This week on HST

HST Programs: June 21, 2010 - June 28, 2010

Program Number Principal Investigator Program Title
11536 James C. Green, University of Colorado at Boulder COS-GTO: Sleuthing the Source of Distant Cometary Activity
11541 James C. Green, University of Colorado at Boulder COS-GTO: COOL, WARM AND HOT GAS IN THE COSMIC WEB AND IN GALAXY HALOS
11556 Marc W. Buie, Southwest Research Institute Investigations of the Pluto System
11565 Sebastien Lepine, American Museum of Natural History A search for astrometric companions to very low-mass, Population II stars
11567 Charles R. Proffitt, Computer Sciences Corporation Boron Abundances in Rapidly Rotating Early-B Stars.
11568 Seth Redfield, Wesleyan University A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
11579 Alessandra Aloisi, Space Telescope Science Institute The Difference Between Neutral- and Ionized-Gas Metal Abundances in Local Star-Forming Galaxies with COS
11591 Jean-Paul Kneib, Laboratoire d'Astrophysique de Marseille Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?
11597 S. Adam Stanford, University of California - Davis Spectroscopy of IR-Selected Galaxy Clusters at 1 < z < 1.5
11598 Jason Tumlinson, Space Telescope Science Institute How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
11604 David J. Axon, Rochester Institute of Technology The Nuclear Structure of OH Megamaser Galaxies
11613 Roelof S. de Jong, Astrophysikalisches Institut Potsdam GHOSTS: Stellar Outskirts of Massive Spiral Galaxies
11619 Adam Gabriel Jensen, Wesleyan University Definitive ISM Abundances through Low-mass X-ray Binaries as Lighthouses
11625 Ivan Hubeny, University of Arizona Beyond the classical paradigm of stellar winds: Investigating clumping, rotation and the weak wind problem in SMC O stars
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
11648 Emanuele Daddi, Commissariat a l'Energie Atomique (CEA) WFC3 spectroscopy of an X-ray luminous galaxy cluster at z>2
11655 Konrad Kuijken, Universiteit Leiden Dynamics of the Galactic bulge/bar
11662 Misty C. Bentz, University of California - Irvine Improving the Radius-Luminosity Relationship for Broad-Lined AGNs with a New Reverberation Sample
11664 Thomas M. Brown, Space Telescope Science Institute The WFC3 Galactic Bulge Treasury Program: Populations, Formation History, and Planets
11666 Adam J. Burgasser, University of California - San Diego Chilly Pairs: A Search for the Latest-type Brown Dwarf Binaries and the Prototype Y Dwarf
11667 Christopher W. Churchill, New Mexico State University Detailed Probing of a 3000 km/s Ly-alpha + Metal Line Absorption Complex Near Two Galaxies at z=0.67
11669 Andrew S. Fruchter, Space Telescope Science Institute The Origins of Short Gamma-Ray Bursts
11693 John Krist, Jet Propulsion Laboratory Follow-up Observations of Debris Disks around Two Solar-Type Stars
11696 Matthew A. Malkan, University of California - Los Angeles Infrared Survey of Star Formation Across Cosmic Time
11697 Slawomir Stanislaw Piatek, New Jersey Institute of Technology Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies
11698 Mary E. Putman, Columbia University in the City of New York The Structure and Dynamics of Virgo's Multi-Phase Intracluster Medium
11707 Kailash Sahu, Space Telescope Science Institute Detecting Isolated Black Holes through Astrometric Microlensing
11710 John P. Blakeslee, Dominion Astrophysical Observatory The Extreme Globular Cluster System of Abell 1689: The Ultimate Test of Universal Formation Efficiency
11712 John P. Blakeslee, Dominion Astrophysical Observatory Calibration of Surface Brightness Fluctuations for WFC3/IR
11730 Nitya Jacob Kallivayalil, Massachusetts Institute of Technology Continued Proper Motions of the Magellanic Clouds: Orbits, Internal Kinematics, and Distance
11789 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators
12016 Carol A. Grady, Eureka Scientific Inc. The Stars and Edge-on Disks of PDS 144: An Intermediate-Mass Analog of Wide T Tauri Multiple Stars
12118 Mansi Kasliwal, California Institute of Technology PTF10fqs: A Luminous Red Nova in the Spiral Messier 99
12295 Howard E. Bond, Space Telescope Science Institute Searching for the Progenitor of the Type Ib Supernova 2010O

Selected highlights

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 11568: A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observation

A map of the Local Stellar Neighbourhood Understanding the nature and structure of gas within the interstellar medium is a key step towards understanding how material is recycled and how energetic processes, such as stellar winds and outflows, feed energy into the overall system. UV spectroscopy plays a key role in probing these effects: hot, background objects that produce relatively few intrinsic absorption features serve to map the the velocities and temperatures within the intervening gas along the line of sight. Observations of quasars are used to probe galaxy halos at moderate and high redshift; observations of hot stars provide similar information for gas in the Milky Way. The present program is using STIS to target stars within 100 parsecs of the Sun, studying the nearby interstellar medium. All of these stars have prior observations at far-UV wavelengths; the STIS data will cover the near-UV, survey Fe II and Mg II absorption.

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 11669: The Origins of Short Gamma-Ray Bursts

An artist's impression of a gamma-ray burst Gamma ray bursts are events that tap extraordinary energies (1045 to 1047 joules) in remarkably short periods of time. Several thousands bursts have been detected over the last 30+ years, and analyses indicate that they can be divided into two classes with durations longer or shorter than 2 seconds. The short bursts appear to release more high energy radiation, so the two subsets are known as long/soft and short/hard bursts. The long/soft bursts appear to originate in the collapse of very massive stars, while the short/hard bursts are coalescing binary systems (probably pairs of netron stars or black holes). The first optical counterpart to a gamma ray burst was identified in 1998, allowing confirmation of their extragalactic nature, and, since then, more than 60 bursts have been detected at X-ray wavelengths, and half that number detected at either optical or radio wavelengths; all of these detections are long/soft bursts. The present program will use a two-pronged approach to probe the nature of soft GRB progenitors by gaining a better understanding of the nature of the surrounding stellar population. One approach is statistical, with high angular resolution WFC3 imaging used to examine the colours of stellar populations in a sample of galaxies that have hosted past GRBs - are they characteristic of young, star-forming regions, or of older, more mature environments? The drawback with this study lies in the modest accuracies associated with the GRB positions in those galaxies. Complementing that analysis, the program will trigger ToO observations of two yet-to-be discovered GRBs, one in a star-forming galaxy and the other in an elliptical. The HST imaging of those sources should lead to more precise positoins, and hence a clearer idea of the local stellar environment.

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