This week on HST


HST Programs: August 28 - September 3, 2006

Program Number Principal Investigator Program Title Links
10258 Claudia Kretchmer, The Johns Hopkins University Tracing the Emergence of the Hubble Sequence Among the Most Luminous and Massive Galaxies Abstract
10259 Letizia Stanghellini, National Optical Astronomy Observatories, AURA Planetary nebulae in the SMC: a study of stellar evolution and populations in an extremely low-metallicity environment Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10503 Gary Da Costa, Australian National University The Star Formation Histories of Early Type Dwarf Galaxies in Low Density Environments: Clues from the Sculptor Group Abstract
10505 Carme Gallart, Instituto de Astrofisica de Canarias The Onset of Star Formation in the Universe: Constraints from Nearby Isolated Dwarf Galaxies Abstract
10519 Janet Simpson, NASA Ames Research Center Testing the Stellar Coalescence and Accretion Disk Theories of Massive Star Formation with NICMOS 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
10539 Karl Stapelfeldt, Jet Propulsion Laboratory Coronagraphic Imaging of Bright New Spitzer Debris Disks Abstract
10556 David Turnshek, University of Pittsburgh Neutral Gas at Redshift z=0.5 Abstract
10570 Makoto Kishimoto, University of Edinburgh, Institute for Astronomy Hosts of Quasars with Opaque Partial Covering Abstract
10578 Ignasi Ribas, Institut d'Estudis Espacials de Catalunya Eclipsing Binaries in the Local Group: Calibration of the Zero-point of the Cosmic Distance Scale and Fundamental Properties of Stars in M31 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
10630 Anna Pasquali, Eidgenossiche Technische Hochschule (ETH) The Fine Structure of Elliptical Galaxies in Voids Abstract
10632 Massimo Stiavelli, Space Telescope Science Institute Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field 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
10816 Tom Brown, Space Telescope Science Institute The Formation History of Andromeda's Extended Metal-Poor Halo 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 Phio 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
10846 Michael Gladders, Carnegie Institution of Washington The Halo Structure of RCS2-2327.4-0204 Abstract
10847 Dean Hines, Space Science Institute Coronagraphic Polarimetry of HST-Resolved Debris Disks Abstract
10860 Michael Brown, California Institute of Technology The largest Kuiper belt objects Abstract
10870 Mark Showalter, SETI Institute The Ring Plane Crossings of Uranus in 2007 Abstract
10878 John O'Meara, The Pennsylvania State University An ACS Prism Snapshot Survey for z~2 Lyman Limit Systems Abstract
10928 John Subasavage, Georgia State University Research Foundation Calibrating Cosmological Chronometers: White Dwarf Masses Abstract
10989 George Benedict, University of Texas at Austin Astrometric Masses of Extrasolar Planets and Brown Dwarfs Abstract

Some selected highlights

GO 10539: Coronagraphic Imaging of Bright New Spitzer Debris Disks

HST image of the face-on debris disk in the G2 dwarf, HD 107146 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. Analysis of the rangle of morphological structure in these systems provides insight into the distribution of properties of planetary systems. HST currently provides the most effective means of achieving the high-contrast required for the detection of scattered light from these disks in the presence of the bright parent stars. To date, only a handful of systems have such observations. The present program aims to expand the sample by using Spitzer observations to search for nearby stars with excess flxu at mid-infrared wavelengths - a signature of thermal radiation from circumstellar dust. The present proposal will use the NICMOS coronagraph to search for scattered light from those disks in the near-infrared.

GO 10592 An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

A NICMOS image of the interacting LIRG, NGC 6090 Luminous infrared galaxies (LIRGs) have total luminosities that exceed 1011.4 LSun, with most of the energy emitted at wavelengths longward of 10 microns. Many (perhaps most) of these galaxies are interacting or merging disk galaxies, with the excess infrared luminosity generated by warm dust associated with the extensive star formation regions. Many systems also exhibit an active nucleus, and may be in the process of evolving towards an S0 or elliptical merger remnant. The present program surveys a total of 88 such systems from the IRAS Revised Bright Galaxy Sample, imaging each system with the ACS using the F439W (B) and F814W (I) filters. The observations will probe
  • the distribution of star formation activity and the presence of bars and bridges, funneling gas towards active regions
  • the relationship between star formation and AGN activity
  • the overall structural properties of the LIRGS as a function of luminosity and environment
Observations of the interacting system, IRAS14348-1447, are scheduled for this week.

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 10989: Astrometric masses of extrasolar planets and brown dwarfs

Artist's impression of the planets circling the M dwarf, Gl 876 The overwhelming majority of extrasolar planetary systems have been identified through radial velocity monitoring, and the detection of the reflex motion of the parent star as it orbits the common center of mass of the system. Just as radial velocities measure the stellar "wobble" introduced along the line of sight, so high precision astrometry can be used to measure motion in the plane of the sky. Combining these data gives the full three-dimensional motions of the system, and a direct measure of the mass of the planetary companion. The Fine Guidance Sensors on HST are the only system currently capable of making observations at the required sub-milliarcscond accuracy, and has already been used for astrometry of four systems, including the M dwarf Gl 876. The current GO program pursues observations of six planetary hosts, and FGS observations of two targets, HD 47536 and HD 33636, are scheduled over the next week.

Past weeks:
page by Neill Reid, updated 25/7/2006