This week on HST


HST Programs: July 17 - July 23, 2006

Program Number Principal Investigator Program Title Links
10487 David Ardila, California Institute of Technology A Search for Debris Disks in the Coeval Beta Pictoris Moving Group Abstract
10490 Megan Donahue, Michigan State University A Snapshot Survey of a Complete Sample of X-ray Luminous Galaxy Clusters from Redshift 0.3 to 0.7 Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10504 Richard Ellis, California Institute of Technology Characterizing the Sources Responsible for Cosmic Reionization Abstract
10512 William Merline, Southwest Research Institute Search for Binaries Among Faint Jupiter Trojan Asteroids Abstract
10514 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution Abstract
10527 Dean Hines, Space Science Institute Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope Around 20 Sun-like Stars Abstract
10534 Kathy Rages, SETI Institute Active Atmospheres on Uranus and Neptune Abstract
10536 Raghvendra Sahai, Jet Propulsion Laboratory What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey Abstract
10551 Shri Kulkarni, California Institute of Technology Gamma-Ray Bursts from Start to Finish: A Legacy Approach 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
10588 Michael Brotherton, University of Wyoming The Host Galaxies of Post-Starburst Quasars Abstract
10592 Aaron Evans, State University of New York at Stony Brook An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe Abstract
10597 Andres Jordan, European Southern Observatory - Germany Resolving the Connection Between Globular Clusters and Low-Mass X-ray Binaries Abstract
10598 Paul Kalas, University of California - Berkeley ACS Imaging of Fomalhaut: A Rosetta Stone for Debris Disks Sculpted by Planets Abstract
10603 Deborah Padgett, California Institute of Technology Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust Abstract
10608 David Thilker, The Johns Hopkins University Probing the star formation law in the extreme outer limits of M83, a prototypical XUV-disk galax Abstract
10616 Edo Berger, Carnegie Institution of Washington Gotcha: Using Swift GRBs to Pinpoint the Highest Redshift Galaxies Abstract
10624 Derek B. Fox, California Institute of Technology Solving the Mystery of the Short-Hard Gamma-Ray Bursts Abstract
10626 Yeong-Shang Loh, University of Colorado at Boulder A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to z = 0.9 Abstract
10627 Margaret Meixner, Space Telescope Science Institute A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae Abstract
10629 Sally Oey, University of Michigan Are Field OB Stars Alone? Abstract
10767 Thomas Ayres, University of Colorado at Boulder Further Resolving the Puzzle of Hybrid Star X-rays Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters Abstract
10801 Keith Noll, Space Telescope Science Institute Direct Determination of Kuiper Belt Object Diameters with HST Abstract
10860 Michael Brown, California Institute of Technology The largest Kuiper belt objects Abstract
10896 Paul Kalas, University of California - Berkeley An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars Abstract
10906 Sylvain Veilleux, University of Maryland The Fundamental Plane of Massive Gas-Rich Mergers: II. The QUEST QSOs Abstract
10927 Wei-Chun Jao, Georgia State University The Weight-Watcher Program for Subdwarfs Abstract
11004 Michael Bode, Liverpool John Moores University The 2006 outburst of RS Oph - A rapidly evolving SNR analogue with jets Abstract

Some selected highlights

GO 10487: A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

WFPC2 image of Beta Pic's disk Over the last few years, there has been growing recognition of the presence of a number of young stellar associations, each comprising 20-50 stars and brown dwarfs, passing through the Solar Neighbourhood. Beta Pictoris (or Gl 219), a relatively young (~20 Myrs old) A5 dwarf, lying at a distance of just under 20 parsecs form the Sun, is the `flagship' member of one of those groups.. The IRAS satellite originally singled out this A star as unusual, detecting significant excess radiation over the expected photospheric fluxes at mid-infrared wavelengths; Smith & Terrile (1984) used ground-based coronagraphic observations to show that this was due re-radiation from a substantial debris disk. A further 30 stars are associated with this young group, with spectral types ranging from A to late M. Several of these stare are known to also have dusty disks, including the binary HR 7329 (A0 + M7) and the nearby active M1 dwarf, AU Mic (Gl 803). The present proposal aims to extend the sample, using the ACS/HRC in coronagraphic mode to search for debris disks around 21 members of the moving group.

GO 10587: Measuring the Mass Dependence of Early-Type Galaxy Structure

Galaxy-galaxy lensing Gravitational lensing amplifies and distorts the light from background sources. Most recent studies have focused either on micolensing, where the lensed sources are individual stars in either the Milky Way or its immediate neighbours, or on lensing of background galaxies by clusters of galaxies. In the former case, the main goal has been searching for possible contributors to the dark matter halo of our Galaxy (and M31); in the latter, the extended background sources are distorted into arcs and arclets whose morphjology allows an estimate of the mass distribution within the foreground cluster. Individual galaxies can also act as gravitational lenses, in a manner analogous to galaxy clusters. In that case, the morphology of the lensed source probes the mass distribution of the foreground galaxy. This proposal capitalises on these circumstances by using ACS to target a sample of 118 early-type lens candidates in a Snapshot survey. These systems were identified from Sloan Digital SKy Survey (SDSS) data, have known redshifts and their internal dynamics are currently the subject of ground-based spectrscopic study. Combining those data with the detailed photometric profiles obtained by ACS will constrain the mass profiles of the luminous and dark matter components in a range of early-type galaxies.

GO 10860: The largest Kuiper Belt Objects

An artist's impression of the view from Sedna 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 were 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.).Both HST and the Spitzer infrared space telescope have played an important role in these recent discoveries, measuring the angular diameter 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 11004: The 2006 outburst of RS Oph - A rapidly evolving SNR analogue with jets

The interacting binary system, RS Ophiuchi (image by David Hardy) RS Ophiuchi is a recurrent nova. These systems consist of two evolved stars, a white dwarf and a red giant, that are orbiting in such close proximity that the red giant fills its Roche lobe, leading to mass loss onto the secondary. That material is heated during the accretion process and accumulates on the white dwarf surface. Periodically, the temperature rises to the extent that thermonuclear reactions occur, leading to a thermal runaway, during which time the star can brighten over ten-thousandfold. In the case of RS Oph, the period between these explosions is approximately 20 years: RS Oph erupted in 1985 (five years prior to the launch of HST) and underwent a similar event earlier this year (see this link for further details). The present set of HST observations employs narrowband filters with the High Resolution Camera of ACS to image the nebular ejecta in a series of important emission lines. The aim is to trace the development of circumstellar shells and their interaction with the immediate environs of this recurrent nova.

Past weeks:
page by Neill Reid, updated 5/7/2006