This week on HST

HST Programs: August 4 - August 10, 2008

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
11072 Carole A. Haswell, Open University Measuring the Physical Properties of the first two WASP transiting extrasolar planets Abstract
11079 Luciana Bianchi, The Johns Hopkins University Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys Abstract
11101 Gabriela Canalizo, University of California - Riverside The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies Abstract
11110 Stephan McCandliss, The Johns Hopkins University Searching for Lyman alpha Emission from FUSE Lyman Continuum Candidates Abstract
11122 Bruce Balick, University of Washington Expanding PNe: Distances and Hydro Models Abstract
11134 Karen Knierman, University of Arizona WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge Abstract
11135 Mariska Kriek, Universiteit Leiden Extreme makeovers: Tracing the transformation of massive galaxies at z~2.5 Abstract
11136 Michael C. Liu, University of Hawaii Resolving Ultracool Astrophysics with Brown Dwarf Binaries Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11147 Rupali Chandar, Carnegie Institution of Washington The Origin of Diffuse UV Light from Spiral Disks Abstract
11151 Gregory J. Herczeg, California Institute of Technology Evaluating the Role of Photoevaporation of Protoplanetary Disk Dispersal Abstract
11164 David A. Weintraub, Vanderbilt University Molecular Hydrogen Disks Around T Tauri Stars Abstract
11172 Arlin Crotts, Columbia University in the City of New York Defining Classes of Long Period Variable Stars in M31 Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11197 Peter Garnavich, University of Notre Dame Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11203 Kevin Luhman, The Pennsylvania State University A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus Abstract
11210 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11212 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries 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
11222 Michael Eracleous, The Pennsylvania State University Direct Detection and Mapping of Star Forming Regions in Nearby, Luminous Quasars Abstract
11227 Jifeng Liu, Smithsonian Institution Astrophysical Observatory The orbital period for an ultraluminous X-ray source in NGC1313 Abstract
11548 S. Thomas Megeath, University of Toledo NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation Abstract
11807 M. Livio, Space Telescope Science Institute Hubble WFPC2 imaging of NGC 2074 in the Large Magellanic Cloud Abstract

Some selected highlights

GO 11072: Measuring the Physical Properties of the first two WASP transiting extrasolar planets

Artist's impression of a planetary transit & a partial light curve Transiting extrasolar planets offer particularly valuable insight into the structure of these non-Solar System gas giants. 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 first such systems, including HD 209658b and HD 189733b, were originally discovered as radial velocity variables, and only subsequently identified as transits based on follow-up photometry. However, the last few years have seen the instigation of almost a dozen wide-field photometric surveys that are searching specifically for such systems - and those surveys are starting to bear fruit. The present HST program aims to obtaina time series of NICMOS narrowband images of two exoplanet hosts identified by the Wide Angle Search for Planets (WASP) project. Like most wide-field surveys, this program uses a battery of mini-telescopes (or large camera) to rapidly scan selected areas of the celestial sphere. The original data have sufficient photometric accuracy to allow the detection of transiting planets (which typically produce photometric signatures of depth 0.5-1%). The higher-precision follow-up observations with HST will allow more accurate determinations of the eclipse depth, and hence stronger constraints on the planetary radii.

GO 11110: Searching for Lyman alpha Emission from FUSE Lyman Continuum Candidates

The starburst galaxy, M82 Ultraviolet light plays an important role in ionising the interstellar and intergalactic medium. Hot, massive stars are the one of the principal sources of UV flux in the present universe. It is therefore important to understand the efficiency with which that light manages to escape from star forming regions, particularly as a means of estimating the relative importance of star formation as an ionising source in the early universe. The present program targets a number of star forming galaxies that have been observed by the Far Ultraviolet Satellite Explorer (FUSE) and detected in the Lyman continuum (shortward of 912 Angstroms). The ACS/SBC camera is being used to image those systems at Lyman alpha; ground-based imaging has already been used to map the Balmer line emission. All of these data will be combined in models that will be used to estimate the global effect of star formation on the surrounding gaseous environment.

GO 11134: WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge

ACS image of the spectacular tidal tail of the Tadpole galaxy, Arp 188 Gravitational interactions between close galaxy pairs produce tidal tails, which can often be sites of extensive star formation in young, gas-rich spiral systems. Within the Milky Way, we know that most stars are born in fairly dense clusters, comparable with the Orion Nebula Cluster, and observatios of nearby sprials (M31, M33) suggest that the same situation pervades in those systems. However, observations suggest that star clusters tend to be rare in tidal tails. The present program is using WFPC2 to obtain R (F606W) and I (F814W) band observations of 12 tidal tail systems, with the aim of quantifying the contribution made by star clusters to star formation in these sparse environments.

GO 11136: Resolving Ultracool Astrophysics with Brown Dwarf Binaries

NICMOS images of the ultracool L/T binary, 2MASS J22521073-1730134; the northern component, notably fainter at F160W, is the T dwarf. Ultracool dwarfs are defined as having spectral types later than M7, and therefore include the recently discovered L and T dwarfs. They encompass the lowest mass stars (masses < ~0.1 MSub) and sub-stellar mass brown dwarfs, with surface temperatures ranging from ~2500K (~M7) to ~700K (late-type T dwarfs). Following their discovery over a decade ago, considerable theoretical attention has focused on the evolution of the intrinsic properties, particularly the details of the atmospheric changes in the evolution from type L to type T. This point marks the emergence of methane as a dominant absorber at near-infrared wavelengths. Current models suggest this transition occurs at ~1400-1200K, and that the spectral changes are at least correlated with, and perhaps driven by, the distribution and properties of dust layers ("clouds"). The overall timescales associated with this process remains unclear. The present proposal aims to tackle this issue through observations of ultracool binary systems. Since these systems are almost certainly coeval, the relative spectral energy distributions of the two components can be used to set constraints on evolutionary models. More than 40 ultracool binary systems are currently known; almost all have relatively small linear separations (<15 AU), and components with mass ratios close to one. The present program targets 13 systems with spectral types near the L/T boundary.

Past weeks:
page by Neill Reid, updated 18/5/2008