This week on HST


HST Programs: January 14 - January 20, 2008


Program Number Principal Investigator Program Title Links
10829 Paul Martini, The Ohio State University Secular Evolution at the End of the Hubble Sequence Abstract
10890 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies Abstract
10901 Robert W. O'Connell, The University of Virginia UV-Luminous Globular Clusters in NGC 1399 Abstract
10998 Peter McCullough, Space Telescope Science Institute Exoplanet XO-1b: light curve and parallax Abstract
11101 Gabriela Canalizo, University of California - Riverside The Relevance of Mergers for Fueling AGNs: Answers from QSO Host Galaxies 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
11125 Joel N. Bregman, University of Michigan The Dynamical Evolution of Globular Clusters Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11134 Karen Knierman, University of Arizona WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge Abstract
11140 Klaus Werner, Universitat Tubingen, Institut fur Astronomie & Astrophysik Can mass-ejections from late He-shell flash stars constrain convective/reactive flow modeling of stellar interiors? 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
11153 Sangeeta Malhotra, Arizona State University The Physical Nature and Age of Lyman Alpha Galaxies Abstract
11162 Paula Szkody, University of Washington Understanding the Long Term Impacts of Low Magnetic Accretion Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11195 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources Abstract
11198 Anthony H. Gonzalez, University of Florida Pure Parallel Imaging in the NDWFS Bootes Field Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii 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
11213 Gerard T. van Belle, California Institute of Technology Distances to Eclipsing M Dwarf Binaries Abstract
11229 Margaret Meixner, Space Telescope Science Institute SEEDS: The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11301 Edmund Nelan, Space Telescope Science Institute Dynamical Masses and Radii of Four White Dwarf Stars Abstract
11312 Graham Smith, University of Birmingham The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2 Abstract
11339 Andreas Zezas, Smithsonian Institution Astrophysical Observatory A deep observation of NGC4261: understanding its unique X-ray source population, gas morphology, and jet properties Abstract
11341 Sarah Gallagher, University of California - Los Angeles Lower Luminosity AGNs at Cosmologically Interesting Redshifts: SEDs and Accretion Rates of z~0.36 Seyferts Abstract

Some selected highlights

GO 10998: Exoplanet XO-1b: light curve and parallax

Artist's impression of a planetary transit against an active solar-type star Transiting extrasolar planets offer the opportunity to gain valuable insight into the interior structure and atmospheres of gas giants beyond the Solar System. Besides providing direct measures of mass (with no complications for v sin(i)) and radius (from accurate time-series photometry), spectroscopic observations obtained during either transit or planetary eclipse can probe the atmospheric structure and chemical composition. The present proposal targets the transiting system designated XO-1, which was discovered in 2006 by an international team of professional and amateur astronomers using a fleet of telescopes with very modest apertures - the primary survey telescope, the XO telescope, is a pair of 200-mm telephoto lenses - but a very wide field of view. These small telescopes are used to survey large areas of the celestial sphere, searching for photometric variations characteristic of planetary transits (i.e. periodic dips in brightness of 1-2%); transit candidates are then verified using higher accuracy photometric observations with larger telescopes, and finally radial velocity measurements to confirm the companion mass. XO-1b, the first planeray companiondiscovered in this campaign, is a Jupiter mass gas giant (0.9 MJ) in a 3.94 day orbit around a 12th magitude solar-type star in the Corona Borealis constellation. The present HST observations are designed to use NICMOS imaging (with the grism) to derive a more accurate light curve, and hence a refined estimate of the diameter (ground-based data suggest R ~ 1.3 RJ). The program is also using precise astrometry with the FGS to derive an accurate trigonometric parallax.

GO 11101: The Relevance of Mergers for Fueling AGNs - Answers from QSO Host Galaxies

Composite optical/radio image of CenA, the elltipical merger that harbours the nearest AGN Quasars are highly energetic sources that can achieve luminosities substantially exceeding 1012 LSun. These objects are generally believed to be powered by accretion onto a central supermassive black hole, with M > 107 MSun. Many QSOs reside within galaxies that are morphologically similar to elliptical galaxies, which are predominantly gas poor at th present epoch. This raises the issue of how one fuels the central, active black hole. One possibility is through mergers, with the QSO host assimilating smaller, gas-rich neighbours. Many nearby ellipticals are known to exhibit characteristics signatures of mergers - tidal tails, dust lanes and shells. Cen A is the classic example, which also happens to support a weak AGN and mild star formation within the dust lane. The present proposal builds on previous HST observations of five (much more distant) QSO host galaxies, where the ACS imaging revealed evidence for tidal features. This program will use WFPC2 to image a further 13 low-redshift QSO host galaxies. Observations of PG2349-014 (z=0.174) are scheduled for this week.

GO 11134: WFPC2 Tidal Tail Survey: Probing Star Cluster Formation on the Edge

ACS image of the spectacular tidal tail of the Tadpole galaxy, Arp 188 Gravitational interactions between close galaxy pairs produce tidal tails, which can often be sites of extensive star formation in young, gas-rich spiral systems. Within the Milky Way, we know that most stars are born in fairly dense clusters, comparable with the Orion Nebula Cluster, and observatios of nearby sprials (M31, M33) suggest that the same situation pervades in those systems. However, observations suggest that star clusters tend to be rare in tidal tails. The present program is using WFPC2 to obtain R (F606W) and I (F814W) band observations of 12 tidal tail systems, with the aim of quantifying the contribution made by star clusters to star formation in these sparse environments.

GO 11312: The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2

Combined optical and X-ray (Chandra) image of a lensing galaxy cluster Gravitational lensing supplies a powerful method of tracing the mass distribution in galaxy clusters; at the same time, the amplified the light from background galaxies provides a means of probing the early stages of galaxy formation. These measurements are particularly effective when X-ray imaging data are also available, allowing direct measurement of the mass density and distribution of the hot intracluster medium. This snapshot proposal aims to use the Wide Field Camera on ACS to observe the central regions of low redshift (0.15 < z < 0.3) clusters with the requisite Chandra observations. The HST images will allow the resolution of lensed arcs in the cluster cores (due to strong lensing) and characterisation of weak-lensing distortions of the image profiles of faint background galaxies. The frequency and detailed distribution (size, multiplicity, redshifts) of the strong lens systems sets strong constraints on the total mass content, and its structure, in the central regions of low-redshift clusters. Those results, in turn, constrain cluster evolution, and offer insight into likely schemes for studying dark energy at higher redshifts.

Past weeks:
page by Neill Reid, updated 24/12/2007