This week on HST

HST Programs: October 12 - October 18, 2009

Program Number Principal Investigator Program Title Links
11108 Esther M. Hu, University of Hawaii Near Infrared Observations of a Sample of z~6.5-6.7 Galaxies Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11343 Andrew J. Levan, The University of Warwick Identifying the host galaxies for optically dark gamma-ray bursts Abstract
11548 S. Thomas Megeath, University of Toledo NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation Abstract
11565 Sebastien Lepine, American Museum of Natural History A search for astrometric companions to very low-mass, Population II stars Abstract
11580 Bruce Balick, University of Washington Watching Young Planetary Nebulae Grow: The Movie Abstract
11586 Aaron Dotter, University of Victoria Exceptional Galactic Halo Globular Clusters and the Second Parameter Abstract
11594 John M. O'Meara, Saint Michaels College A WFC3 Grism Survey for Lyman limit absorption at z=2 Abstract
11618 Tracy L. Huard, University of Maryland WFC3 Observations of VeLLOs and the Youngest Star Forming Environments Abstract
11627 Gijs Nelemans, Katholieke Universiteit Nijmegen Resolving the puzzling nature of the ultra-compact binary V407 Vul Abstract
11630 Kathy Rages, SETI Institute Monitoring Active Atmospheres on Uranus and Neptune Abstract
11644 Michael E. Brown, California Institute of Technology A dynamical-compositional survey of the Kuiper belt: a new window into the formation of the outer solar system Abstract
11657 Letizia Stanghellini, National Optical Astronomy Observatories The population of compact planetary nebulae in the Galactic Disk Abstract
11664 Thomas M. Brown, Space Telescope Science Institute The WFC3 Galactic Bulge Treasury Program: Populations, Formation History, and Planets Abstract
11670 Peter Garnavich, University of Notre Dame The Host Environments of Type Ia Supernovae in the SDSS Survey Abstract
11687 Thomas R. Ayres, University of Colorado at Boulder SNAPing Coronal Iron Abstract
11694 David R. Law, California Institute of Technology Mapping the Interaction between High-Redshift Galaxies and the Intergalactic Environment Abstract
11704 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale Abstract
11719 Julianne Dalcanton, University of Washington A Calibration Database for Stellar Models of Asymptotic Giant Branch Stars Abstract
11788 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11835 Mark Birkinshaw, University of Bristol The multi-faceted X-ray activity of low-redshift active galaxies Abstract
11838 Herman L. Marshall, Massachusetts Institute of Technology Completing a Flux-limited Survey for X-ray Emission from Radio Jets Abstract
11840 Andrew J. Levan, The University of Warwick Identifying the host galaxies for optically dark gamma-ray bursts Abstract

Selected highlights

GO 11630 Monitoring active Atmospheres on Uranus and Neptune

Nicmos image of aurorae on Uranus The atmospheres of the gas giant planets in the solar system are dynamic entities that can exhibit dramatic changes over a variety of timescales. Those changes are most apparent in Jovian atmosphere, which displays a wide variety of bands and spots, reflecting complex meteorological phenomena (see, e.g., previous ACS observations of the upper atmosphere and of the new little red spot ). This is not surprising since Jupiter atmosphere receives the highest input of solar energy. However, secular variations are also evident in the atmospheres of the outer planets, albeit usually at a more subtle level. The present program builds on past HST programs (see
SN 2007uy and 2008D in NGC 2770 Supernovae have long attracted the attention of both amateur and professional astronomers as a means of studying the violent eruption and death of massive stars and degenerates. However, in the last decade they have also acquired considerable importance as distance indicators, tracing the expansion of the universe to redshifts well beyond the reach of more conventional yardsticks, such as cepheids, and providing a key underpinning for the hypothesised existcen of dark energy. Understanding the supernovae themselves, and, in particular, their progenitors, is key to accurately interpreting their luminosities and distances. The present program aims to tackle that aspect of the problem by using ACS to obtain deep, high resolution images of galaxies that have harboured recent type Ia supernovae. The targets are all drawn from the Sloan Digital Sky Survey, which has uncovered more than than 500 type Ia supernovae,. The supernovae themselves are long gone from view, but the ACS data will be used to probe the stellar populations in the immediate vicinity of the explosion, and hence gain a better understanding of the likely progenitor.

GO 11704: The Ages of Globular Clusters and the Population II Distance Scale

Hubble Heritage image of the globular cluster, M15 Globular clusters are the oldest structures within the Milky Way that are directly accessible to observation. They are relatively simple systems, with relatively simple colour-magnitude diagrams (albeit with some complexities adduced from recent HST observations, see GO 11233 ). Matching those CMDs against theoretical models allows us to set constraints on the age of the oldest stars in the Galaxy, and hence on the age of the Milky Way and the epoch of galaxy formation. However, the accuracy of those age determinations rest crucially on the accuracy of the cluster distance determinations. The clusters themselves lie at distances of several kpc at best, and tens of kpc at worst; thus, direct trigonometric parallax measurements must await microacrsecond astrometric missions. The classical method of deriving distances is main sequence fitting - using nearby stars, with similar chemical abundances and accurate parallax measurements, to map out the main sequence in absolute units, and then scaling the cluster data to fit. The problem with this method is that metal-poor subdwarfs are rare, so even Hipparcos was only able to obtain accurate distances to a handful of stars. The present program aims to improve the distance measurements by using the Fine Guidance Sensors on HST to determine sub-millarcsecond trigonometric parallaxes to 9 subdwarfs, almost doubling the sample available for MS fitting.

GO 11840: Identifying the host galaxies for optically dark gamma-ray bursts

Artist's impression of a gamma-ray burst Gamma ray bursts are events that tap extraordinary energies (1045 to 1047 joules) in remarkably short periods of time. Several thousands bursts have been detected over the last 30+ years, and analyses indicate that they can be divided into two classes with durations longer or shorter than 2 seconds. The short bursts appear to release more high energy radiation, so the two subsets are known as long/soft and short/hard bursts.The short/hard bursts appear to arise from coalescing binary systems (probably pairs of neutron stars or black holes), but the long/soft bursts appear to originate in the collapse of very massive stars. The latter sources are therefore almost certainly associated with star formation, so they act as signposts to active star-forming regions in the high redshift universe. This program will target a specific subset of GRBs, those with no optical afterglow, but strong X-ray flux. The Chandra satellite will be used in ToO mode to zero in on the co-ordinates of the GRB itself; HST will be used to obtain deep imaging with ACS at optical wavelengths (F606W filter) and with WFC3 in the infrared (F160W). Since the goal is to identify the host galaxy, the HST observations will be obtained well after the event itself.

Past weeks:
page by Neill Reid, updated 23/9/2009