This week on HST

HST Programs: November 30 - December 6, 2008

Program Number Principal Investigator Program Title Links
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11110 Stephan McCandliss, The Johns Hopkins University Searching for Lyman alpha Emission from FUSE Lyman Continuum Candidates Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11158 R. Michael Rich, University of California - Los Angeles HST Imaging of UV emission in Quiescent Early-type Galaxies Abstract
11201 Nitya Kallivayalil, Harvard University Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images Abstract
11213 Gerard T. van Belle, California Institute of Technology Distances to Eclipsing M Dwarf Binaries Abstract
11218 Howard E. Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group Abstract
11230 Christopher P. O'Dea, Rochester Institute of Technology HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11612 Kris Davidson, University of Minnesota - Twin Cities Eta Carinae's Continuing Instability and Recovery - the 2009 Event Abstract
11943 Douglas R. Gies, Georgia State University Research Foundation Binaries at the Extremes of the H-R Diagram Abstract
11957 Harold A. Weaver, The Johns Hopkins University Applied Physics Lab Hubble Investigation of Asteroid 21 Lutetia in Support of the Rosetta Mission Flyby Abstract
11962 Adam Riess, The Johns Hopkins University A New Supernova in the Antennae; Narrowing in on the Hubble Constant and Dark Energy Abstract

Some selected highlights

GO 11213: Distances to Eclipsing M Dwarf Binaries

Artist's impression of a cool binary system Eclipsing binaries are stellar systems where the orbital plane lies in the line of sight, leading to the components undergoing mutual eclipses. These systems are extremely powerful probes of stellar properties, since (given the appropriate radial velocity measurements) they permit direct measurement of both stellar masses and radii. Accurate distances can also be derived from these systems. These results are particularly interesting for stars near the bottom of the main sequence, approaching the hydrogen buyrning limit. The present program aims to use the Fine Guidance Sensors on HST to determine sub-milliarcsecond trigonometric parallaxes for five M-dwarf binaries: YY Gem, GU Boo, CM Dra, NSVS0103 and TRES-HER0-R

GO 11289: SL2S - The Strong Lensing Legacy Survey

ACS images of galaxy-galaxy Einstein ring lenses from the Sloan survey Gravitational lensing is a consequence the theory of general relativity. Its importance as an astrophysical tool first became apparent with the realisation (in 1979) that the quasar pair Q0957+561 actually comprised two lensed images of the same background quasar. In the succeeding years, lensing has been used primarily to probe the mass distribution of galaxy clusters, using theoretical models to analyse the arcs and arclets that are produced by strong lensing of background galaxies, and the large-scale mass distribution, through analysis of weak lensing effects on galaxy morphologies. Gravitational lensing can also be used to investigate the mass distribution of individual galaxies. Until recently, the most common background sources were quasars. Galaxy-galaxy lenses, however, offer a distinct advantage, since the background source is extended, and therefore imposes a stronger constraints on the mass distribution of the lensing galaxy than a point-source QSO. The CFHT Legacy survey provides a powerful tool for identifying candidate galaxy-galaxy lenses. Optical ground-based imaging, even from Hawaii, cannot match the results from a 2.4-metre telescope in orbit. Thus, the present program is using WFPC2 imaging to verify the nature of those candidates. The high resolution images can then be analysed to model the underlying mass distribution.

GO 11957: Hubble Investigation of Asteroid 21 Lutetia in Support of the Rosetta Mission Flyby

A comparison between fly-by images of the asteroid Gaspra and the two martian satellites, Phobos (lower) and Deimos (upper) ESA's Rosetta mission aims to make the first ever landing on a cometary nucleus. As such, it is a follow-up to the Giotto mission, which encountered, imaged and was sand-blasted by Comet Halley during the latter's 1986 perihelion passage. Rosetta was launched on 2 March 2004, and will rendezvous with Comet 67P/Churyumov-Gerasimenko in early 2014. After an extensive period of mapping the comet, Rosetta will release the lander, named Philae (the island in the Nile river where the Rosetta stone was found), which will land on the comet's surface and transmit back data on the chemical composition. On its way to Comet 67P/Churyumov-Gerasimenko, Rosetta will make a number of fly-bys of Earth and Mars, boosting the orbital energy, and will encounter two asteroids: 2867 Steins (September 5, 2008) and 21 Lutetia (July 10, 2010). The current HST observations are in preparation for the second encounter. Lutetia is a main-belt asteroid with an estimated diameter of 100 kilometres and a potentially unusual composition: although classified as a metallic (type M) asteroid, the spectral characteristics are somewhat unusual. Deep HST imaging with WFPC2 will be used to search for dust debris and for low-mass companions.

Past weeks:
page by Neill Reid, updated 1/10/2008