This week on HST

HST Programs: February 8, 2010 - February 15, 2010

Program Number Principal Investigator Program Title Links
11524 James Green, University of Colorado COS-GTO: WARM AND HOT ISM IN AND NEAR THE MILKY WAY 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
11557 Gabriela Canalizo, University of California - Riverside The Nature of low-ionization BAL QSOs Abstract 11563 Garth Illingworth, University of California, Santa Cruz Galaxies at z~7-10 in the Reionization Epoch: Luminosity Functions to <0.2L* from Deep IR Imaging of the HUDF and HUDF05 Fields Abstract
11570 Adam Riess, The Johns Hopkins University & Space Telescope Science Institute Narrowing in on the Hubble Constant and Dark Energy 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
11597 S. Adam Stanford, University of California - Davis Spectroscopy of IR-Selected Galaxy Clusters at 1 < z < 1.5 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
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
11670 Peter Garnavich, University of Notre Dame The Host Environments of Type Ia Supernovae in the SDSS Survey Abstract
11677 Harvey B. Richer, University of British Columbia Is 47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing a Hubble Legacy Abstract
11696 Matthew A. Malkan, University of California - Los Angeles Infrared Survey of Star Formation Across Cosmic Time Abstract
11697 Slawomir Stanislaw Piatek, New Jersey Institute of Technology Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies Abstract
11730 Nitya Jacob Kallivayalil, Massachusetts Institute of Technology Continued Proper Motions of the Magellanic Clouds: Orbits, Internal Kinematics, and Distance Abstract
11741 Todd Tripp, University of Massachusetts Probing Warm-Hot Intergalactic Gas at 0.5 < z < 1.3 with a Blind Survey for O VI, Ne VIII, Mg X, and Si XII Absorption Systems Abstract
11803 Holland Ford, The Johns Hopkins University Observing Cluster Assembly Around the Massive Cluster RXJ0152-13 Abstract
11836 Andrea H. Prestwich, Smithsonian Institution Astrophysical Observatory Chandra Imaging of NGC 922 -- the closest collisional ring galaxy Abstract

Selected highlights

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 11670: The Host Environments of Type Ia Supernovae in the SDSS Survey

SN 2007uy and 2008D in NGC 2770 Supernovae have long attracted the attention of both amateur and professional astronomers as a means of studying the violent eruption and death of massive stars and degenerates. However, in the last decade they have also acquired considerable importance as distance indicators, tracing the expansion of the universe to redshifts well beyond the reach of more conventional yardsticks, such as cepheids, and providing a key underpinning for the hypothesised existcen of dark energy. Understanding the supernovae themselves, and, in particular, their progenitors, is key to accurately interpreting their luminosities and distances. The present program aims to tackle that aspect of the problem by using ACS to obtain deep, high resolution images of galaxies that have harboured recent type Ia supernovae. The targets are all drawn from the Sloan Digital Sky Survey, which has uncovered more than than 500 type Ia supernovae,. The supernovae themselves are long gone from view, but the ACS data will be used to probe the stellar populations in the immediate vicinity of the explosion, and hence gain a better understanding of the likely progenitor.

GO 11677: Is 47 Tuc Young? Measuring its White Dwarf Cooling Age and Completing a Hubble Legacy

Hubble image of the globular cluster, 47 Tucanae Globular clusters are members of the Galactic halo population, which formed during the first extensive period of star formation in the Milky Way. As such, the properties of the 106 to 107 stellar constituents can provide crucial insight into the earliest stages of galaxy formation. Hubble has conducted a significant number of observing programs targeting these systems, with the majority designed to obtain moderately deep, multicolour imaging data of a range of clusters. Those programs probw evolved stars, on the red giant and horizotal branch, and generally extend no more than a few magnitudes below the main-sequence turnoff. A few clusters, however, have been studied in detail - specifically, the two nearest clusters, NGC 6397, an extremely metal-poor cluster, and M4, a moderately metal-rich systems; Omega Centauri, one of the most massive clusters, perhaps even the remnant core of a dwarf galaxy; and 47 Tucanae, one of the higher metallicity systems, lying in the foreground of the Small Magellanic Cloud. Deep imaging of NGC 6397 and M4 has succeeded in clear detecion of the white dwarf cooling sequence in those clusters, and those data have been used to derive age estimates. The present observation aims to obtain similar data for 47 Tucanae, permitting an estimate of the relative age of these three, disparate clusters.

GO 11741: Probing Warm-Hot Intergalactic Gas at 0.5 < z < 1.3 with a Blind Survey for O VI, Ne VIII, Mg X, and Si XII Absorption Systems

Probing the intergalactic medium via QSO absorption lines One of the key issues facing modern cosmology is the "missing baryon" problem. In brief, a census of all the constituents in the local universe accounts for less than half of the baryonic mass expected based on measurements of the fractional abundanmce of deuterium and observations of the cosmic microwave background. It is generally believed that the missing material lurks in the form of extremely hot gas in the intergalactic medium. The most effective means of probing that medium, and testing this hypothesis, is to search for the appropriate absorption lines in the spectrum of a background source. QSOs are particularly effective cosmic searchlights, since they have strong continuum flux levels at the ultraviolet wavelengths where most of the important absorption lines fall. Following SM4, and the installation of the Cosmic Origins Spectrograph, HST is now well equipped to tackle this type of program, and search fgor a full accounting of the baryonic universe. The present program weill use COS to obtain spectra of nine QSOs at redshifts beyond z=0.89, and will search for warm-hot intergalactic gas in the redshift range 0.5 < z < 1.3.

Past weeks:
page by Neill Reid, updated 19/2/2010