This week on HST

HST Programs: June 16 - June 22, 2008

Program Number Principal Investigator Program Title Links
10487 David Ardila, California Institute of Technology A Search for Debris Disks in the Coeval Beta Pictoris Moving Group 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
11110 Stephan McCandliss, The Johns Hopkins University Searching for Lyman alpha Emission from FUSE Lyman Continuum Candidates Abstract
11137 Anthony F.J. Moffat, Universite de Montreal First Accurate Geometric Distance to a Galactic Wolf-Rayet Star: Knots in the Ejecta M1-67 Abstract
11143 Andrew J. Baker, Rutgers the State University of New Jersey NICMOS imaging of submillimeter galaxies with CO and PAH redshifts Abstract
11144 Richard Bouwens, University of California, Santa Cruz Building on the Significant NICMOS Investment in GOODS: A Bright, Wide-Area Search for z>=7 Galaxies Abstract
11147 Rupali Chandar, Carnegie Institution of Washington The Origin of Diffuse UV Light from Spiral Disks Abstract
11158 R. Michael Rich, University of California - Los Angeles HST Imaging of UV emission in Quiescent Early-type Galaxies Abstract
11172 Arlin Crotts, Columbia University in the City of New York Defining Classes of Long Period Variable Stars in M31 Abstract
11175 Sandra M. Faber, University of California - Santa Cruz UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence Abstract
11192 Hao-Jing Yan, Observatories of the Carnegie Institution of Washington NICMOS Confirmation of Candidates of the Most Luminous Galaxies at z > 7 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
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
11215 Scott F. Anderson, University of Washington New Sightlines for the Study of Intergalactic Helium: Dozens of High-Confidence, UV-Bright Quasars from SDSS/GALEX Abstract
11218 Howard E. Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group Abstract
11225 C. S. Kochanek, The Ohio State University Research Foundation The Wavelength Dependence of Accretion Disk Structure 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

Some selected highlights

GO 11144: Building on the Significant NICMOS Investment in GOODS: A Bright, Wide-Area Search for z>=7 Galaxies

Part of the GOODS/Chandra Deep Field South field, as imaged by HST The Great Observatory Origins Deep Survey (GOODS) is a multi-wavelength survey that covers two 150 sq. arcmin. fields, centred on the northern Hubble Deep Field (HDF) in Ursa Major and the Chandra Deep Field-South in Fornax. In addition to deep HST data at optical and near-infrared wavelengths, the fields have been covered at X-ray wavelengths by Chandra (obviously) and XMM-Newton; at mid-infrared wavelengths with Spitzer; and ground-based imaging and spectroscopy using numerous telescopes, including the Kecks, Surbaru and the ESO VLT. The prime aim of the GOODS program is to reconstruct the history of galaxy formation, star formation and nuclear galactic activity from the epoch of reionisation to the present. The present HST program builds on past results and aims to push observations to the highest redshifts, searching for galaxies at z > 7. Previously obtained GOODS data have been used to identify z-H dropouts - objects visible on F160W NICMOS images, but not on F098 ACS images. deeper NICMOS images of those candidates will be obtained in the J-band (F110W filter) to confirm whether the fluxes are consistent with 7 < z < 8 star-forming galaxies.

GO 11172: Defining Classes of Long Period Variable Stars in M31

M31, The Andromeda galaxy Most long period variable stars (LPVs) are red giants on the asymptotic giant branch (AGB). These are intermediate mass stars, between ~1.5 and ~7 solar masses, that are powered by hydrogen and helium shell-burning. The interactions between the two energy sources lead to instabilities that can generate substantial pulsations, with periods from ~50 to ~500 days. Mira, or omicron Ceti, is the Galactic prototype for this type of variable, and numerous LPVs have been identified throughout the Milky Way and in the neighbouring Small and Large Magellanic Clouds. The LMC and SMC variables show a clear period-luminosity relation, particularly at near-infrared wavelengths, with longer period stars having higher intrinsic luminosities. This P-L relation, while not as well established for classical cepheids, allows LPVs to contribute to measurements of the extragalactic distance scale. The present program aims to expand LPV surveys to M31, using the NIC1 and NIC2 cameras within NICMOS to obtain follow-up near-infrared imaging of regions of the Andromeda galaxy that have been observed with ACS and WFPC2 in previous cycles. These new observations will both provide detailed colour-magnitude diagrams for the selected areas and allow the identification of LPVs within the Andromeda disk population.

GO 11175: UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence

Galaxy mergers and the red sequence

The overwhelming majority of galaxies are found in clusters. Observations show that almost all well-defined cluster systems at low and moderate redshift have a significant population of elliptical galaxies which have red colours, indicative of old stellar populations and minimal current star formation. The elliptical galaxies outline a distinct sequence in the colour-magnitude (or colour-mass) diagram, the so-called red sequence. Over the last few years, there has been considerable interest in understanding the origins of this sequence: how did the ellipticals form (most theories envisage mergers of gas-rich systems at moderate redshifts)? when did star formation cease in these galaxies (most galaxies in clusters at redshifts 1.5 < z < 3 seem to have active star formation)? are there environmentally-dependent effects? This proposal aims to address some of these questions through WFPC2 BVI and ACS/SBC observations of a number of low-redshift (0.04 < z < 0.10) galaxies that appear to have only recently arrived on the red sequence. The WFPC2 data will provide detailed morphologies, while the SBC ultraviolet imaging will be ued to search for traces of residual star formation.

GO 11211: An Astrometric Calibration of Population II Distance Indicators

Measuring trigonometric parallax Trigonometric parallax measurement remains the fundamental method of determining distances to astronomical objects. The best ground-based parallax measurements can achieve accuracies of ~1 milliarcsecond, comparable with the typical accuracies achieved by the ESA Hipparcos astrometric satellite. This level of accuracy allows us to obtain reliable distances and luminosities for main sequence stars, subgiants, red giants and even a number of metal poor subdwarfs. However, with an effective distance limit of 100-150 parsecs, the sampling volume includes less than a handful of rarer, shorter-lived celestial objects. In particular, there are no RR Lyraes or Cepheids, two of the principal calibrators in the extragalactic distance scale. There is only one instrument currently available that can achieve astrometry of higher accuracy - the Fine Guidance Sensors (FGS) on HST. The present team used the FGS to measure a parallax of 3.82+/10.2 milliarseconds for RR Lyrae, the nearest star of its type. this corresponds to a distance of 262 parsecs. The present program aims to improve the calibration by extending observations to four more relatively nearby RR Lyraes (XZ Cyg, UV Oct, RZ Cep and SU Dra) and two Pop II Cepheids (Kappa Pav and VY Pyx).

Past weeks:
page by Neill Reid, updated 18/5/2008