This week on HST

HST Programs: March 3 - March 9, 2008

Program Number Principal Investigator Program Title Links
10827 Gerard A. Kriss, Space Telescope Science Institute Imaging Polarimetry of the Seyfert 1 MCG-6-30-15: Clues to the Structure of Warm Absorbers Abstract
10852 Glenn Schneider, University of Arizona Coronagraphic Polarimetry with NICMOS: Dust grain evolution in T Tauri stars Abstract
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies 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
11113 Keith S. Noll, Space Telescope Science Institute Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution Abstract
11122 Bruce Balick, University of Washington Expanding PNe: Distances and Hydro Models Abstract
11124 David V. Bowen, Princeton University The Origin of QSO Absorption Lines from QSOs Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11138 Eric S. Perlman, Florida Institute of Technology The Physics of the Jets of Powerful Radio Galaxies and Quasars Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11146 Daniela Calzetti, University of Massachusetts The Role of Stellar Feedback in Galaxy Evolution Abstract
11153 Sangeeta Malhotra, Arizona State University The Physical Nature and Age of Lyman Alpha Galaxies Abstract
11154 George G. Pavlov, The Pennsylvania State University Optical-UV Spectrum of the Middle-aged Pulsar B1055-52 Abstract
11157 Joseph H. Rhee, University of California - Los Angeles NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum Abstract
11168 Bernhard R. Brandl, Universiteit Leiden The IMF in the Hidden Galactic Starburst W49A Abstract
11180 Roberta M. Humphreys, University of Minnesota - Twin Cities The Morphology of the Post-Red Supergiant IRC+10420's Circumstellar Ejecta 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
11198 Anthony H. Gonzalez, University of Florida Pure Parallel Imaging in the NDWFS Bootes Field Abstract
11201 Nitya Kallivayalil, Harvard University Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images Abstract
11206 Kai G. Noeske, University of California - Santa Cruz At the cradle of the Milky Way: Formation of the most massive field disk galaxies at z>1 Abstract
11210 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11211 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11212 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries Abstract
11230 Christopher P. O'Dea, Rochester Institute of Technology HST FUV Observations of Brightest Cluster Galaxies: The Role of Star Formation in Cooling Flows and BCG Evolution Abstract
11233 Giampaolo Piotto, Universita di Padova Multiple Generations of Stars in Massive Galactic Globular Clusters Abstract
11235 Jason A. Surace, California Institute of Technology HST NICMOS Survey of the Nuclear Regions of Luminous Infrared Galaxies in the Local Universe Abstract
11295 Howard E. Bond, Space Telescope Science Institute Trigonometric Calibration of the Distance Scale for Classical Novae Abstract
11297 Wendy L. Freedmanm Carnegie Institution of Washington Reducing Systematic Errors on the Hubble Constant: Metallicity Calibration of the Cepheid PL Relation Abstract
11301 Edmund Nelan, Space Telescope Science Institute Dynamical Masses and Radii of Four White Dwarf Stars Abstract

Some selected highlights

GO 11142: Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3

NICMOS image of the nearby luminous IR galaxy, Arp 299 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. The present program is targeting systems with redshifts in the range 0.3 < z < 2.7, combining imaging at near-infrared (NICMOS on HST) and mid-infrared (MIPS on Spitzer) wavelengths. All of the systems already have Spitzer mid-infrared spectra, allowing not only an accurate characterisation of the over all flux distribution, and a \ determination of the total luminosity, but also providing insight into the galaxian dust content and chemical evolution.

GO 11168: The IMF in the Hidden Galactic Starburst W49A

Ground-based images (from ESO) of the star forming regions, W49A W49 was the 49th source catalogued by Gert Westerhout in his thesis survey, using the Dwingeloo 25-metre telescope, for 22-cm continuum sources lying within a section of the Galactic Plane. Subsequent observations resolved W49 into two sources, separated by 12.5 arcseconds. W49B proves to be a supernova remnant, while W49A is an active star forming region lying at a distance of ~11 kiloparsecs from the Sun in the constellation of Aquila. W49A is clearly very young, with observations revealing several massive OB clusters lying within a giant molecular cloud that is still at an early stage of disruption. These clusters are highly reddened, however, due to both dust within the parent molecular cloud and foreground material along the line of sight, which runs squarely along the Galactic Plane. Consequently, infrared observations offer the only means of probing lower mass stars and the IMF within these obscured clusters. The present program will use the NIC2 camera on NICMOS to image five fields across the W49A complex.

GO 11201: Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images

The Large Magellanic Cloud (upper left) with the Small Magellanic Cloud (right) and the (foreground) Galactic globular cluster47 Tucanae The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are the most massive satellites of the Milky Way galaxy. The orbital motions of these systems can be used to probe the mass distribution of Milky Way, and backtracking the orbits can shed light on how the three systems have interacted, In particular, the well known Magellanic Stream, stretching between the two Clouds, is thought to be a product either of interactions between the Clouds, or of ram-stripping of gas from the LMC on its last passage through the Plane of the Milky Way. The present program builds on observations obtained at two epochs with the now-defunct (but perhaps soon to be revived) ACS High Resolution Camera (ACS/HRC). The previous programs targeted known QSOs lying behind the Clouds; the QSOs serve as fixed reference points for absoltue astrometry of the numerous foreground LMC/SMC stars. First epoch observations were made in late 2002 (GO 9462), with the follow-up imaging in late 2004 (GO 10130). The tangential motions of the Clouds amount to only a few milliarcseconds, but the high spatial resolution and high stability of HST imaging makes such measurements possible, even with only a 2-year baseline. Surprisingly, the initial results suggest that the 3-D motions of both clouds are much higher than expected, suggesting either that the LMC/SMC/MW is either dynamically very young, or unbound. The present program will use WFPC2 to obtain third-epoch data in the same fields, providjng a crucial test of the initial results

GO 10297: Reducing Systematic Errors on the Hubble Constant: Metallicity Calibration of the Cepheid PL Relation

M101, the spiral galaxy targetted in this program Cepheids are the original distance indicator, and remain the primary calibrator for the extragalactic distance scale. Most investigations tie the zeropoint for the latter scale to the Large Magellanic Cloud, which has a large population of Cepheid variables that provide a well-populated period-luminosity-colour (PLC) relation. However, the Cepheid period-Luminosity relation has long been suspected of being dependent on metallicity. The LMC Cepheids have a lower average metallicity than both the Galactic Cepheids that define the local calibration and the Cepheids in more distant galaxies used to derive H0 - setting the stage for potential systematic errors in the distance scale. The present program aims to address this issue through HST ACS imaging of Cepheids in several fields in the relatively nearby spiral galaxy, M101. The M101 disk has a metallicity gradient, and the targeted fields have been chosen to sample a range of metallicities. Comparison of the perid-luminosity relations from the separate fields will allow direct measurement of any systematic metallicity-based variations.
Past weeks:
page by Neill Reid, updated 27/2/2008