b HST this week: 212

This week on HST

HST Programs: July 31 - August 6, 2006

Program Number Principal Investigator Program Title Links
10103 George Benedict, University of Texas at Austin FGS Astrometry of a Star Hosting an Extrasolar Planet: The Mass of Upsilon Andromedae d Abstract
10258 Claudia Kretchmer, The Johns Hopkins University Tracing the Emergence of the Hubble Sequence Among the Most Luminous and Massive Galaxies Abstract
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters Abstract
10504 Richard Ellis, California Institute of Technology Characterizing the Sources Responsible for Cosmic Reionization 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
10538 Glenn Schneider, University of Arizona Near-IR Spectrophotometry of 2MASSWJ 1207334-393254B - An Extra-Solar Planetary Mass Companion to a Young Brown Dwarf Abstract
10546 Andrew Fabian, University of Cambridge The filaments of NGC1275 Abstract
10623 Aaron S. Evans, State University of New York at Stony Brook HST Optical Snapshot Survey of Intermediate Redshift Ultraluminous Infrared Galaxies Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters Abstract
10796 Roberta M. Humphreys, University of Minnesota - Twin Cities A SNAP Image of the Circumstellar Ejecta of AE And in M31 Abstract
10800 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10829 Paul Martini, The Phio State University Secular Evolution at the End of the Hubble Sequence Abstract
10844 Kris Davidson, University of Minnesota - Twin Cities Following Eta Carinae's Change of State Abstract
10847 Dean Hines, Space Science Institute Coronagraphic Polarimetry of HST-Resolved Debris Disks Abstract
10898 Jesus Maiz-Apellaniz, Space Telescope Science Institute The orbit of the most massive known astrometric binary Abstract
10911 John P. Blakeslee, Washington State University Calibration of ACS F814W Surface Brightness Fluctuations Abstract
10920 Charles Hoopes, The Johns Hopkins University High-Resolution Imaging of Nearby Lyman Break Galaxy Analogs in the GALEX All-Sky Survey Abstract

Some selected highlights

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

Recent HST/ACS images of a supernova in a galazy at z=1.2 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, and Hubble offers almost the only way of obtaining reliable post-maximum photometry of these objects to determine the full shape of the light curve. Most previous HST supernovae programs have concentrated on field galaxies, such as those illustrated here, but applying appropriate corrections for in situ reddening by dust remains an issue in these systems. 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 10546: The filaments of NGC 1275

A composite image of NGC 1275 NGC 1275 is the central galaxy in the relatively nearby (~80 Mpc) Perseus galaxy cluster. It has long been known as an unusual system: it is an original Seyfert galaxy (from Carl Seyfert's 1943 paper); in 1954, Baade & Minkowski identified it as the optical counterpart of Perseus A, one of the first extragalactic radio sources (it is also 3C 84); and it is the brightest extraglactic X-ray source, originally detected by Uhuru in 1971. Optically, NGC 1275 has a complex structure, with dust lanes superimposed on an elliptical-like structure. Baade & Minkowski originally suggested that we might be witnessing a galaxy collision, and subsequent observations generally support this hypothesis. There is evidence for substantial star formation, as well as a central black hole that is probably responsible for the strong radio and X-ray emission. Most recently, narrowband images have revealed an extensive network of gaseous filaments that extend more than 100 kpc from the nucleus (see the Hubble Heritage site ). The present proposal aims to us ACS on HST to image NGC 1275 and its immediate surroundings using several filters that sample both continuum radiation and line emission from H-alpha and O II. The observations will be combined with a deep (1 Megasecond) Chandra image, probing the physical mechanisms present in the filamentary structure.

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 4833 are scheduled over the next week.

GO 10911: Calibration of ACS F814W Surface Brightness Fluctuations

Simulations of a nearby dwarf galaxy, a nearby giant galaxy and a distant giant galaxy; note that the last is similar in angular size to the dwarf, but has a much smoother brightness distribution (simulations from Ned Wright's ABC of distances The determination of the Cosmic Distance Scale remains one of the major goals of cosmological programs in the early 21st century. Achieving this goal requires a reliable distance indicator. While observing programs continue to pursue conventional primary distance indicators (such as RR Lyraes and Cepheids) and secondary distance indicators (such as the RGB tip and the Tully-Fisher relation), attention is also being given to the method of surface brightness fluctuations. This method rests primarily on the hypothesis that the stellar populations in most galaxies have similar colour-magnitude diagrams. Thus, the total luminosity of the galaxy is generated by similar stars - mainly red giants. In a nearby low-luminosity galaxy, most of the light comes from a relatively small numebr of giant branch stars; consequently, that galaxy has a "grainier" appearance than a distant high-luminosity galaxy of the same apparent magnitude (see figure). The degree of granularity can therefore serve as a distance indicator. The present program will use ACS (F814W filter) to observe half a dozen galaxies in the Fornax cluster to provide a reliable calibration of this technique.

Past weeks:
page by Neill Reid, updated 25/7/2006