This week on HST

HST Programs: February 4 - February 10, 2008

Program Number Principal Investigator Program Title Links
10827 Gerard A. Kriss, Space Telescope Science Institute Imaging Polarimetry of the Seyfert 1 MCG-6-30-15: Clues to the Structure of Warm Absorbers Abstract
10862 John Clarke, Boston University Comprehensive Auroral Imaging of Jupiter and Saturn during the International Heliophysical Year Abstract
10998 Peter McCullough, Space Telescope Science Institute Exoplanet XO-1b: light curve and parallax Abstract
11080 Daniela Calzetti, University of Massachusetts Exploring the Scaling Laws of Star Formation Abstract
11083 Patrick Cote, Dominion Astrophysical Observatory The Structure, Formation and Evolution of Galactic Cores and Nuclei Abstract
11084 Dan Zucker, Institute of Astronomy, Cambridge Probing the Least Luminous Galaxies in the Local Universe Abstract
11101 Gabriela Canalizo, University of California - Riverside The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies 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
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11161 Alicia M. Soderberg, California Institute of Technology Revealing the Explosion Geometry of Nearby GRB-SNe Abstract
11165 Joshua Winn, Massachusetts Institute of Technology The Radius of the Super-Neptune HD 149026b Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11195 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11210 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11213 Gerard T. van Belle, California Institute of Technology Distances to Eclipsing M Dwarf Binaries Abstract
11216 John A. Biretta, Space Telescope Science Institute HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet Abstract
11219 Alessandro Capetti, Osservatorio Astronomico di Torino Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio-quiet dichotomy? 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
11337 Daniel James Patnaude, Smithsonian Institution Astrophysical Observatory Investigating the X-ray Variability of Cassiopeia A Abstract

Some selected highlights

GO 10998: Exoplanet XO-1b: light curve and parallax

Artist's impression of a planetary transit against an active solar-type star Transiting extrasolar planets offer the opportunity to gain valuable insight into the interior structure and atmospheres of gas giants beyond the Solar System. Besides providing direct measures of mass (with no complications for v sin(i)) and radius (from accurate time-series photometry), spectroscopic observations obtained during either transit or planetary eclipse can probe the atmospheric structure and chemical composition. The present proposal targets the transiting system designated XO-1, which was discovered in 2006 by an international team of professional and amateur astronomers using a fleet of telescopes with very modest apertures - the primary survey telescope, the XO telescope, is a pair of 200-mm telephoto lenses - but a very wide field of view. These small telescopes are used to survey large areas of the celestial sphere, searching for photometric variations characteristic of planetary transits (i.e. periodic dips in brightness of 1-2%); transit candidates are then verified using higher accuracy photometric observations with larger telescopes, and finally radial velocity measurements to confirm the companion mass. XO-1b, the first planetary companion discovered in this campaign, is a Jupiter mass gas giant (0.9 MJ) in a 3.94 day orbit around a 12th magitude solar-type star in the Corona Borealis constellation. The present HST observations are designed to use NICMOS imaging (with the grism) to derive a more accurate light curve, and hence a refined estimate of the diameter (ground-based data suggest R ~ 1.3 RJ). The program is also using precise astrometry with the FGS to derive an accurate trigonometric parallax.

GO 11083: The Structure, Formation and Evolution of Galactic Cores and Nuclei

A wide-field view of the Virgo cluster The Virgo cluster, lying at a distance of ~20 MPc, is the nearest large galaxy cluster. The cluster embraces more than 2,000 galaxies, with masses ranging from ~3 x1012 MSun for the central giant elliptical, M87, to ~109 MSun dwarf systems, predominantly ellipticals but with a smattering of irregulars. In Cycle 11, the same proposal used the Advanced Camera for Surveys to observe more than 100 elliptical and S0 galaxies in Virgo, obtaining deep images in the SDSS g (green) and z (far-red) passbands. These observations show a systematic variation with luminosity in the surfacve brightness profile. Giant ellipticals have a relatively flat brightness profile in the central regions, while dwarfs tends to have compact nuclei. The aim of the current proposal is to use ultraviolet (WFPC2/F225W) and near-infrared (NIC1/F160W) images of the central regions to probe star formation and the star formation history on scales of 0.1-1.0 arcsecond (10-100 parsecs).

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 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).

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