This week on HST


HST Programs: December 24 - December 30, 2012

Program Number Principal Investigator Program Title
12023 James C. Green, University of Colorado at Boulder COS-GTO: Cold ISM
12112 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12113 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12442 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-North Field, Non-SNe-Searched Visits
12668 Slawomir Stanislaw Piatek, New Jersey Institute of Technology Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies
12787 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12788 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12918 Kristin Chiboucas, Gemini Observatory, Northern Operations Origin of UCDs in the Coma Cluster
12926 Michael Shara, American Museum of Natural History Local Thermonuclear Runaways in Dwarf Novae?
12971 Harvey B. Richer, University of British Columbia Completing the Empirical White Dwarf Cooling Sequence: Hot White Dwarfs in 47 Tucanae
12989 Alvio Renzini, Osservatorio Astronomico di Padova The Ultraviolet View of Globular Clusters in the Giant Elliptical M87
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

Selected highlights

GO 12668: 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 12787: Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos


The cluster MACS J1206.2-0.47, imaged by HST as part of the CLASH program
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 17-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 1423 at z=0.213.

GO 13007: UV Imaging of Luminous Infrared Galaxies in the GOALS Sample


An HST NICMOS image of the interacting LIRG, NGC 6090
Luminous infrared galaxies (LIRGs) have total luminosities that exceed 1011.4 LSun, with most of the energy emitted at wavelengths longward of 10 microns. Many (perhaps most) of these galaxies are interacting or merging disk galaxies, with the excess infrared luminosity generated by warm dust associated with the extensive star formation regions. Many systems also exhibit an active nucleus, and may be in the process of evolving towards an S0 or elliptical merger remnant. HST has undertaken extensive observations of these systems in past cycles, using ACS at blue and red wavelengths, and WFPC2 and then WFC3 in the ultraviolet and near-infrared. The present program focuses on the Great Observatories All-sky LIRG Survey (GOALS), a complete sample of low-redshift LIRGs that has been studied extensively over wide wavelength range by observatories as varied as Chandra, GALEX, HST, Spitzer,Herschel, ALMA and the EVLA. The present program aims to use imagign witht he F225W filter on Wide-Field Camera 3 to determine the flux emitted at ultraviolet wavelengths. 84 galaxies will be targetted for observation. Combing the data with observatons at other wavelengths will enable the identification and age-calibration of star clusters and active star-formign regions, and measurement of the dust obscuration and properties within these systems.

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