This week on HST

HST Programs: November 30 - December 6, 2009

Program Number Principal Investigator Program Title Links
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11143 Andrew J. Baker, Rutgers the State University of New Jersey NICMOS imaging of submillimeter galaxies with CO and PAH redshifts Abstract
11189 Nial R. Tanvir, University of Leicester Probing the early universe with GRBs Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11235 Jason A. Surace, California Institute of Technology HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies in the Local Universe 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
11570 Adam Riess, The Johns Hopkins University & Space Telescope Science Institute Narrowing in on the Hubble Constant and Dark Energy 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
11595 John M. O'Meara, Saint Michaels College Turning out the Light: A WFC3 Program to Image z>2 Damped Lyman Alpha Systems Abstract
11599 Richard A. Wade, The Pennsylvania State University Distances of Planetary Nebulae from SNAPshots of Resolved Companions Abstract
11604 David Axon, Rochester Institute of Technology The Nuclear Structure of OH Megamaser Galaxies Abstract
11607 Thomas John Bethell , University of Michigan Ly-alpha propagation in the planet-forming region of a circumstellar disk Abstract
11616 Gregory J. Herczeg, California Institute of Technology The Disks, Accretion, and Outflows (DAO) of T Tau stars 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
11657 Letizia Stanghellini, National Optical Astronomy Observatories The population of compact planetary nebulae in the Galactic Disk Abstract
11662 Misty C. Bentz, University of California - Irvine Improving the Radius-Luminosity Relationship for Broad-Lined AGNs with a New Reverberation Sample 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
11692 J. Christopher Howk, University of Notre Dame The LMC as a QSO Absorption Line System Abstract
11700 Michele Trenti, University of Colorado at Boulder Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey Abstract
11704 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale Abstract
11714 Howard E. Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Local Group Globular Clusters Abstract
11720 Patrick Dufour, University of Arizona Detailed analysis of carbon atmosphere white dwarfs Abstract
11721 Richard S. Ellis, California Institute of Technology Verifying the Utility of Type Ia Supernovae as Cosmological Probes: Evolution and Dispersion in the Ultraviolet Spectra Abstract
11724 Marla C. Geha, Yale University Direct Age Determination of the Local Group dE Galaxies NGC 147 and NGC 185 Abstract
11732 C. S. Kochanek, The Ohio State University Research Foundation The Temperature Profiles of Quasar Accretion Disks Abstract
11789 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11790 John Wisniewski, NASA Goddard Space Flight Center HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic Abstract
11801 Holland Ford, The Johns Hopkins University Black Holes in Globular Clusters Abstract
11835 Mark Birkinshaw, University of Bristol The multi-faceted X-ray activity of low-redshift active galaxies Abstract

Selected highlights

GO 11570: Narrowing in on the Hubble Constant and Dark Energy

A GALEX image of Messier 106 (NGC 4258), one of the galaxies targeted in this program The Hubble constant remains a key parameter in understanding cosmology and the evolution of the Universe. Refining measurements of H0 therefore still represents a vital means of probing the nature of dark energy. The present program aims to tackle this question by laying a firmer foundation to the SNe Ia distance scale. The WFC3 IR camera will be used to identify and characterise Cepheid variables in eight relatively nearby galaxies that have hosted Type Ia SNe. Cepheids have signficantly lower amplitude at near-infrared wavelengths, and the measured magnitudes are less subject to uncertainties due to foreground reddening and variations in metallicity. As a consequence, determining the mean apparent magnitude, and hence the period/apparent magnitude relation, is substantially more straightforward than at optical wavelengths. Matching the observed relation against reference stars from the LMC allows a more reliable determination of the distance to the parent galaxy, and hence a firmer zeropoint for the SNe Ia distance scale. The aim is to reduce the level of systematics in determinations oif H0 to the 3 percent level.

GO 11666: Chilly Pairs: A Search for the Latest-type Brown Dwarf Binaries and the Prototype Y Dwarf

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 the 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") within the atmosphere. The overall timescales associated with the process remain unclear. The present proposal aims to tackle this issue through identifying, and characterising, ultracool binary systems with extremely cool components. 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 80 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 27 ultracool dwarfs with spectral types in the range T5 to T9, and will use WFC3 IR observations to search for previously unrecognised close, faint companions.

GO 11724: Direct Age Determination of the Local Group dE Galaxies NGC 147 and NGC 185

An image of the Andromeda galaxy and the dwarf elliptical NGC 205 taken on the Canada-france-Hawaii telescope using the CFH12K camera The Andromeda galaxy, M31, is the nearest large spiral to the Milky Way system, and, like the Milky Way, it is acccompanied by a large number of much smaller, satellite galaxies. The majority of those systems are dwarf spheroidals, similar to Milky Way satellites like Sextans, Draco and Leo. M31 lacks any moderately massive irregular galaxies as companions, like the LMC and SMC, but it does posses the four nearest examples of dwarf elliptical systems: NGC 147, NGC 185, NGC 205 (M110) and NGC 221 (M32). The latter two systems lie too close to the body of M31 itself to allow detailed investigation of its constituent populations, but NGC 147 and NGC 185 lie at large projected distances. Both of these galaxies have been studied extensively by ground- and space-based telescopes. Those observations strongly suggest that both galaxies are dominated by old stellar populations, although it remains unclear whether there is a significant contribution from intermediate age stars, as are present in some dwarf spheroidal satellites of the Milky Way. The present proposal will use ACS and WFC3 to obtain deep imaging of fields in both galaxies, with the aim of deriving deep, accurate colour-magnitude diagrams that will reach below the main-sequence turnoff and can be used to probe the detailed star formation history.

GO 11790: HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

The exozodiacal disk around Beta Pic Planet formation occurs in circumstellar disks around young stars. Most of the gaseous content of those disks dissipates in less than 10 million years, leaving dusty debris disks that are detectable through reflect light at near-infrared and, to a lesser extent, optical wavelengths. The disk structure is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Two of the most prominent and best characterised disks are those acompanying the A-type star Beta Pictoris, and the nearby M dwarf, AU Mic. Both stars are young, with age estimates ranging from 8 to 20 million years for beta Pic and 5 to 10 million years for AU Mic. beta Pic's disk, in particular, shows evidence for significant sub-structure that has been attributed to planetary companions. The present HST program aims to use the Fine Guidance Sensors to obtain high precision astrometry of these two young stars, and search for systematic astrometric residuals due to the hypothesised planetary companions.

Past weeks:
page by Neill Reid, updated 23/10/2009