This week on HST

HST Programs: November 16 - November 22, 2009

Program Number Principal Investigator Program Title Links
10897 Michael Liu, University of Hawaii Coronagraphic imaging of the submillimeter debris disk of a 200Myr old M-dwarf Abstract
11099 Marusa Bradac, Stanford University Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11150 James R. Graham, University of California - Berkeley Beta Pic Polarimetry with NICMOS Abstract
11166 Jong-Hak Woo, University of California - Santa Barbara The Mass-dependent Evolution of the Black Hole-Bulge Relations Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11338 Michael R. Garcia, Smithsonian Institution Astrophysical Observatory Continued M31 Monitoring for Black Hole X-ray Nova Abstract
11360 Robert W. O'Connell, The University of Virginia Star Formation in Nearby Galaxies 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
11565 Sebastien Lepine, American Museum of Natural History A search for astrometric companions to very low-mass, Population II stars Abstract
11588 Raphael Gavazzi, CNRS, Institut d'Astrophysique de Paris Galaxy-Scale Strong Lenses from the CFHTLS survey Abstract
11589 Oleg Y. Gnedin, University of Michigan Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo Abstract
11594 John M. O'Meara, Saint Michaels College A WFC3 Grism Survey for Lyman limit absorption at z=2 Abstract
11644 Michael E. Brown, California Institute of Technology A dynamical-compositional survey of the Kuiper belt: a new window into the formation of the outer solar system Abstract
11666 Adam J. Burgasser, Massachusetts Institute of Technology Chilly Pairs: A Search for the Latest-type Brown Dwarf Binaries and the Prototype Y Dwarf Abstract
11697 Slawomir Stanislaw Piatek, New Jersey Institute of Technology Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies Abstract
11704 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale Abstract
11724 Marla C. Geha, Yale University Direct Age Determination of the Local Group dE Galaxies NGC 147 and NGC 185 Abstract
11735 Filippo Mannucci, INAF - IRA, Firenze The LSD project: dynamics, merging and stellar populations of a sample of well-studied LBGs at z~3 Abstract
11740 Frederic J. Pont, University of Bern A Complete Optical and NIR Atmospheric Transmission Spectrum of the Exoplanet HD189733b Abstract
11783 Nancy R. Evans, Smithsonian Institution Astrophysical Observatory A Complete Optical and NIR Atmospheric Transmission Spectrum of the Exoplanet HD189733b Abstract
11788 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract

Selected highlights

GO 11360: Star Formation in Nearby Galaxies

WFC3 image of star forming regions in M83 Star formation remains a (perhaps "the") key astrophysical process in determining the overall evolution of galactic systems. Wide Field Camera 3, the new imaging camera installed in HST during Servicing Mission 4, has two channels, semsitive to UVIS and IR wavelengths respectively, each equipped with a wide range of filters, sampling broad- and narrow-band wavelengths ranges from 2000 Angstroms to 1.7 microns. This panchromatic capability, coupled with the availability of the Advanced Camera for Surveys at visual and red wavelengths, is being being applied to survey active star forming regions in a number of nearby galaxies. The targets include M85, NGC 4150, 30 Doradus in the Large Magellanic Cloud, Centaurus A (NGC 5128) and (pictured above) M83.

GO 11565: A search for astrometric companions to very low-mass, Population II stars

HST image of Gliese 623AB, a nearby disk-dwarf binary system Binary stars provide an important avenue for setting constraints on stellar evolution, particularly binary stars that consist of components with significantly different masses. The simplest means of producing stars in a dynamically bound system is during the formation process; consequently, it is reasonable to assume that the the stars are coeval and a comparison between the observed properties and predictions can constrain stellar models. Binary systems are common in stars in the Galactic disk, although the overall frequency does decrease with stellar mass, ranging from ~60-70% for G dwarfs to closer to 20% for late-type M dwarfs and ultracool dwarfs. Binaries are much rarer among the metal-poor members of the Galactic halo, with only a handful known among cool, late-type subdwarfs. The present program aims to expand the sample by using WFC3 on HST to image low-mass, metal-poor subdwarfs within 120 parsecs of the Sun, searching for close, faint companions that can be monitored for astrometric orbit determinations.

GO 11589: Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo

Artistic view of a hypervelocity star Hypervelocity stars are stars that have velocities that exceed the escape velocity of the Milky Way by a very substantial margin. Stars can only achieve such velocities through violent gravitational interactions with other bodies. Indeed, to achieve velocities of 1,000 km/sec or more, the proposed mechanism involves binary stars interacting with the black hole at the Galactic Centre: one of the binary components is lost to the black hole, and the other ejected at from the core. The existence of such objects was hypothesised over 20 years ago, but the first candidate was only identified in 2005: SDSS J090745.0+024507, an apparently non-descript sunlike star, lying at a distance of 71 kpc from the Sun in the Galactic, and moving at a velocity of 850 km/sec, or more than twice the escape velocity. Since then, a number of other candidates have been identified, and the present HST program aims to measure precise proper motions that will quantify their space motions.

GO 11594: A WFC3 Grism Survey for Lyman limit absorption at z=2

HRC grism image of SN 1987A, as displayed in the Hubble Legacy Archive Grisms are optical components with finely ruled gratings that canbe introduced into the beam of an imaging camera to produce low-resolution spectra of objects within the field of view. Wide Field Camera 3 on HST has three such components: an ultraviolet grism, G280, providing spectroscopy from ~2100 to 3900 Angstroms; and two grisms, G102 and G141, for use at near-infrared wavelengths. The present program aims to use the UV grism to search for galaxies at redshifts in the range 1.8 < z < 2.5. The observations target 64 quasars, drawn from the Sloan Digital Sky Survey, that have absorption features that are characteristic of that redshift range. Those features are likely due to foreground galaxies, whose extended gaseous halos absorb light from the QSO. The grism data will used to search for sources with emission lines that indciate that they are at the appropriate redshift.
Past weeks:
page by Neill Reid, updated 23/10/2009