This week on HST

HST Programs: April 24 - April 30, 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
10505 Carme Gallart, Instituto de Astrofisica de Canarias The Onset of Star Formation in the Universe: Constraints from Nearby Isolated Dwarf Galaxies 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
10523 Roelof de Jong, Space Telescope Science Institute The Halo Shape and Metallicity of Massive Spiral Galaxies Abstract
10524 Francesco Ferraro, Universita di Bologna Blue Stragglers: a key stellar population to probe internal cluster dynamics 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
10536 Raghvendra Sahai, Jet Propulsion Laboratory What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey Abstract
10545 Michael Brown, California Institute of Technology Icy planetoids of the outer solar system Abstract
10549 Robert Kirshner, Harvard University SAINTS - Supernova 1987A INTensive Survey Abstract
10554 Ray Sharples, University of Durham Globular Cluster Systems of Elliptical Galaxies in Low Density Environments Abstract
10568 Oleg Kargaltsev, The Pennsylvania State University Ultraviolet spectrum of the binary millisecond pulsar J0437-4715 Abstract
10573 Mario Mateo, University of Michigan Globular Clusters in the Direction of the Inner Galaxy Abstract
10576 Gabriel Prochter, University of California - Santa Cruz An ACS Imaging Survey of the Galaxies Hosting Strong Mg II Absorption Abstract
10587 Adam Bolton, Smithsonian Institution Astrophysical Observatory Measuring the Mass Dependence of Early-Type Galaxy Structure 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
10602 Jesus Maiz-Apellaniz, Space Telescope Science Institute - ESA Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS 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
10782 Imke de Pater, University of California - Berkeley Quit winking: Jupiter opens its other eye Abstract

Some selected highlights

GO 10496: Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

HST images of intermediate redshift supernovae The last few years of the twentieth century saw a revolution in cosmology, with the measurement of the acceleration term in expansion at high redshifts and the identification of dark energy as a major cosmological component. Type Ia supernovae are the prime yardstick for measuring the rate of expansion at moderate and high redshifts, and Hubble offers almost the only way of obtaining reliable post-maximum photometry of these objects to determine the full shape of the light curve. Most previous HST supernovae programs have concentrated on field galaxies, such as those illustrated here, but applying appropriate corrections for in situ reddening by dust remains an issue in these systems. The present program aims to minimise the uncertainties by searching for supernovae in massive, high-redshift clusters, with the expectation that the majority of detections lie within dust-poor elliptical galaxies. ACS survey observations of eight clusters are scheduled for the coming week, together with follow-up NICMOS observations of a supernova detected in previous ACS images.

GO 10514: Kuiper Belt Binaries: Probes of Early Solar System Evolution

A composite of HST images 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 10573: Globular Clusters in the Direction of the Inner Galaxy

Colour-magnitude diagram for the bulge globular cluster, NGC 5927 (ground-based data) Globular clusters have served as important probes of Galactic structure since the early years of the twentieth century, when Harlow Shapley used their spatial distribution as evidence for his `Large Galaxy' model. Their ages, chemical abundances and kinematics provide insight into the formation and early evolution of the Milky Way. A substantial number of globulars lie in the inner Galaxy, many of which are probably associated with the Bulge, rather than the halo (as originally proposed by Robert Zinn in 1980). The line of sight towards these systems passes through the heart of the Galactic disk, and most are subject to significant reddening by foreground dust. This can prove a severe hindrance to reliable interpretation on the colour magnitude diagrams. This proposal will obtain ACS/WFC observations in the F435W, F555W and F814W filters, and will use the resultant B, V and I data to map the differential extinction across 27 Bulge globular clusters. All of these clusters are inc highly crowded fields, so the ACS observations are necessary to derive accurate CMDs and determine reliable intrinsic properties.

GO 10626: A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to z = 0.9

Lensed arcs in an intermediate redshift galaxy cluster Gravitational lensing provides a powerful method of tracing the mass distribution in galaxy clusters, while amplifying the light from background galaxies. This proposal will obtain ACS observations of a subset of 150 galaxy clusters, searching for the tell-tale arcs that reveal gravitational lensing. The aim is to use those data to measure the mass distribution in the targeted clusters, and constrain the evolution of both the baryonic and dark mass in cluster cores at redshifts less than z=0.9. These images will also yield a well-defined sample of arcs formed by strong lensing; the frequency and detailed distribution (size, multiplicity, redshifts) of these strong lens systems sets strong constraints on the total mass content (and its structure) in the centers of the targeted clusters.

Past weeks:
page by Neill Reid, updated 21/4/2006