This week on HST


HST Programs: January 10, 2011 - January 16, 2011

Program Number Principal Investigator Program Title
11585 Neil H. Crighton, Max-Planck-Institut fur Astronomie, Heidelberg Tracing the distribution of gas and galaxies using three closely-spaced background QSOs
11640 Fabian Walter, Max-Planck-Institut fur Astronomie, Heidelberg Lyman Alpha Imaging of Two Quasar Host Galaxies at z>6
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
12055 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12056 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12061 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-South Field, Early Visits of SNe Search
12064 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- UDS Field
12068 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12099 Adam Riess, The Johns Hopkins University Supernova Follow-up for MCT
12212 D. Michael Crenshaw, Georgia State University Research Foundation What are the Locations and Kinematics of Mass Outflows in AGN?
12228 Glenn Schneider, University of Arizona Probing for Exoplanets Hiding in Dusty Debris Disks: Inner {<10 AU} Disk Imaging, Characterization, and Exploration
12234 Wesley Fraser, California Institute of Technology Differentiation in the Kuiper belt: a search for silicates on icy bodies.
12289 J. Christopher Howk, University of Notre Dame A COS Snapshot Survey for z < 1.25 Lyman Limit Systems
12307 Andrew J. Levan, The University of Warwick A public SNAPSHOT survey of gamma-ray burst host galaxies
12308 Eric M. Monier, State University of New York College at Brockport Cosmic Metallicity from ZnII-Selected QSO Absorption Line Systems Near Redshift z=1.2
12438 Nial R. Tanvir, University of Leicester HST observations of the exceptional Christmas-day gamma-ray burst

Selected highlights

GO 11697: Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies

The low-mass dwarf galaxy, Leo II The Milky Way, m31 and M33 are the three largest galaxies in the Local Group. The system, however, includes more than 25 other members, the majority being dwarf spheroidal galaxies that are satellites of either M31 or the Milky Way. Those galaxies have old, evolved stellar populations, and even the most prominent have masses that are less than a few x 107 MSun, or 10-4 that of the Milky Way. All of these galaxies are moving in the potential set by the overall Local Group system, but dominated by M31 and the Milky Way. Determining full space motions for the dwarfs therefore provide a means of constraining that potential. Even thought the galaxies, and their brightest stellar constituents, are faint, measuring radial velocity is a relatively straightforward procedure. Deriving tangential motions is not, since the typical proper motions of these systems are a few mas/year at best. The present proposal aims to capitalise on the exceptional resolution and high stability of HST to address this issue. WFC3 will target 7 dwarf galaxies, imaging fields that are centred on a background QSO. That QSO serves as a reference point for measurement of the transverse motion of stars in the foreground dwarf galaxy.

GO 11698: The Structure and Dynamics of Virgo's Multi-Phase Intracluster Medium

The central regions of the Virgo cluster Galaxy clusters are building blocks for the largest structures in the universe. Star formation ensures that galaxies are the most prominent constituents of the cluster structure, but the bulk of the baryonic material (perhaps as much as 90%) resides in hot gas that permeates the potential well defined by the underlying dark matter. The low density (10-3 particles cm-3) gas is extremely hot (temperatures of 107 to 108 Kelvin), and therefore directly detectable at X-ray wavelengths. Those observations provide a means of mapping the gas density distribution, but they are not able to determine the dynamical properties of the intracluster medium (ICM). The most effective means of probing the dynamics is through spectroscopic observations of background sources, where the line-of-sight absorption features introduced by the ICM gas allow one to identify velocity structure. The present program aims to use 15 background QSOs, identified by SDSS, as a first step in tracing the dynamics within the Virgo cluster ICM.

GO 12234: Differentiation in the Kuiper belt: a search for silicates on icy bodies

Some of the larger Solar System trans-Neptunian objects The Kuiper Belt lies beyond the orbit of Neptune, extending from ~30 AU to ~50 AU from the Sun, and includes at least 70,000 objects with diameters exceeding 100 km. Setting aside Pluto, the first trans-Neptunian objects were discovered in the early 1990s. Most are relatively modest in size, with diameters of a few hundred km and photometric properties that suggested an icy composition, similar to Pluto and its main satellite, Charon. Over the last three years, a handful of substantially larger bodies have been discovered, with diameters of more than 1000 km; one of the objects, 2003 UB313, is comparable in size to Pluto (2320 km.). At the same time, ground-based surveys, such as the Deep Ecliptic Survey, the Canada-France Ecliptic plane Survey and the Palomar Quest Survey, scanned the ecliptic for fainter, lower-mass objects, with the aim of using their properties to assess the likely chemical composition and dynamical history of the early Solar System. HST itself is being used by a number of programs to push observations to even fainter magnitude limits, and obtain accurate multi-colour photometryy of these objects. Interestingly, the KBOs observed in the course of these HST programs have shown evidence for a range of spectral properties, possibly indicative of difference composition. The present program aims to further probe this issue through narrow-band 1-1.3 micron imaging of 13 KBOs.

GO 12438: HST observations of the exceptional Christmas-day gamma-ray burst

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 short/hard bursts appear to arise from coalescing binary systems (probably pairs of neutron stars or black holes), but the long/soft bursts appear to originate in the collapse of very massive stars. The latter sources are therefore almost certainly associated with star formation, so they act as signposts to active star-forming regions in the high redshift universe. Some of these bursts are sufficiently bright that ground-based spectroscopic observations allow reliable measurement of the redshift. As the 2 second threshold suggests, even "long" gamma-ray bursts typically have relatively short durations, usually less than 1 minute. However, on Christmas Day 2010, the Swift high-energy observatory detected a gamma-ray event that persisted for more than 1000 seconds, with an even longer-lived X-ray afterglow. Ground-based observations have established that the host galaxy lies at z=0.4. The current HST observations are aimed at resolving the system with WFC3, and probing the stelar environment local to the GRB.

Past weeks:
page by Neill Reid, updated 10/1/2011