This week on HST

HST Programs: January 26, 2009 - February 1, 2009

Program Number Principal Investigator Program Title Links
10877 Weidong Li, University of California - Berkeley A Snapshot Survey of the Sites of Recent, Nearby Supernovae Abstract
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11113 Keith S. Noll, Space Telescope Science Institute Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution Abstract
11236 Harry Teplitz, California Institute of Technology Did Rare, Large Escape-Fraction Galaxies Reionize the Universe? Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11566 Jonathan D. Nichols, Boston University Imaging Saturn's Equinoctal Auroras Abstract
11579 Alessandra Aloisi, Space Telescope Science Institute The Difference Between Neutral- and Ionized-Gas Metal Abundances in Local Star-Forming Galaxies with COS Abstract
11612 Kris Davidson, University of Minnesota - Twin Cities Eta Carinae's Continuing Instability and Recovery - the 2009 Event Abstract
11681 William B. Sparks, Space Telescope Science Institute A Search for Ultraviolet Emission Filaments in Cool Core Clusters Abstract
11788 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11789 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11942 George Fritz Benedict, University of Texas at Austin Increasing the Accuracy of HST Astrometry with FGS1r Abstract
11943 Douglas R. Gies, Georgia State University Research Foundation Binaries at the Extremes of the H-R Diagram Abstract
11956 Keith Noll, Space Telescope Science Institute Hubble Heritage: Side B Abstract
11962 Adam Riess, The Johns Hopkins University A New Supernova in the Antennae; Narrowing in on the Hubble Constant and Dark Energy Abstract
11966 Michael W. Regan, Space Telescope Science Institute The Recent Star Formation History of SINGS Galaxies Abstract
11969 Jian-Yang Li, University of Maryland Satellite Search for Dawn Mission Targets, Vesta and Ceres Abstract
11970 John Clarke, Boston University HST Observations of Titan's Escaping Atmosphere in Transit and in Emission Abstract
11991 Andrew J. Levan, The University of Warwick Constraining the late time lightcurve and energy of GRB 090102 Abstract

Selected highlights

GO 11236: Did Rare, Large Escape-Fraction Galaxies Reionize the Universe?

Lyman alpha image of the radio galaxy, 4C41.17 In Big Bang cosmology, the early history of the unverise is characterised by three distinct phases: the initial expansion, during which time Big Bang nucleosynthesis occurs, and the universe cools from its initial exceedingly high temperatures; recombination, which occurs at a redshift z~1,100 (or an age of ~400,000 years), when the Universe was cool enough to allow neutral hydrogen to become dominant, leading to high opacity and the cosmic microwave background; and reionisation, when energy sources reionised hydrogen, reducing the opacity of the intergalactic medium and restoring transparency. Reionisation is generally believed to have occurred at a redshift between z~6 and z~20, with the ionising sources either (or both) the first generation of stars (Population III starbursts) and/or proto-quasars. The IGM remains ionised thereafter. A key issue in developing an understanding of this process is assessing how readily starburst-generated Lyman-alpha emission escapes from galaxies, and how starbursts contribute to reionisation at intermediate redshifts. This proposal aims to quantify this issue by targeting a large sample of starburst galaxies at redshifts z~0.7. the galaxies all lie within the region covered by the COSMOS survey, and will be observed at ultraviolet wavelengths using the Advanced Camera for Surveys Solar Blind Channel (ACS/SBC).

GO 11942: Increasing the Accuracy of HST Astrometry with FGS1r

Artist's impression of a young planetary system This FGS program is a follow-up to GO 11210, "The Architecture of Exoplanetary Systems". Immanuel Kant is generally credited with first proposing that the planets in the Solar System coalesced from a flat, rotating disk formed by the Solar Nebula. Direct confirmation of that process only came in the early 1990s, when millimetre-wave interferometers were able to detect molecular gas in Keplerian rotation around a handful of nearby young stars. Since then, there have been numerous other observations, including Hubble's images of proplyds (protoplanetary disks) in the Orion Cluster, and Hubble and Spitzer observations of edge-on disks in other young stars. One of the clear selling points of the Solar Nebula disk model is that it appears to offer a natural path to forming planets with coplanar orbits, matching (most of) our observations of the Solar System. On the other hand, as our knowledge of exoplanetary systems has accumulated over the last decade, it has become clear that dynamical interactions may play a very important role in the evolution of these systems. In particular, disk/planet interactions are generally regarded as responsible for the inward migration of gas giants to form hot Jupiters in <3 day period orbits. Planet-planet interactions could lead to significant changes in orbital inclination. Radial velocity planet searches are uncovering more and more multi-planet systems. Program GO 11210 focused the high precision of HST's astrometric detectors, the Fine Guidance Sensors, on four of those systems. The aim is to complement the existing radial velocity measurements with sub-milliarcsecond precision astrometry, allowing determination of the true orbital paths - specifically, the relative inclination - of the low-mass objects in these systems. The present observations build on this program by adding longer-baseline measurements, providing a better basis for subtracting the systemic proper motion and identifying anomalous motions.

GO 11969: Satellite Search for Dawn Mission Targets, Vesta and Ceres

HST images of the dwarf planet, Ceres Ceres and Vesta are the two largest members of the main belt asteroids. Indeed, Ceres was the first member discovered, by Giuseppe Piazzi in 1801, while Vesta was the fourth discovery, in 1807 by Heinrich Wilhelm Olbers. Ceres is roughly spherical, with a diameter of 950 km, while Vesta is an oblate spheroid, ~580 x 560 x 485 km. Both have been studied extensively, using both ground-based telescopes and space observatories, including Spitzer and HST, and will be targeted for study by NASA's DAWN mission, launched on September 27 2007. Dawn will encounter Vesta in August 2011 and depart for ceres in May 2012, arriving in February 2015, with the mission ending in July 2015. Both asteroids (or dwarf planets) are known to have heavily cratered surfaces, particularly Vesta, suggesting a history of violent collisions. Indeed, fragments of Vesta are generally believed to account for a significant fraction of HED meteorites (Howardites, Eucrites and Diogenites). The present program aims to use deep WFPC2 imaging with HST to search for very low mass companions to these two dwarf planets, whose presence could be of significance to planning the details of the DAWN encounters.

Past weeks:
page by Neill Reid, updated 26/1/2009