This week on HST


HST Programs: October 3, 2011 - October 9, 2011


Program Number Principal Investigator Program Title
11616 Gregory J. Herczeg, Max-Planck-Institut fur extraterrestrische Physik The Disks, Accretion, and Outflows {DAO} of T Tau stars
12041 James C. Green, University of Colorado at Boulder COS-GTO: Io Atmosphere/STIS
12101 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12188 Jay B. Holberg, University of Arizona Tests of Extreme Physics in Very Cool White Dwarfs
12192 James T. Lauroesch, University of Louisville Research Foundation, Inc. A SNAPSHOT Survey of Interstellar Absorption Lines
12200 Gregory James Schwarz, American Astronomical Society STIS UV spectroscopy of a bright classical nova during its super soft X-ray phase
12211 Nuria Calvet, University of Michigan Are Weak-Line T Tauri Stars Still Accreting?
12218 Derck L. Massa, Space Telescope Science Institute Toward Resolving the Mass loss Discrepancy
12228 Glenn Schneider, University of Arizona Probing for Exoplanets Hiding in Dusty Debris Disks: Inner {<10 AU} Disk Imaging, Characterization, and Exploration
12246 Christopher W. Stubbs, Harvard University Weak Lensing Mass Calibration of SZ-Selected Clusters
12249 Wei Zheng, The Johns Hopkins University Reionization of Intergalactic Helium at the Highest Redshifts
12257 Leo Girardi, Osservatorio Astronomico di Padova The Nature of Multiple Main Sequence Turn-offs and Dual Red Clumps in Magellanic Cloud Star Clusters
12264 Simon L. Morris, University of Durham The Relationship between Gas and Galaxies for 0
12276 Bart P. Wakker, University of Wisconsin - Madison Mapping a nearby galaxy filament
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, University of Missouri - Columbia Hubble Infrared Pure Parallel Imaging Extragalactic Survey {HIPPIES}
12288 Douglas R. Gies, Georgia State University Research Foundation Hot Evolved Companions to Intermediate-Mass Main-Sequence Stars: Solving the Mystery of KOI-81
12291 John Krist, Jet Propulsion Laboratory STIS coronagraphy of Spitzer-selected debris disks
12298 Richard S. Ellis, California Institute of Technology Towards a Physical Understanding of the Diversity of Type Ia Supernovae
12310 Goeran Oestlin, Stockholm University LARS - The Lyman Alpha Reference Sample
12452 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12474 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs
12477 Fredrick W. High, University of Chicago Weak lensing masses of the highest redshift galaxy clusters from the South Pole Telescope SZ survey
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
12502 Andrew S. Fruchter, Space Telescope Science Institute From the Locations to the Origins of Short Gamma-Ray Bursts
12546 R. Brent Tully, University of Hawaii The Geometry and Kinematics of the Local Volume
12550 Daniel Apai, University of Arizona Physics and Chemistry of Condensate Clouds across the L/T Transition - A SNAP Spectral Mapping Survey
12605 Giampaolo Piotto, Universita di Padova Advances in Understanding Multiple Stellar Generations in Globular Clusters
12659 Joaquin Vieira, California Institute of Technology Strongly Lensed Dusty Star Forming Galaxies: Probing the Physics of Massive Galaxy Formation

Selected highlights

GO 12188: Tests of Extreme Physics in Very Cool White Dwarfs


HST ACS images of white dwarfs in the globular cluster, M4
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 is mass dependent (high mass dwarfs cool faster), and can be predicted using sophisticated models of white dwarf interiors. As white dwarfs cool, their spectral characteristics change. The majority of degenerates have hydrogen-rich envelopes with some metallic content (e.g. Ca, Mg), and the spectra are dominated by strong Balmer absorption features at temperatures above ~6,000K (DA white dwarfs). At hot temperatures (>30,000K), a subset of white dwarfs have pure helium atmospheres, and consequently show only helium lines (DB white dwarfs). At cooler temperatures, some metal lines persist, and molecular carbon features are occasionally present, but with ever decreasing temperature, the spectra become featureless and white dwarfs enter the all-embracing DC (featureless spectrum )class. The present program will use near-UV STIS spectroscopy to map the the overall spectral energy distribution at these short wavelengths. The results will be matched against state-of-the-art models, setting constraintsn on the detailed atmosphere composition of these cool objects.

GO 12228: Probing for Exoplanets Hiding in Dusty Debris Disks: Inner <10 AU Disk Imaging, Characterization, and Exploration


HST-ACS image of the disk surrounding the nearby M dwarf, AU Mic
Planet formation occurs in circumstellar disks around young stars. Most of the gaseous content of those disks dissipates in less than 10 million years, leaving dusty debris disks that are detectable through reflect light at near-infrared and, to a lesser extent, optical wavelengths. The disk structure is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Over the past decade, HST and Spitzer have provided complementary information on this subject, with Spitzer measuring thermal radiation from circumstellar dust and HST providing high-resolution mapping of debris disks in reflected light. Most recently, HST ACS coronagraphic imaging have revealed the presence of a planetary object within the disk of the nearby A star, . Planetary companions to the young (60 Myr-old) F star, HR 8799, have also been imaged by both ground-based telescopes and HST. The ACS coronagraph was associated with the High Resolution Camera, which is no longer functioning; nor is NICMOS. However, coronagraphy is still possible using the occulting bar on the Space Telescope Imaging Spectrograph (STIS). The present program aims to expand the catalogue of imaged exoplanets to other nearby young stars that are known to harbour debris disks. The present set of observations targets the young, nearby M dwarf, AU Mic (or Gliese 803).

GO 12276: Mapping a galaxy filament


Cosmological simulations of structure in the WHIM
Only a small fraction of the baryons in the Universe, perhaps 10%, are thought to reside in visible matter in galaxies. About 30% of the total likely contributes to the ionised gas detected in Lyman-alpha absorption studies. The remainder is generally believed to reside in the WHIM - the Warm-Hot Intergalactic Medium. This material is generally expected to form highly filamentary structures, some of which collapse and condense to for galaxies in the early Universe. Such structures can only be detected through the effect that they have on the light emitted by background sources. As the light passes through the filament, absorption occurs at specific wavelengths that depend on the composition and ionisation of the component materials. The present program focuses on 10-Mpc long filamentary structure that has been identified by mapping the distribution of galaxies in the (relatively) local universe (the measured velocities correspond to a redshift, z~0.01). Ultraviolet observations already exist for four QSOs lying behind this putative structure. The present program aims to use the Cosmic Origins Spectrograph to extend observations to a further 23 QSOs and/or AGN, providing a more detailed map of the density and ionisation structure.

GO 12283: WISP - A Survey of Star Formation Across Cosmic Time


A region of massive star formation
Star formation is the key astrophysical process in determining the overall evolution of galactic systems, the generation of heavy elements, and the overall enrichment of interstellar and intergalactic material. 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 builds on the ability of HST to carry out parallel observations, using more than one instrument. While the Cosmic Origins Spectrograph is focused on obtaining ultraviolet spectra of unparalleled signal-to-noise, this program uses the near-infrared grisms mounted on the Wide-Field Camera 3 infrared channel to obtain low resolution spectra between 1 and 1.6 microns of randomly-selected nearby fields. The goal is to search for emission lines characteristic of star-forming regions. In particular, these observations are capable of detecting Lyman-alpha emission generated by star formation at redshfits z > 5.6. A total of up to 40 "deep" (4-5 orbit) and 20 "shallow" (2-3 orbit) fields will be targeted in the course of this observing campaign.

Past weeks:
page by Neill Reid, updated 2/5/2011