This week on HST

HST Programs: November 26 - December 2, 2007

Program Number Principal Investigator Program Title Links
10840 Nuria Calvet, University of Michigan The FUV fluxes of Tauri stars in the Taurus molecular cloud Abstract
10852 Glenn Schneider, University of Arizona Coronagraphic Polarimetry with NICMOS: Dust grain evolution in T Tauri stars Abstract
10896 Paul Kalas, University of California - Berkeley An Efficient ACS Coronagraphic Survey for Debris Disks around Nearby Stars Abstract
10905 R. Tully, University of Hawaii The Dynamic State of the Dwarf Galaxy Rich Canes Venatici I Region Abstract
10907 Scott F. Anderson, University of Washington New Sightlines for the Study of Intergalactic Helium: A Dozen High-Confidence, UV-Bright Quasars from SDSS/GALEX Abstract
10915 Julianne Dalcanton, University of Washington ACS Nearby Galaxy Survey Abstract
11011 C. S. Kochanek, The Ohio State University Research Foundation Dissecting An Accretion Disk 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
11082 Christopher Conselice, Univ. of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Obscured Universe Abstract
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11125 Joel N. Bregman, University of Michigan The Dynamical Evolution of Globular Clusters Abstract
11128 David Bradley Fisher, University of Texas at Austin Time Scales Of Bulge Formation In Nearby Galaxies Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11140 Klaus Werner, Universitat Tubingen, Institut fur Astronomie & Astrophysik Can mass-ejections from late He-shell flash stars constrain convective/reactive flow modeling of stellar interiors? Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11175 Sandra M. Faber, University of California - Santa Cruz UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence 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
11211 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11212 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11299 Todd J. Henry, Georgia State University Research Foundation Calibrating the Mass-Luminosity Relation at the End of the Main Sequence Abstract

Some selected highlights

GO 10907: New Sightlines for the Study of Intergalactic Helium: A Dozen High-Confidence, UV-Bright Quasars from SDSS/GALEX

GALEX, the Galaxy Evolution Explorer GALEX is a NASA small explorer-class mission equipped with a 50-cm diameter telescope. Launched on 28th April 2003, it has beaten its nominal lifetime by 17 months (and counting), conducting ultraviolet imaging and low-resolution grism spectroscopy at far-UV (125-175 nm) and near-UV (175-280 nm) wavelengths. The principal science goal is investigating the star formation history of the universe, focusing particularly on star formation in nearby galaxies but also probing to higher redshifts. The present HST proposal aims to target the more distant regime. The GALEX source catalogues have been cross-referenced against SDSS catalogues of high redshift (z > 3.1) quasars, aiming to identify UV-bright QSOs. These sources can serve as effective probes of the ionisation state of the intergalactic medium at intervening redshifts. In particular, analysis of the He II Lyman-alpha absorption will shed light on the epoch of reionisation of intergalactic helium, generall placed between redshifts 3 and 4.

GO 11142: Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3

NICMOS image of the nearby luminous IR galaxy, Arp 299 Luminous infrared galaxies (LIRGs) have total luminosities that exceed 1011.4 LSun, with most of the energy emitted at wavelengths longward of 10 microns. Many (perhaps most) of these galaxies are interacting or merging disk galaxies, with the excess infrared luminosity generated by warm dust associated with the extensive star formation regions. Many systems also exhibit an active nucleus, and may be in the process of evolving towards an S0 or elliptical merger remnant. The present program is targeting systems with redshifts in the range 0.3 < z < 2.7, combining imaging at near-infrared (NICMOS on HST) and mid-infrared (MIPS on Spitzer) wavelengths. All of the systems already have Spitzer mid-infrared spectra, allowing not only an accurate characterisation of the over all flux distribution, and a \ determination of the total luminosity, but also providing insight into the galaxian dust content and chemical evolution.

GO 11178: Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries

Preliminary orbital determination for the KBO WW31, based on C. Veillet's analysis of CFHT observations; the linked image shows the improved orbital derivation, following the addition of HST imaging 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 (or trans-Neptunian objects, TNOs) 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. These issues can be addressed, at least in part, through deriving a better understanding of the composition of KBOs - and those properties can be deduced by measuring the orbital parameters for binary systems. The present proposal will use the Planetary camera on WFPC2 to determine the relative orbits for several known KBO binaries. Just as with binary stars, the orbital period and semi-major axis give the total system mass, while the mid-infrared properties (measured by Spitzer) allow an assessment of the surface area/diameters; combining these measurements gives an estimate of the mean density.

GO 11299: Calibrating the Mass-Luminosity Relation at the End of the Main Sequence

The MV-mass relation for low-mass stars (from T. Henry) The mass-luminosity relation remains one of the key underpinnings of stellar astrophysics, notably in probing the grey area that separates hydrogen-burning stars from cooling-powered brown dwarfs. The calibration of thsi relation rests on observations of binary systems, primarily eclipsing binaries at masses above 1 MSun, and primarily astrometric binaries at sub-solar masses. In the latter case, reliable mass determinations require orbital measurements of extremely high accuracy, which, in turn, requires high precision astrometry over at least one orbital period. The Fine Guidance Sensors on HST have proven invaluable in this regard, since they allow sub-milliarcsecond accuracy astrometry of binary systems with sub-arcsecond separations; in other words, HST allows measurement of nearby, low-mass binaries with periods short enough to allow completion of the observations in significantly less than an astronomer's lifetime. The current program is using the FGS to monitor six close binary systems. Observations are scheduled of G250-29 (also known as LHS 221). Lying at a distance of 10.6 parsecs, this system comprises an M2.5 primary and an ~M3.5 secondary, with a magnitude difference of ~1.6 magnitudes at visual wavelengths.

Past weeks:
page by Neill Reid, updated 7/11/2007