HST this week: 077



This week on HST


HST Programs: March 18 - March 24, 2013

Program Number Principal Investigator Program Title
12473 David Kent Sing, University of Exeter An Optical Transmission Spectral Survey of hot-Jupiter Exoplanetary Atmospheres
12488 Mattia Negrello, Open University SNAPshot observations of gravitational lens systems discovered via wide-field Herschel imaging
12555 Robert Louis da Silva, University of California - Santa Cruz On the Triggering of Quasars During First Passage
12577 Armin Rest, Space Telescope Science Institute Spectral Time Series of the Cas A Supernova
12584 Amy E. Reines, Associated Universities, Inc. Confirming the First Supermassive Black Hole in a Dwarf Starburst Galaxy
12870 Boris T. Gaensicke, The University of Warwick The mass and temperature distribution of accreting white dwarfs
12874 David Floyd, Monash University Quasar accretion disks: is the standard model valid?
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12889 Sherry H. Suyu, Academia Sinica, Institute of Astronomy and Astrophysics Accurate Cosmology from Gravitational Lens Time Delays
12893 Ronald L Gilliland, The Pennsylvania State University Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging
12898 Leon Koopmans, Kapteyn Astronomical Institute Discovering the Dark Side of CDM Substructure
12902 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12906 Klaus Werner, Eberhard Karls Universitat, Tubingen Chemical composition of an exo-planetary debris disk
12924 Nathan Smith, University of Arizona Measuring the Wind Properties of a Galactic SN1987A analog with COS
12930 Carrie Bridge, California Institute of Technology WISE Discovered Ly-alpha Blobs at High-z: The missing link?
12935 Martin A. Guerrero, Instituto de Astrofisica de Andalucia (IAA) Witnessing the Expansion of Hydrogen-Poor Ejecta in Born-Again Planetary Nebulae
12938 Sergio B. Dieterich, Georgia State University Research Foundation Probing Fundamental Stellar Parameters with HST/STIS Spectroscopy of M Dwarf Binaries
12942 Eilat Glikman, Yale University Testing the Merger Hypothesis for Black Hole/Galaxy Co-Evolution at z~2
12944 Katelyn Allers, Bucknell University A High-Resolution Survey of the Very Youngest Brown Dwarfs
12945 Gregory Rudnick, University of Kansas Center for Research, Inc. Spatially Resolved Observations of Gas Stripping in Intermediate Redshift Clusters and Groups
12949 Daniel Perley, California Institute of Technology Unveiling the Dusty Universe with the Host Galaxies of Obscured GRBs
12951 Aida H. Wofford, Space Telescope Science Institute Do Lyman-alpha photons escape from star-forming galaxies through dust-holes?
12977 Ivana Damjanov, Smithsonian Institution Astrophysical Observatory Local Turbulent Disks: analogs of high-redshift vigorously star-forming disks and laboratories for galaxy assembly?
12982 Nicolas Lehner, University of Notre Dame Are the Milky Way's High Velocity Clouds Fuel for Star Formation or for the Galactic Corona?
13007 Lee Armus, California Institute of Technology UV Imaging of Luminous Infrared Galaxies in the GOALS Sample
13024 John S. Mulchaey, Carnegie Institution of Washington A Public Snapshot Survey of Galaxies Associated with O VI and Ne VIII Absorbers
13025 Andrew J. Levan, The University of Warwick Unveiling the progenitors of the most luminous supernovae
13027 Goeran Oestlin, Stockholm University Escape of Lyman photons from Tololo 1247-232
13032 Carol A. Grady, Eureka Scientific Inc. Crossing the Snow Line: Mapping Ice Photodesorption products in the Disks of Herbig Ae-Fe stars
13033 Jason Tumlinson, Space Telescope Science Institute COS-Halos: New FUV Measurements of Baryons and Metals in the Inner Circumgalactic Medium
13034 Jon Mauerhan, University of Arizona A Homunculus Around the Star NaSt1 {WR122}?
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13060 Thomas R. Ayres, University of Colorado at Boulder Alpha Cen: Climbing out of a Coronal Recession? {year 2 continuation}
13062 Howard E. Bond, Space Telescope Science Institute HST Observations of Astrophysically Important Visual Binaries
13063 Adam Riess, The Johns Hopkins University Supernova Follow-up for MCT
13112 Xin Liu, University of California - Los Angeles The Hierarchical Assembly of Massive Black Holes: Identifying Kpc-Scale Triple AGNs with Chandra, HST, and EVLA
13178 J. Davy Kirkpatrick, California Institute of Technology Spitzer Trigonometric Parallaxes of the Solar Neighborhood's Coldest Brown Dwarfs

Selected highlights

GO 12893: Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging

The Kepler satellite Kepler is a NASA Discovery-class mission, designed to search for extrasolar planets by using high-precision photometric observations to detect transits. Launched on 7 March 2009, Kepler continuously monitors ~100,000 (mainly) solar-type stare within a ~100 square degree region in Cygnus. The mission has been an astounding success. Ground-based observations have successfully detected a couple of dozen transiting planets (e.g. HD 209458); almost all are "hot jupiters", gas giants on short-period orbits which produce a photometric dip of ~10-2 with a periopd of a few days, with a smattering of neptune-sized "super-Earths". Kepler, in contrast, has so far identified 1,790 exoplanet host stars and a total of 2,321 transiting exoplanets. More significantly, the exquisite precision of Kepler's photometric observations enables it to detect the 0.01% transit signature of earth analogues in these systems. A subset of stellar binaries provide one of the main sources of confusion in searching for planetary transits, since "grazing" transits can mimic the planetary signature. This is particularly an issue with Kepler, since the optical system is designed to provide a broad psf, spreading the stellar flux over a large area on the detector to allow high photometric accuracy. As a result, faint eclipsing stellar binaries will contribute to the source counts. Moreover, since the target field is (intentionally) within the Milky Way, there is a significant potential for unresolved stars within the (relatively broad) Kepler psf to increase the total signal, and hence dilute the depth of transits, giving the appearance of a smaller diameter exoplanet. This program is using the high spatial resolution imaging provided by HST to study a subset of the Kepler Earth-like candidates to assess the potential of this effect.

GO 12930: WISE Discovered Ly-alpha Blobs at High-z: The missing link?


Lab-1, the largest Lyman-alpha blob currently known, at z=3.1
Lyman-alpha blobs are large concentrations of gas that have been detected through their strong emission of Lyman alpha radiation. Most of those found have been foudnt rhough imaging at optical wavelengths, and therefore tend to lie at reshifts exceeding z=2. Some of these form coherent structures, including 3-D ~70-Mpc-scale filamentary structures. The present program aims to capitalise on recent discoveries made by the Wide-field infrare Survey Explorer. WISE has identified a number of Ly-alpha emitting blobs that have strikingly different energy distributions at near- and mid-infrared wavelengths, strongly suggestive of the presence of substantial quantities of dust. These objects have radically different energy distributions that the optically-identified LABs at z>2. The present program builds on a Cycle 19 program (GO 12481) and will use H-band observations with the WFC3-IR camera to obtain high-resolution images of these unusual systems in ther est-frame optical wavelengths, mapping both the overall energy distribution and the detailed morphology in Lyman-alpha and the rest-frame UV continuum.

GO 12942: Testing the Merger Hypothesis for Black Hole/Galaxy Co-Evolution at z~2

Composite optical/radio image of CenA, the elltipical merger that harbours the nearest AGN Quasars are highly energetic sources that can achieve luminosities substantially exceeding 1012 LSun. These objects are generally believed to be powered by accretion onto a central supermassive black hole, with M > 107 MSun. Many QSOs reside within galaxies that are morphologically similar to elliptical galaxies, which are predominantly gas poor at th present epoch. This raises the issue of how one fuels the central, active black hole. One possibility is through mergers, with the QSO host assimilating gas-rich neighbours. The persent program aims to test this hypothesis through observations of luminous, dusty QSOs at redshifts z>2. The targets were selected by cross-referencing the FIRST radio catalogue with 2MASS near-IR survey data, combined with follow-up spectroscopic confirmation of the nature of the sources. The goal of this prorgam is to use near-infrared imaging with the WFC3-IR camera to search for morphological evidence of merging systems that coudl power the central black hole.

GO 13178: Spitzer Trigonometric Parallaxes of the Solar Neighborhood's Coldest Brown Dwarfs


The stellar menagerie: Sun to Jupiter, via brown dwarfs
Brown dwarfs are objects that form in the same manner as stars, by gravitational collapse within molecular clouds, but which do not accrete sufficient mass to raise the central temperature above ~2 million Kelvin and ignite hydrogen fusion. As a result, these objects, which have masses less than 0.075 MSun or ~75 M<\sub>Jup, lack a sustained source of energy, and they fade and cool on relatively short astronomical (albeit, long anthropological) timescales. Following their discovery over a decade ago, considerable observational and theoretical attention has focused on the evolution of their intrinsic properties, particularly the details of the atmospheric changes. At their formation, most brown dwarfs have temperatures of ~3,000 to 3,500K, comparable with early-type M dwarfs, but they rapidly cool, with the rate of cooling increasing with decreasing mass. As temperatures drop below ~2,000K, dust condenses within the atmosphere, molecular bands of titanium oxide and vanadium oxide disappear from the spectrum to be replaced by metal hydrides, and the objects are characterised as spectral type L. Below 1,300K, strong methane bands appear in the near-infrared, characteristics of spectral type T. At present, the coolest T dwarfs known have temperatures of ~650 to 700K. At lower temperatures, other species, notably ammonia, are expected to become prominent, and a number of efforts have been undertaken recently to find examples of these "Y" dwarfs. The search is complicated by the fact that such objects are extremely faint instrinsically, so only the nearest will be detectable. Identifying such ultra-ultracool dwarfs was a goal of the WISE satellite mission, which recently completed its all-sky survey. WISE has succeeded in identifying close to a dozen very red, and therefore very cool, stellar sources. Initial follow-up observations with both Spitzer and HST suggest that at least may have effective temperatures less than 400K, although subsequent analyses suggests that those temperatures may be udnerestimated. These are the first examples of the new spectral class of Y dwarfs. The present program follows up on the initial discoveries by combining astrometry from Spitzer imaging, deriving proper motions and parallaxes, with low-resolution spectroscopy with the G102 and G141 grisms on WFC3-IR. The overall goal is to establish reliable distances, luminosities and temperatures, defining these sources as benchmarks in the lowest reaches of the brown dwarf regime.

Past weeks:
page by Neill Reid, updated 14/10/2012
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