This week on HST

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

Program Number Principal Investigator Program Title
11600 Benjamin Weiner, University of Arizona Star formation, extinction and metallicity at 0.7
12017 John P. Hughes, Rutgers the State University of New Jersey The Proper Motion of SNR E0519-69.0
12025 James C. Green, University of Colorado at Boulder COS-GTO: QSO Absorbers, Galaxies and Large-scale Structures in the Local Universe Part 2
12027 James C. Green, University of Colorado at Boulder COS-GTO: STAR FORMATION/LYMAN-ALPHA Part 2
12066 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12104 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
12167 Marijn Franx, Universiteit Leiden Resolving the Matter of Massive Quiescent Galaxies at z=1.5-2
12169 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of planetary debris discs around young white dwarfs
12192 James T. Lauroesch, University of Louisville Research Foundation, Inc. A SNAPSHOT Survey of Interstellar Absorption Lines
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
12212 D. Michael Crenshaw, Georgia State University Research Foundation What are the Locations and Kinematics of Mass Outflows in AGN?
12213 Roelof S. de Jong, Astrophysikalisches Institut Potsdam The Stellar Halo Profiles of Massive Disk Galaxies
12222 Norbert Przybilla, Universitat Erlangen-Nurnberg Constraints on Super/Hypernova Nucleosynthesis from the Hyper-Runaway Star HD271791
12235 Jean-Claude M. Gerard, Universite de Liege The energy of auroral electrons at Saturn and the associated atmospheric heating
12237 William M. Grundy, Lowell Observatory Orbits, Masses, Densities, and Colors of Two Transneptunian Binaries
12272 Christy A. Tremonti, University of Wisconsin - Madison Testing Feedback: Morphologies of Extreme Post-starburst Galaxies
12276 Bart P. Wakker, University of Wisconsin - Madison Mapping a nearby galaxy filament
12277 Daniel E. Welty, University of Illinois at Urbana - Champaign HD 62542: Probing the Bare, Dense Core of an Interstellar Cloud
12278 Thomas R. Ayres, University of Colorado at Boulder Advanced Spectral Library Project: Cool Stars
12279 Thomas R. Ayres, University of Colorado at Boulder FK Comae, King of Spin: the Movie
12287 Scott D. Friedman, Space Telescope Science Institute Constraining Models of Deuterium Depletion and Galactic Chemical Evolution with Improved Measurements of D/H
12289 J. Christopher Howk, University of Notre Dame COS Snapshot Survey for z < 1.25 Lyman Limit Systems
12292 Tommaso L. Treu, University of California - Santa Barbara SWELLS: doubling the number of disk-dominated edge-on spiral lens galaxies
12299 Michael Eracleous, The Pennsylvania State University Spectroscopic Signatures of Binary and Recoiling Black Holes
12310 Goeran Oestlin, Stockholm University LARS - The Lyman Alpha Reference Sample
12315 Hans Moritz Guenther, Smithsonian Institution Astrophysical Observatory Winds, accretion and activity: Deciphering the FUV lines in TW Hya
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12322 Kailash Sahu, Space Telescope Science Institute Detecting Isolated Black Holes through Astrometric Microlensing
12370 Andrew S. Fruchter, Space Telescope Science Institute The Astrophysics of the Most Energetic Gamma-Ray Bursts
12376 Vinay Kashyap, Smithsonian Institution Astrophysical Observatory The Spinning Corona of FK Comae
12446 Michael Shara, American Museum of Natural History Ionization and Light Echoes in the T Pyxidis Nebula /td>

Selected highlights

GO 12066: Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos

The ACS optical/far-red image of the galaxy cluster, Abell 2218; note the lensed arcs The overwhelming majority of galaxies in the universe are found in clusters. As such, these systems offer an important means of tracing the development of large-scale structure through the history of the universe. Moreover, as intense concentrations of mass, galaxy clusters provide highly efficient gravitational lenses, capable of concentrating and magnifying light from background high redshift galaxies to allow detailed spectropic investigations of star formation in the early universe. Hubble imaging has already revealed lensed arcs and detailed sub-structure within a handful of rich clusters. At the same time, the lensing characteristics provide information on the mass distribution within the lensing cluster. The present program aims to capitalise fully on HST's imaging capabilities, utilising the refurbished Advanced Camera for Surveys and the newly-installed Wide-Field Camera 3 to obtain 14-colour imaging of 25 rich clusters. The data will be use to map the mass profiles of the clusters and probe the characteristics of the high-redshift lensed galaxies. Since ACS and WFC3 can be operated in parallel, the program will also use parallel imaging in offset fields to search for high-redshift supernovae. The present observations target the cluster Abell 2261, at redshift z=0.224.

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 12237: Orbits, Masses, and Densities of Two Transneptunian Binaries

Preliminary orbital determination for the KBO WW31, based on C. Veillet's analysis of CFHT observations; the linked image shows the improved orbital derivation, following the addition of HST imaging The Kuiper Belt consists of icy planetoids that orbit the Sun within a broad band stretching from Neptune's orbit (~30 AU) to distance sof ~50 AU from the Sun (see David Jewitt's Kuiper Belt page for details). Over 500 KBOs (or trans-Neptunian objects, TNOs) are currently known out of a population of perhaps 70,000 objects with diameters exceeding 100 km. Approximately 2% of the known KBOs are binary (including Pluto, one of the largest known KBOs, regardless of whether one considers it a planet or not). This is a surprisingly high fraction, given the difficulties involved in forming such systems and the relative ease with which they can be disrupted. It remains unclear whether these systems formed from single KBOs (through collisions or 3-body interactions) as the Kuiper Belt and the Solar System have evolved, or whether they represent the final tail of an initial (much larger) population of primordial binaries. These issues can be addressed, at least in part, through deriving a better understanding of the composition of KBOs - and those properties can be deduced by measuring the orbital parameters for binary systems. The present proposal aims to use the WFC3/UVIS camera to determine the relative orbits for two known KBO binaries, selecting targets that are also being observed at mid-IR wavelengths by herschel. Just as with binary stars, the orbital period and semi-major axis give the total system mass, while the mid-infrared properties (measured by Spitzer) allow an assessment of the surface area/diameters; combining these measurements gives an estimate of the mean density.

GO 12446: Ionization and Light Echoes in the T Pyxidis Nebula

Artist's impression of the recurrent nova, RS Oph (by David Hardy) Recurrent novae are generally agreed to be close binary systems, comprising a white dwarf and a companion main sequence star that is overflowing its Roche lobe, leading to period transfers of mass onto the white dwarf surface. The mass transfer episode triggers nuclear ractions, which lead the star increasing significantly in it luminosity. T Pyxidis is one such system, and it exhibited fairly regular outbursts every 20 years between its discovery, in 1890, and 1966. Since then, however, it has been dormant, a prolonged period of quiescence that led to suggestions, earlier this year, that it might either be headed for hibernation, or in the process of accumulating sufficient mass to trigger a type Ia supernova explosion (in about 1 million years). Perhaps prompted by these suggestions (a la Monty Python Mary Queen of Scots radio sketch), T Pyxidis erupted into activity on or around April 15th. The present observation with HST is designed to obtain H-alpha images of the illuminated ejecta. Further observations may be obtained at future dates to trace the evolution of this interesting system.
Past weeks:
page by Neill Reid, updated 2/5/2011