This week on HST


HST Programs: June 12 - June 18, 2006

Program Number Principal Investigator Program Title Links
10410 Clive Tadhunter, University of Sheffield Anisotropy and obscuration in the near-nuclear regions of powerful radio galaxies Abstract
10430 Taft Armandroff, National Optical Astronomy Observatories, AURA Identifying the Major Star Formation Epoch(s) in the Outlying M31 Dwarf Spheroidal Companion Cassiopeia Abstract
10473 Mark Showalter, SETI Institute Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10512 William Merline, Southwest Research Institute Search for Binaries Among Faint Jupiter Trojan Asteroids Abstract
10514 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution Abstract
10523 Roelof de Jong, Space Telescope Science Institute The Halo Shape and Metallicity of Massive Spiral Galaxies 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
10534 Kathy Rages, SETI Institute Active Atmospheres on Uranus and Neptune Abstract
10536 Raghvendra Sahai, Jet Propulsion Laboratory What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey Abstract
10544 David Bennett, University of Notre Dame Resolved Images of LMC Microlensing Events Observed by a Telescope at 2 AU from Earth Abstract
10556 David Turnshek, University of Pittsburgh Neutral Gas at Redshift z=0.5 Abstract
10559 Herve Bouy, University of California - Berkeley Astrometric monitoring of binary L and T dwarfs Abstract
10571 Tod Lauer, National Optical Astronomy Observatories, AURA The Compact Disk of Blue Stars Orbiting the M31 Black Hole Abstract
10573 Mario Mateo, University of Michigan Globular Clusters in the Direction of the Inner Galaxy 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
10589 Remi Cabanac, Canada-France-Hawaii Telescope Corporation The highest redshift Einstein ring: probing a dark matter halo at z=1 and galaxy morphology at z=3.8 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
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
10626 Yeong-Shang Loh, University of Colorado at Boulder A Snapshot Survey of Brightest Cluster Galaxies and Strong Lensing to z = 0.9 Abstract
10631 Thomas Puzia, Space Telescope Science Institute Intermediate-Age Globular Clusters in M31 Abstract
10632 Massimo Stiavelli, Space Telescope Science Institute Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field Abstract
10761 Victoria Kaspi, McGill University The X-ray Spectral and Optical/IR Flux Variability in Magnetars Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters Abstract

Some selected highlights

GO 10473: Rings of Uranus: Dynamics, Particle Properties and Shepherding Moons

Hubble WFPC2 image of the main Uranian rings from July 1995 The Saturnian ring system is the most prominent in the Solar System, visible in Galileo's refractor and first clearly identified by Huyghens in 1679. However, all of the Jovian planets have ring systems. The Uranian system was discovered in 1977, when the planet occulted the relatively anonymous 10th magnitude K1 subgiant, HD 128598. Photometry from the Kuiper Airborne Observatory, which was able to continuously monitor the event, showed a symmetric sequence of ten events (five before occultation, five after); combined with ground-based observations from Perth, Australia, a total of nine rings were identified. Subsequent observations by Voyager 2, both occultations and during its flyby, identified a few additional rings and revealed belts of dust. The more prominent rings have also been imaged with HST. The present program aims to use the ACS HRC to image the rings over a range of wavelengths and phase angles, studying the interactions between these dynamically-sensitive entities and the smaller Uranian satellites.

GO 10523: The Halo Shape and Metallicity 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 seven other nearby spiral systems. ACS is being used to obtain WFC observations in the F550W and F814W filters at a series of locations along the major and minor axes, and along an intermediate-angle axis. A comparison of the colour-magnitude diagrams at different radial distances should permit separation of the contributions from disk, thick disk and bulge, and isolation of the halo population in those systems. The observations should allow measurement of the halo metallicity distribution and an estimate of the shape of the halo in these systems.

GO 10571: The Compact Disk of Blue Stars Orbiting the M31 Black Hole

Chandra X-ray image of the M31 nucleus; the blue dot marks the source associated with the central black hole. M31, the Andromeda galaxy, is the nearest spiral system, Hubble type Sb, lying at a distance of ~ 800 kpc and with a radius and (probably) mass somewhat larger than the Milky Way. Comparative studies of the two systems can be very informative, particularly since our exterior vantage point on M31 offers significant advantages in probing issues such as large-scale spiral structure and the detailed properties of the galactic nucleus (regions that are highly obscured by dust in our own Milky Way). One of the first observations with the original Planetary Camera on Hubble (in 1991) revealed that M31 appears to have a double nucleus. Initially, these observations were interpreted as potential evidence for a merger, with the secondary nucleus attributed to the surviving core of the absorbed satellite. However, subsequent observations have shown that these "nuclei" are actually a line-of-sight effect. Follow-up WFPC2 imaging (1995) showed an excess of blue light, attributed to a young cluster of blue stars, while Chandra observations identified numerous X-ray sources, including a source associated with the supermassive (~108 M Sun) central black hole. Recently, STIS observations have demonstrated that the excess blue light originates from a disk of blue stars centred on the black hole. That disk, coupled with an elliptical ring of red stars, account for the apparently-binary nuclear structure. \\ The present set of ACS HRC observations is designed to map the detailed morphology of the disk in the U and B passbands.

GO 10632: Searching for galaxies at z>6.5 in the Hubble Ultra Deep Field
The Hubble Ultra-Deep Field (the UDF) is the deepest image so far obtained of the Cosmos. The original program comprised 412 orbits directed at a single ACS field within the Chandra Deep Field-South (CDF-S) GOODS area. Those 412 orbits were divided among four filters - F435W (56 orbits), F606W (56 orbits), F775W (150 orbits), and F850LP (150 orbits). A further 144 orbits were devoted to a 3x3 grid of F110W (J) and F160W (H) NICMOS images covering the same field.(GO program 9803). NICMOS was also employed in parallel with the ACS observations to obtain deep J- and H-band images of adjacent fields. The present proposal devotes 204 orbits to new observations of the prime and parallel fields, but with HST inverted; thus, the program will obtain ACS imaging (in F606W, F775W and F750LP) of the parallel fields, and deeper NICM (F110W, F160W) data for part of the original ACS UDF. The primary goal of the program is identify candidate very high redshift (6.5 < z < 8.5) sources, using photometric redshifts derived by combining the optical and near-infrared photometric catalogues.

GO 10775: An ACS Survey of Galactic Globular Clusters

Hubble image of the globular cluster M15 Globular clusters are members of the Galactic halo population, which formed during the first extensive period of star formation in the Milky Way. As such, the properties of the 106 to 107 stellar constituents can provide crucial insight into the earliest stages of galaxy formation. The present HST program will obtain two-colour (F606W, F814W) ACS images of the central regions of 66 of the ~150 Galactic clusters, with the goals of
  • determining cluster ages and distances;
  • studying the main sequence luminosity function, mass function and mass segregation within the cluster;
  • investigating the internal motions and dynamical evolution; and
  • using absolute cluster motions to determine cluster orbits and probe the galactic potential.
Observations of the cluster NGC 2298 are scheduled over the next week.

Past weeks:
page by Neill Reid, updated 5/6/2006