This week on HST


HST Programs: October 4, 2010 - October 10, 2010

Program Number Principal Investigator Program Title
11298 John P. Subasavage, National Optical Astronomy Observatory - CTIO Calibrating Cosmological Chronometers: White Dwarf Masses
11575 Schuyler D. Van Dyk, Jet Propulsion Laboratory The Stellar Origins of Supernovae
11582 Andrew Blain, California Institute of Technology The spatial distribution of radiation in the complex ISM of distant ultraluminous galaxies
11694 David R. Law, University of California - Los Angeles Mapping the Interaction between High-Redshift Galaxies and the Intergalactic Environment
11700 Michele Trenti, University of Colorado at Boulder Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey
11734 Andrew J. Levan, The University of Warwick The hosts of high redshift gamma-ray bursts
11741 Todd Tripp, University of Massachusetts Probing Warm-Hot Intergalactic Gas at 0.5 < z < 1.3 with a Blind Survey for O VI, Ne VIII, Mg X, and Si XII Absorption Systems
12019 Christy A. Tremonti, University of Wisconsin - Madison After the Fall: Fading AGN in Post-starburst Galaxies
12041 James C. Green, University of Colorado at Boulder COS-GTO: Io Atmosphere/STIS
12061 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-South Field, Early Visits of SNe Search
12163 Aaron J. Barth, University of California - Irvine Structure and Stellar Content of the Nearest Nuclear Clusters in Late-Type Spiral Galaxies
12169 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of planetary debris discs around young white dwarfs
12178 Scott F. Anderson, University of Washington Spanning the Reionization History of IGM Helium: a Highly Efficient Spectral Survey of the Far-UV-Brightest Quasars
12181 Drake Deming, NASA Goddard Space Flight Center The Atmospheric Structure of Giant Hot Exoplanets
12184 Xiaohui Fan, University of Arizona A SNAP Survey for Gravitational Lenses Among z~6 Quasars
12209 Adam S. Bolton, University of Utah A Strong Lensing Measurement of the Evolution of Mass Structure in Giant Elliptical Galaxies
12210 Adam S. Bolton, University of Utah SLACS for the Masses: Extending Strong Lensing to Lower Masses and Smaller Radii
12212 D. Michael Crenshaw, Georgia State University Research Foundation What are the Locations and Kinematics of Mass Outflows in AGN?
12215 Nancy R. Evans, Smithsonian Institution Astrophysical Observatory Searching for the Missing Low-Mass Companions of Massive Stars
12217 Philip Lucas, University of Hertfordshire Spectroscopy of faint T dwarf calibrators: understanding the substellar mass function and the coolest brown dwarfs
12234 Wesley Fraser, California Institute of Technology Differentiation in the Kuiper belt: a search for silicates on icy bodies.
12245 Mark R. Showalter, SETI Institute Orbital Evolution and Stability of the Inner Uranian Moons
12248 Jason Tumlinson, Space Telescope Science Institute How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L*
12251 Zachory K. Berta, Harvard University The First Characterization of a Super-Earth Atmosphere
12283 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey {WISP}: A Survey of Star Formation Across Cosmic Time
12286 Hao-Jing Yan, The Ohio State University Hubble Infrared Pure Parallel Imaging Extragalactic Survey {HIPPIES}
12291 John Krist, Jet Propulsion Laboratory STIS coronagraphy of Spitzer-selected debris disks
12299 Michael Eracleous, The Pennsylvania State University Spectroscopic Signatures of Binary and Recoiling Black Holes
12307 Andrew J. Levan, The University of Warwick A public SNAPSHOT survey of gamma-ray burst host galaxies
12324 C. S. Kochanek, The Ohio State University The Temperature Profiles of Quasar Accretion Disks

Selected highlights

GO 11298: Calibrating Cosmological Chronometers: White Dwarf Masses

HST image of the white dwarf companion to Sirius - which isn't a target of the present program White dwarfs are the evolutionary end point for most stars with masses less than ~7 MSun. These compact degenerate objects lack any internal heat source, and therefore gradually cool from their initial temperatures of ~100,000-200,000K. As they cool, the luminosity decreases from Mbol ~ 2-3 (for the immediate post-PN object) to Mbol ~ 17 (for 10-12 Gyr-old Galactic halo white dwarfs). The rate of cooling can be predicted using sophisticated models of white dwarf interiors. These models show that the rates are mass dependent, but the overwhelming majority of field white dwarfs are expected to have masses in the range 0.6-0.7 MSun, reflecting the steep slope to the IMF above ~1 MSun (high mass stars are rare, so high mass remnants, like Sirius B, are also rare). Confirming that hypothesis demands reliable mass measurements for individual white dwarfs. Fortunately, a number of white dwarfs are known in binary systems, and a subset of those systems are close enough to each other and to the Sun that their orbits can be mapped (and hence their dynamical masses determined) using the Fine Guidance Sensors on HST. The present program targets 4 white dwarf/white dwarf binary systems.

GO 11694: Mapping the Interaction between High-Redshift Galaxies and the Intergalactic Environmen

Selected moderate and high-redshift galaxies from the HDF Understanding the processes that govern galaxy formation and evolution remains a key goal for observational and theoretical astronomy. Analyses of data accrued over the past decade, notably deep imaging with HST, indicate that star formation peaked in ther edshift range 2 < z < 3. Tracing the overall evolution through a wide redshift range is crucial to understanding how gas and stars evolved to form the galaxies that we see around us now. The present program focuses on the redshift range 1.6 < z < 3.4, and will use the WFC3 IR camera to obtain F160W (H-aband) images of several hundred galaxies that are spectroscopically tagged to lie in this redshift range. At those redshifts, the IR images correspond to rest-framer optical wavelengths, permitting detailed measurement of galactic morphology.

GO 11982: Spanning the Reionization History of IGM Helium: a Large and Efficient HST Spectral Survey of Far-UV-Bright Quasars

GALEX image of the nearby spiral, M81 The reionisation epoch for intergalactic helium is thought to occur somewhere between redshifts 3 and 4. Observations with the GALEX satellite, a NASA small explorer-class mission equipped with a 50-cm diameter telescope, are proving critical in testing this hypothesis through the identification of UV bright quasars in the appropriate redshift range. Galex was launched on 28th April 2003, and continues to operate more than 30 months beyond its nominal lifetime, conducting ultraviolet imaging and low-resolution grism spectroscopy at far-UV (125-175 nm) and near-UV (175-280 nm) wavelengths. Past HST programs by this research have used the ACS/SBC to target sources identified by cross-referencing GALEX against SDSS catalogues of moderate (1 < z < 3) and high redshift (z > 3.1) quasars. These sources can serve as effective probes of the ionisation state of the intergalactic medium at intervening redshifts. In particular, analysis of the He II Lyman-alpha absorption will shed light on the epoch of reionisation of intergalactic helium, generall placed between redshifts 3 and 4. The present program will use the ACS/SBC PR120L prism for spectroscopy of 40 QSOs with redshifts in the range 3.1 < z < 5.1.

GO 12324: The Temperature Profiles of Quasar Accretion Disks

The first Einstein cross, the gravitational lensed QSO, G2237+0305 Gravitational lensing is a consequence the theory of general relativity. Its importance as an astrophysical tool first became apparent with the realisation (in 1979) that the quasar pair Q0957+561 actually comprised two lensed images of the same background quasar. In the succeeding years, lensing has been used to probe the mass distributions on a variety of scales: of galaxies (primarily via multiply-imaged quasars); of galaxy clusters (arcs and arclets); and at the largest scales (weak lensing). However, lensing can also provide insight on the small-scale properties of the object being lensed. In a lensed QSO, the light from the QSO follows different paths to produce the separate images; each of those paths has a different length; consequently, flux variations in the source show up at different times in the separate images. The present program aims to take advantage of this property to probe the structure of the accretion disks surrounding the central black hole in a number of lensed QSOs. The program will combine ultraviolet observations with the WFC3/UVIS camera on HST with GALEX UV data for 5 lenses spanning as broad range of black hole masses. Studying the variation as a function of wavelength should probe the accretion disk structure, since light from the inner regions are expected to dominate at shorter wavelengths, while the outer regions dominate at longer wavelengths.

Past weeks:
page by Neill Reid, updated 12/11/2010