This week on HST


HST Programs: April 3 - April 9, 2006

Program number
Principal Investigator
Program title
Links

Abstract
10350 Haldan Cohn, Indiana University System X-ray Binaries in the Ultrahigh Collision Rate Globular Cluster NGC 6388
Abstract
10474 Gordon Drukier, Yale University Shooting Stars: Looking for Direct Evidence of Massive Central Black Holes in Globular Clusters
Abstract
10487 David Ardila, California Institute of Technology A Search for Debris Disks in the Coeval Beta Pictoris Moving Group
Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters
Abstract
10519 Janet Simpson, NASA Ames Research Center Testing the Stellar Coalescence and Accretion Disk Theories of Massive Star Formation with NICMOS
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
10535 Edward Robinson, University of Texas at Austin High Temperature Accretion Flows and Reprocessing in X-ray Binaries: The ADC Source 4U 1822-371
Abstract
10540 Alycia Weinberger, Carnegie Institution of Washington Imaging Nearby Dusty Disks
Abstract
10545 Michael Brown, California Institute of Technology Icy planetoids of the outer solar system
Abstract
10559 Herve Bouy, Instituto de Astrofisica de Canarias Astrometric monitoring of binary L and T dwarfs
Abstract
10563 Simon Dye, University of Wales, College of Cardiff (UWCC) Accurate dark-matter mass profiles in 3 elliptical galaxies as a test of CDM
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
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
10602 Jesus Maiz-Apellaniz, Space Telescope Science Institute - ESA A Complete Multiplicity Survey of Galactic O2/O3/O3.5 Stars with ACS
Abstract
10609 William Vacca, Universities Space Research Association Sizes, Shapes, and SEDs: Searching for Mass Segregation in the Super Star Clusters of Nearby Starburst Galaxies
Abstract
10610 George Benedict, University of Texas at Austin Astrometric Masses of Extrasolar Planets and Brown Dwarfs
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
10615 Scott Anderson, University of Washington Timing Studies of the X-ray Binary Populations in Globular Clusters
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
10695 Holland Ford, The Johns Hopkins University Coronagraphic Search for Disks around Nearby Stars
Abstract
10718 Jeff Valenti, Space Telescope Science Institute The Exosphere of a Newly Discovered Transiting Planet
Abstract
10764 Carol Grady, Eureka Scientific Inc. X-Ray Activity and Winds in Young A Stars at the Epoch of Disk Clearing
Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters
Abstract
10783 Amy Simon-Miller, NASA Goddard Space Flight Center Rapid Response: Jupiter's White Oval Turns Red
Abstract

Some selected highlights


GO 10474: Shooting Stars: Looking for Direct Evidence of Massive Central Black Holes in Globular Clusters

An artist's impression of a black hole in a globular cluster

The formation, and subsequent evolution, of intermediate-mass black holes (IMBHs) is a process of considerable importance for understanding th development of active galactic nuclei at high redshifts. IMBHs are generally expected to originate in globular-cluster-mass structures; hence, one might expect such objects to be present in some present-day Galactic clusters, particularly those that have undergone dynamical core collapse. The present program targets the bulge globular clusters, NGC 6388 and NGC 6441. These are both fairly massive globular clusters, and therefore good candidates to have central black holes. This program will obtain second-epoch ACS images of the central regions of these clusters. The proper motions derived by combining those data with observations from Cycle 12 will have an accuracy of ~6 km/sec, and therefore should be sufficient to detect the kinematic signature of a central massive object.

GO 10496: Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters

Dark energy and the accelerating universe

The last few years of the twentieth century saw a revolution in cosmology, with the measurement of the acceleration term in expansion at high redshifts and the identification of dark energy as a major cosmological component. Type Ia supernovae are the prime yardstick for measuring the rate of expansion at moderate and high redshifts, but applying appropriate corrections for in situ reddening by dust remains an issue. The present program aims to minimise the uncertainties by searching for supernovae in massive, high-redshift clusters, with the expectation that the majority of detections lie within dust-poor elliptical galaxies. ACS survey observations of eight clusters are scheduled for the coming week, together with follow-up NICMOS observations of a supernova detected in previous ACS images.

GO 10563: Accurate dark-matter mass profiles in 3 elliptical galaxies as a test of CDM

A WFPC2 image of the optical Einstein Ring galaxy, 0047-2808

Most current models of galaxy formation are tied to Lambda-CDM cosmology. That scheme makes predictions of the expected density profile and density stucture (specifically, the clumpiness of sub-structure) of the dark matter halos that underlie visible galaxies. Rotation curves of some low surface brightness galaxies appear to contradict the predictions of these models, but the observations are difficult and the analysis rests on assumptions that are difficult to verify (e.g. axisymmetry). Strong gravitational lensing, where a distant galaxy happens to line up nearly perfectly with a foreground (inr elative terms) elliptical, supplies a means of probing the dark-matter dominated potential. The background galaxy is lensed to form a series of arcs, whose brightness distribution probes the potential along the line of sight. HST optical images, with sub-arcsecond resolution, have hundreds of resolution elements distributed across the lensed galaxies; each element provides a constraint on the underlying mass profile. Such lensed systems are exceedingly rare (0047-2808 is the classic example); the investigators in this proposal have recently discovered a number of new examples, and this proposal aims to use the ACS HRC (high resolution camera) to obtain red (F606W) images of those systems.

GO 10540: Imaging Nearby Dusty Disks

HST image of the face-on debris disk in the G2 dwarf, HD 107146

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 structure of those disks is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Analysis of the rangle of morphological structure in these systems provides insight into the distribution of properties of planetary systems. Disk imaging programs have demonstrated that the HST currently provides the only means of achieving the high-contrast required for the detection of these scattered light disks in the presence of the bright parent stars. The present proposal is using NICMOS to image ten nearby F-type dwarfs.

GO 10718: The exosphere of a newly discovered transiting planet

An artist's impression of the hot Jupiter circling HD 149026 (U.C. Santa Cruz)

Transiting extrasolar planets offer particularly valuable insight into the structure of these non-Solar System gas giants. 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. This proposal aims to use the ultraviolet prism on ACS to search for Lyman-alpha absorption during planetary transit. This is an extremely sensitive exospheric diagnostic that only HST can measure. If the HD 149026 planet is evaporating, then hydrogen in the exosphere should fill or overfill the Roche lobe, which has a size 4 times the diameter of Jupiter. The newly discovered planet has 3 times the mean density and at least 3 times the core mass of the planet that transits HD 209458, which is consistent with significant exospheric evaporation in the past. In addition, these observations will measure the stellar limb darkening in the near-UV, detecting Mg in the lower atmosphere of the planet, and searching for evidence of a moon or planetary rings.

GO 10783: Rapid Response - Jupiter's White Oval(s) Turns Red

HST image

In the late 1930s, bright white clouds expanded and encircled Jupiter's southern hemisphere in a band near 33 degrees south planetographic latitude. Those clouds collapsed into three large anticyclonic storms, later named the White Ovals, that were second in size only to the Great Red Spot. In the mid to late 1990s these storms suddenly approached each other very closely, resulting in the 1998 merger of two of the storms. In 2000, the third oval also merged, leaving one remaining large White Oval. Early in 2006, amateur observers noted that the oval appeared to be changing in appearance and turning red. While small red spots do appear on Jupiter from time to time, they usually form as a colored spot, cloud over, and become white, rather than the opposite. This proposal aims to use multiwavelength observations with the HRC on ACS to study the vertical structure of the storm, and investigate possible mechanisms that might have prompted these changes.

Past weeks:
page by Neill Reid, updated 31/3/2006