This week on HST

HST Programs: August 13 - August 19, 2007

Program Number Principal Investigator Program Title Links
10599 Paul Kalas, University of California - Berkeley Multi-color imaging of two 1 Gyr old debris disks within 20 pc of the Sun: Astrophysical mirrors of our Kuiper Belt Abstract
10787 Jane Charlton, The Pennsylvania State University Modes of Star Formation and Nuclear Activity in an Early Universe Laboratory Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10840 Nuria Calvet, University of Michigan The FUV fluxes of Tauri stars in the Taurus molecular cloud Abstract
10864 Carol A. Grady, Eureka Scientific Inc. Mapping the Gaseous Content of Protoplanetary and Young Planetary Systems with ACS Abstract
10872 Harry Teplitz, California Institute of Technology Lyman Continuum Emission in Galaxies at z=1.2 Abstract
11128 David Bradley Fisher, University of Texas at Austin Time Scales Of Bulge Formation In Nearby Galaxies Abstract
11133 Saurabh Jha, Rutgers the State University of New Jersey Late-Time Photometry of SN 2005hk: A New Kind of Type Ia Supernova Abstract
11156 Kathy Rages, SETI Institute Monitoring Active Atmospheres on Uranus and Neptune Abstract
11169 Michael E. Brown, California Institute of Technology Collisions in the Kuiper belt 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
11176 Andrew S. Fruchter, Space Telescope Science Institute Location and the Origin of Short Gamma-Ray Bursts Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11179 Patrick Hartigan, Rice University Dynamics of Clumpy Supersonic Flows in Stellar Jets and in the Laboratory Abstract
11190 Laurence M. Trafton, University of Texas at Austin Probing Uranus' Vertical Aerosol Structure at Equinox Abstract
11201 Nitya Kallivayalil, Harvard University Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images Abstract
11203 Kevin Luhman, The Pennsylvania State University A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus Abstract
11212 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries Abstract
11219 Alessandro Capetti, Osservatorio Astronomico di Torino Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio-quiet dichotomy? Abstract
11229 Margaret Meixner, Space Telescope Science Institute SEEDS: The Search for Evolution of Emission from Dust in Supernovae with HST and Spitzer Abstract
11292 Mark R. Showalter, SETI Institute The Ring Plane Crossings of Uranus in 2007 Abstract
11312 Graham Smith, University of Birmingham The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2 Abstract

Some selected highlights

GO 10872: Lyman Continuum Emission in Galaxies at z=1.2

Lyman alpha image of the radio galaxy, 4C41.17 In Big Bang cosmology, the early history of the unverise is characterised by three distinct phases: the initial expansion, during which time Big Bang nucleosynthesis occurs, and the universe cools from its initial exceedingly high temperatures; recombination, which occurs at a redshift z~1,100 (or an age of ~400,000 years), when the Universe was cool enough to allow neutral hydrogen to become dominant, leading to high opacity and the cosmic microwave background; and reionisation, when energy sources reionised hydrogen, reducing the opacity of the intergalactic medium and restoring transparency. Reionisation is generally believed to have occurred at a redshift between z~6 and z~20, with the ionising sources either (or both) the first generation of stars (Population III starbursts) and/or proto-quasars. The IGM remains ionised thereafter. A key issue in developing an understanding of this process is assessing how readily starburst-generated Lyman-alpha emission escapes from galaxies, and how starbursts contribute to reionisation at intermediate redshifts. This proposal aims to quantify this matter by targeting galaxies at redshifts 1 < z < 2 for observations at ultraviolet wavelengths with the Advanced Camera for Surveys Solar Blind Channel (ACS/SBC).

GO 11178: Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries

Preliminary orbital determination for the KBO WW31, based on C. Veillet's analysis of CFHT observations; the linked image shows the improved orbital derivation, following the addition of HST imaging The Kuiper Belt consists of icy planetoids that orbit the Sun within a broad band stretching from Neptune's orbit (~30 AU) to distance sof ~50 AU from the Sun (see David Jewitt's Kuiper Belt page for details). Over 500 KBOs (or trans-Neptunian objects, TNOs) are currently known out of a population of perhaps 70,000 objects with diameters exceeding 100 km. Approximately 2% of the known KBOs are binary (including Pluto, one of the largest known KBOs, regardless of whether one considers it a planet or not). This is a surprisingly high fraction, given the difficulties involved in forming such systems and the relative ease with which they can be disrupted. It remains unclear whether these systems formed from single KBOs (through collisions or 3-body interactions) as the Kuiper Belt and the Solar System have evolved, or whether they represent the final tail of an initial (much larger) population of primordial binaries. These issues can be addressed, at least in part, through deriving a better understanding of the composition of KBOs - and those properties can be deduced by measuring the orbital parameters for binary systems. The present proposal will use the Planetary camera on WFPC2 to determine the relative orbits for several known KBO binaries. Just as with binary stars, the orbital period and semi-major axis give the total system mass, while the mid-infrared properties (measured by Spitzer) allow an assessment of the surface area/diameters; combining these measurements gives an estimate of the mean density.

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
Past weeks:
page by Neill Reid, updated 10/8/2007