This week on HST

HST Programs: February 22, 2010 - February 28, 2010

Program Number Principal Investigator Program Title Links
11189 Nial R. Tanvir, University of Leicester Probing the early universe with GRBs Abstract
11208 Tommaso L. Treu, University of California - Santa Barbara The co-evolution of spheroids and black holes in the last six billion years Abstract
11522 James Green, University of Colorado COS-GTO: STAR FORMATION/LYMAN-ALPHA Abstract
11541 James Green, University of Colorado COS-GTO: COOL, WARM AND HOT GAS IN THE COSMIC WEB AND IN GALAXY HALOS 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
11565 Sebastien Lepine, American Museum of Natural History A search for astrometric companions to very low-mass, Population II stars Abstract
11570 Adam Riess, The Johns Hopkins University & Space Telescope Science Institute Narrowing in on the Hubble Constant and Dark Energy Abstract
11584 Kristin Chiboucas, University of Hawaii Resolving the Smallest Galaxies with ACS Abstract
11589 Oleg Y. Gnedin, University of Michigan Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo Abstract
11594 John M. O'Meara, Saint Michaels College A WFC3 Grism Survey for Lyman limit absorption at z=2 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
11613 Roelof S. de Jong, Astrophys. Inst. Potsdam GHOSTS: Stellar Outskirts of Massive Spiral Galaxies Abstract
11635 Michael Shara, American Museum of Natural History In Search of SNIb/Ic Wolf-Rayet Progenitors and Comparison with Red Supergiants (SNII Progenitors) in the Giant ScI Spiral M101 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
11650 William M. Grundy, Lowell Observatory Mutual Orbits, Colors, Masses, and Bulk Densities of 3 Cold Classical Transneptunian Binaries Abstract
11657 Letizia Stanghellini, National Optical Astronomy Observatories The population of compact planetary nebulae in the Galactic Disk Abstract
11662 Misty C. Bentz, University of California - Irvine Improving the Radius-Luminosity Relationship for Broad-Lined AGNs with a New Reverberation Sample 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
11679 Craig L. Sarazin, The University of Virginia Probing The Globular Cluster / Low Mass X-ray Binary Connection in Early-type Galaxies At Low X-ray Luminositie Abstract
11684 Roeland P. van der Marel, Space Telescope Science Institute The First Proper Motion Measurement for M31: Dynamics and Mass of the Local Group Abstract
11687 Thomas R. Ayres, University of Colorado at Boulder SNAPing Coronal Iron Abstract
11698 Mary E. Putman, Columbia University in the City of New York The Structure and Dynamics of Virgo's Multi-Phase Intracluster Medium Abstract
11702 Hao-Jing Yan, Carnegie Institution of Washington Search for Very High-z Galaxies with WFC3 Pure Parallel Abstract
11711 John P. Blakeslee, Dominion Astrophysical Observatory A Definitive Distance to the Coma Core Ellipticals Abstract
11714 Howard E. Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Local Group Globular Clusters Abstract
11718 Julianne Dalcanton, University of Washington The Stellar Halos of Dwarf Galaxies Abstract
11719 Julianne Dalcanton, University of Washington A Calibration Database for Stellar Models of Asymptotic Giant Branch Stars Abstract
11727 Timothy M. Heckman, The Johns Hopkins University UV spectroscopy of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe Abstract
11732 C. S. Kochanek, The Ohio State University Research Foundation The Temperature Profiles of Quasar Accretion Disks Abstract
11735 Filippo Mannucci, INAF - IRA, Firenze The LSD project: dynamics, merging and stellar populations of a sample of well-studied LBGs at z~3 Abstract
11786 Howard E. Bond, Space Telescope Science Institute HST Observations of Astrophysically Important Visual Binaries Abstract
11835 Mark Birkinshaw, University of Bristol The multi-faceted X-ray activity of low-redshift active galaxies Abstract
12011 Rachel A. Osten, Space Telescope Science Institute Magnetic Heating of the Outer Atmospheres of Very Low Mass Dwarfs Abstract
12018 Andrea H. Prestwich, Smithsonian Institution Astrophysical Observatory Ultra-Luminous x-Ray Sources in the Most Metal-Poor Galaxies Abstract
12019 Christy A. Tremonti, University of Wisconsin - Madison After the Fall: Fading AGN in Post-starburst Galaxies Abstract

Selected highlights

GO 11589: Hypervelocity Stars as Unique Probes of the Galactic Center and Outer Halo

Artistic view of a hypervelocity star Hypervelocity stars are stars that have velocities that exceed the escape velocity of the Milky Way by a very substantial margin. Stars can only achieve such velocities through violent gravitational interactions with other bodies. Indeed, to achieve velocities of 1,000 km/sec or more, the proposed mechanism involves binary stars interacting with the black hole at the Galactic Centre: one of the binary components is lost to the black hole, and the other ejected at from the core. The existence of such objects was hypothesised over 20 years ago, but the first candidate was only identified in 2005: SDSS J090745.0+024507, an apparently non-descript sunlike star, lying at a distance of 71 kpc from the Sun in the Galactic, and moving at a velocity of 850 km/sec, or more than twice the escape velocity. Since then, a number of other candidates have been identified, and the present HST program aims to measure precise proper motions that will quantify their space motions.

GO 11613: GHOSTS: Stellar Outskirts of Massive Spiral Galaxies

The (relatively) nearby barred spiral galaxy, NGC 253 The subdwarf stars that populate the Galactic halo are generally recognised as fossil remnants of the first episode of substantial star formation to afflict the Milky Way galaxy. The structure and density distribution of our own halo has been inferred partly from deep starcounts, partly from globular cluster systems and partly from the kinematics of local subdwarfs; most analyses favour a near-spherical system with density r-3.5. The aim of this proposal is to extend these studies to a number of other nearby spiral systems. ACS and WFC3/UVIS are being used to obtain SNAP observations in the F606W and F814W filters in regions within the galactic halos. The observations are capable of obtaining photometry extending 2-3 magnitudes below the tip of the red giant branch in those galaxies. The data should permit separation of the contributions from disk, thick disk and bulge, and isolation of the halo population. The observations will allow measurement of the halo metallicity distribution and an estimate of the shape of the halo in these systems.

GO 11650: Orbits, Masses, and Densities of Three Cold Classical 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 HST WFC3 observations to map the orbits of three binary systems. Those observations will be ued to determine the orbital period and semi-major axis and 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 12011: Magnetic Heating of the Outer Atmospheres of Very Low Mass Dwarfs

Artist's impression of a flaring low-mass star. One of the major surprises delivered by the Einstein Observatory was the high level of chromospheric activity present in cool, late-type dwarfs. Proportionately,. low-mass dwarfs are significantly more active than (and often as luminous as) solar-type stars, and are frequently subject to high energy flares and outbursts. This was surprising since these cool dwarfs are fully convective, and are therefore incapable of supporting the rotational dynamo that is believed to power magnetic activity in sun-like stars. In the succeeding 30 years, subsequent observatories, notably Chandra and HST, with increasingly sensitive X-ray and UV detectors have pushed observations to fainter flux limits and lower luminosity stars. Those observations demonstrate that activity persists through spectral class M and is even present among ultracool L dwarfs, probably powered through shear dynamos maintrained by convective motions. The present program targets two late-type M dwarf: LHS 3003 (M7) and LHS 2065 (M9) and will use COS observations of the far-UV spectra to probe the conditions in the transition region between the chromosphere and corona, and search for coronal structures.

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