This week on HST


HST Programs: January 15 - January 21, 2007

Program Number Principal Investigator Program Title Links
10793 Avishay Gal-Yam, California Institute of Technology A Survey for for Supernovae in Massive High-Redshift Clusters Abstract
10800 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10829 Paul Martini, The Ohio State University Secular Evolution at the End of the Hubble Sequence Abstract
10833 Bradley Peterson, The Ohio State University Research Foundation Host Galaxies of Reverberation Mapped AGNs Abstract
10842 Kem Cook, Lawrence Livermore National Laboratory A Cepheid Distance to the Coma Cluster Abstract
10844 Kris Davidson, University of Minnesota - Twin Cities Following Eta Carinae's Change of State Abstract
10849 Stanimir Metchev, University of California - Los Angeles Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope around 21 Sun-like Star Abstract
10861 David Carter, Liverpool John Moores University An ACS Treasury Survey of the Coma cluster of galaxies Abstract
10862 John Clarke, Boston University Comprehensive Auroral Imaging of Jupiter and Saturn during the International Heliophysical Year Abstract
10877 Weidong Li, University of California - Berkeley A Snapshot Survey of the Sites of Recent, Nearby Supernovae Abstract
10878 John O'Meara, The Pennsylvania State University An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems Abstract
10886 Adam Bolton, Smithsonian Institution Astrophysical Observatory The Sloan Lens ACS Survey: Towards 100 New Strong Lenses Abstract
10890 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies Abstract
10899 Matthew Malkan, University of California - Los Angeles Identifying z>7 galaxies from J dropouts Abstract
10904 David Thilker, The Johns Hopkins University Star formation in extended UV disk (XUV-disk) galaxies Abstract
10905 R. Tully, University of Hawaii The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region Abstract
10906 Sylvain Veilleux, University of Maryland The Fundamental Plane of Massive Gas-Rich Mergers: II. The QUEST QSOs Abstract
10918 Wendy Freedman, Carnegie Institution of Washington Reducing Systematic Errors on the Hubble Constant: Metallicity Calibration of the Cepheid PL Relation Abstract
10931 Edmund Nelan, Space Telescope Science Institute Dynamical Masses and Radii of Four White Dwarf Stars Abstract
10998 Peter McCullough, Space Telescope Science Institute Exoplanet XO-1b: light curve and parallax Abstract

Some selected highlights

GO 10793: A Survey for Supernovae in Massive High-Redshift Clusters

Images of supernova 2005cs in M51; this supernova happens to be a (slightly unusual) Type II Supernovae are the most spectacular form of stellar obituary. In recent years, these celestial explosions have acquired even more significance through their use as distance indicators in mapping out the `dark energy' acceleration term of cosmic expansion. However, while there are well-established models for the two main types of supernovae - runaway fusion on the surface of a white dwarf in a binary system (type Ia), and implosion of the core of a massive star (type II) - substantive questions remain regarding the expected supernova rates, and the potential variation in those rates as a function of look-back time. This proposal aims to address that question through observations of galaxy clusters with redshifts in the range 0.5 < z < 0.9. Candidate supernovae are identified by ACS imaging in the F814W or F775W, with follow-up Keck spectroscopy used to determine the redshift of the parent galaxy.

GO 10800: Kuiper Belt Binaries: Probes of Early Solar System Evolution

Composite HST image of the Kuiper Belt binary, WW31 The Kuiper Belt consists of icy planetoids that orbit the Sun within a broad band stretching from Neptune's orbit (~30 AU) to distance sof ~50 AU from the Sun (see David Jewitt's Kuiper Belt page for details). Over 500 KBOs are currently known out of a population of perhaps 70,000 objects with diameters exceeding 100 km. Approximately 2% of the known KBOs are binary (including Pluto, one of the largest known KBOs, regardless of whether one considers it a planet or not). This is a surprisingly high fraction, given the difficulties involved in forming such systems and the relative ease with which they can be disrupted. It remains unclear whether these systems formed from single KBOs (through collisions or 3-body interactions) as the Kuiper Belt and the Solar System have evolved, or whether they represent the final tail of an initial (much larger) population of primordial binaries. This proposal aims to use ACS/HRC images of known KBOs toidentify new binary systems.

GO 10861 An ACS Treasury Survey of the Coma cluster of galaxies

The Coma cluster The Coma cluster is the nearest rich galaxy cluster, lying at a distance of ~100 Mpc from the Milky Way. The cluster includes well over 1000 major galaxies, centred on two giant ellipticals, NGC 4874 and NGC 4889. Chandra observations show that the galaxies are embedded in very hot intracluster gas (see this site ). Cluster galaxies have also been surveyed at mid-infrared wavelengths by Spitzer, and in the ultraviolet by GALEX. Individual galaxies have been studied in the past using HST. The present program aims to obtain systematic imaging with ACS (and parallel observations with NICMOS) of the cluster core ( a 7x6 mosaic, covering approximately 400 sq. arcmin.), together with 40 fields at larger radii, sampling infalling galaxies in the outer cluster. Those observations will be capable of detecting dwarf galaxies with absolute magnitudes as faint as MB ~ -8, fainter than most of the Milky Way's dwarf spheroidal companions. Besides completing a detailed census of the low luminosity tail of the galaxian mass function, the observations will be used to probe colour gradients and internal chemical evolution.

GO 10886: The Sloan Lens ACS Survey: Towards 100 New Strong Lenses

ACS images of galaxy-galaxy Einstein ring lenses from the Sloan survey 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 primarily to probe the mass distribution of galaxy clusters, using theoretical models to analyse the arcs and arclets that are produced by strong lensing of background galaxies, and the large-scale mass distribution, through analysis of weak lensing effects on galaxy morphologies. Gravitational lensing can also be used to investigate the mass distribution of individual galaxies. Until recently, the most common background sources were quasars. Galaxy-galaxy lenses, however, offer a distinct advantage, since the background source is extended, and therefore imposes a stronger constraints on the mass distribution of the lensing galaxy than a point-source QSO. The Sloan sky survey provides a powerful tool for identifying candidate galaxy-galaxy lenses; this program is using HST-ACS imaging to verify the nature of those candidates, and provide the angular resolution necessary to model the mass distribution.

Past weeks:
page by Neill Reid, updated 21/12/2006