This week on HST

HST Programs: July 18, 2011 - July 24, 2011

Program Number Principal Investigator Program Title
12025 James C. Green, University of Colorado at Boulder COS-GTO: QSO Absorbers, Galaxies and Large-scale Structures in the Local Universe Part 2
12034 James C. Green, University of Colorado at Boulder COS-GTO: Brown Dwarf Activity Part 2
12036 James C. Green, University of Colorado at Boulder COS-GTO: Accretion Flows and Winds of Pre-Main Sequence Stars Part 2
12069 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12072 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12100 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12166 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies
12181 Drake Deming, University of Maryland The Atmospheric Structure of Giant Hot Exoplanets
12186 Hans Moritz Guenther, Smithsonian Institution Astrophysical Observatory Jet launching and evolution in the weakly magnetized Herbig Ae star HD 163296
12189 Walter Jaffe, Sterrewacht Leiden Do stars ionise the filaments in NGC 1275 ?
12192 James T. Lauroesch, University of Louisville Research Foundation, Inc. A SNAPSHOT Survey of Interstellar Absorption Lines
12199 Peter Christian Schneider, Universitat Hamburg, Hamburger Sternwarte The shocking truth about DG Tau's jet
12209 Adam S. Bolton, University of Utah A Strong Lensing Measurement of the Evolution of Mass Structure in Giant Elliptical Galaxies
12210 Adam S. Bolton, University of Utah SLACS for the Masses: Extending Strong Lensing to Lower Masses and Smaller Radii
12211 Nuria Calvet, University of Michigan Are Weak-Line T Tauri Stars Still Accreting?
12214 Sara Ellison, University of Victoria Low redshift damped Lyman alpha systems selected by 21cm absorption: A new route to high efficiency?
12224 Naveen A. Reddy, University of California - Riverside Measuring the Stellar Populations of Individual Lyman Alpha Emitters During the Epoch of Peak Star Formation
12248 Jason Tumlinson, Space Telescope Science Institute How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L*
12251 Zachory K. Berta, Harvard University The First Characterization of a Super-Earth Atmosphere
12268 Ian U. Roederer, Carnegie Institution of Washington Production of the Heavy Elements in the Universe
12271 William B. Sparks, Space Telescope Science Institute Probing the Physics of Gas in Cool Core Clusters: Virgo
12275 Bart P. Wakker, University of Wisconsin - Madison Measuring gas flow rates in the Milky Way
12283 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey {WISP}: A Survey of Star Formation Across Cosmic Time
12286 Hao-Jing Yan, University of Missouri - Columbia Hubble Infrared Pure Parallel Imaging Extragalactic Survey {HIPPIES}
12287 Scott D. Friedman, Space Telescope Science Institute Constraining Models of Deuterium Depletion and Galactic Chemical Evolution with Improved Measurements of D/H
12291 John Krist, Jet Propulsion Laboratory STIS coronagraphy of Spitzer-selected debris disks
12299 Michael Eracleous, The Pennsylvania State University Spectroscopic Signatures of Binary and Recoiling Black Holes
12307 Andrew J. Levan, The University of Warwick A public SNAPSHOT survey of gamma-ray burst host galaxies
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12322 Kailash C. Sahu, Space Telescope Science Institute Detecting Isolated Black Holes through Astrometric Microlensing
12367 Michael R. Garcia, Smithsonian Institution Astrophysical Observatory Monitoring M31 for BHXNe
12436 Mark R. Showalter, SETI Institute New Horizons Mission Planning Support: A Deep Search for Faint Rings of Pluto

Selected highlights

GO 12036: Accretion flows and winds in pre-main sequence stars

Wide-field image, from NOAO, of T Tauri and its immediate environs The T Tauri stage of evolution occurs early in a star's lifetime, within ~10 Myrs of its birth, when it still retains a dense, dust and gas-rich circumstellar disk. During this phase, there is substantial accretion of material onto the central star. This leads to heating of the inner regions of the accretion disk, and significant emission at ultraviolet and X-ray wavelengths. Previous HST programs (e.g. GO 10840 ) have used the STIS and the ACS/SBC to investigate these processes at FUV wavelengths. The present program extends those investigations using COS, which provides more than an order of magnitude more sensitivity and resolution. The observations focus on two well-known stars: BP Tau, spectral type K5, a member of the Taurus-Auriga association; and RU Lupi, a mid-G type member of the Lupus star forming cloud. Both stars lie at distances of ~140 parsecs, are known to harbour circumstellar disks, and have ages less than ~10 myrs. The COS observations will be used to probe the temperature distribution, flow velocities and column densities in the disk and outflow regions.

GO 12210: SLACS for the Masses: Extending Strong Lensing to Lower Masses and Smaller Radii

ACS images of galaxy-galaxy Einstein ring lenses from the Sloan survey Gravitational lensing is a consequence the theory of general relativity. Its importance as an astrophysical tool first became apparent with the realisation (in 1979) that the quasar pair Q0957+561 actually comprised two lensed images of the same background quasar. In the succeeding years, lensing has been used primarily to probe the mass distribution of galaxy clusters, using theoretical models to analyse the arcs and arclets that are produced by strong lensing of background galaxies, and the large-scale mass distribution, through analysis of weak lensing effects on galaxy morphologies. Gravitational lensing can also be used to investigate the mass distribution of individual galaxies. Until recently, the most common background sources were quasars. Galaxy-galaxy lenses, however, offer a distinct advantage, since the background source is extended, and therefore imposes a stronger constraints on the mass distribution of the lensing galaxy than a point-source QSO. The Sloan Digital Sky Survey is a powerful tool for identifying candidate galaxy-galaxy lenses, and has provided targets for HST imaging programs in several previous cycles. The presentprogram is using HST-ACS imaging to survey a further 135 strong lens candidates. The HST data will verify the nature of those candidates, and provide the angular resolution necessary to model the mass distribution.

GO 12251: The first characterization of a super-earth atmosphere

Probing the atmosphere of a transiting exoplanet The first exoplanet, 51 Peg b, was discovered through radial velocity measurements in 1995. 51 Pegb was followed by a trickle, and then a flood of other discoveries, as astronomers realised that there were other solar systems radically different from our own, where "hot jupiters" led to short-period, high-amplitude velocity variations. Then, in 1999, came the inevitable discovery that one of those hot jupiters. HD 209458b, was in an orbit aligned with our line of sight to the star, resulting in transits. Since that date, the number of known transiting exoplanet systems has grown to more than 700, with the overwhelming majority stemming from Kepler's high-sensitivity, high-fidelity survey of ~100 square degrees in Cygnus and the remainder are drawn from wide-field photometric surveys. Kepler's prime focus is solar-type stars, so the field surveys add an important element of diversity into planetary cataglogues. These transiting systems are invaluable not only in providing unambiguous measurements of mass and diameter, but also in providing an opportunity to probe the atmospheric structure by differencing spectra taken during and between primary secondary transit. Such observations are best done from space: indeed, the only successful atmospheric observations to date have been with HST and Spitzer. The present program tagets one of the more unusual systems identified to date, GJ 1214b, the 6.7 Earth-mass companion of a mid-type M dwarf that lies ~13 pc from the Sun. The planet has a 1.6-day period transitting orbit, allowing an accurate measurement of its radius (6.6 Earth radii, assuming a stellar radius of 0.21 RSun). Observations with Spitzer hace suggested that the planet may have a metal-rich atmosphere. The rpesent program will use the WFC3-IR G141 grism to search for characteristic near-infrared spectral features in those systems.

GO 12322: Detecting Isolated Black Holes through Astrometric Microlensing

A rather spectacular version of black hole lensing. Gravitational lensing is a consequence of general relativity. Its effects were originally quantified by Einstein himself in the mid-1920s. In the 1930s, Fritz Zwicky suggested that galaxies could serve as lenses, but lower mass objects can also also lens background sources. Bohdan Paczynski pointed out in the mid-1980s that this offered a means of detecting dark, compact objects that might contribute to the dark-matter halo. Paczcynski's suggestion prompted the inception of several large-scale lensing surveys, notably MACHO, OGLE, EROS and DUO. Those wide-field imaging surveys have target high density starfields towards the Magellanic Clouds and the Galactic Bulge, and have succeeded in identifying numerous lensing events. The duration of each event depends on several factors, including the tangential motion of the lens and its mass. Long-term events are generally associated with a massive lens. Duration alone is not sufficient to identify a lens as a black hole - a source with very low tangential motion relative to the Sun can produce the same effect. However, microlensing not only leads to flux amplification, but also to small astrometric motions, caused by the appearance and disappearance of features in the lensed light. Those motions serve as a mass discriminant - higher mass lenses produce larger amplitude motions. The expected astrometric signal from a black hole lens is > 1.4 millarcseconds, just measureable with HST. This program aims to capitalise on this fact by searching for lensing by black holes in the Galactic field. The observations target long-duration lensing events in the Galactic Bulge.

Past weeks:
page by Neill Reid, updated 2/5/2011