This week on HST


HST Programs: August 20 - August 26, 2007

Program Number Principal Investigator Program Title Links
10487 David Ardila, California Institute of Technology A Search for Debris Disks in the Coeval Beta Pictoris Moving Group Abstract
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
10789 Christopher J. Conselice, University of Nottingham The Role of Environment in the Formation of Dwarf Galaxies Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10847 Dean Hines, Space Science Institute Coronagraphic Polarimetry of HST-Resolved Debris Disks Abstract
10901 Robert W. O'Connell, The University of Virginia UV-Luminous Globular Clusters in NGC 1399 Abstract
11080 Daniela Calzetti, University of Massachusetts Exploring the Scaling Laws of Star Formation Abstract
11082 Christopher Conselice, Univ. of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Obscured Universe 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
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
11234 Luciana C. Bianchi, The Johns Hopkins University A Brief Revisit of the Crab Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11291 Farhad Yusef-Zadeh, Northwestern University Following Eta Carinae's Change of State Abstract
11292 Mark R. Showalter, SETI Institute The Ring Plane Crossings of Uranus in 2007 Abstract
11295 Howard E. Bond, Space Telescope Science Institute Trigonometric Calibration of the Distance Scale for Classical Novae Abstract
11304 Stanimir A. Metchev, University of California - Los Angeles The L/T Transition in the Photospheres of Young Sub-Stellar Companions Abstract
11329 Adam Riess, Space Telescope Science Institute The Final SHOE; Completing a Rich Cepheid Field in NGC 1309 Abstract

Some selected highlights

GO 10847: Coronagraphic Polarimetry of HST-Resolved Debris Disks

HST ACS/HRC coronagraphic images of debris disks around two nearby stars The last decade has seen the identification of debris disks around a number of stars in the Solar neighbourhood. The coronagraphic capabilities available on HST have been particularly useful in this regards, since the lower background present in space-based observations offers significant advantages in detecting these low surface brightness features. Indeed, this week is "disk week" on HST, with observations scheduled for programs GO 10847, GO 10599 and GO 11203, as well as the present program. Those observations are complemented by mid-infrared surveys (notably by Spitzer) of denser, warmer disks in young stars. The latter observations detect thermal emission from the dust grains, permitting some constraints to be set on the chemical composition. The present program aims to use polarimetric observations of debris disks to probe the distribution of grain sizes and the density distribution of dust in those somewhat older systems. Observations of the A0 star, HD 32297, and the G3 dwarf, HD 61005, are scheduled in the coming week.

GO 11082: NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Observational Universe

ACS images of a section of the GOODS fields The Great Observatories Origins Deep Survey, is a large-scale program that is designed to probe galaxy formation and evolution at redshifts from z~1 to z~6. GOODS covers two ~150 sq. arcminute fields, one centred on the Hubble Deep Field and the second on the Chandra Deep Field South, and combines deep oppical/far-red imaging (F435W, F606W, F775W and F850LP filters) using ACS on HST with deep IRAC (3.6 to 8 micron) and MIPS (25 micron) imaging with Spitzer. Chandra data are also available for the bulkd of the field. The present program is supplementing those data with near-infrared H-band (F160W) imaging with NICMOS, coupled (eventually) with parallel ultraviolet observations using the ACS/SBC.

GO 11289: SL2S - The Strong Lensing Legacy Survey

ACS images of galaxy-galaxy Einstein ring lenses from the Sloan survey 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 primarily to probe the mass distribution of galaxy clusters, using theoretical models to analyse the arcs and arclets that are produced by strong lensing of background galaxies, and the large-scale mass distribution, through analysis of weak lensing effects on galaxy morphologies. Gravitational lensing can also be used to investigate the mass distribution of individual galaxies. Until recently, the most common background sources were quasars. Galaxy-galaxy lenses, however, offer a distinct advantage, since the background source is extended, and therefore imposes a stronger constraints on the mass distribution of the lensing galaxy than a point-source QSO. The CFHT Legacy survey provides a powerful tool for identifying candidate galaxy-galaxy lenses. Optical ground-based imaging, even from Hawaii, cannot match the results from a 2.4-metre telescope in orbit. Thus, the present program is using WFPC2 imaging to verify the nature of those candidates. The high resolution images can then be analysed to model the underlying mass distribution.

GO 11292: The Ring Plane Crossings of Uranus in 2007

Images of Uranus spanning 2000 to 2004, showing the rotation of the ring plane Like the other Solar System gas giants, Uranus not only has an extensive number of satellite moons, but also possesses a ring system. Unlike the other giant planets, Uranus has a polar obliquity of 98o degrees, so its equator is close to perpendicular to the ecliptic plane. Consequently, from our vantage point on Earth, we view the north and south poles alternately during Uranus' 84-year circling of the Sun. Midway between the polar apparitions, of course, we view Uranus' equatorial plane - and see the ring system edge-on. The next ring plane crossing will occur in May and August 2007. At this juncture, the denser and more prominent rings will almost disappear from view, providing an opportunity to search for small satellite "shepherd" moons. These moons are expected to be present, acting as gravitational delineators, defining the radial size of the individual rings. Besides searching for the shepherds, the current HST program will use the the Planetary camera on WFPC2 to measure the thickness of the rings, and study the colours of the recently discovered fainter rings.

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