This week on HST

HST Programs: July 24 - July 31, 2006

Program Number Principal Investigator Program Title Links
10103 George Benedict, University of Texas at Austin FGS Astrometry of a Star Hosting an Extrasolar Planet: The Mass of Upsilon Andromedae d Abstract
10258 Claudia Kretchmer, The Johns Hopkins University Tracing the Emergence of the Hubble Sequence Among the Most Luminous and Massive Galaxies 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
10517 Steven Pravdo, Jet Propulsion Laboratory Imaging Astrometrically-Discovered Brown Dwarfs 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
10532 Kai Noeske, University of California - Santa Cruz Kinematics and morphology of the most massive field disk galaxies at z>1 Abstract
10546 Andrew Fabian, University of Cambridge The filaments of NGC1275 Abstract
10587 Adam Bolton, Smithsonian Institution Astrophysical Observatory Measuring the Mass Dependence of Early-Type Galaxy Structure Abstract
10596 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: A Test of the Black Hole-Bulge Paradigm Abstract
10602 Jesus Maiz-Apellaniz, Space Telescope Science Institute - ESA Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS 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
10624 Derek B. Fox, California Institute of Technology Solving the Mystery of the Short-Hard Gamma-Ray Bursts Abstract
10761 Victoria Kaspi, McGill University The X-ray Spectral and Optical/IR Flux Variability in Magnetars 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
10800 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution 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
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
10860 Michael Brown, California Institute of Technology The largest Kuiper belt objects Abstract
10879 I. Neill Reid, Space Telescope Science Institute A search for planetary-mass companions to the nearest L dwarfs - completing the survey Abstract
10889 Roelof de Jong, Space Telescope Science Institute The Nature of the Halos and Thick Disks of Spiral Galaxies Abstract
10928 John Subasavage, Georgia State University Research Foundation Calibrating Cosmological Chronometers: White Dwarf Masses Abstract

Some selected highlights

GO 10504 Characterizing the Sources Responsible for Cosmic Reionization

A 3-D model of cosmic reionisation at redshift z=5.81 The standard cartoon for the evolution of the Universe envisages three distinct phases following the Big Bang: the `recombination era', spanning the first few hundred thousand years, where the ionised hydrogen and helium plasma generated by the Big Bang gives way to cooler, neutral atomic gas; the `dark ages', lasting ~500,000 years, where the Universe is populated by neutral absorbing gas; and `cosmic reionisation', where the first episodes of star and black hole formation lead to photoionisation of neutral hydrogen, and much increased transparency in the inter(proto-)galactic medium. A key question for cosmological investigations is the identity of the cosmic reionisers - were quasars (i.e. massive black holes) primarily responsible, or were more conventional star clusters, or Population III objects, the key ingredient?
The aim of this proposal is to use gravitational lensing by massive clusters to probe the universe at redshifts beyond z=6. Combining NICMOS and ACS imaging with mid-infrared observations with Spitzer, the goal is to identify a representative sample of luminous objects at redshifts 6 < z < 10, laying the foundation for future more detailed investigations with JWST.

GO 10761: The X-ray Spectral and Optical/IR Flux Variability in Magnetars

The immediate environment of a magnetar (SGR 1806-20) Magnetars are neutron stars that possess extremely strong magnetic fields; measurements indicate values of 1011 Gauss or more (as compared with ~0.5 Gauss for the magnetic terrestrial field). The fields are sufficiently strong that they can induce star-quakes, producing very short-lived bursts of hard X-rays and soft gamma-rays, characteristics of the class of object known as "soft gamma repeaters". Some magnetars are pulsars, where the energy source is decay of the magnetic field, rather than accretion or rotation. The aim of the present program is to identify the source of the optical and near-infrared emission associated with magnetars. If this radiation is associated with the magnetosphere, then variations in the optical & IR should be mirrored by changes in the X-ray spectrum. This program will therefore use NICMOS on HST and ACIS on Chandra to obtain simultaneous near-IR and X-ray data for the magnetar 1E1048-5937.

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 10847: Coronagraphic Polarimetry of HST-Resolved Debris Disks

HST ACS/HRC coronagraphic images of debris disks around two nearby stars The last decade has seen the identification of debris disks around a number of stars in the Solar neighbourhood. The coronagraphic capabilities available on HST have been particularly useful in this regards, since the lower background present in space-based observations offers significant advantages in detecting these low surface brightness features. Those observations are complemented by mid-infrared surveys (notably by Spitzer) of denser, warmer disks in young stars. The latter observations detect thermal emission from the dust grains, permitting some constraints to be set on the chemical composition. The present program aims to use polarimetric observations of debris disks to probe the distribution of grain sizes and the density distribution of dust in those somewhat older systems.

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