This week on HST

HST Programs: July 18, 2010 - July 24, 2010

Program Number Principal Investigator Program Title
11527 James C. Green, University of Colorado at Boulder COS-GTO: An absorption study of galactic intermediate velocity clouds using hot stars in globular clusters
11556 Marc W. Buie, Southwest Research Institute Investigations of the Pluto System
11568 Seth Redfield, Wesleyan University A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
11570 Adam Riess, The Johns Hopkins University Narrowing in on the Hubble Constant and Dark Energy
11591 Jean-Paul Kneib, Laboratoire d'Astrophysique de Marseille Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?
11598 Jason Tumlinson, Space Telescope Science Institute How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
11613 Roelof S. de Jong, Astrophysikalisches Institut Potsdam GHOSTS: Stellar Outskirts of Massive Spiral Galaxies
11631 Iain Neill Reid, Space Telescope Science Institute Binary brown dwarfs and the L/T transition
11636 Brian Siana, California Institute of Technology First Resolved Imaging of Escaping Lyman Continuum
11643 Ann Zabludoff, University of Arizona A Timeline for Early-Type Galaxy Formation: Mapping the Evolution of Star Formation, Globular Clusters, Dust, and Black Holes
11644 Michael E Brown, California Institute of Technology A dynamical-compositional survey of the Kuiper belt: a new window into the formation of the outer solar system
11657 Letizia Stanghellini, National Optical Astronomy Observatory, AURA The population of compact planetary nebulae in the Galactic Disk
11662 Misty C. Bentz, University of California - Irvine Improving the Radius-Luminosity Relationship for Broad-Lined AGNs with a New Reverberation Sample
11666 Adam J. Burgasser, University of California - San Diego Chilly Pairs: A Search for the Latest-type Brown Dwarf Binaries and the Prototype Y Dwarf
11668 Anna Frebel, Smithsonian Institution Astrophysical Observatory Cosmo-chronometry and Elemental Abundance Distribution of the Ancient Star HE1523-0901
11670 Peter Garnavich, University of Notre Dame The Host Environments of Type Ia Supernovae in the SDSS Survey
11686 Nahum Arav, Virginia Polytechnic Institute and State University The Cosmological Impact of AGN Outflows: Measuring Absolute Abundances and Kinetic Luminosities
11696 Matthew A. Malkan, University of California - Los Angeles Infrared Survey of Star Formation Across Cosmic Time
11697 Slawomir Stanislaw Piatek, New Jersey Institute of Technology Proper Motion Survey of Classical and SDSS Local Group Dwarf Galaxies
11712 John P. Blakeslee, Dominion Astrophysical Observatory Calibration of Surface Brightness Fluctuations for WFC3/IR
11721 Richard S. Ellis, California Institute of Technology Verifying the Utility of Type Ia Supernovae as Cosmological Probes: Evolution and Dispersion in the Ultraviolet Spectra
11728 Timothy M. Heckman, The Johns Hopkins University The Impact of Starbursts on the Gaseous Halos of Galaxies
11730 Nitya Kallivayalil, Massachusetts Institute of Technology Continued Proper Motions of the Magellanic Clouds: Orbits, Internal Kinematics, and Distance
11732 C. S. Kochanek, The Ohio State University The Temperature Profiles of Quasar Accretion Disks
11735 Filippo Mannucci, Osservatorio Astrofisico di Arcetri The LSD project: dynamics, merging and stellar populations of a sample of well-studied LBGs at z~3
11833 Michael R. Garcia, Smithsonian Institution Astrophysical Observatory Monitoring M31 for BHXNe
12005 Hsiao-Wen Chen, University of Chicago Unveiling the Dusty Starburst Galaxy Hosting GRB080607
12058 Julianne Dalcanton, University of Washington A Panchromatic Hubble Andromeda Treasury - I
12316 John P. Wisniewski, University of Washington HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

Selected highlights

GO 11570: Narrowing in on the Hubble Constant and Dark Energy

A GALEX image of Messier 106 (NGC 4258), one of the galaxies targeted in this program The Hubble constant remains a key parameter in understanding cosmology and the evolution of the Universe. Refining measurements of H0 therefore still represents a vital means of probing the nature of dark energy. The present program aims to tackle this question by laying a firmer foundation to the SNe Ia distance scale. The WFC3 IR camera will be used to identify and characterise Cepheid variables in eight relatively nearby galaxies that have hosted Type Ia SNe. Cepheids have signficantly lower amplitude at near-infrared wavelengths, and the measured magnitudes are less subject to uncertainties due to foreground reddening and variations in metallicity. As a consequence, determining the mean apparent magnitude, and hence the period/apparent magnitude relation, is substantially more straightforward than at optical wavelengths. Matching the observed relation against reference stars from the LMC allows a more reliable determination of the distance to the parent galaxy, and hence a firmer zeropoint for the SNe Ia distance scale. The aim is to reduce the level of systematics in determinations oif H0 to the 3 percent level.

GO 11613: GHOSTS: Stellar Outskirts of Massive Spiral Galaxies

The (relatively) nearby barred spiral galaxy, NGC 253 The subdwarf stars that populate the Galactic halo are generally recognised as fossil remnants of the first episode of substantial star formation to afflict the Milky Way galaxy. The structure and density distribution of our own halo has been inferred partly from deep starcounts, partly from globular cluster systems and partly from the kinematics of local subdwarfs; most analyses favour a near-spherical system with density r-3.5. The aim of this proposal is to extend these studies to a number of other nearby spiral systems. ACS and WFC3/UVIS are being used to obtain SNAP observations in the F606W and F814W filters in regions within the galactic halos. The observations are capable of obtaining photometry extending 2-3 magnitudes below the tip of the red giant branch in those galaxies. The data should permit separation of the contributions from disk, thick disk and bulge, and isolation of the halo population. The observations will allow measurement of the halo metallicity distribution and an estimate of the shape of the halo in these systems.

GO 12316: HST/FGS Astrometric Search for Young Planets Around Beta Pic and AU Mic

The extended disk around the M dwarf, AU Mic Planet formation occurs in circumstellar disks around young stars. Most of the gaseous content of those disks dissipates in less than 10 million years, leaving dusty debris disks that are detectable through reflect light at near-infrared and, to a lesser extent, optical wavelengths. The disk structure is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Two of the most prominent and best characterised disks are those acompanying the A-type star Beta Pictoris, and the nearby (d~10 parsec) early-type M dwarf, AU Mic. Both stars are young, with age estimates ranging from 8 to 20 million years for beta Pic and 5 to 10 million years for AU Mic. beta Pic's disk, in particular, shows evidence for significant sub-structure that has been attributed to planetary companions. The present HST program aims to use the Fine Guidance Sensors to obtain high precision astrometry of these two young stars, and search for systematic astrometric residuals due to the hypothesised planetary companions. Upcoming observations focus primarily on AU Mic.

GO 11732: The Temperature Profiles of Quasar Accretion Disks

The first Einstein cross, the gravitational lensed QSO, G2237+0305 Gravitational lensing is a consequence the theory of general relativity. Its importance as an astrophysical tool first became apparent with the realisation (in 1979) that the quasar pair Q0957+561 actually comprised two lensed images of the same background quasar. In the succeeding years, lensing has been used to probe the mass distributions on a variety of scales: of galaxies (primarily via multiply-imaged quasars); of galaxy clusters (arcs and arclets); and at the largest scales (weak lensing). However, lensing can also provide insight on the small-scale properties of the object being lensed. In a lensed QSO, the light from the QSO follows different paths to produce the separate images; each of those paths has a different length; consequently, flux variations in the source show up at different times in the separate images. The present program aims to take advantage of this property to probe the structure of the accretion disks surrounding the central black hole in a number of lensed QSOs. The program will combine ultraviolet observations with the WFC3/UVIS camera on HST with GALEX UV data for 5 lenses spanning as broad range of black hole masses. Studying the variation as a function of wavelength should probe the accretion disk structure, since light from the inner regions are expected to dominate at shorter wavelengths, while the outer regions dominate at longer wavelengths.

Past weeks:
page by Neill Reid, updated 19/2/2010