This week on HST


HST Programs: April 7 - April 13, 2008


Program Number Principal Investigator Program Title Links
10841 Rupali Chandar, Observatories of the Carnegie Institution of Washington A Proper Motion Search for Intermediate Mass Black Holes in Globular Clusters (2nd Epoch Observations) Abstract
11017 Keith S. Noll, Space Telescope Science Institute Hubble Heritage Observations of SN1006 Abstract
11099 Marusa Bradac, Stanford University A "silver bullet" for the sources of reionization Abstract
11113 Keith S. Noll, Space Telescope Science Institute Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution Abstract
11120 Daniel Wang, University of Massachusetts A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center Abstract
11139 Ian Andrew Smith, Rice University NICMOS Observations of the Microquasar GRS 1758-258 Abstract
11143 Andrew J. Baker, Rutgers the State University of New Jersey NICMOS imaging of submillimeter galaxies with CO and PAH redshifts Abstract
11149 Eiichi Egami, University of Arizona Characterizing the Stellar Populations in Lyman-Alpha Emitters and Lyman Break Galaxies at 5.7 Abstract
11150 James R. Graham, University of California - Berkeley Beta Pic Polarimetry with NICMOS Abstract
11155 Marshall D. Perrin, University of California - Berkeley Dust Grain Evolution in Herbig Ae Stars: NICMOS Coronagraphic Imaging and Polarimetry Abstract
11157 Joseph H. Rhee, University of California - Los Angeles NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum Abstract
11159 R. Michael Rich, University of California - Los Angeles The True Galactic Bulge Luminosity Function Abstract
11176 Andrew S. Fruchter, Space Telescope Science Institute Location and the Origin of Short Gamma-Ray Bursts Abstract
11195 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources Abstract
11201 Nitya Kallivayalil, Harvard University Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images Abstract
11208 Tommaso L. Treu, University of California - Santa Barbara The co-evolution of spheroids and black holes in the last six billion years Abstract
11210 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11211 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11235 Jason A. Surace, California Institute of Technology HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies in the Local Universe Abstract
11295 Howard E. Bond, Space Telescope Science Institute Trigonometric Calibration of the Distance Scale for Classical Novae Abstract
11298 John P. Subasavage, Georgia State University Research Calibrating Cosmological Chronometers: White Dwarf Masses Abstract
11312 Graham Smith, University of Birmingham The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2 Abstract
11513 Nial Tanvir, University of Leicester The afterglow and host galaxy of GRB 080319: the first "naked eye" burst Abstract

Some selected highlights

GO 11113: Binaries in the Kuiper Belt: Probes of Solar System Formation and 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 will use WFPC2 imaging of known KBOs to identify new binary systems.

GO 11211: An Astrometric Calibration of Population II Distance Indicators

Measuring trigonometric parallax Trigonometric parallax measurement remains the fundamental method of determining distances to astronomical objects. The best ground-based parallax measurements can achieve accuracies of ~1 milliarcsecond, comparable with the typical accuracies achieved by the ESA Hipparcos astrometric satellite. This level of accuracy allows us to obtain reliable distances and luminosities for main sequence stars, subgiants, red giants and even a number of metal poor subdwarfs. However, with an effective distance limit of 100-150 parsecs, the sampling volume includes less than a handful of rarer, shorter-lived celestial objects. In particular, there are no RR Lyraes or Cepheids, two of the principal calibrators in the extragalactic distance scale. There is only one instrument currently available that can achieve astrometry of higher accuracy - the Fine Guidance Sensors (FGS) on HST. The present team used the FGS to measure a parallax of 3.82+/10.2 milliarseconds for RR Lyrae, the nearest star of its type. this corresponds toa distance of 262 parsecs. The present program aims to improve the calibration by extending observations to four more relatively nearby RR Lyraes (XZ Cyg, UV Oct, RZ Cep and SU Dra) and two Pop II Cepheids (Kappa Pav and VY Pyx).

GO 11312: The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2

Combined optical and X-ray (Chandra) image of a lensing galaxy cluster Gravitational lensing supplies a powerful method of tracing the mass distribution in galaxy clusters; at the same time, the amplified the light from background galaxies provides a means of probing the early stages of galaxy formation. These measurements are particularly effective when X-ray imaging data are also available, allowing direct measurement of the mass density and distribution of the hot intracluster medium. This snapshot proposal aims to use the Wide Field Camera on ACS to observe the central regions of low redshift (0.15 < z < 0.3) clusters with the requisite Chandra observations. The HST images will allow the resolution of lensed arcs in the cluster cores (due to strong lensing) and characterisation of weak-lensing distortions of the image profiles of faint background galaxies. The frequency and detailed distribution (size, multiplicity, redshifts) of the strong lens systems sets strong constraints on the total mass content, and its structure, in the central regions of low-redshift clusters. Those results, in turn, constrain cluster evolution, and offer insight into likely schemes for studying dark energy at higher redshifts.

GO 11513: The afterglow and host galaxy of GRB 080319: the first "naked eye" burst

The life history of a gamma-ray burst Gamma ray bursts are described colloquially as the biggest bangs since the Big Bang. Originally detected by US spy satellites in the 1960s, these short-lived bursts of high energy radiation resisted characterisation for over 30 years. It is only within the last decade that the Galactic vs. Extragalactic debate on their origins has been setled in favour of the latter. Generically, gamma ray bursts are believed to originate in the death throes of an extremely massive star, as it collapses to form either a black hole or a highly magnetised neutron star. Most occur at moderate to high redshifts, and the optical flashes reach magnitudes between 12th and 15th at their peak. However, GRB 080319B , detected by the SWIFT satellite at 06:12 UT on March 19th 2008 (one of four bursts detected on that date), shattered all previous records. Optical imaging by the "Pi of the sky" wide-field monitoring survey shows that the source reached a peak brightness of mV~5.5 , remaining above the naked-eye threshold for ~30 seconds. The parent galaxy lies at redshift z~0.94, so the peak brightness was close to 1017 solar luminosities. The burst has faded significantly, but may still be visible to HST, which can also resolve the detailed structure of the host galaxy.

Past weeks:
page by Neill Reid, updated 2/4/2008