This week on HST

HST Programs: November 6 - November 12, 2006

Program Number Principal Investigator Program Title Links
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10498 Stephen J. Smartt, The Queen's University of Belfast Detecting the progenitors of core-collapse supernovae Abstract
10500 Luigi R. Bedin, European Southern Observatory - Germany Exploring the Bottom End of the White Dwarf Cooling Sequence in the Galactic Open Cluster NGC2158 Abstract
10556 David Turnshek, University of Pittsburgh Neutral Gas at Redshift z=0.5 Abstract
10587 Adam Bolton, Smithsonian Institution Astrophysical Observatory Measuring the Mass Dependence of Early-Type Galaxy Structure Abstract
10605 Evan Skillman, University of Minnesota - Twin Cities Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies Abstract
10611 George Benedict, University of Texas at Austin Precise Distances to Nearby Planetary Nebulae Abstract
10793 Avishay Gal-Yam, California Institute of Technology A Survey for Supernovae in Massive High-Redshift Clusters Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10820 Alan Dressler, Carnegie Institution of Washington Galaxy properties in a Filament in Abell 851 Abstract
10824 Oleg Gnedin, The Ohio State University Research Foundation Measuring the Shape and Orientation of the Galactic Dark-Matter Halo using Hypervelocity Stars Abstract
10829 Paul Martini, The Ohio State University Secular Evolution at the End of the Hubble Sequence Abstract
10831 Leonidas Moustakas, Jet Propulsion Laboratory A new wide-separation Einstein Cross at z=2.7 Abstract
10832 Brian M. Patten, Smithsonian Institution Astrophysical Observatory Solving the microlensing puzzle: An HST high-resolution imaging approach Abstract
10833 Bradley Peterson, The Ohio State University Research Foundation Host Galaxies of Reverberation Mapped AGNs Abstract
10847 Dean Hines, Space Science Institute Coronagraphic Polarimetry of HST-Resolved Debris Disks 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
10856 Rodger I. Thompson, University of Arizona Delayed Negative Feedback in the Super Star Clusters of SBS0335-052E Abstract
10860 Michael Brown, California Institute of Technology The largest Kuiper belt objects Abstract
10875 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
10876 Jean-Paul Kneib, Observatoire de Marseille SL2S: The Strong Lensing Legacy Survey Abstract
10880 Henrique Schmitt, Naval Research Laboratiry The host galaxies of QSO2s: AGN feeding and evolution at high luminosities Abstract
10881 Graham Smith, University of Birmingham The Ultimate Gravitational Lensing Survey of Cluster Mass and Substructure Abstract
10882 William Sparks, Space Telescope Science Institute Emission Line Snapshots of 3CR Radio Galaxies Abstract
10883 Lifan Wang, Lawrence Berkeley National Laboratory Light Echoes for Type Ia Supernovae Abstract
10886 Adam Bolton, Smithsonian Institution Astrophysical Observatory The Sloan Lens ACS Survey: Towards 100 New Strong Lenses Abstract
10893 Peter Garnavich, University of Notre Dame Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram Abstract
10895 Paul Kalas, University of California - Berkeley Closure on the IRAS Big Four: A High Contrast Study of Epsilon Eridani's Dust Belt in Scattered Light Abstract
10905 R. Tully, University of Hawaii The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region Abstract
10915 Julianne Dalcanton, University of Washington ACS Nearby Galaxy Survey Abstract
10920 Charles Hoopes, The Johns Hopkins University High-Resolution Imaging of Nearby Lyman Break Galaxy Analogs in the GALEX All-Sky Survey Abstract
10927 Wei-Chun Jao, Georgia State University The Weight-Watcher Program for Subdwarfs Abstract
10929 Todd Henry, Georgia State University Research Foundation Calibrating the Mass-Luminosity Relation at the End of the Main Sequence Abstract
10994 Holland Ford, The Johns Hopkins University Infalling Groups and the Origin of Early-Type Galaxies 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 10831: A new wide-separation Einstein Cross at z=2.7

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 distribution of galaxies (mainly through multiply-imaged quasars), galaxy clusters (arcs and arclets) and the large-scale mass distribution (weak lensing). The present program centres on SDSSJ1011+0143, an average luminosity galaxy at a redshift z=2.699 that is being lensed by a foreground galaxy. The source was identified as a gravitational lens through analysis of ground-based imaging obtained by the Sloan Digital Sky Survey, but those data have insufficient resolution to map the location of all the potential lensed images. These HST observations, using the F555W and F814W filters on ACS, should resolve all the sources, and allow detailed modelling of the dark matter distribution in the lensing galaxy.

GO 10860: The largest Kuiper Belt Objects

The view from sedna: an artist's impression The Kuiper Belt lies beyond the orbit of Neptune, extending from ~30 AU to ~50 AU from the Sun, and includes at least 70,000 objects with diameters exceeding 100 km. Setting aside Pluto, the first trans-Neptunian objects were discovered in the early 1990s. Most are relatively modest in size, with diameters of a few hundred km and photometric properties that suggested an icy composition, similar to Pluto and its main satellite, Charon. Over the last three years, however, a handful of substantially larger bodies have been discovered, with diameters of more than 1000 km; one of the objects, 2003 UB313, is comparable in size to Pluto (2320 km.). These recent results, of course, were one of the main stimuli for the IAU's recent revision of Pluto's status from planet to `dwarf planet' - an issue that still remains contentious in some quarters. However, regardless of spats over nomenclature, it is clear that these objects (ice planets?) are a significant component in the outer Solar System. Both HST and the Spitzer infrared space telescope have played an important role in these recent investigations, measuring the angular diameter of the larger KBOs, and the albedo over a wide range of wavelengths. The aim of the present set of observations is to target ~20 trans-Neptunian objects, using red (F606W) images and low-resolution spectra, obtained with the High Resolution Camera on the Advanced Camera for Surveys, to probe their size and chemical composition.

GO 10929: Calibrating the Mass-Luminosity Relation at the End of the Main Sequence

The MV-mass relation for low-mass stars (from T. Henry) The mass-luminosity relation remains one of the key underpinnings of stellar astrophysics, notably in probing the grey area that separates hydrogen-burning stars from cooling-powered brown dwarfs. The calibration of thsi relation rests on observations of binary systems, primarily eclipsing binaries at masses above 1 MSun, and primarily astrometric binaries at sub-solar masses. In the latter case, reliable mass determinations require orbital measurements of extremely high accuracy, which, in turn, requires high precision astrometry over at least one orbital period. The Fine Guidance Sensors on HST have proven invaluable in this regard, since they allow sub-milliarcsecond accuracy astrometry of binary systems with sub-arcsecond separations; in other words, HST allows measurement of nearby, low-mass binaries with periods short enough to allow completion of the observations in significantly less than an astronomer's lifetime. The current program is using the FGS to monitor six close binary systems. Observations are scheduled of G250-29 (also known as LHS 221). Lying at a distance of 10.6 parsecs, this system comprises an M2.5 primary and an ~M3.5 secondary, with a magnitude difference of ~1.6 magnitudes at visual wavelengths.

Past weeks:
page by Neill Reid, updated 27/10/2006