This week on HST


HST Programs: April 9 - April 15, 2007

Program Number Principal Investigator Program Title Links
10166 William Borucki, NASA Ames Research Center ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field Abstract
10468 Erich Karkoschka, University of Arizona Jupiter's Upper Stratospheric Hazes Probed with Ganymede Abstract
10612 Douglas Gies, Georgia State University Binary Stars in Cyg OB2: Relics of Massive Star Formation in a Super-Star Cluster Abstract
10786 Marc Buie, Lowell Observatory Rotational state and composition of Pluto's outer satellites Abstract
10792 Matthias Dietrich, The Ohio State University Research Foundation Quasars at Redshift z=6 and Early Star Formation History Abstract
10798 Leon Koopmans, Kapteyn Astronomical Institute Dark Halos and Substructure from Arcs & Einstein Rings Abstract
10809 Pieter van Dokkum, Yale University The nature of dry mergers in the nearby Universe Abstract
10814 Joel Bregman, University of Michigan The Masses for ultraluminous X-ray sources Abstract
10827 Gerard A. Kriss, Space Telescope Science Institute Imaging Polarimetry of the Seyfert 1 MCG-6-30-15: Clues to the Structure of Warm Absorber Abstract
10839 Dan Batcheldor Rochester Institute of Technology The NICMOS Polarimetric Calibration Abstract
10847 Dean Hines, Space Science Institute Coronagraphic Polarimetry of HST-Resolved Debris Disks Abstract
10858 Lin Yan, California Institute of Technology NICMOS Imaging of the z ~ 2 Spitzer Spectroscopic Sample of Ultraluminous Infrared Galaxies Abstract
10862 John Clarke, Boston University Comprehensive Auroral Imaging of Jupiter and Saturn during the International Heliophysical Year Abstract
10872 Harry Teplitz, California Institute of Technology Lyman Continuum Emission in Galaxies at z=1.2 Abstract
10873 Mark Whittle, The University of Virginia The Radio-quiet Jet Flow in Markarian 34 Abstract
10877 Weidong Li, University of California - Berkeley A Snapshot Survey of the Sites of Recent, Nearby Supernovae Abstract
10880 Henrique R. Schmitt, Naval Research Laboratory The host galaxies of QSO2s: AGN feeding and evolution at high luminosities Abstract
10890 Arjun Dey, NOAO Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies Abstract
10907 Scott Anderson, University of Washington New Sightlines for the Study of Intergalactic Helium: A Dozen High-Confidence, UV-Bright Quasars from SDSS/GALEX Abstract
11082 Christopher J. Conselice, University of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization and the High Redshift Obscured Universe Abstract
11083 Pat Cote, Herzberg Institute The Structure, Formation and Evolution of Galactic Cores and Nuclei Abstract
11085 Bill Sparks, Space Telescope Science Institute Europa in Eclipse: Tenuous Atmosphere, Electromagnetic Activity and Surface Luminescence Abstract

Some selected highlights

GO 10166: ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field

The Kepler satellite Kepler, a NASA Discovery mission, is designed to search for extrasolar planets by using high-precision photometric observations to detect transits. Scheduled for launch in June 2008, Kepler will continuously monitor ~100,000 (mainly) so lar-type stare within a ~100 square degree region in Cygnus. Ground-based observations have successfully detected several transiting planets (e.g. HD 209458); all are "hot jupiters", gas giants on short-period orbits which produce a photometric dip of ~10-2 with a periopd of a few days. In contrast, Kepler aims at detecting terrestrial planets within the habitable zone, and therefore must detect photometric transit signatures at the 10-4 level that last for 2-16 hours and recur on timescales of 1-2 years. This is a challenging task.
A subset of stellar binaries provide one of the main sources of confusion in searching for planetary transits, since "grazing" transits can mimic the planetary signature. This is particularly an issue with Kepler, since the optical system is designed to provide a broad psf, spreading the stellar flux over a large area on the detector to allow high photometric accuracy. As a result, faint eclipsing stellar binaries will contribute to the source counts. This program is using the high spatial resolution imaging provided by HST to study a small subset of the full Kepler target field to assess the likely statistical impact of these false positives.

GO 10468: Jupiter's Upper Stratospheric Hazes Probed with Ganymede

Ganymede and Jupiter, as imaged by Cassini on 3 December 2000 Over the next week, Hubhle will use WFPC2 to take a series of images of Ganymede, catching the satellite as it slips into occultation behind Jupiter. The observations, in five different passbands spanning the ultraviolet (250 nm) to the far red (892 nm), will probe the upper layers of the parent planet's atmosphere, and permit investigation of the structure of haze within the Jovian stratosphere. Until now, studies of the creation, growth and motions of these layers has been limited to theoretical analyses; the WFPC2 images will provide the first empirical measurements of the aerosols responsible for the high haze.

GO 10798: Dark Halos and Substructure from Arcs & Einstein Rings

Hubble imanges of Einstein ring gravitational lenses Gravitational lensing provides a powerful method of tracing the mass distribution of individual galaxies and galaxy clusters; at the same time, the amplified the light from background galaxies provides a means of probing the early stages of galaxy formation. The Sloan Digital Sky Survey (SDSS) has proven a powerful tool for identifying new lens candidates, although high angular resolution HST observations are essential for confirming those candidates as genuine gravitational lensing systems (see Program GO 10886). The present program focuses on that sample, targeting confirmed lenses for deep, multicolour imaging that aims to measure the overall mass distribution of the lens galaxies, and quantify the existence of small-scale sub-structure. The current cosmological paradigm, cold dark matter, predicts that sub-clustering within galactic halos should scale with increasing redshift; observations of lenses at different redshifts will serve to test this prediction.
GO 10847: Coronagraphic Polarimetry of HST-Resolved Debris Disks

HST ACS/HRC coronagraphic images of debris disks around two nearby stars The last decade has seen the identification of debris disks around a number of stars in the Solar neighbourhood. The coronagraphic capabilities available on HST have been particularly useful in this regards, since the lower background present in space-based observations offers significant advantages in detecting these low surface brightness features. Those observations are complemented by mid-infrared surveys (notably by Spitzer) of denser, warmer disks in young stars. The latter observations detect thermal emission from the dust grains, permitting some constraints to be set on the chemical composition. The present program aims to use polarimetric observations of debris disks to probe the distribution of grain sizes and the density distribution of dust in those somewhat older systems. NICMOS observations of the nearby M dwarf, AU Mic, and the F5 dwarf, HD 181327, are scheduled in the coming week.

Past weeks:
page by Neill Reid, updated 24/3/2007