Massimino. The other goals of the mission are replacing the Power Control Unit, removing the Faint Object Camera and installing the Advanced Camera for Surveys, installing the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Cooling System, and installing New Outer Blanket Layer insulation on bays 5 through 8. Mission STS-109 is scheduled for launch Feb. 14, 2002

An Extensive Census of Hubble Space Telescope Counterparts to Chandra X-Ray Sources in the Globular Cluster 47 Tucanae. II. Time Series and Analysis

NASA Astrophysics Data System (ADS)

Edmonds, Peter D.; Gilliland, Ronald L.; Heinke, Craig O.; Grindlay, Jonathan E.

2003-10-01

We report time series and variability information for the optical identifications of X-ray sources in 47 Tucanae reported in Paper I (at least 22 cataclysmic variables [CVs] and 29 active binaries). The radial distribution of the CVs is indistinguishable from that of the millisecond pulsars (MSPs) detected by Freire et al. A study of the eight CVs with secure orbital periods (two obtained from the Chandra study of Grindlay et al.) shows that the 47 Tuc CVs have fainter accretion disks, in the V band, than field CVs with similar periods. These faint disks and the faint absolute magnitudes (MV) of the 47 Tuc CVs suggests they have low accretion rates. One possible explanation is that the 47 Tuc objects may be a more representative sample of CVs, down to our detection threshold, than the CVs found in the field (where many low accretion rate systems are believed to be undiscovered), showing the advantages of deep globular cluster observations. The median FX/Fopt value for the 47 Tuc CVs is higher than that of all known classes of field CV, partly because of the faint MV values and partly because of the relatively high X-ray luminosities (LX). The latter are only seen in DQ Her systems in the field, but the 47 Tuc CVs are much fainter optically than most field DQ Her's. Previous work by Edmonds et al. has shown that the four brightest CVs in NGC 6397 have optical spectra and broadband colors that are consistent with DQ Her's having lower than average accretion rates. Some combination of magnetic behavior and low accretion rates may be able to explain our observations, but the results at present are ambiguous, since no class of field CV has distributions of both LX and MV that are consistent with those of the 47 Tuc CVs. The radial distribution of the X-ray detected active binaries is indistinguishable from that of the much larger sample of optical variables (eclipsing and contact binaries and BY Dra variables) detected in previous Wide Field Planetary Camera 2 (WFPC2) studies by Albrow et al. The X-ray properties of these objects (luminosity, hardness ratios, and variability) are consistent with those of active binaries found in field studies, and the FX/Fopt distribution is significantly different from those of the CVs and the MSPs that are detected (or possibly detected) in the optical. Despite these results, we examine the possibility that a few of the active binaries are MSPs with main-sequence companions resulting from double exchanges in the crowded core of 47 Tuc. No solid evidence is found for a significant population of such objects, and therefore, using the methods of Grindlay et al., we estimate that the number of MSPs in 47 Tuc with luminosities above 1030 ergs s-1 is ~30-40, near the previous lower limit. We present the results of a new, deeper search for faint low-mass X-ray binaries (LMXBs) in quiescence. One reasonable and one marginal candidate for optical identification of a quiescent LMXB was found (one is already known). Finally, it is shown that the periods of the blue variables showing little or no evidence for X-ray emission are too long for Roche lobe filling (if the variations are ellipsoidal). These blue variables also show no evidence for the large flickering levels seen in comparably bright CVs. At present we have no satisfactory explanation for these objects, although some may be detached white dwarf-main-sequence star binaries. Based on observations with the NASA/ESA Hubble Space Telescope obtained at STScI, which is operated by AURA, Inc. under NASA contract NAS 5-26555.

Spitzer observations of two mission-accessible, tiny asteroids

NASA Astrophysics Data System (ADS)

Mommert, M.; Hora, J.; Farnocchia, D.; Chesley, S.; Vokrouhlicky, D.; Trilling, D.; Mueller, M.; Harris, A.; Smith, H.; Fazio, G.

2014-07-01

Small asteroids are most likely collisional fragments of larger objects and make up a large fraction of the near-Earth-object (NEO) population. Despite their abundance, little is known about the physical properties of these objects, which is mainly due to their faintness, which also impedes their discovery. We report on Spitzer Space Telescope observations of two small NEOs, both of which are of interest as potential spacecraft targets. We observed NEOs 2009 BD using 25 hrs and 2011 MD using ˜20 hrs of Spitzer Infrared Array Camera Channel 2 time. For each target, we have combined the data into maps in the moving frame of the target, minimizing the background confusion. We did not detect 2009 BD and place an upper limit on its flux density, but we detected 2011 MD as a 2.2σ detection. We have analyzed the data on both objects in a combined model approach, using an asteroid thermophysical model and a model of non-gravitational forces acting on the object. As a result, we are able to constrain the physical properties of both objects. In the case of 2009 BD (Mommert et al. 2014), a wealth of existing astrometry data significantly constrains the physical properties of the object. We find two physically possible solutions. The first solution shows 2009 BD as a 2.9±0.3 m-sized massive rock body (bulk density ρ=2.9±0.5 g cm^{-3}) with an extremely high albedo of 0.85_{-0.10}^{+0.20} that is covered with regolith-like material, causing it to exhibit a low thermal inertia (thermal inertia Γ=30_{-10}^{+20} SI units). The second solution suggests 2009 BD to be a 4±1 m-sized asteroid with p_{V}=0.45_{-0.15}^{+0.35} that consists of a collection of individual bare rock slabs (Γ = 2000±1000 SI units, ρ = 1.7_{-0.4}^{+0.7} g cm^{-3}). We are unable to rule out either solution based on physical reasoning. The preliminary analysis of 2011 MD shows this object as a ˜6 m-sized asteroid with an albedo of ˜0.3. Additional constraints on the physical properties of these objects will be available at the time of the conference (Mommert et al., in preparation). 2009 BD and 2011 MD are the smallest asteroids for which physical properties have been constrained, providing unique insights into a population of asteroids that gives rise to frequent impacts on the Earth and the Moon. Furthermore, both asteroids are among the most easily accessible objects in space.

Spatiotemporal distribution of location and object effects in the electromyographic activity of upper extremity muscles during reach-to-grasp

PubMed Central

Rouse, Adam G.

2016-01-01

In reaching to grasp an object, proximal muscles that act on the shoulder and elbow classically have been viewed as transporting the hand to the intended location, while distal muscles that act on the fingers simultaneously shape the hand to grasp the object. Prior studies of electromyographic (EMG) activity in upper extremity muscles therefore have focused, by and large, either on proximal muscle activity during reaching to different locations or on distal muscle activity as the subject grasps various objects. Here, we examined the EMG activity of muscles from the shoulder to the hand, as monkeys reached and grasped in a task that dissociated location and object. We quantified the extent to which variation in the EMG activity of each muscle depended on location, on object, and on their interaction—all as a function of time. Although EMG variation depended on both location and object beginning early in the movement, an early phase of substantial location effects in muscles from proximal to distal was followed by a later phase in which object effects predominated throughout the extremity. Interaction effects remained relatively small. Our findings indicate that neural control of reach-to-grasp may occur largely in two sequential phases: the first, serving to project the entire upper extremity toward the intended location, and the second, acting predominantly to shape the entire extremity for grasping the object. PMID:27009156

Activities of JAXA's Innovative Technology Center on Space Debris Observation

NASA Astrophysics Data System (ADS)

Yanagisawa, T.; Kurosaki, H.; Nakajima, A.

The innovative technology research center of JAXA is developing observational technologies for GEO objects in order to cope with the space debris problem. The center had constructed the optical observational facility for space debris at Mt. Nyukasa, Nagano in 2006. As observational equipments such as CCD cameras and telescopes were set up, the normal observation started. In this paper, the detail of the facilities and its activities are introduced. The observational facility contains two telescopes and two CCD cameras. The apertures of the telescopes are 35cm and 25 cm, respectively. One CCD camera in which 2K2K chip is installed can observe a sky region of 1.3 times 1.3-degree using the 35cm telescope. The other CCD camera that contains two 4K2K chips has an ability to observe 2.6 times 2.6-degree's region with the 25cm telescope. One of our main objectives is to detect faint GEO objects that are not catalogued. Generally, the detection limit of GEO object is determined by the aperture of the telescope. However, by improving image processing techniques, the limit may become low. We are developing some image processing methods that use many CCD frames to detect faint objects. We are trying to use FPGA (Field Programmable Gate Array) system to reduce analyzing time. By applying these methods to the data taken by a large telescope, the detection limit will be significantly lowered. The orbital determination of detected GEO debris is one of the important things to do. Especially, the narrow field view of an optical telescope hinders us from re-detection of the GEO debris for the orbital determination. Long observation time is required for one GEO object for the orbital determination that is inefficient. An effective observation strategy should be considered. We are testing one observation method invented by Umehara that observes one inertia position in the space. By observing one inertia position for two nights, a GEO object that passed through the position in the first night must pass through the position in the second night. The rough orbit is determined from two nights' data. The test observation showed that this method was able to detect many GEO objects and determined their orbits by three nights' observations. We also joined the campaign observations of IADC(Inter-Agency Space Debris Coordination Committee). By analyzing the observed data with the method that we developed, 88 catalogued and 38 un-catalogued objects were detected. The magnitude of the faintest object detected in this campaign observation was 18.5. The object is un-detectable by human inspection.

VLT/X-shooter Spectroscopy of a dusty planetary nebula discovered with Spitzer/IRS

NASA Astrophysics Data System (ADS)

Oliveira, I.; Overzier, R. A.; Pontoppidan, K. M.; van Dishoeck, E. F.; Spezzi, L.

2011-02-01

As part of a mid-infrared spectroscopic survey of young stars with the Spitzer Space Telescope, an unclassified red emission line object was discovered. Based on its high ionization state indicated by the Spitzer spectrum, this object could either be a dusty supernova remnant (SNR) or a planetary nebula (PN). In this research note, the object is classified and the available spectroscopic data are presented to the community for further analysis. UV/optical/NIR spectra were obtained during the science verification run of the VLT/X-shooter. A large number of emission lines are identified allowing the determination of the nature of this object. The presence of strong, narrow (Δv ~8 - 74 km s-1) emission lines, combined with very low line ratios of, e.g., [N ii]/Hα and [S ii]/Hα show that the object is a PN that lies at an undetermined distance behind the Serpens Molecular Cloud. This illustrates the potential of X-shooter as an efficient tool for constraining the nature of faint sources with unknown spectral properties or colors.

Evolution in High Spatial Resolution Imaging of Faint, Complex Objects

NASA Astrophysics Data System (ADS)

van Belle, G.

The astrophysical community has been working at the task of obtaining image information of the smallest structures in the sky via the use of optical interferometry for well over a century. A richly diverse family of technology architectures has been explored over the years, and yet the current family of facilities are all striking similar. Although there may be other, heretofore undeployed, architectures that support the goal of collecting image information at the highest resolutions, we expect dramatic advances at the component level of long-baseline interferometry to be the best avenue for advancing the technique, rather than entirely new architectures.

Observations of jets from low-luminosity stars - DG Tauri B

NASA Technical Reports Server (NTRS)

Jones, B. F.; Cohen, Martin

1986-01-01

Low spectral resolution studies of DG Tau B, the faint system of knots south of the T Tauri star DG Tau, are described. The observations show this object to be bipolar, with the blueshifted lobe having extraordinarily low excitation. Infrared observations of the exciting star show it to be of very low luminosity, with a bolometric luminosity of 0.88 solar luminosity. The visual extinction indicates a highly nonspherical distribution of circumstellar dust around the exciting star. In spite of this lack of embedding within an obvious dark cloud, the system is identified as a young one.

Adaptive optics for high-contrast imaging of faint substellar companions

NASA Astrophysics Data System (ADS)

Morzinski, Katie M.

Direct imaging of faint objects around bright stars is challenging because the primary star's diffracted light can overwhelm low-mass companions. Nevertheless, advances in adaptive optics (AO) and high-contrast imaging have revealed the first pictures of extrasolar planets. In this dissertation I employ today's high-contrast AO techniques to image brown dwarfs around stars in the nearby Hyades cluster. Furthermore, I prepare for the next generation of high-contrast AO instrumentation, by qualifying MEMS deformable mirrors for wavefront control in the Gemini Planet Imager. In Part I, I present discovery of 3 new brown dwarfs and 36 low-mass stellar companions to 85 stars in the Hyades, imaged with AO at Keck and Lick Observatories. The "locally-optimized combination of images" (LOCI) image-diversity technique filters out the primary star to reveal faint companions. This survey is complete to the hydrogen-burning limit at separations beyond 20 AU. In the complete sample, multiplicity increases as primary star mass decreases. Additionally, the brown dwarfs are at wide >150 AU separations. Finding this preference for low binding-energy systems is an unexpected result, as the Hyades is 625 Myr old and dynamically relaxed. Future work will continue to explore this trend to understand the dynamical and star formation history of the Hyades. The brown dwarfs are near interesting transition regimes for low-mass objects; therefore, characterizing their atmospheres with spectrophotometry will serve as an important benchmark for our understanding of these cool objects. In Part II, I demonstrate micro-electro-mechanical systems (MEMS) deformable mirrors for high-order wavefront control in the Gemini Planet Imager (GPI). MEMS micromirrors have thousands of degrees of freedom and represent a significant cost efficiency over conventional glass deformable mirrors, making them ideal for high-contrast AO. In Chapter 7, I present experimental evidence that MEMS actuators function well and are stable and repeatable at the sub-nm level over the course of an hour. In Chapter 8, I prove MEMS ability to correct high-order Kolmogorov turbulence and maintain the high-contrast "dark hole" in the GPI woofer-tweeter architecture. Finally, in Chapter 9, I analyze MEMS performance on sky with Villages, a telescope testbed for MEMS technology, visible-light AO, and open-loop control. The MEMS remains repeatably flat and controllable over ˜4 years and ˜800 hours of operation. Open loop control of the hysteresis-free MEMS produces a diffraction-limited core in I-band, while internal static errors dominate the on-sky error budget. This work establishes MEMS deformable mirrors as excellent wavefront correctors for high-order AO. The MEMS in GPI will produce a deeper, broader dark hole, allowing for detection and characterization of directly-imaged planets in a fainter, wider search space.

Hartmann wavefront sensing of the corrective optics for the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Davila, Pam S.; Eichhorn, William L.; Wilson, Mark E.

1994-06-01

There is no doubt that astronomy with the `new, improved' Hubble Space Telescope will significantly advance our knowledge and understanding of the universe for years to come. The Corrective Optics Space Telescope Axial Replacement (COSTAR) was designed to restore the image quality to nearly diffraction limited performance for three of the first generation instruments; the faint object camera, the faint object spectrograph, and the Goddard high resolution spectrograph. Spectacular images have been obtained from the faint object camera after the installation of the corrective optics during the first servicing mission in December of 1993. About 85% of the light in the central core of the corrected image is contained within a circle with a diameter of 0.2 arcsec. This is a vast improvement over the previous 15 to 17% encircled energies obtained before COSTAR. Clearly COSTAR is a success. One reason for the overwhelming success of COSTAR was the ambitious and comprehensive test program conducted by various groups throughout the program. For optical testing of COSTAR on the ground, engineers at Ball Aerospace designed and built the refractive Hubble simulator to produce known amounts of spherical aberration and astigmatism at specific points in the field of view. The design goal for this refractive aberrated simulator (RAS) was to match the aberrations of the Hubble Space Telescope to within (lambda) /20 rms over the field at a wavelength of 632.8 nm. When the COSTAR optics were combined with the RAS optics, the corrected COSTAR output images were produced. These COSTAR images were recorded with a high resolution 1024 by 1024 array CCD camera, the Ball image analyzer (BIA). The image quality criteria used for assessment of COSTAR performance was encircled energy in the COSTAR focal plane. This test with the BIA was very important because it was a direct measurement of the point spread function. But it was difficult with this test to say anything quantitative about the aberration content of the corrected images. Also, from only this test it was difficult to measure important pupil parameters, such as pupil intensity profiles and pupil sizes and location. To measure the COSTAR wavefront accurately and to determine pupil parameters, another very important test was performed on the COSTAR optics. A Hartmann test of the optical system consisting of the RAS and COSTAR was conducted by the Goddard Independent Verification Team (IVT). In this paper, we first describe the unique Hartmann sensor that was developed by the IVT. Then we briefly describe the RAS and COSTAR optical systems and the test setup. Finally, we present the results of the test and compare our results with results obtained from optical analysis and from image tests with the BIA.

The Gemini Planet Imager Calibration Wavefront Sensor Instrument

NASA Technical Reports Server (NTRS)

Wallace, J. Kent; Burruss, Rick S.; Bartos, Randall D.; Trinh, Thang Q.; Pueyo, Laurent A.; Fregoso, Santos F.; Angione, John R.; Shelton, J. Chris

2010-01-01

The Gemini Planet Imager is an extreme adaptive optics system that will employ an apodized-pupil coronagraph to make direct detections of faint companions of nearby stars to a contrast level of the 10(exp -7) within a few lambda/D of the parent star. Such high contrasts from the ground require exquisite wavefront sensing and control both for the AO system as well as for the coronagraph. Un-sensed non-common path phase and amplitude errors after the wavefront sensor dichroic but before the coronagraph would lead to speckles which would ultimately limit the contrast. The calibration wavefront system for GPI will measure the complex wavefront at the system pupil before the apodizer and provide slow phase corrections to the AO system to mitigate errors that would cause a loss in contrast. The calibration wavefront sensor instrument for GPI has been built. We will describe the instrument and its performance.

The bright optical afterglow of the nearby gamma-ray burst of 29 March 2003.

PubMed

Price, P A; Fox, D W; Kulkarni, S R; Peterson, B A; Schmidt, B P; Soderberg, A M; Yost, S A; Berger, E; Djorgovski, S G; Frail, D A; Harrison, F A; Sari, R; Blain, A W; Chapman, S C

2003-06-19

Past studies of cosmological gamma-ray bursts (GRBs) have been hampered by their extreme distances, resulting in faint afterglows. A nearby GRB could potentially shed much light on the origin of these events, but GRBs with a redshift z

ARC-1979-A79-7086

NASA Image and Video Library

1979-07-09

P-21757 BW Range: 2 million kilometers (1.25 million miles) Jupiter's thin ring of particles was photographed by Voyager 2 on its approach to the giant planet. The spacecraft was 2.5° above the plane of the ring. Segments of both sides of the faint ring were captured in this picture. The ring was first photographed in an edge-on configuration by Voyager 1 and was measured then to have a radial extent of about 55, 000 kilometers (34,000 miles) from Jupiter's cloud tops. With this picture, it is possible to determine that the ring is much narrower radially than the individual rings of Saturn. This image has had an extreme contrast enhancement process applied to it which brought out some white blotches in the central region and makes the ring appear discontinuous and non-uniform in brightness. These effects are all artifacts of the processing.

SEEDS - Strategic explorations of exoplanets and disks with the Subaru Telescope -

NASA Astrophysics Data System (ADS)

Tamura, M.

2016-02-01

The first convincing detection of planets orbiting stars other than the Sun, or exoplanets, was made in 1995. In only 20 years, the number of the exoplanets including promising candidates has already accumulated to more than 5000. Most of the exoplanets discovered so far are detected by indirect methods because the direct imaging of exoplanets needs to overcome the extreme contrast between the bright central star and the faint planets. Using the large Subaru 8.2-m Telescope, a new high-contrast imager, HiCIAO, and second-generation adaptive optics (AO188), the most ambitious high-contrast direct imaging survey to date for giant planets and planet-forming disks has been conducted, the SEEDS project. In this review, we describe the aims and results of the SEEDS project for exoplanet/disk science. The completeness and uniformity of this systematic survey mean that the resulting data set will dominate this field of research for many years.

The dynamic quiet solar corona: 4 days of joint observing with MDI and EIT

NASA Technical Reports Server (NTRS)

Schrijver, C. J.; Shine, R. A.; Hurlburt, N. E.; Tarbell, T. D.; Lemen, J. R.

1997-01-01

The analysis of a sequence of joint extreme ultraviolet imaging telescope (EIT) Fe XII and Michelson Doppler imager (MDI) magnetogram observations of the quiet sun near disk center is presented. It was found that: all the emerging flux above the threshold of approximately 10(sup 17) Mx is associated with enhanced coronal emissions; loop systems between the polarities in ephemeral regions remain visible up to separations of 10000 up to 30000 km; brightenings between approaching opposite polarity network concentrations form when the concentrations are between 5000 and 25000 km apart, and that faint connections up to 40000 km in length form as sets of concentrations of the same polarity coagulate. The coronal emission over patches of the quiet sun depends on the total flux in connected concentrations, on their distance and on the positions and strengths of neighboring concentrations.

High-Resolution Near-Infrared Spectroscopy of an Equivalent Width-Selected Sample of Starbursting Dwarf Galaxies

NASA Technical Reports Server (NTRS)

Maseda, Michael V.; VanDerWeL, Arjen; DaChuna, Elisabete; Rix, Hans-Walter; Pacafichi, Camilla; Momcheva, Ivelina; Brammer, Gabriel B.; Franx, Marijn; VanDokkum, Pieter; Bell, Eric F.;

SEEDS - Strategic explorations of exoplanets and disks with the Subaru Telescope.

PubMed

Tamura, Motohide

2016-01-01

The first convincing detection of planets orbiting stars other than the Sun, or exoplanets, was made in 1995. In only 20 years, the number of the exoplanets including promising candidates has already accumulated to more than 5000. Most of the exoplanets discovered so far are detected by indirect methods because the direct imaging of exoplanets needs to overcome the extreme contrast between the bright central star and the faint planets. Using the large Subaru 8.2-m Telescope, a new high-contrast imager, HiCIAO, and second-generation adaptive optics (AO188), the most ambitious high-contrast direct imaging survey to date for giant planets and planet-forming disks has been conducted, the SEEDS project. In this review, we describe the aims and results of the SEEDS project for exoplanet/disk science. The completeness and uniformity of this systematic survey mean that the resulting data set will dominate this field of research for many years.

Massive 70 μm quiet clumps I: evidence of embedded low/intermediate-mass star formation activity

NASA Astrophysics Data System (ADS)

Traficante, A.; Fuller, G. A.; Billot, N.; Duarte-Cabral, A.; Merello, M.; Molinari, S.; Peretto, N.; Schisano, E.

2017-10-01

Massive clumps, prior to the formation of any visible protostars, are the best candidates to search for the elusive massive starless cores. In this work, we investigate the dust and gas properties of massive clumps selected to be 70 μm quiet, therefore good starless candidates. Our sample of 18 clumps has masses 300 ≲ M ≲ 3000 M⊙, radius 0.54 ≤ R ≤ 1.00 pc, surface densities Σ ≥ 0.05 g cm-2 and luminosity/mass ratio L/M ≤ 0.3. We show that half of these 70 μm quiet clumps embed faint 24 μm sources. Comparison with GLIMPSE counterparts shows that five clumps embed young stars of intermediate stellar mass up to ≃5.5 M⊙. We study the clump dynamics with observations of N2H+ (1-0), HNC (1-0) and HCO+ (1-0) made with the IRAM 30 m telescope. Seven clumps have blue-shifted spectra compatible with infall signatures, for which we estimate a mass accretion rate 0.04≲ \\dot{M}≲ 2.0× 10^{-3} M⊙ yr-1, comparable with values found in high-mass protostellar regions, and free-fall time of the order of tff ≃ 3 × 105 yr. The only appreciable difference we find between objects with and without embedded 24 μm sources is that the infall rate appears to increase from 24 μm dark to 24 μm bright objects. We conclude that all 70 μm quiet objects have similar properties on clump scales, independently of the presence of an embedded protostar. Based on our data, we speculate that the majority, if not all of these clumps, may already embed faint, low-mass protostellar cores. If these clumps are to form massive stars, this must occur after the formation of these lower mass stars.

The faint-end of galaxy luminosity functions at the Epoch of Reionization

NASA Astrophysics Data System (ADS)

Yue, B.; Castellano, M.; Ferrara, A.; Fontana, A.; Merlin, E.; Amorín, R.; Grazian, A.; Mármol-Queralto, E.; Michałowski, M. J.; Mortlock, A.; Paris, D.; Parsa, S.; Pilo, S.; Santini, P.; Di Criscienzo, M.

2018-05-01

During the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ~ 6, MUVT >~-13.3 for the circular velocity threshold of quenching star formation process, vc* <~ 47 km s-1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies.

Extreme Trust Region Policy Optimization for Active Object Recognition.

PubMed

Liu, Huaping; Wu, Yupei; Sun, Fuchun; Huaping Liu; Yupei Wu; Fuchun Sun; Sun, Fuchun; Liu, Huaping; Wu, Yupei

2018-06-01

In this brief, we develop a deep reinforcement learning method to actively recognize objects by choosing a sequence of actions for an active camera that helps to discriminate between the objects. The method is realized using trust region policy optimization, in which the policy is realized by an extreme learning machine and, therefore, leads to efficient optimization algorithm. The experimental results on the publicly available data set show the advantages of the developed extreme trust region optimization method.

Coronagraphic Imaging with HST and STIS

NASA Technical Reports Server (NTRS)

Grady, C. A.; Proffitt, C.; Malumuth, E.; Woodgate, B. E.; Gull, T. R.; Bowers, C. W.; Heap, S. R.; Kimble, R. A.; Lindler, D.; Plait, P.

2002-01-01

Revealing faint circumstellar nebulosity and faint stellar or substellar companions to bright stars typically requires use of techniques for rejecting the direct, scattered, and diffracted light of the star. One such technique is Lyot coronagraphy. We summarize the performance of the white-light coronagraphic capability of the Space Telescope Imaging spectrograph, on board the Hubble Space Telescope.

Faint Submillimeter Galaxies Behind Lensing Clusters

NASA Astrophysics Data System (ADS)

Hsu, Li-Yen; Lauchlan Cowie, Lennox; Barger, Amy J.; Desai, Vandana; Murphy, Eric J.

2017-01-01

Faint submillimeter galaxies are the major contributors to the submillimeter extragalactic background light and hence the dominant star-forming population in the dusty universe. Determining how much these galaxies overlap the optically selected samples is critical to fully account for the cosmic star formation history. Observations of massive cluster fields are the best way to explore this faint submillimeter population, thanks to gravitational lensing effects. We have been undertaking a lensing cluster survey with the SCUBA-2 camera on the James Clerk Maxwell Telescope to map nine galaxy clusters, including the northern five clusters in the HST Frontier Fields program. We have also been using the Submillimeter Array and the Very Large Array to determine the accurate positions of our detected sources. Our observations have discovered high-redshift dusty galaxies with far-infrared luminosities similar to that of the Milky Way or luminous infrared galaxies. Some of these galaxies are still undetected in deep optical and near-infrared images. These results suggest that a substantial amount of star formation in even the faint submillimeter population may be hidden from rest-frame optical surveys.

An Ultra-faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey

NASA Astrophysics Data System (ADS)

Drlica-Wagner, A.; Bechtol, K.; Allam, S.; Tucker, D. L.; Gruendl, R. A.; Johnson, M. D.; Walker, A. R.; James, D. J.; Nidever, D. L.; Olsen, K. A. G.; Wechsler, R. H.; Cioni, M. R. L.; Conn, B. C.; Kuehn, K.; Li, T. S.; Mao, Y.-Y.; Martin, N. F.; Neilsen, E.; Noel, N. E. D.; Pieres, A.; Simon, J. D.; Stringfellow, G. S.; van der Marel, R. P.; Yanny, B.

2016-12-01

We report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644-5953 (Pictor II or Pic II) is a low surface brightness (μ ={28.5}-1+1 {mag} {arcsec}{}-2 within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of {45}-4+5 {kpc}. The physical size ({r}1/2={46}-11+15 {pc} ) and low luminosity ({M}V=-{3.2}-0.5+0.4 {mag} ) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644-5953 (Pic II) is located {11.3}-0.9+3.1 {kpc} from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644-5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.

Galaxy luminosity function: evolution at high redshift

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Guennou, L.; Adami, C.

2014-12-01

There are some disagreements about the abundance of faint galaxies in high redshift clusters. DAFT/FADA (Dark energy American French Team) is a medium redshift (0.4

Orbital solution leading to an acceptable interpretation for the enigmatic gamma-ray binary HESS J0632+057

NASA Astrophysics Data System (ADS)

Moritani, Yuki; Kawano, Takafumi; Chimasu, Sho; Kawachi, Akiko; Takahashi, Hiromitsu; Takata, Jumpei; Carciofi, Alex C.

2018-05-01

High-dispersion spectroscopic monitoring of HESS J0632+057 has been carried out over four orbital cycles in order to search for orbital modulation, covering the entire orbital phase. We have measured the radial velocity of the Hα emission line with the method introduced by Shafter, Szkody, and Thorstensen (1986, ApJ, 308, 765), which has been successfully applied to some Be stars. The velocity is seen to increase much earlier than expected for the orbital period of 315 d, and much more steeply than expected at around "apastron." The period of the Hα modulation is found to be 308^{+26}_{-23} d. We have also analyzed Swift/XRT data from 2009 to 2015 to study the orbital modulation, selecting the data with good statistics (≥30 counts). With additional two-year data to the previous works, the orbital period has been updated to 313^{+11}_{-8} d, which is consistent with the previous X-ray periods and the spectroscopic one. Previous XMM-Newton and Chandra observations prefer a period of 313 d. With the new period, assuming that Hα velocities accurately trace the motion of the Be star, we have derived a new set of orbital parameters. In the new orbit, which is less eccentric (e ≃ 0.6), two outbursts occur: after apastron and just after periastron. Also, the column density in bright phase (4.7^{+0.9}_{-08}× 10^{21} cm^{-2}) is higher than in faint phase (2.2 ± 0.5 × 1021 cm-2). These facts suggest that outbursts occur when the compact object passes nearby/through the Be disk. The mass function implies that the mass of the compact object is less than 2.5 M⊙, assuming that the mass of the Be star is 13.2-18.2 M⊙ (Aragona et al. 2010, ApJ, 724, 306), unless the inclination is extremely small. The photon index indicates that the spectra become softer when the system is bright. These suggest that the compact object is a pulsar.

On the faint-end of the high-z galaxy luminosity function

NASA Astrophysics Data System (ADS)

Yue, Bin; Ferrara, Andrea; Xu, Yidong

2016-12-01

Recent measurements of the luminosity function (LF) of galaxies in the Epoch of Reionization (EoR, z ≳ 6) indicate a very steep increase of the number density of low-mass galaxies populating the LF faint-end. However, as star formation in low-mass haloes can be easily depressed or even quenched by ionizing radiation, a turnover is expected at some faint UV magnitudes. Using a physically motivated analytical model, we quantify reionization feedback effects on the LF faint-end shape. We find that if reionization feedback is neglected, the power-law Schechter parametrization characterizing the LF faint-end remains valid up to absolute UV magnitude ˜-9. If instead radiative feedback is strong enough that quenches star formation in haloes with circular velocity smaller than 50 km s-1, the LF starts to drop at absolute UV magnitude ˜-15, I.e. slightly below the detection limits of current (unlensed) surveys at z ˜ 5. The LFs may rise again at higher absolute UV magnitude, where, as a result of interplay between reionization process and galaxy formation, most of the galaxy light is from relic stars formed before the EoR. We suggest that the galaxy number counts data, particularly in lensed fields, can put strong constraints on reionization feedback. In models with stronger reionization feedback, stars in galaxies with absolute UV magnitude higher than ˜-13 and smaller than ˜-8 are typically older. Hence, the stellar age-UV magnitude relation can be used as an alternative feedback probe.

DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

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

Kim, Yongjung; Im, Myungshin; Jeon, Yiseul

2015-11-10

Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to zmore » = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.« less

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

Weisz, Daniel R.; Johnson, Benjamin D.; Conroy, Charlie, E-mail: drw@ucsc.edu

We present a new technique to estimate the evolution of the very faint end of the UV luminosity function (LF) out to z ∼ 5. Measured star formation histories (SFHs) from the fossil record of Local Group (LG) galaxies are used to reconstruct the LF down to M {sub UV} ∼–5 at z ∼ 5 and M {sub UV} ∼–1.5 at z < 1. Such faint limits are well beyond the current observational limits and are likely to remain beyond the limits of next-generation facilities. The reconstructed LFs, when combined with direct measurements of the LFs at higher luminosity, aremore » well-fit by a standard Schechter function with no evidence of a break to the faintest limits probed by this technique. The derived faint-end slope, α, steepens from ≈ – 1.2 at z < 1 to ≈ – 1.6 at 4 < z < 5. We test the effects of burstiness in the SFHs and find the recovered LFs to be only modestly affected. Incompleteness corrections for the faintest LG galaxies and the (unlikely) possibility of significant luminosity-dependent destruction of dwarf galaxies between high redshift and the present epoch are important uncertainties. These and other uncertainties can be mitigated with more detailed modeling and future observations. The reconstructed faint end LF from the fossil record can therefore be a powerful and complementary probe of the high-redshift faint galaxies believed to play a key role in the reionization of the universe.« less

VEGAS: A VST Early-type GAlaxy Survey. II. Photometric study of giant ellipticals and their stellar halos

NASA Astrophysics Data System (ADS)

Spavone, Marilena; Capaccioli, Massimo; Napolitano, Nicola R.; Iodice, Enrichetta; Grado, Aniello; Limatola, Luca; Cooper, Andrew P.; Cantiello, Michele; Forbes, Duncan A.; Paolillo, Maurizio; Schipani, Pietro

2017-07-01

Observations of diffuse starlight in the outskirts of galaxies are thought to be a fundamental source of constraint on the cosmological context of galaxy assembly in the ΛCDM model. Such observations are not trivial because of the extreme faintness of such regions. In this work, we investigated the photometric properties of six massive early-type galaxies (ETGs) in the VEGAS sample (NGC 1399, NGC 3923, NGC 4365, NGC 4472, NGC 5044, and NGC 5846) out to extremely low surface brightness levels with the goal of characterizing the global structure of their light profiles for comparison to state-of-the-art galaxy formation models. We carried out deep and detailed photometric mapping of our ETG sample taking advantage of deep imaging with VST/OmegaCAM in the g and I bands. By fitting the light profiles, and comparing the results to simulations of elliptical galaxy assembly, we have identified signatures of a transition between relaxed and unrelaxed accreted components and can constrain the balance between in situ and accreted stars. The very good agreement of our results with predictions from theoretical simulations demonstrates that the full VEGAS sample of 100 ETGs will allow us to use the distribution of diffuse light as a robust statistical probe of the hierarchical assembly of massive galaxies.

DEEP ULTRAVIOLET LUMINOSITY FUNCTIONS AT THE INFALL REGION OF THE COMA CLUSTER

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

Hammer, D. M.; Hornschemeier, A. E.; Jenkins, L.

2012-02-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M{sub UV} = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes ({alpha} Almost-Equal-To -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechtermore » model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of {alpha} Almost-Equal-To -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than {alpha} = -1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M{sub UV} Almost-Equal-To -14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M{sub *} = 10{sup 8} M{sub Sun }. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.« less

Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

NASA Technical Reports Server (NTRS)

Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

2011-01-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

Stacked Denoising Autoencoders Applied to Star/Galaxy Classification

NASA Astrophysics Data System (ADS)

Qin, Hao-ran; Lin, Ji-ming; Wang, Jun-yi

2017-04-01

In recent years, the deep learning algorithm, with the characteristics of strong adaptability, high accuracy, and structural complexity, has become more and more popular, but it has not yet been used in astronomy. In order to solve the problem that the star/galaxy classification accuracy is high for the bright source set, but low for the faint source set of the Sloan Digital Sky Survey (SDSS) data, we introduced the new deep learning algorithm, namely the SDA (stacked denoising autoencoder) neural network and the dropout fine-tuning technique, which can greatly improve the robustness and antinoise performance. We randomly selected respectively the bright source sets and faint source sets from the SDSS DR12 and DR7 data with spectroscopic measurements, and made preprocessing on them. Then, we randomly selected respectively the training sets and testing sets without replacement from the bright source sets and faint source sets. At last, using these training sets we made the training to obtain the SDA models of the bright sources and faint sources in the SDSS DR7 and DR12, respectively. We compared the test result of the SDA model on the DR12 testing set with the test results of the Library for Support Vector Machines (LibSVM), J48 decision tree, Logistic Model Tree (LMT), Support Vector Machine (SVM), Logistic Regression, and Decision Stump algorithm, and compared the test result of the SDA model on the DR7 testing set with the test results of six kinds of decision trees. The experiments show that the SDA has a better classification accuracy than other machine learning algorithms for the faint source sets of DR7 and DR12. Especially, when the completeness function is used as the evaluation index, compared with the decision tree algorithms, the correctness rate of SDA has improved about 15% for the faint source set of SDSS-DR7.

WISE Brown Dwarf Binaries: The Discovery of a T5+T5 and a T8.5+T9 System

NASA Astrophysics Data System (ADS)

Gelino, Christopher R.; Kirkpatrick, J. Davy; Cushing, Michael C.; Eisenhardt, Peter R.; Griffith, Roger L.; Mainzer, Amanda K.; Marsh, Kenneth A.; Skrutskie, Michael F.; Wright, Edward L.

2011-08-01

The multiplicity properties of brown dwarfs are critical empirical constraints for formation theories, while multiples themselves provide unique opportunities to test evolutionary and atmospheric models and examine empirical trends. Studies using high-resolution imaging cannot only uncover faint companions, but they can also be used to determine dynamical masses through long-term monitoring of binary systems. We have begun a search for the coolest brown dwarfs using preliminary processing of data from the Wide-field Infrared Survey Explorer and have confirmed many of the candidates as late-type T dwarfs. In order to search for companions to these objects, we are conducting observations using the Laser Guide Star Adaptive Optics system on Keck II. Here we present the first results of that search, including a T5 binary with nearly equal mass components and a faint companion to a T8.5 dwarf with an estimated spectral type of T9. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

A population of faint low surface brightness galaxies in the Perseus cluster core

NASA Astrophysics Data System (ADS)

Wittmann, Carolin; Lisker, Thorsten; Ambachew Tilahun, Liyualem; Grebel, Eva K.; Conselice, Christopher J.; Penny, Samantha; Janz, Joachim; Gallagher, John S.; Kotulla, Ralf; McCormac, James

2017-09-01

We present the detection of 89 low surface brightness (LSB), and thus low stellar density galaxy candidates in the Perseus cluster core, of the kind named 'ultra-diffuse galaxies', with mean effective V-band surface brightnesses 24.8-27.1 mag arcsec-2, total V-band magnitudes -11.8 to -15.5 mag, and half-light radii 0.7-4.1 kpc. The candidates have been identified in a deep mosaic covering 0.3 deg2, based on wide-field imaging data obtained with the William Herschel Telescope. We find that the LSB galaxy population is depleted in the cluster centre and only very few LSB candidates have half-light radii larger than 3 kpc. This appears consistent with an estimate of their tidal radius, which does not reach beyond the stellar extent even if we assume a high dark matter content (M/L = 100). In fact, three of our candidates seem to be associated with tidal streams, which points to their current disruption. Given that published data on faint LSB candidates in the Coma cluster - with its comparable central density to Perseus - show the same dearth of large objects in the core region, we conclude that these cannot survive the strong tides in the centres of massive clusters.

Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive

NASA Astrophysics Data System (ADS)

Pueyo, Laurent

2013-10-01

We propose to conduct WFC3 high contrast observations of six faint planetary candidates orbiting young {1 to 100 Myrs} stars identified in archival HST NICMOS coronagraphic data as part of our team's program AR-12652. Such rare objects are of the utmost importance to comparative exo-planetology as their physical properties reflect the initial conditions of still poorly constrained planetary formation mechanisms. Moreover directly imaged systems are precious artifacts in the expanding exo-planetary treasure trove as they are readily available for spectroscopic characterization. Our statistical analysis, which combines population synthesis models and empirical inspections of the entire NICMOS field of view for all sources observed in coronaraphic mode, almost guarantees that one of these six faint candidates is associated with its putative host star. We will conduct our observation in four near infrared filter, F125W, F160W to establish the baseline luminosity of our candidates and in F127M and F139M in order to probe the depth their water absorption features, characteristic of substellar /exo-planetary like atmospheres. Because of the youth of our targets, this program, which only requires a modest 12 HST orbits, will almost certainly identify and image a young or adolescent exo-planet.

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1993-12-01

Astronaut Hoffman held the Hubble Space Telescope (HST) Wide Field/Planetary Camera-1 (WF/PC1) that was replaced by WF/PC2 in the cargo bay of the Space Shuttle orbiter Endeavour during Extravehicular Activity (EVA). The STS-61 mission was the first of the series of the HST servicing missions. Two months after its deployment in space, scientists detected a 2-micron spherical aberration in the primary mirror of the HST that affected the telescope's ability to focus faint light sources into a precise point. This imperfection was very slight, one-fiftieth of the width of a human hair. During four spacewalks, the STS-61 crew replaced the solar panel with its flexing problems; the WF/PC1 with WF/PC2, with built-in corrective optics; and the High-Speed Photometer with the Corrective Optics Space Telescope Axial Replacement (COSTAR) to correct the aberration for the remaining instruments. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit for 15 years or more. The HST provides fine detail imaging, produces ultraviolet images and spectra, and detects very faint objects. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

Two-sample discrimination of Poisson means

NASA Technical Reports Server (NTRS)

Lampton, M.

1994-01-01

This paper presents a statistical test for detecting significant differences between two random count accumulations. The null hypothesis is that the two samples share a common random arrival process with a mean count proportional to each sample's exposure. The model represents the partition of N total events into two counts, A and B, as a sequence of N independent Bernoulli trials whose partition fraction, f, is determined by the ratio of the exposures of A and B. The detection of a significant difference is claimed when the background (null) hypothesis is rejected, which occurs when the observed sample falls in a critical region of (A, B) space. The critical region depends on f and the desired significance level, alpha. The model correctly takes into account the fluctuations in both the signals and the background data, including the important case of small numbers of counts in the signal, the background, or both. The significance can be exactly determined from the cumulative binomial distribution, which in turn can be inverted to determine the critical A(B) or B(A) contour. This paper gives efficient implementations of these tests, based on lookup tables. Applications include the detection of clustering of astronomical objects, the detection of faint emission or absorption lines in photon-limited spectroscopy, the detection of faint emitters or absorbers in photon-limited imaging, and dosimetry.

The DLR AsteroidFinder for NEOs

NASA Astrophysics Data System (ADS)

Mottola, Stefano; Kuehrt, Ekkehard; Michaelis, Harald; Hoffmann, Harald; Spietz, Peter; Jansen, Frank; Thimo Grundmann, Jan; Hahn, Gerhard; Montenegro, Sergio; Findlay, Ross; Boerner, Anko; Messina, Gabriele; Behnke, Thomas; Tschentscher, Matthias; Scheibe, Karsten; Mertens, Volker; Heidecke, Ansgar

Potential Earth-impacting asteroids that spend most of their time interior to Earth's orbit are extremely difficult to be observed from the ground and remain largely undetected. Firstly, they are mostly located at small solar elongations, where the sky brightness and their faintness due to the large phase angle prevents their discovery. Secondly, these objects tend to have very long synodic orbital periods, which makes observation opportunities rare and impact warning times short. Because of these limitations, even the advent of next generation ground-based asteroid surveys is not likely to radically improve the situation (Veres et al. Icarus 203, p472, 2009). On the other hand, a small satellite with a suitable design can observe close to the Sun and detect these objects efficiently against a dark sky background. For this reason, DLR, the German Aerospace Center, has selected AsteroidFinder as the first experiment to be launched under its new compact satellite national program. The primary goal of the mission is to detect and characterize Near Earth Objects (NEOs), with a particular focus on the population of objects completely contained within Earth's orbit (IEOs or Inner Earth Objects). Current dynamical models predict the existence of more than 1000 such objects down to a size of 100m, of which, due to the abovementioned observation difficulties, only 10 have been discovered to date. Benefitting from the vantage point of a Low Earth Orbit (LEO), AsteroidFinder makes use of a small optical telescope to scan those regions of the sky that are close to the Sun, and therefore beyond the reach of ground based observatories. By estimating the population, the size and the orbital distribution of IEOs, AsteroidFinder will contribute to our knowledge of the inner Solar System, and to the assessment of the impact hazard for the Earth. A secondary goal of the mission is to demonstrate techniques that enable the space-based detection of space debris in the cm size range. With these mission goals, AsteroidFinder also addresses the programmatic goals of the ESA SSA initiative, both for the NEO and space debris domain. The AsteroidFinder mission is based on the DLR SSB standard platform, it employs a 400-cm2 clear-aperture, off-axis design telescope and an array of new technology CCDs. AsteroidFinder, which is presently in its Phase-B development stage, is planned to launch in 2013 with a one-year nominal mission duration and the possibility of an extension.

Future Sky Surveys: New Discovery Frontiers

NASA Astrophysics Data System (ADS)

Tyson, J. Anthony; Borne, Kirk D.

2012-03-01

Driven by the availability of new instrumentation, there has been an evolution in astronomical science toward comprehensive investigations of new phenomena. Major advances in our understanding of the Universe over the history of astronomy have often arisen from dramatic improvements in our capability to observe the sky to greater depth, in previously unexplored wavebands, with higher precision, or with improved spatial, spectral, or temporal resolution. Substantial progress in the important scientific problems of the next decade (determining the nature of dark energy and dark matter, studying the evolution of galaxies and the structure of our own Milky Way, opening up the time domain to discover faint variable objects, and mapping both the inner and outer Solar System) can be achieved through the application of advanced data mining methods and machine learning algorithms operating on the numerous large astronomical databases that will be generated from a variety of revolutionary future sky surveys. Over the next decade, astronomy will irrevocably enter the era of big surveys and of really big telescopes. New sky surveys (some of which will produce petabyte-scale data collections) will begin their operations, and one or more very large telescopes (ELTs = Extremely Large Telescopes) will enter the construction phase. These programs and facilities will generate a remarkable wealth of data of high complexity, endowed with enormous scientific knowledge discovery potential. New parameter spaces will be opened, in multiple wavelength domains as well as the time domain, across wide areas of the sky, and down to unprecedented faint source flux limits. The synergies of grand facilities, massive data collections, and advanced machine learning algorithms will come together to enable discoveries within most areas of astronomical science, including Solar System, exo-planets, star formation, stellar populations, stellar death, galaxy assembly, galaxy evolution, quasar evolution, and cosmology. Current and future sky surveys, comprising an alphabet soup of project names (e.g., Pan- STARRS, WISE, Kepler, DES, VST, VISTA, GAIA, EUCLID, SKA, LSST, and WFIRST; some of which are discussed in Chapters 17, 18, and 20),will contribute to the exponential explosion of complex data in astronomy. The scientific goals of these projects are as monumental as the programs themselves. The core scientific output of all of these will be their scientific data collection. Consequently, data mining and machine learning algorithms and specialists will become a common component of future astronomical research with these facilities. This synergistic combination and collaboration among multiple disciplines are essential in order to maximize the scientific discovery potential, the science output, the research efficiency, and the success of these projects.

The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

NASA Astrophysics Data System (ADS)

Akiyama, Masayuki; He, Wanqiu; Ikeda, Hiroyuki; Niida, Mana; Nagao, Tohru; Bosch, James; Coupon, Jean; Enoki, Motohiro; Imanishi, Masatoshi; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Onoue, Masafusa; Ouchi, Masami; Schulze, Andreas; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Terashima, Yuichi; Toba, Yoshiki; Ueda, Yoshihiro

2018-01-01

We present the luminosity function of z ˜ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ˜ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29 mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ˜ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

On the Nature of Ultra-faint Dwarf Galaxy Candidates. I. DES1, Eridanus III, and Tucana V

NASA Astrophysics Data System (ADS)

Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

2018-01-01

We use deep Gemini/GMOS-S g, r photometry to study the three ultra-faint dwarf galaxy candidates DES1, Eridanus III (Eri III), and Tucana V (Tuc V). Their total luminosities, M V (DES1) = ‑1.42 ± 0.50 and M V (Eri III) = ‑2.07 ± 0.50, and mean metallicities, [{Fe}/{{H}}]=-{2.38}-0.19+0.21 and [{Fe}/{{H}}]=-{2.40}-0.12+0.19, are consistent with them being ultra-faint dwarf galaxies, as they fall just outside the 1σ confidence band of the luminosity–metallicity relation for Milky Way satellite galaxies. However, their positions in the size–luminosity relation suggest that they are star clusters. Interestingly, DES1 and Eri III are at relatively large Galactocentric distances, with DES1 located at {D}{GC}=74+/- 4 {kpc} and Eri III at {D}{GC}=91+/- 4 {kpc}. In projection, both objects are in the tail of gaseous filaments trailing the Magellanic Clouds and have similar 3D separations from the Small Magellanic Cloud (SMC): {{Δ }}{D}{SMC,{DES}1}=31.7 kpc and {{Δ }}{D}{SMC,{Eri}{III}}=41.0 kpc, respectively. It is plausible that these stellar systems are metal-poor SMC satellites. Tuc V represents an interesting phenomenon in its own right. Our deep photometry at the nominal position of Tuc V reveals a low-level excess of stars at various locations across the GMOS field without a well-defined center. An SMC Northern Overdensity–like isochrone would be an adequate match to the Tuc V color–magnitude diagram, and the proximity to the SMC (12.°1 {{Δ }}{D}{SMC,{Tuc}{{V}}}=13 kpc) suggests that Tuc V is either a chance grouping of stars related to the SMC halo or a star cluster in an advanced stage of dissolution.

An IRAS-Based Search for New Dusty Late-Type WC Wolf-Rayet Stars

NASA Technical Reports Server (NTRS)

Cohen, Martin

1995-01-01

I have examined all Infrared Astronomical Satellite (IRAS) data relevant to the 173 Galactic Wolf-Rayet (W-R) stars in an updated catalog, including the 13 stars newly discovered by Shara and coworkers. Using the W-R coordinates in these lists, I have examined the IRAS Point Source Catalog (PSC), the Faint Source Catalog, and the Faint Source Reject Catalog, and have generated one-dimensional spatial profiles, 'ADDSCANs', and two-dimensional full-resolution images, 'FRESCOS'. The goal was to assemble the best set of observed IRAS color indices for different W-R types, in particular for known dusty late-type WC Wolf-Rayet (WCL) objects. I have also unsuccessfully sought differences in IRAS colors and absolute magnitudes between single and binary W-R stars. The color indices for the entire ensemble of W-R stars define zones in the IRAS color-color ([12] - [25], [25] - [60])-plane. By searching the PSC for otherwise unassociated sources that satisfy these colors, I have identified potential new W-R candidates, perhaps too faint to have been recognized in previous optical searches. I have extracted these candidates' IRAS low-resolution spectrometer (LRS) data and compared the spectra with the highly characteristic LRS shape for known dusty WCL stars. The 13 surviving candidates must now be ex amined by optical spectroscopy. This work represents a much more rigorous and exhaustive version of the LRS study that identified IRAS 17380 - 3031 (WR98a) as the first new W-R (WC9) star discovered by IPAS. This search should have detected dusty WCL stars to a distance of 7.0 kpc from the Sun, for l is greater than 30 degrees, and to 2.9 kpc even in the innermost galaxy. For free-free-dominated W-R stars the corresponding distances are 2.5 and 1.0 kpc, respectively.

An IRAS-based search for new Dusty Late-Type WC Wolf-Rayet stars

NASA Technical Reports Server (NTRS)

Cohen, Martin

1995-01-01

I have examined all Infrared Astronomical Satellite (IRAS) data relevant to the 173 Galactic Wolf-Rayet (W-R) stars in an updated catalog, including the 13 stars newly discovered by Shara and coworkers. Using the W-R coordinates in these lists, I have examined the IRAS Point Source Catalog (PSC), the Faint Source Catalog, and the Faint Source Reject Catalog, and have generated one-dimensional spatial profiles ('ADDSCANs') and two-dimensional full-resolution images ('FRESCOs'). The goal was to assemble the best set of observed IRAS color indices for different W-R types, in particular for known dusty late-type WC Wolf-Rayet (WCL) objects. I have also unsuccessfully sought differences in IRAS colors and absolute magnitudes between single and binary W-R stars. The color indices for the entire ensemble of W-R stars define zones in the IRAS color-color plane. By searching the PSC for otherwise unassociated sources that satisfy these colors, I have identified potential new W-R candidates, perhaps too faint to have been recognized in previous optical searches. I have extracted these candidates' IRAS low-resolution spectrometer (LRS) data and compared the spectra with the highly characteristic LRS shape for known dusty WCL stars. The 13 surviving candidates must now be examined by optical spectroscopy. This work represents a much more rigorous and exhaustive version of the LRS study that identified IRAS 17380 - 3031 (WR98a) as the first new W-R (WC9) star discovered by IRAS. This search should have detected dusty WCL stars to a distance of 7.0 kpc from the Sun, for the absolute value of l greater than 30 deg, and to 2.9 kpc even in the innermost Galaxy. For free-free-dominated W-R stars the corresponding distances are 2.5 and 1.0 kpc, respectively.

Solar system astronomy with the 3.6-m DOT and the 4-m ILMT

NASA Astrophysics Data System (ADS)

Ganesh, Shashikiran; Venkataramani, Kumar; Baliyan, Kiran Singh; Joshi, Umesh Chandra

2018-04-01

Solar system astronomy would be an important field of study with the 3.6-m Devasthal Optical Telescope (DOT) and the 4-m International Liquid Mirror Telescope (ILMT). In this contribution, we highlight the work that could be done in reaching a better understanding of the Solar system and its constituents - particularly the minor bodies and other smaller objects. There may be a large number of very faint objects in the vicinity of the Earth orbit. In fact only recently a 'second moon' of the Earth has been found and has been designated 2016 H03. This is a quasi-satellite with the same period of revolution around Earth and Sun. There could be many such objects and it is important to have a full characterization and understanding of these potentially hazardous objects. They are generally fainter than 18th magnitude and one would need a lot of telescope time to fully characterize these objects using techniques of spectropolarimetry. In a similar fashion, a deep census of the Kuiper Belt Objects and the TNOs is needed. In this census, the concept of pencil beam surveys could be extended to cylindrical transit imaging technique available with the 4-m ILMT.

The nature of radio emission from distant galaxies

NASA Astrophysics Data System (ADS)

Richards, Eric A.

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

What and whence 1I/`Oumuamua: a contact binary from the debris of a young planetary system?

NASA Astrophysics Data System (ADS)

Gaidos, E.

2018-07-01

The first confirmed interstellar interloper in our Solar system, 1I/`Oumuamua, is likely to be a minor body ejected from another star, but its brief flyby and faintness made it difficult to study. Two remarkable properties are its large (up to 2.5 mag) rotational variability and its motion relative to the Sun before encounter. The former suggests an extremely elongated shape (aspect ratio ≥ 10) and the latter an origin from the protoplanetary disc of a young star in a nearby association. Against expectations, it is also not comet-like. 1I/`Oumuamua's variability can also be explained if it is a contact binary composed of near-equilibrium ellipsoidal components and heterogeneous surfaces, i.e. brighter, dust-mantled inner-facing hemispheres and darker, dust-free outer-facing poles. Such shapes are a plausible outcome of radiation, tides, and collisions in systems where planets are clearing planetesimal discs. The probability that 1I/`Oumuamua has the same motion as a young (≲100 Myr) stellar association by coincidence is <1 per cent. If it is young, its detection versus more numerous, older counterparts could be explained as a selection effect due to darkening of surfaces by Galactic cosmic rays and loss of dust. 1I/`Oumuamua's apparent lack of ices can be explained if ejected rocky planetesimals are characteristically smaller and thus far more numerous than their icy counterparts: the Solar system may currently host several such objects captured by the combined gravity of Jupiter and the Sun.

Using r-process enhanced galaxies to estimate the neutron star merger rate at high redshift

NASA Astrophysics Data System (ADS)

Roederer, Ian

2018-01-01

The rapid neutron-capture process, or r-process, is one of the fundamental ways that stars produce heavy elements. I describe a new approach that uses the existence of r-process enhanced galaxies, like the recently discovered ultra-faint dwarf galaxy Reticulum II, to derive a rate for neutron star mergers at high redshift. This method relies on three assertions. First, several lines of reasoning point to neutron star mergers as a rare yet prolific producer of r-process elements, and one merger event is capable of enriching most of the stars in a low-mass dwarf galaxy. Second, the Local Group is cosmologically representative of the halo mass function at the mass scales of low-luminosity dwarf galaxies, and the volume that their progenitors spanned at high redshifts can be estimated from simulations. Third, many of these dwarf galaxies are extremely old, and the metals found in their stars today date from the earliest times at high redshift. These galaxies occupy a quantifiable volume of the Universe, from which the frequency of r-process enhanced galaxies can be estimated. This frequency may be interpreted as lower limit to the neutron star merger rate at a redshift (z ~ 5-10) that is much higher than is accessible to gravitational wave observatories. I will present a proof of concept demonstration using medium-resolution multi-object spectroscopy from the Michigan/Magellan Fiber System (M2FS) to recover the known r-process galaxy Reticulum II, and I will discuss future plans to apply this method to other Local Group dwarf galaxies.

THINK OUTSIDE THE COLOR BOX: PROBABILISTIC TARGET SELECTION AND THE SDSS-XDQSOQUASAR TARGETING CATALOG

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

BOVY, J.; Sheldon, E.; Hennawi, J.F.

2011-03-10

We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the Sloan Digital Sky Survey (SDSS) catalog, even at medium redshifts (2.5 {approx}< z {approx}< 3) where the stellar contamination is significant. We build models of the distributions of stars and quasars in flux space down to the flux limit by applying the extreme-deconvolution method to estimate the underlying density. We convolve this density with the flux uncertainties when evaluating the probability that an object is a quasar. This approach results in a targeting algorithm that is more principled, more efficient,more » and faster than other similar methods. We apply the algorithm to derive low-redshift (z < 2.2), medium-redshift (2.2 {le} z {le} 3.5), and high-redshift (z > 3.5) quasar probabilities for all 160,904,060 point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in the 14,555 deg{sup 2} of imaging from SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar-selection technique at low redshift, and outperforms all other flux-based methods for selecting the medium-redshift quasars of our primary interest. We make code to reproduce the XDQSO quasar target selection publicly available.« less

Estimating sizes of faint, distant galaxies in the submillimetre regime

NASA Astrophysics Data System (ADS)

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

2016-10-01

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

Confirming the least massive members of the Pleiades star cluster

NASA Astrophysics Data System (ADS)

Zapatero Osorio, M. R.; Béjar, V. J. S.; Lodieu, N.; Manjavacas, E.

2018-03-01

We present optical photometry (i and Z band) and low-resolution spectroscopy (640-1015 nm) of very faint candidate members (J = 20.2-21.2 mag) of the Pleiades star cluster (120 Myr). The main goal is to address their cluster membership via photometric, astrometric, and spectroscopic studies, and to determine the properties of the least massive population of the cluster through the comparison of the data with younger and older spectral counterparts and state-of-the art model atmospheres. We confirm three bona fide Pleiades members that have extremely red optical and infrared colours, effective temperatures of ≈1150 and ≈1350 K, and masses in the interval 11-20 MJup, and one additional likely member that shares the same motion as the cluster but does not appear to be as red as the other members with similar brightness. This latter object requires further near-infrared spectroscopy to fully address its membership in the Pleiades. The optical spectra of two bona fide members were classified as L6-L7 and show features of K I, a tentative detection of Cs I, hydrides, and water vapour with an intensity similar to high-gravity dwarfs of related classification despite their young age. The properties of the Pleiades L6-L7 members clearly indicate that very red colours of L dwarfs are not a direct evidence of ages younger than ≈100 Myr. We also report on the determination of the bolometric corrections for the coolest Pleiades members. These data can be used to interpret the observations of the atmospheres of exoplanets orbiting stars.

What and Whence 1I/`Oumuamua: A Contact Binary from the Debris of a Young Planetary System?

NASA Astrophysics Data System (ADS)

Gaidos, E.

2018-04-01

The first confirmed interstellar interloper in our Solar System, 1I/`Oumuamua, is likely to be a minor body ejected from another star, but its brief flyby and faintness made it difficult to study. Two remarkable properties are its large (up to 2.5 mag) rotational variability and its motion relative to the Sun before encounter. The former suggests an extremely elongated shape (aspect ratio ≥10) and the latter an origin from the protoplanetary disk of a young star in a nearby association. Against expectations, it is also not comet-like. 1I/`Oumuamua's variability can also be explained if it is a contact binary composed of near-equilibrium ellipsoidal components and heterogeneous surfaces, i.e. brighter, dust-mantled inner-facing hemispheres and darker, dust-free outer-facing poles. Such shapes are a plausible outcome of radiation, tides and collisions in systems where planets are clearing planetesimal disks. The probability that 1I/'Oumuamua has the same motion as a young (≲ 100 Myr) stellar association by coincidence is <1%. If it is young, its detection vs. more numerous, older counterparts could be explained as a selection effect due to darkening of surfaces by Galactic cosmic rays and loss of dust. 1I/`Oumuamua's apparent lack of ices can be explained if ejected rocky planetesimals are characteristically smaller and thus far more numerous than their icy counterparts: the Solar System may currently host several such objects captured by the combined gravity of Jupiter and the Sun.

Adaptive Optics Observations of Exoplanets, Brown Dwarfs, and Binary Stars

NASA Astrophysics Data System (ADS)

Hinkley, Sasha

2012-04-01

The current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Further, the prevalence of aperture masking interferometry in the field of high contrast imaging is also allowing observers to sense massive, young planets at solar system scales (~3-30 AU)- separations out of reach to conventional direct imaging techniques. Such observations can provide snapshots at the earliest phases of planet formation-information essential for constraining formation mechanisms as well as evolutionary models of planetary mass companions. As a demonstration of the power of this technique, I briefly review recent aperture masking observations of the HR 8799 system. Moreover, all of the aforementioned techniques are already extremely adept at detecting low-mass stellar companions to their target stars, and I present some recent highlights.

Limited role for methane in the mid-Proterozoic greenhouse

PubMed Central

Olson, Stephanie L.; Reinhard, Christopher T.; Lyons, Timothy W.

2016-01-01

Pervasive anoxia in the subsurface ocean during the Proterozoic may have allowed large fluxes of biogenic CH4 to the atmosphere, enhancing the climatic significance of CH4 early in Earth’s history. Indeed, the assumption of elevated pCH4 during the Proterozoic underlies most models for both anomalous climatic stasis during the mid-Proterozoic and extreme climate perturbation during the Neoproterozoic; however, the geologic record cannot directly constrain atmospheric CH4 levels and attendant radiative forcing. Here, we revisit the role of CH4 in Earth’s climate system during Proterozoic time. We use an Earth system model to quantify CH4 fluxes from the marine biosphere and to examine the capacity of biogenic CH4 to compensate for the faint young Sun during the “boring billion” years before the emergence of metazoan life. Our calculations demonstrate that anaerobic oxidation of CH4 coupled to SO42− reduction is a highly effective obstacle to CH4 accumulation in the atmosphere, possibly limiting atmospheric pCH4 to less than 10 ppm by volume for the second half of Earth history regardless of atmospheric pO2. If recent pO2 constraints from Cr isotopes are correct, we predict that reduced UV shielding by O3 should further limit pCH4 to very low levels similar to those seen today. Thus, our model results likely limit the potential climate warming by CH4 for the majority of Earth history—possibly reviving the faint young Sun paradox during Proterozoic time and challenging existing models for the initiation of low-latitude glaciation that depend on the oxidative collapse of a steady-state CH4 greenhouse. PMID:27671638

Mystery solved: discovery of extended radio emission in the merging galaxy cluster Abell 2146

NASA Astrophysics Data System (ADS)

Hlavacek-Larrondo, J.; Gendron-Marsolais, M.-L.; Fecteau-Beaucage, D.; van Weeren, R. J.; Russell, H. R.; Edge, A.; Olamaie, M.; Rumsey, C.; King, L.; Fabian, A. C.; McNamara, B.; Hogan, M.; Mezcua, M.; Taylor, G.

2018-04-01

Abell 2146 (z = 0.232) is a massive galaxy cluster currently undergoing a spectacular merger in the plane of the sky with a bullet-like morphology. It was the first system in which both the bow and upstream shock fronts were detected at X-ray wavelengths (Mach ˜2), yet deep Giant MetreWave Telescope 325 MHz observations failed to detect extended radio emission associated with the cluster as is typically seen in such systems. We present new, multiconfiguration 1-2 GHz Karl G. Jansky Very Large Array (VLA) observations of Abell 2146 totalling 16 h of observations. These data reveal for the first time the presence of an extended (≈850 kpc), faint radio structure associated with Abell 2146. The structure appears to harbour multiple components, one associated with the upstream shock that we classify as a radio relic and one associated with the subcluster core that is consisted as being a radio halo bounded by the bow shock. The newly detected structures have some of the lowest radio powers detected thus far in any cluster (P1.4 GHz, halo = 2.4 ± 0.2 × 1023 W Hz-1 and P1.4 GHz, relic = 2.2 ± 0.2 × 1023 W Hz-1). The flux measurement of the halo, as well as its morphology, also suggests that the halo was recently created (≈0.3 Gyr after core passage), consistent with the dynamical state of the cluster. These observations demonstrate the capacity of the upgraded VLA to detect extremely faint and extended radio structures. Based on these observations, we predict that many more radio relics and radio haloes in merging clusters should be detected by future radio facilities such as the Square Kilometre Array.

Rats Can Acquire Conditional Fear of Faint Light Leaking through the Acrylic Resin Used to Mount Fiber Optic Cannulas

ERIC Educational Resources Information Center

Eckmier, Adam; de Marcillac, Willy Daney; Maître, Agnès; Jay, Thérèse M.; Sanders, Matthew J.; Godsil, Bill P.

2016-01-01

Rodents are exquisitely sensitive to light and optogenetic behavioral experiments routinely introduce light-delivery materials into experimental situations, which raises the possibility that light could leak and influence behavioral performance. We examined whether rats respond to a faint diffusion of light, termed caplight, which emanated through…

Correlation between low level fluctuations in the x ray background and faint galaxies

NASA Technical Reports Server (NTRS)

Tolstoy, Eline; Griffiths, R. E.

1993-01-01

A correlation between low-level x-ray fluctuations in the cosmic x-ray background flux and the large numbers of galaxies found in deep optical imaging, to m(sub v) is less than or equal to 24 - 26, is desired. These (faint) galaxies by their morphology and color in deep multi-color CCD images and plate material were optically identified. Statistically significant correlations between these galaxies and low-level x-ray fluctuations at the same positions in multiple deep Einstein HRI observations in PAVO and in a ROSAT PSPC field were searched for. Our aim is to test the hypothesis that faint 'star burst' galaxies might contribute significantly to the cosmic x-ray background (at approximately 1 keV).

The effect of unresolved contaminant stars on the cross-matching of photometric catalogues

NASA Astrophysics Data System (ADS)

Wilson, Tom J.; Naylor, Tim

2017-07-01

A fundamental process in astrophysics is the matching of two photometric catalogues. It is crucial that the correct objects be paired, and that their photometry does not suffer from any spurious additional flux. We compare the positions of sources in Wide-field Infrared Survey Explorer (WISE), INT Photometric H α Survey, Two Micron All Sky Survey and AAVSO Photometric All Sky Survey with Gaia Data Release 1 astrometric positions. We find that the separations are described by a combination of a Gaussian distribution, wider than naively assumed based on their quoted uncertainties, and a large wing, which some authors ascribe to proper motions. We show that this is caused by flux contamination from blended stars not treated separately. We provide linear fits between the quoted Gaussian uncertainty and the core fit to the separation distributions. We show that at least one in three of the stars in the faint half of a given catalogue will suffer from flux contamination above the 1 per cent level when the density of catalogue objects per point spread function area is above approximately 0.005. This has important implications for the creation of composite catalogues. It is important for any closest neighbour matches as there will be a given fraction of matches that are flux contaminated, while some matches will be missed due to significant astrometric perturbation by faint contaminants. In the case of probability-based matching, this contamination affects the probability density function of matches as a function of distance. This effect results in up to 50 per cent fewer counterparts being returned as matches, assuming Gaussian astrometric uncertainties for WISE-Gaia matching in crowded Galactic plane regions, compared with a closest neighbour match.

Hubble Space Telescope: Faint object spectrograph instrument handbook. Version 1.1

NASA Technical Reports Server (NTRS)

Ford, Holland C. (Editor)

1990-01-01

The Faint Object Spectrograph (FOS) has undergone substantial rework since the 1985 FOS Instrument Handbook was published, and we are now more knowledgeable regarding the spacecraft and instrument operations requirements and constraints. The formal system for observation specification has also evolved considerably, as the GTO programs were defined in detail. This supplement to the FOS Instrument Handbook addresses the important aspects of these changes, to facilitate proper selection and specification of FOS observing programs. Since the Handbook was published, the FOS red detector has been replaced twice, first with the best available spare in 1985 (which proved to have a poor, and steadily degrading red response), and later with a newly developed Digicon, which exhibits a high, stable efficiency and a dark-count rate less than half that of its predecessors. Also, the FOS optical train was realigned in 1987-88 to eliminate considerable beam-vignetting losses, and the collimators were both removed and recoated for greater reflectivity. Following the optics and detector rework, the FOS was carefully recalibrated (although only ambient measurements were possible, so the far-UV characteristics could not be re-evaluated directly). The resulting efficiency curves, including improved estimates of the telescope throughput, are shown. A number of changes in the observing-mode specifications and addition of several optional parameters resulted as the Proposal Instructions were honed during the last year. Target-brightness limitations, which have only recently been formulated carefully, are described. Although these restrictions are very conservative, it is imperative that the detector safety be guarded closely, especially during the initial stages of flight operations. Restrictions on the use of the internal calibration lamps and aperture-illumination sources (TA LEDs), also resulting from detector safety considerations, are outlined. Finally, many changes have been made to the instructions for target acquisition specification.

Central Stars of Planetary Nebulae in the LMC

NASA Technical Reports Server (NTRS)

Bianchi, Luciana

2004-01-01

In FUSE cycle 2's program B001 we studied Central Stars of Planetary Nebulae (CSPN) in the Large Magellanic Could. All FUSE observations have been successfully completed and have been reduced, analyzed and published. The analysis and the results are summarized below. The FUSE data were reduced using the latest available version of the FUSE calibration pipeline (CALFUSE v2.2.2). The flux of these LMC post-AGB objects is at the threshold of FUSE's sensitivity, and thus special care in the background subtraction was needed during the reduction. Because of their faintness, the targets required many orbit-long exposures, each of which typically had low (target) count-rates. Each calibrated extracted sequence was checked for unacceptable count-rate variations (a sign of detector drift), misplaced extraction windows, and other anomalies. All the good calibrated exposures were combined using FUSE pipeline routines. The default FUSE pipeline attempts to model the background measured off-target and subtracts it from the target spectrum. We found that, for these faint objects, the background appeared to be over-estimated by this method, particularly at shorter wavelengths (i.e., < 1000 A). We therefore tried two other reductions. In the first method, subtraction of the measured background is turned off and and the background is taken to be the model scattered-light scaled by the exposure time. In the second one, the first few steps of the pipeline were run on the individual exposures (correcting for effects unique to each exposure such as Doppler shift, grating motions, etc). Then the photon lists from the individual exposures were combined, and the remaining steps of the pipeline run on the combined file. Thus, more total counts for both the target and background allowed for a better extraction.

A LUMINOUS, FAST RISING UV-TRANSIENT DISCOVERED BY ROTSE: A TIDAL DISRUPTION EVENT?

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

Vinkó, J.; Wheeler, J. C.; Chatzopoulos, E.

2015-01-01

We present follow-up observations of an optical transient (OT) discovered by ROTSE on 2009 January 21. Photometric monitoring was carried out with ROTSE-IIIb in the optical and Swift in the UV up to +70 days after discovery. The light curve showed a fast rise time of ∼10 days followed by a steep decline over the next 60 days, which was much faster than that implied by {sup 56}Ni—{sup 56}Co radioactive decay. The Sloan Digital Sky Survey Data Release 10 database contains a faint, red object at the position of the OT, which appears slightly extended. This and other lines ofmore » evidence suggest that the OT is of extragalactic origin, and this faint object is likely the host galaxy. A sequence of optical spectra obtained with the 9.2 m Hobby-Eberly Telescope between +8 and +45 days after discovery revealed a hot, blue continuum with no visible spectral features. A few weak features that appeared after +30 days probably originated from the underlying host. Fitting synthetic templates to the observed spectrum of the host galaxy revealed a redshift of z = 0.19. At this redshift, the peak magnitude of the OT is close to –22.5, similar to the brightest super-luminous supernovae; however, the lack of identifiable spectral features makes the massive stellar death hypothesis less likely. A more plausible explanation appears to be the tidal disruption of a Sun-like star by the central supermassive black hole. We argue that this transient likely belongs to a class of super-Eddington tidal disruption events.« less

Investigating the Bright End of LSST Photometry

NASA Astrophysics Data System (ADS)

Ojala, Elle; Pepper, Joshua; LSST Collaboration

2018-01-01

The Large Synoptic Survey Telescope (LSST) will begin operations in 2022, conducting a wide-field, synoptic multiband survey of the southern sky. Some fraction of objects at the bright end of the magnitude regime observed by LSST will overlap with other wide-sky surveys, allowing for calibration and cross-checking between surveys. The LSST is optimized for observations of very faint objects, so much of this data overlap will be comprised of saturated images. This project provides the first in-depth analysis of saturation in LSST images. Using the PhoSim package to create simulated LSST images, we evaluate saturation properties of several types of stars to determine the brightness limitations of LSST. We also collect metadata from many wide-field photometric surveys to provide cross-survey accounting and comparison. Additionally, we evaluate the accuracy of the PhoSim modeling parameters to determine the reliability of the software. These efforts will allow us to determine the expected useable data overlap between bright-end LSST images and faint-end images in other wide-sky surveys. Our next steps are developing methods to extract photometry from saturated images.This material is based upon work supported in part by the National Science Foundation through Cooperative Agreement 1258333 managed by the Association of Universities for Research in Astronomy (AURA), and the Department of Energy under Contract No. DE-AC02-76SF00515 with the SLAC National Accelerator Laboratory. Additional LSST funding comes from private donations, grants to universities, and in-kind support from LSSTC Institutional Members.Thanks to NSF grant PHY-135195 and the 2017 LSSTC Grant Award #2017-UG06 for making this project possible.

Ionized and Neutral Outflows in the QUEST QSOs

NASA Astrophysics Data System (ADS)

Veilleux, Sylvain

2011-10-01

The role of galactic winds in gas-rich mergers is of crucial importance to understand galaxy and SMBH evolution. In recent months, our group has had three major scientific breakthroughs in this area: {1} The discovery with Herschel of massive molecular {OH-absorbing} outflows in several ULIRGs, including the nearest quasar, Mrk 231. {2} The independent discovery from mm-wave interferometric observations in the same object of a spatially resolved molecular {CO-emitting} wind with estimated mass outflow rate 3x larger than the star formation rate and spatially coincident with blueshifted neutral {Na ID-absorbing} gas in optical long-slit spectra. {3} The unambiguous determination from recent Gemini/IFU observations that the Na ID outflow in this object is wide-angle, thus driven by a QSO wind rather than a jet. This powerful outflow may be the long-sought "smoking gun" of quasar mechanical feedback purported to transform gas-rich mergers. However, our Herschel survey excludes all FIR-faint {UV-bright} "classic" QSOs by necessity. So here we propose a complementary FUV absorption-line survey of all FIR-bright -and- FIR-faint QSOs from the same parent sample. New {19 targets} and archival {11} spectra will be used to study, for the first time, the gaseous environments of QSOs as a function of host properties and age across the merger sequence ULIRG -> QSO. These data will allow us to distinguish between ionized & neutral quasar-driven outflows, starburst-driven winds, and tidal debris around the mergers. They will also be uniquely suited for a shallow but broad study of the warm & warm-hot intergalactic media, complementary to on-going surveys that are deeper but narrower.

The radio properties of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

2011-02-01

Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

Clinical Presentation of Acute Pulmonary Embolism: Survey of 800 Cases

PubMed Central

Miniati, Massimo; Cenci, Caterina; Monti, Simonetta; Poli, Daniela

2012-01-01

Background Pulmonary embolism (PE) is a common and potentially fatal disease that is still underdiagnosed. The objective of our study was to reappraise the clinical presentation of PE with emphasis on the identification of the symptoms and signs that prompt the patients to seek medical attention. Methodology/Principal Findings We studied 800 patients with PE from two different clinical settings: 440 were recruited in Pisa (Italy) as part of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISAPED); 360 were diagnosed with and treated for PE in seven hospitals of central Tuscany, and evaluated at the Atherothrombotic Disorders Unit, Firenze (Italy), shortly after hospital discharge. We interviewed the patients directly using a standardized, self-administered questionnaire originally utilized in the PISAPED. The two samples differed significantly as regards age, proportion of outpatients, prevalence of unprovoked PE, and of active cancer. Sudden onset dyspnea was the most frequent symptom in both samples (81 and 78%), followed by chest pain (56 and 39%), fainting or syncope (26 and 22%), and hemoptysis (7 and 5%). At least one of the above symptoms was reported by 756 (94%) of 800 patients. Isolated symptoms and signs of deep vein thrombosis occurred in 3% of the cases. Only 7 (1%) of 800 patients had no symptoms before PE was diagnosed. Conclusions/Significance Most patients with PE feature at least one of four symptoms which, in decreasing order of frequency, are sudden onset dyspnea, chest pain, fainting (or syncope), and hemoptysis. The occurrence of such symptoms, if not explained otherwise, should alert the clinicians to consider PE in differential diagnosis, and order the appropriate objective test. PMID:22383978

Establishing a Network of faint DA white dwarfs as Spectrophotometric Standards

NASA Astrophysics Data System (ADS)

Saha, Abhijit; Narayan, Gautham; Holberg, Jay; Matheson, Thomas; Olszewski, Edward; Stubbs, Christopher; Bohlin, Ralph; Sabbi, Elena; Deustua, Susana; Rest, Armin; Axelrod, Tim; MacKenty, John W.; Camarota, Larry; Gilliland, Ron

2015-08-01

Systematic uncertainties in photometric calibration are the dominant source of error in current type Ia supernova dark energy studies, as well as other forefront cosmology efforts, e.g. photo-redshift determinations for weak lensing mass tomography. Current and next-generation ground-based all-sky surveys require a network of calibration stars with 1) known SEDs (to properly and unambiguously take into account filter differences), and 2) that are on a common photometric zeropoint scale across the sky to sub-percent accuracy. We are using a combination of HST panchromatic photometry and ground based spectroscopy to establish such an essential network of faint primary photometric standards, exploiting the well-understood spectral energy distributions of DA white dwarf stars that are free from the complications of observing through the Earth's time-variable atmosphere. The Balmer features in the spectra are used to deduce the two parameters (temperature and log(g)) from which we model the spectral energy distribution (SED) from these stars which have pure hydrogen atmospheres. By comparing against panchromatic broadband HST photometry, and allowing for an achromatic zero-point adjustment and mild scaling of the interstellar reddening, we find that model prediction and observation agree to a few milli-mag. By combining the zero-point and reddening adjustments with the modeled SED, for each star we obtain the incident SED above the terrestrial atmosphere, thus establishing these objects as spectrophotometric standards. We are pursuing 23 objects between 16 and 19 mag spread over the sky uniformly around the equator and northern mid-latitudes, with plans to extend this to southern latitudes. This precision photometric heritage from HST will benefit essentially all existing and upcoming survey projects, and in prticular, directly addresses one of the current barriers to understanding the nature of dark energy.

The possible nature of socket stars in H II regions

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

Castelaz, M.W.

1990-01-01

Close inspection of faint stars (V of about 14 mag) in H II regions show that they appear to be surrounded by circumstellar envelopes of about 10 arcsecs in diameter (as reported by Feibelman in 1989). The present premise is that the sockets are envelopes of obscuring dust which should emit a measurable amount of infrared radiation based on a simple thermal equilibrium model. A search of literature shows that, of 36 socket stars listed by Feibelman, 17 have been measured in the infrared. Of the 17, 14 show excess IR emission. This is very strong evidence that the socketmore » stars are really stars with circumstellar envelopes. Socket stars may be a new type of astronomical object or well-known astronomical objects in environments or evolutionary states not previously seen. 22 refs.« less

1WHSP: An IR-based sample of ~1000 VHE γ -ray blazar candidates

DOE PAGES

Arsioli, B.; Fraga, B.; Giommi, P.; ...

2015-06-23

Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E > ≳ 100 GeV) a large fraction of high Galactic latitude sources are blazars of the High Synchrotron Peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims. HSP blazars are remarkably rare,more » with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods. The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray) we estimated synchrotron peak frequencies and fluxes of each object. Results. We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no optical spectra is available yet. The full 1WHSP catalogue is on-line at http://www.asdc.asi.it/1whsp/ providing a direct link to the SED building tool where multifrequency data for each source can be easily visualised.« less

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 M. Brown, Charles W. Bowers, Randy A. Kimble, Allen V. Sweigart (NASA Goddard Space Flight Center) and Henry C. Ferguson (Space Telescope Science Institute).

The radio spectral energy distribution of infrared-faint radio sources

NASA Astrophysics Data System (ADS)

Herzog, A.; Norris, R. P.; Middelberg, E.; Seymour, N.; Spitler, L. R.; Emonts, B. H. C.; Franzen, T. M. O.; Hunstead, R.; Intema, H. T.; Marvil, J.; Parker, Q. A.; Sirothia, S. K.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Callingham, J. R.; Deshpande, A. A.; Dwarakanath, K. S.; For, B.-Q.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Kaplan, D. L.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S. M.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Zheng, Q.; Bannister, K. W.; Chippendale, A. P.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R. J.; Whiting, M. T.

2016-10-01

Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z ≥ 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims: Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods: We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results: We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (α < -0.8; %), but we also find ultra-steep SEDs (α < -1.3; %). In particular, IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least % of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi-wavelength SED modelling of one IFRS shows that it is different from ordinary AGN, although it is consistent with a composite starburst-AGN model with a star formation rate of 170 M⊙ yr-1. Based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

The Gamma-Ray Bright BL Lac Object RX J1211+2242

NASA Technical Reports Server (NTRS)

Beckmann, V.; Favre, P.; Tavecchio, F.; Bussien, T.; Fliri, J.; Wolter, A.

2004-01-01

RX J1211+2242 is an optically faint (B approximately equal to 19.2mag) but X-ray bright (f2-10kev = 5 x l0(exp -12)erg per square centimeter per second) AGN, which has been shown to be a BL Lac object at redshift z = 0.455. The ROSAT X-ray, Calar Alto optical, and NVSS radio data suggest that the peak of the synchrotron emission of this object is at energies as high as several keV. BeppoSAX observations have been carried out simultaneously with optical observations in order to extend the coverage to higher energies. The new data indeed indicate a turn-over in the 2 - 10keV energy region. We propose that RX J1211+2242 is the counterpart of the unidentified EGRET source 3EG J1212+2304, making it a gamma-ray emitter with properties similar to, for example, Markarian 501 in its bright state, though being at a much larger distance.

The near-infrared counterpart of a variable galactic plane radio source

NASA Technical Reports Server (NTRS)

Margon, Bruce; Phillips, Andrew C.; Ciardullo, Robin; Jacoby, George H.

1992-01-01

A near-infrared counterpart to the highly variable, unresolved galactic plane radio source GT 0116 + 622 is identified. This source is of particular interest, as it has been previously suggested to be the counterpart of the gamma-ray source Cas gamma-l. The present NIR and red images detect a faint, spatially extended (3 arcsec FWHM), very red object coincident with the radio position. There is complex spatial structure which may be due in part to an unrelated superposed foreground object. Observations on multiple nights show no evidence for flux variability, despite the high amplitude variability on a time-scale of days reported for the radio source. The data are consistent with an interpretation of GT 0116 + 622 as an unusually variable, obscured active galaxy at a distance of several hundred megaparsecs, although more exotic, and in particular galactic, interpretations cannot yet be ruled out. If the object is extragalactic, the previously suggested identification with the gamma-ray source would seem unlikely.

The structure of the inner arcsecond of R Aquarii observed with the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Burgarella, Denis; Paresce, Francesco

1992-01-01

The inner arcsec of R Aquarii has been observed with the Faint Object Camera on the Hubble Space Telescope. A simple and reliable linear deconvolution method is used to resolve the two features, designated C1 and C2 from radio observations, into several condensations. C1 is composed of four objects, designated C1a, C1b located at 0.099 arcsec from C1a, C3 at 0.162 arcsec from C1a, and C4 at 0.137 arcsec from C1a. The source C3, detected at 2 cm in the radio and in H-alpha, might be the V = 6-11 Mira variable. The nature of feature C4 is still unknown. Features C1a and C1b have not been resolved by another instrument, and it might be possible that the hot star is one of the two or a nearby nondetected object.

VizieR Online Data Catalog: CANDID code for interferometric observations (Gallenne+, 2015)

NASA Astrophysics Data System (ADS)

Gallenne, A.; Merand, A.; Kervella, P.; Monnier, J. D.; Schaefer, G. H.; Baron, F.; Breitfelder, J.; Le Bouquin, J. B.; Roettenbacher, R. M.; Gieren, W.; Pietrzynski, G.; McAlister, H.; Ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Ridgway, S.; Kraus, S.

2015-07-01

This is a suite of Python2.7 tools to find faint companion around star in interferometric data in the OIFITS format. This tool allows to systematically search for faint companions in OIFITS data, and if not found, estimates the detection limit. All files are also available at https://github.com/amerand/CANDID . (3 data files).

An ultra-faint galaxy candidate discovered in early data from the Magellanic Satellites Survey

DOE PAGES

Drlica-Wagner, A.; Bechtol, Keith; Allam, S.; ...

2016-11-30

Here, we report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644–5953 (Pictor II or Pic II) is a low surface brightness (more » $$\\mu ={28.5}_{-1}^{+1}\\,\\mathrm{mag}\\,\\,\\mathrm{arcsec}{}^{-2}$$ within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of $${45}_{-4}^{+5}\\,\\mathrm{kpc}$$. The physical size ($${r}_{1/2}={46}_{-11}^{+15}\\,\\mathrm{pc}\\,$$) and low luminosity ($${M}_{V}=-{3.2}_{-0.5}^{+0.4}\\,\\mathrm{mag}\\,$$) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644–5953 (Pic II) is located $${11.3}_{-0.9}^{+3.1}\\,\\mathrm{kpc}\\,$$ from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644–5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.« less

An ultra-faint galaxy candidate discovered in early data from the Magellanic Satellites Survey

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

Drlica-Wagner, A.; Bechtol, Keith; Allam, S.

Here, we report a new ultra-faint stellar system found in Dark Energy Camera data from the first observing run of the Magellanic Satellites Survey (MagLiteS). MagLiteS J0644–5953 (Pictor II or Pic II) is a low surface brightness (more » $$\\mu ={28.5}_{-1}^{+1}\\,\\mathrm{mag}\\,\\,\\mathrm{arcsec}{}^{-2}$$ within its half-light radius) resolved overdensity of old and metal-poor stars located at a heliocentric distance of $${45}_{-4}^{+5}\\,\\mathrm{kpc}$$. The physical size ($${r}_{1/2}={46}_{-11}^{+15}\\,\\mathrm{pc}\\,$$) and low luminosity ($${M}_{V}=-{3.2}_{-0.5}^{+0.4}\\,\\mathrm{mag}\\,$$) of this satellite are consistent with the locus of spectroscopically confirmed ultra-faint galaxies. MagLiteS J0644–5953 (Pic II) is located $${11.3}_{-0.9}^{+3.1}\\,\\mathrm{kpc}\\,$$ from the Large Magellanic Cloud (LMC), and comparisons with simulation results in the literature suggest that this satellite was likely accreted with the LMC. The close proximity of MagLiteS J0644–5953 (Pic II) to the LMC also makes it the most likely ultra-faint galaxy candidate to still be gravitationally bound to the LMC.« less

The Faint End of the Lyman Alpha Luminosity Function at 2 < z < 3.8

NASA Astrophysics Data System (ADS)

Devarakonda, Yaswant; Livermore, Rachael; Indahl, Briana; Wold, Isak; Davis, Dustin; Finkelstein, Steven

2018-01-01

Most current models predict that our universe is mostly composed of small, dim galaxies. Due to these galaxies being so faint, it is very difficult to study these types of galaxies outside of our local universe. This is particularly an issue for studying how these small galaxies evolved over their lifetimes. With the benefit of gravitational lensing, however, we are able to observe galaxies that are farther and fainter than ever before possible. In this particular study, we focus on Lyman-Alpha emitting galaxies between the redshifts of 2-3.8, so that we may study these galaxies during the epoch of peak star formation in the universe. We use the McDonald Observatory 2.7, Harlan Smith telescope with the VIRUS-P IFU spectrograph to observe several Hubble Frontier Field lensing clusters to spectroscopically discover faint galaxies over this redshift range. In addition to providing insight into the faint-end slope of the Lyman alpha luminosity function, the spectroscopic redshifts will allow us to better constrain the mass models of the foreground clusters, such as Abell 370, so that we may better understand lensing effects for this and future studies.

RX J1548.9+0851, a fossil cluster?

NASA Astrophysics Data System (ADS)

Eigenthaler, P.; Zeilinger, W. W.

2012-04-01

Context. Fossil galaxy groups are spatially extended X-ray sources with X-ray luminosities above L{X, bol ≥ 1042 h50-2} erg s-1 and a central elliptical galaxy dominating the optical, the second-brightest galaxy being at least 2 mag fainter in the R band. Whether these systems are a distinct class of objects resulting from exceptional formation and evolution histories is still unclear, mainly due to the small number of objects studied so far, mostly lacking spectroscopy of group members for group membership confirmation and a detailed kinematical analysis. Aims: To complement the scarce sample of spectroscopically studied fossils down to their faint galaxy populations, the fossil candidate RX J1548.9+0851 (z = 0.072) is studied in this work. Our results are compared with existing data from fossils in the literature. Methods: We use ESO VLT VIMOS multi-object spectroscopy to determine redshifts of the faint galaxy population and study the luminosity-weighted dynamics and luminosity function of the system. The full-spectrum fitting package ULySS is used to determine ages and metallicities of group members. VIMOS imaging data are used to study the morphology of the central elliptical. Results: We identify 40 group members spectroscopically within the central 300 kpc of the system and find 31 additional redshifts from the literature, resulting in a total number of 54 spectroscopically confirmed group members within 1 Mpc. RX J1548.9+0851 is made up of two bright ellipticals in the central region with a magnitude gap of Δm1,2 = 1.34 in the SDSS r' band leaving the definition of RX J1548.9+0851 being a fossil to the assumption of the virial radius. We find a luminosity-weighted velocity dispersion of 568 km s-1 and a mass of 2.5 × 1014 M⊙ for the system confirming previous studies that revealed fossils to be massive. An average mass-to-light ratio of M/L 400 M⊙/L⊙ is derived from the SDSS g', r', and i' bands. The central elliptical is well-fitted by a pure deVaucouleurs r1/4 law without a cD envelope. Symmetric shells are revealed along the major axis of the galaxy indicating a recent minor merger. RX J1548.9+0851 shows a steep, increasing luminosity function with a faint-end slope of α = -1.4 ± 0.1. Satellite galaxies show a clear spatial segregation with respect to their stellar populations - objects with old stars are confined to an elongated, central distribution aligned with the major axis of the central elliptical. Conclusions: Although RX J1548.9+0851 shows similar properties compared to other fossils studied recently, it might not be a fossil at all, being dominated by 2 bright central ellipticals. Comparing RX J1548.9+0851 with scaling relations from ordinary poor groups and clusters confirm the idea that fossils might simply be normal clusters with the richness and optical luminosity of poor groups.

Applications of independent component analysis in SAR images

NASA Astrophysics Data System (ADS)

Huang, Shiqi; Cai, Xinhua; Hui, Weihua; Xu, Ping

2009-07-01

The detection of faint, small and hidden targets in synthetic aperture radar (SAR) image is still an issue for automatic target recognition (ATR) system. How to effectively separate these targets from the complex background is the aim of this paper. Independent component analysis (ICA) theory can enhance SAR image targets and improve signal clutter ratio (SCR), which benefits to detect and recognize faint targets. Therefore, this paper proposes a new SAR image target detection algorithm based on ICA. In experimental process, the fast ICA (FICA) algorithm is utilized. Finally, some real SAR image data is used to test the method. The experimental results verify that the algorithm is feasible, and it can improve the SCR of SAR image and increase the detection rate for the faint small targets.

Comet Halley passes the halfway mark. Very distant image obtained with the ESO NTT.

NASA Astrophysics Data System (ADS)

1994-02-01

Eight years after the passage of Comet Halley in early 1986, astronomers at the European Southern Observatory have succeeded in obtaining an image [1] of this famous object at a distance of no less than 2,820 million km from the Sun. The comet is now about as far away as giant planet Uranus. It recently passed the halfway mark towards the most distant point of its very elongated 76-year orbit. The image shows the 6 x 15 km avocado-shaped nucleus as an extremely faint point of light without any surrounding dust cloud. It appears that the surface is now completely frozen and the comet has ceased to emit dust and gas. This observation was made with the ESO 3.58 metre New Technology Telescope (NTT). It is by far the faintest and most distant image ever recorded of this comet. A DIFFICULT OBSERVATION The new Halley image was obtained in the course of an observational programme by a small group of astronomers [2], aimed at the investigation of distant solar system objects. The observation was difficult to perform and is close to the limit of what is possible, even with the NTT, one of the technologically most advanced astronomical telescopes. In fact, this observation may be compared to viewing a black golfball, used during a late evening game, from a distance of 12,000 km. At Halley's present, very large distance from the Sun, the intensity of the solar light is over 350 times fainter than here on Earth. The surface of the cometary nucleus is very dark; it reflects only 4 % of the infalling sunlight. The amount of light received from Halley is therefore extremely small: the recorded star-like image of the nucleus is about 160 million times fainter than the faintest star that can be seen with the unaided eye. A long exposure was needed to catch enough light to show the object; even with the very sensitive SuSI CCD camera at the NTT, the shutter had to be kept open for a total of 3 hours 45 minutes. During this time, of the order of 9000 photons from Comet Halley were registered. The extreme faintness of its image is illustrated by the fact that almost 1 million, or 100 times as many photons were simultaneously received in this direction from the luminous atmosphere of the Earth. They must be carefully "subtracted", before the comet can be seen. There is another complication. Due to the motions of the comet and the Earth, the direction to the comet (as seen against the stars in the background) continuously changes during the observation. The movement of the telescope must therefore be accurately offset to "follow" the motion of the comet in order to keep the sparse photons falling on the same spot of the detector during the long exposure. IS HALLEY NOW FROZEN? The measured brightness of the Halley image (visual magnitude 26.5 +- 0.2) closely corresponds to what would be expected, if it results from sunlight being reflected from the nucleus alone. This indicates that there is little, if any, dust left around the nucleus and it must be assumed that its surface layers are now completely frozen. The observation therefore shows that nothing is left of the great mass of dusty material, estimated at 1 million tonnes, that was thrown out during the completely unexpected outburst observed at ESO in February 1991. Nevertheless, the astronomers intend to continue to monitor the behaviour of Halley during the next years - it cannot be excluded that this comet may be good for another surprise! FUTURE OBSERVATIONS WITH THE VLT Comet Halley will continue to move outwards through the solar system at decreasing speed. Thirty years from now it reaches the turning point (the "aphelion") of its elongated orbit, almost 5,300 million kilometres from the Sun. Although the light reflected from its nucleus will then be 15 times fainter than at the present time, it should still be possible to register its image with one of the 8.2 metre unit telescopes of the ESO Very Large Telescope (VLT) during exposures of only a few hours' duration. Comet Halley's next return to our neighbourhood will take place in the year 2061. 1 A B/W photo accompanies this Press Release. 2 The members are Olivier Hainaut and Richard West (ESO), Brian Marsden (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, U.S.A.) and Karen Meech (Institute for Astronomy, Honolulu, Hawaii, U.S.A.). The Halley observation is also described on a Circular of the International Astronomical Union, published today. 3 See ESO Press Release 03/91 of 22 February 1991. FIGURE CAPTION ESO PR PHOTO 04/94-1: COMET HALLEY AT 2,820 MILLION KM This negative photo shows the faint image of periodic comet Halley (in the circle) at the record heliocentric distance 18.82 AU (= 2,820 million km, about the distance of Uranus). It was obtained with the SuSI CCD camera at the ESO 3.58 m New Technology Telescope (NTT) during the night of January 10--11, 1994. Nine individual exposures, each lasting 25 minutes, were used to produce this picture. They were cleaned to remove various sky and instrumental noise, shifted according to the predicted motion of the comet and then co-added. This ensures that all recorded light from the comet is concentrated in one place. At the same time, the images of the other objects that do not share the motion of the comet, are not superposed and will therefore be seen as long trails. The non-uniformities of these trails arise because of varying sky conditions and also due to the time intervals between the individual exposures. In addition to the comet, the picture contains the images of three very different types of objects: stars with relatively sharp trails (e.g. the comparatively bright one, just below the comet image), several extended (diffuse) galaxies, and an artificial Earth satellite which happened to cross the field during one of the exposures (its trail extends from the middle of the left edge to the lower edge). The measured magnitude of P/Halley is V = 26.5 +-0.2. The position in the sky is less than 1 arcsec from that predicted on the basis of the comet's very well-determined orbit. Technical information: The CCD frames were cleaned of cosmics and flat-fielded, but they were neither filtered, nor smoothed. Total exposure time: 13,500 seconds. The seeing varied from 0.6 - 0.9 arcsec. One pixel = 0.13 arcsec. Field size: 310 x 430 pixels or 40 x 56 arcsec. North is up and East is to the left. This photo (ESO PR PHOTO 04/94-1) accompanies ESO Press Release 04/94 and may be reproduced, if credit is given to the European Southern Observatory.