This week on HST


HST Programs: September 24 - September 30, 2007

Program Number Principal Investigator Program Title Links
10787 Jane Charlton, The Pennsylvania State University Modes of Star Formation and Nuclear Activity in an Early Universe Laboratory Abstract
10872 Harry Teplitz, California Institute of Technology Lyman Continuum Emission in Galaxies at z=1.2 Abstract
10889 Roelof de Jong, Space Telescope Science Institute The Nature of the Halos and Thick Disks of Spiral Galaxies Abstract
10900 Roberto Mignani, Mullard Space Science Laboratory Optical polarimetry of PSR B0540-69 and its synchrotron nebula Abstract
10909 David Bersier, Liverpool John Moores University Exploring the diversity of cosmic explosions: The supernovae of gamma-ray bursts Abstract
10924 Alice Shapley, Princeton University Constraints on the Assembly and Dynamical Masses of z~2 Galaxies Abstract
10930 Stefan Jordan, Universitat Tubingen, Institut fur Astronomie & Astrophysik Mass and Radius of a Near-Chandrasekhar-limit magnetic white dwarf Abstract
11079 Luciana Bianchi, The Johns Hopkins University Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys Abstract
11082 Christopher Conselice, Univ. of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Obscured Universe Abstract
11101 Gabriela Canalizo, University of California - Riverside The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies Abstract
11105 Avishay Gal-Yam, California Institute of Technology The LBV progenitor of SN 2005gl - a new key to massive star evolution puzzles Abstract
11107 Timothy M. Heckman, The Johns Hopkins University Imaging of Local Lyman Break Galaxy Analogs: New Clues to Galaxy Formation in the Early Universe Abstract
11151 Gregory J. Herczeg, California Institute of Technology Evaluating the Role of Photoevaporation of Protoplanetary Disk Dispersal Abstract
11193 Wolfgang Brandner, University of California - Los Angeles A comprehensive study of the low-mass stellar population in the Galactic starburst region NGC 3603 Abstract
11196 Aaron S. Evans, State University of New York at Stony Brook An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11218 Howard Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group Abstract
11219 Alessandro Capetti, Osservatorio Astronomico di Torino Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio-quiet dichotomy? Abstract
11312 Graham Smith, University of Birmingham The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2 Abstract

Some selected highlights

GO 10889: The Nature of the Halos and Thick Disks of Spiral Galaxies

Ground-based imaging of the edge-on spiral, NGC 891 The stars in the Milky Way are generally grouped into stellar populations, building blocks that provide insight into the process of galaxy assembly. The traditional populations are the near-spherical, metal-poor Halo, representing the first significant burst of star formation; the Disk, whose constituents have higher metallicities, a flattened density distribution (which defines the Galactic Plane) and significant angular momentum, suggesting a formation history that includes collapse and dissipation; and the central Bulge, which, with a spheroidal distribution and broad metallicity range, may be something of an amalgam of disk and halo. The original models for the Disk envisaged a relatively simple population, with a continuous star formation history and an exponential density distribution, both radially and perpendicular to the Plane. However, in the mid-1980s, starcount analyses revealed more complexity in the vertical density distribution, with evidence for two components with scaleheights ~300 and 1000-1300 pc. Subsequent investigations of the more extended component, dubbed the thick disk, suggest that it probably formed as a result of a merger with a massive satellite early in the Milky Way's history (8-10 Gyrs ago). Ground-based observations suggest that some other spiral galaxies possess a similar component. Clearly, the frequency of such systems and their age distribution offer clues to the merging history of the average spiral galaxy. The present program will use ACS, WFPC2 and NICMOS to image seven edge-on spirals at several locations perpendicular to the Plane, with the aim of resolving the underlying stellar populations and tracing the metallicity distribution and overall morphology of the extended disk components.

GO 11079: Treasury Imaging of Star Forming Regions in the Local Group: Complementing the GALEX and NOAO Surveys

The star forming region, N11, in the Small Magellanic Cloud Star formation is a complex process that takes place on many scales, from diffuse, low-level activity within dispersed clouds like the nearby Taurus association, through massive star forming regions, like Orion and 30 Doradus, to intense starbursts within galactic nucle and mergers. The aim of the present proposal is to use WFPC2 to survey a representative sample of active star-forming regions in local Group galaxies. In particular, the observations will cover a wide range of OB associations in the two nearest large spirals, the Andromeda galaxy, M31, and the Triangulum system, M33. Multicolour, high-resolution images, taken at passbands from the ultraviolet (F170W) to far-red (F814W) will allow H-R diagrams to be constructed, probing the distribution of ages and metallicities, and setting constraints on variations in the underlying initial mass function(s). In the coming week, observations are scheduled of OB associations in the M33.

GO 11202 The Structure of Early-type Galaxies: 0.1-100 Effective Radii

HST16309+8230, a disk galaxy, distorted due to gravitational lensing by a foreground elliptical Despite their apparently simple appearance, the processes responsible for the formation and evolution of elliptical galaxies remain somewhat obscure. It is clear that most star formationin these systems must occur at early epochs, since these systems are highly gas poor at even moderate redshifts. Grabitational lensing provies one of the more important tools for investigating these systems, since it can probe the detailed form of the mass distribution, and test for the presence of sub-structure in the underlying dark matter, as predicted by some theoretical models. The present program is combining high-resolution, multi-colour HST imaging with ground-based low-resolution VLT/Keck spectroscopic observations of over 50 strong lensing systems. The resultant datasets can be used to investigate the structure of elliptical galaxies over a wide range of radii, and test the predictions of relevant theoretical models.

Past weeks:
page by Neill Reid, updated 10/8/2007