This week on HST

HST Programs: October 24, 2011 - October 30, 2011

Program Number Principal Investigator Program Title
12038 James C. Green, University of Colorado at Boulder COS-GTO: COOL, WARM AND HOT GAS IN THE COSMIC WEB AND IN GALAXY HALOS Part 2
12041 James C. Green, University of Colorado at Boulder COS-GTO: Io Atmosphere/STIS
12067 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12101 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12103 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12170 Avishay Gal-Yam, Weizmann Institute of Science A direct UV search for the progenitor of the nearby type Ib SN 2007fo
12177 Pieter van Dokkum, Yale University 3D-HST: A Spectroscopic Galaxy Evolution Treasury
12190 Anton M. Koekemoer, Space Telescope Science Institute WFC3/IR Spectroscopy of the Highest Redshift Black Hole Candidates
12248 Jason Tumlinson, Space Telescope Science Institute How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L*
12278 Thomas R. Ayres, University of Colorado at Boulder Advanced Spectral Library Project: Cool Stars
12286 Hao-Jing Yan, University of Missouri - Columbia Hubble Infrared Pure Parallel Imaging Extragalactic Survey {HIPPIES}
12301 Sarah Gallagher, The University of Western Ontario Precision Age-Dating of Star Clusters in Stephan's Quintet
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12322 Kailash C. Sahu, Space Telescope Science Institute Detecting Isolated Black Holes through Astrometric Microlensing
12474 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs
12486 David V. Bowen, Princeton University QSO Absorption Line Systems from Dwarf Galaxies
12488 Mattia Negrello, Open University SNAPshot observations of gravitational lens systems discovered via wide-field Herschel imaging
12499 Daniel J. Lennon, Space Telescope Science Institute - ESA Proper Motions of Massive Stars in 30 Doradus
12500 Sugata Kaviraj, Imperial College of Science Technology and Medicine High-resolution UV studies of SAURON galaxies with WFC3: constraining recent star formation and its drivers in local early-type galaxies
12502 Andrew S. Fruchter, Space Telescope Science Institute From the Locations to the Origins of Short Gamma-Ray Bursts
12515 Dougal Mackey, Australian National University Probing the outer limits of a galactic halo - deep imaging of exceptionally remote globular clusters in M31
12521 Xin Liu, Harvard University The Frequency and Demographics of Dual Active Galactic Nuclei
12533 Crystal Martin, University of California - Santa Barbara Escape of Lyman-Alpha Photons from Dusty Starbursts
12547 Michael Cooper, University of California - Irvine Measuring the Star-Formation Efficiency of Galaxies at z > 1 with Sizes and SFRs from HST Grism Spectroscopy
12557 Kayhan Gultekin, University of Michigan Low-Mass Black Holes and CIV in Low-Luminosity AGN
12565 Ruth Peterson, SETI Institute Primordial Carbon Abundances in Extremely Metal-Poor Stars
12568 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12569 Sylvain Veilleux, University of Maryland Ionized and Neutral Outflows in the QUEST QSOs
12572 Michele Trenti, University of Colorado at Boulder The Brightest of Reionizing Galaxies Pure Parallel Survey
12586 Kailash C. Sahu, Space Telescope Science Institute Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing
12593 Daniel B. Nestor, University of California - Los Angeles A Survey of Atomic Hydrogen at 0.2 < z < 0.4
12613 Knud Jahnke, Max-Planck-Institut fur Astronomie, Heidelberg Are major galaxy mergers a significant mechanism to trigger massive black hole growth at z=2?

Selected highlights

GO 12103: Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos

The cluster MACS J1206.2-0.47, imaged by HST as part of the CLASH program
The overwhelming majority of galaxies in the universe are found in clusters. As such, these systems offer an important means of tracing the development of large-scale structure through the history of the universe. Moreover, as intense concentrations of mass, galaxy clusters provide highly efficient gravitational lenses, capable of concentrating and magnifying light from background high redshift galaxies to allow detailed spectropic investigations of star formation in the early universe. Hubble imaging has already revealed lensed arcs and detailed sub-structure within a handful of rich clusters. At the same time, the lensing characteristics provide information on the mass distribution within the lensing cluster. The present program aims to capitalise fully on HST's imaging capabilities, utilising the refurbished Advanced Camera for Surveys and the newly-installed Wide-Field Camera 3 to obtain 17-colour imaging of 25 rich clusters. The data will be use to map the mass profiles of the clusters and probe the characteristics of the high-redshift lensed galaxies. Since ACS and WFC3 can be operated in parallel, the program will also use parallel imaging in offset fields to search for high-redshift supernovae. The present observations target the cluster MACS 0717+3745.

GO 12248: How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L*

A computer simulation of galactic gas accretion and outflow
Galaxy formation, and star formation within a galaxy, requires the presence of gas. The detailed evolution of individual galactic systems therefore depends on how gas is accreted, recycled, circulated through the halo and, perhaps, ejected back into the intergalactic medium. Tracing that evolutionary history is difficult, since gas passes through many different phases, some of which are easier to detect than others. During accretion and, probably, subsequent recycling, the gas is expected to be reside predominantly at high temperatures. The most effective means of detecting such gas is through ultraviolet spectroscopy, where gas within nearby systems can be detected as absorption lines superimposed on the spectra of more distant objects, usually quasars. The present program is using the Cosmic Origins Spectrograph to observe low- to moderate redshift QSOs (0.1 < z < 1) that lie at small angular separations from sub-L* mass galaxies (0.02 < M/L* < 0.3) at redshifts between z=0.01 and 0.06. The sightlines run through the halos of the galaxies, and the QSOs therefore provide a pencilbeam backlight that probes hot gas in the foreground systems.

GO 12301: Precision Age-dating of Star Clusters in Stephan's Quintet

HST WFC3 images of four of the five galaxies in Stephan's quintet: the foreground galaxy is to the upper left
Stephan's Quintet is a striking grouping of five moderately sized galaxies in the constellation of Pegasus. It is named after its discoverer, Edouard Stephan of Marseille Observatory, who catalogued the system in 1877, and is the archetypical example of a "compact group". In fact, only four of the five galaxies are actually physically associated, with radial velocities close to ~6600 km/sec, implying distances of ~90 Mpc. Those four galaxies have similar morphological characteristics, with reddish-hued bulge components.NGC 7317, at the bottom left of the image, shows little evidence for ongoing star formation. However, the pair of galaxies at the upper right, NC 7318A and 7318B, are clearly more active which, with the presence of tidal features, is a likely indicator of gravitational interactions. The fifth galaxy in the group, and the fourth in the present image, NGC 7320, is the largest in apparent size, has a radial velocity of only 790 km/sec, indicating that it lies much closer, at a distance of ~10 Mpc. That galaxy shows an abundance of young clusters and HII regions. These galaxies were targeted for observation by Wide Field Camera 3 as part of the Early Release Observations following Servicing Mission 4, resulting in the image shown above.Those images use observations with the F438W (B), F606W (V/R), F665N (H-alpha) and F814W (I) filters on the WFC3 UVIS channel. The present program aims to capitalise on those data, adding observations with the F336W (U) and F547M (V) filters; the latter filter explicitly excludes emission due to H-alpha.

GO 12474: The frequency and chemical composition of rocky planetary debris around young white dwarfs

Artist's impression of a comet spiralling in to the white dwarf variable, G29-38 During the 1980s, one of the techniques used to search for brown dwarfs was to obtain near-infrared photometry of white dwarf stars. Pioneered by Ron Probst (KPNO), the idea rests on the fact that while white dwarfs are hot (5,000 to 15,000K for the typcail targets0, they are also small (Earth-sized), so they have low luminosities; consequently, a low-mass companion should be detected as excess flux at near- and mid-infrared wavelengths. In 1988, Ben Zuckerman and Eric Becklin detected just this kind of excess around G29-38, a relatively hot DA white dwarf that also happens to lie on the WD instability strip. However, follow-up observations showed that the excess peaked at longer wavelengths than would be expected for a white dwarf; rather, G 29-38 is surrounded by a dusty disk. Given the orbital lifetimes, those dust particles must be regularly replenished, presumably from rocky remnants of a solar system. G 29-38 stood as a lone prototype for almost 2 decades, until a handful of other dusty white dwarfs were identified from Spitzer observations within the last couple of years.In subsequent years, a significant number of DA white dwarfs have been found to exhibit narrow metallic absorption lines in their spectra. Those lines are generally attributed to "pollution" of the white dwarf atmospheres. Given that the diffusion time for metals within the atmospheres is short (tens to hundreds of years), the only reasonable means of maintaining such lines in ~20% of the DA population is to envisage continuous accretion from a surrounding debris disk. The present program aims to address this question by using COS to obtain UV observations of young white dwarfs, probing correlations with progenitor mass and examining the detailed composition of the accreted materials.

Past weeks:
page by Neill Reid, updated 10/10/2011