This week on HST

HST Programs: May 22 - May 28, 2006

Program Number Principal Investigator Program Title Links
10488 Mariangela Bernardi, University of Pennsylvania The Most Massive Galaxies in the Universe: Color-Gradients and Texture Abstract
10491 Harald Ebeling, University of Hawaii A Snapshot Survey of the most massive clusters of galaxies Abstract
10493 Avishay Gal-Yam, California Institute of Technology A Survey for Supernovae in Massive High-Redshift Clusters Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10501 Rupali Chandar, The Johns Hopkins University xtending the Heritage: Clusters, Dust, and Star Formation in M51 Abstract
10504 Richard Ellis, California Institute of Technology Characterizing the Sources Responsible for Cosmic Reionization Abstract
10510 Marcella Longhetti, Osservatorio Astronomico di Brera, Milano Morphology of massive early-type galaxies at z>1.2: constraining galaxy formation models Abstract
10512 William Merline, Southwest Research Institute Search for Binaries Among Faint Jupiter Trojan Asteroids Abstract
10515 Eric Peng, Dominion Astrophysical Observatory The Unique Star Cluster System of M85 Abstract
10525 Suzanne Hawley, University of Washington Characterizing the Near-UV Environment of M Dwarfs: Implications for Extrasolar Planetary Searches and Astrobiology Abstract
10527 Dean Hines, Space Science Institute Imaging Scattered Light from Debris Disks Discovered by the Spitzer Space Telescope Around 20 Sun-like Stars Abstract
10532 Kai Noeske, University of California - Santa Cruz Kinematics and morphology of the most massive field disk galaxies at z>1 Abstract
10536 Raghvendra Sahai, Jet Propulsion Laboratory What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey Abstract
10542 Antonella Nota, Space Telescope Science Institute Charting the Sparkling Star Formation in NGC346 Abstract
10587 Adam Bolton, Smithsonian Institution Astrophysical Observatory Measuring the Mass Dependence of Early-Type Galaxy Structure Abstract
10588 Michael Brotherton, University of Wyoming The Host Galaxies of Post-Starburst Quasars Abstract
10592 Aaron Evans, State University of New York at Stony Brook An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe Abstract
10596 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: A Test of the Black Hole-Bulge Paradigm Abstract
10603 Deborah Padgett, California Institute of Technology Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust Abstract
10606 Bill Sparks, Space Telescope Science Institute Ultraviolet Snapshots of 3CR Radio Galaxies Abstract
10612 Douglas Gies, Georgia State University Research Foundation Binary Stars in Cyg OB2: Relics of Massive Star Formation in a Super-Star Cluster Abstract
10617 Andrea Dieball, University of Southampton HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet Abstract
10626 Yeong-Shang Loh, University of Colorado at Boulder A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to z = 0.9 Abstract
10628 C. O'Dell, Vanderbilt University Determining the Lifetime of Planetary Nebula Knots from Observations of the Core of the Helix Nebula. Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters Abstract
10923 Frederic Pont, Observatoire de Geneve Measuring the size of the close-in transiting extrasolar planet HD 189733b Abstract

Some selected highlights

GO 10504 Characterizing the Sources Responsible for Cosmic Reionization

A 3-D model of cosmic reionisation at redshift z=5.81 The standard cartoon for the evolution of the Universe envisages three distinct phases following the Big Bang: the `recombination era', spanning the first few hundred thousand years, where the ionised hydrogen and helium plasma generated by the Big Bang gives way to cooler, neutral atomic gas; the `dark ages', lasting ~500,000 years, where the Universe is populated by neutral absorbing gas; and `cosmic reionisation', where the first episodes of star and black hole formation lead to photoionisation of neutral hydrogen, and much increased transparency in the inter(proto-)galactic medium. A key question for cosmological investigations is the identity of the cosmic reionisers - were quasars (i.e. massive black holes) primarily responsible, or were more conventional star clusters, or Population III objects, the key ingredient?
The aim of this proposal is to use gravitational lensing by massive clusters to probe the universe at redshifts beyond z=6. Combining NICMOS and ACS imaging with mid-infrared observations with Spitzer, the goal is to identify a representative sample of luminous objects at redshifts 6 < z < 10, laying the foundation for future more detailed investigations with JWST.

GO 10512 Search for Binaries Among Faint Jupiter Trojan Asteroids

An artist's impression of the binary asteroid, Patroclus Binary stars have been known for well over 300 years, but it is only within the last decade that it has been clear that asteroids are also often found in pairs. This is somewhat unexpected, since the low mass of asteroids leads to very low binding energy between the components. Both the formation mechanism(s?) and the stability of current systems remain unclear. The present program is using the HRC on ACS to carry out a snapshot survey of faint Trojan asteroids, which reside at the stable L4 and L5 Lagrange points on Jupiter's orbit. Several larger Trojans are known to be binary (e.g. Patroclus, see this link for more information), but data remain spare for the fainter members of this population. The collision environment among the Trojans is similar to that of Main Belt asteroids, but the composition is likely to be very different; thus, sampling the binary fraction over a significant range in mass should help us understand the relative importance of collisional and binary formation mechanisms.

GO 10542 Charting the Sparkling Star Formation in NGC346

WFPC2 image of the SMC cluster, NGC 346 The Small Magellanic Cloud has a mass that is less than 0.5% that of the Milky Way, but it encompasses star-forming complexes that are the equal of any Galactic counterpart. The most massive such system is NGC 346, with a diameter of ~70 parsecs and lying in the main body of the SMC. The cluster includes the eruptive variable, HD 5980, which for a short period in 1994 was the most luminous star in the SMC. Previous ACS observations have revealed many compact star clusters, some still embedded in the parent dust clouds. There are also numerous low mass (< 3 solar masses) pre-main-sequence stars distributed throughout the region. The present proposal will extend observations to cover a broader swathe of the complex, using the ACS images in the V (F606W) and I (F814W) filters to probe the stellar mass function to ~0.6 solar masses, and investigate the degree of mass segregation within this active star-ofrming region.

GO 10592 An ACS Survey of a Complete Sample of Luminous Infrared Galaxies in the Local Universe

A NICMOS image of the interacting LIRG, NGC 6090

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 surveys a total of 88 such systems from the IRAS Revised Bright Galaxy Sample, imaging each system with the ACS using the F439W (B) and F814W (I) filters. The observations will probe
  • the distribution of star formation activity and the presence of bars and bridges, funneling gas towards active regions
  • the relationship between star formation and AGN activity
  • the overall structural properties of the LIRGS as a function of luminosity and environment
Observations of the interacting system, Arp 256, are scheduled for this week.

Past weeks:
page by Neill Reid, updated 15/5/2006