This week on HST

HST Programs: March 13 - March 19, 2006

Program number
Principal Investigator
Program title
10114 Edward Guinan, Villanova University Lyman_alpha FUV observations of the Sun in time and effects on planetary atmospheres
10166 William Borucki, NASA Ames Research Center ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field
10468 Erich Karkoschka, University of Arizona Jupiter's Upper Stratospheric Hazes Probed with Ganymede
10494 Leon Koopmans, Kapteyn Institute Imaging the mass structure of distant lens galaxies
10496 Saul Perlmutter, Lawrence Berkeley National Laboratory Decelerating and Dustfree: Efficient Dark Energy Studies with Supernovae and Clusters
10524 Francesco Ferraro, Universita di Bologna Blue Stragglers: a key stellar population to probe internal cluster dynamics
10532 Kai Noeske, University of California - Santa Cruz Kinematics and morphology of the most massive field disk galaxies at z>1
10547 Edward Fitzpatrick, Villanova University A SNAP Program to Obtain Complete Wavelength Coverage of Interstellar Extinction
10556 David Turnshek, UUniversity of Pittsburgh Neutral Gas at Redshift z=0.5
10587 Adam Bolton, Smithsonian Institution Astrophysical Observatory Measuring the Mass Dependence of Early-Type Galaxy Structure
10588 Michael Brotherton, University of Wyoming The Host Galaxies of Post-Starburst Quasars
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
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
10603 Deborah Padgett, Jet Propulsion Laboratory Multiwavelength Imaging of Edge-on Protoplanetary Disks: Quantifying the Growth of Circumstellar Dust
10605 Evan Skillman, University of Minnesota - Twin Cities Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies
10606 Ultraviolet Snapshots of 3CR Radio Galaxies William Sparks, Space Telescope Science Institute
10610 George Benedict, University of Texas at Austin Astrometric Masses of Extrasolar Planets and Brown Dwarfs
10627 Margaret Meixner, Space Telescope Science Institute A Snapshot Survey of Post-AGB Objects and Proto-Planetary Nebulae
10717 Zhaohui Shang, University of Wyoming Quasar Bolometric Luminosity and Spectral Energy Distributions from Radio to X-ray
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters
10781 Young-Jun Choi, Jet Propulsion Laboratory Observations of the active Centaur 60558 2000 EC98

Some selected highlights

GO 10468: Jupiter's upper stratosphere hazes probed with Ganymede

HST image of Jupiter

Over the next week, ACS will take a series of images of Ganymede, catching the satellite as it slips into occultation behind Jupiter. The observations, in five different passbands spanning the ultraviolet (250 nm) to the far red (892 nm), will probe the upper layers of the parent planet's atmosphere, and permit investigation of the structure of haze within the Jovian stratosphere. Until now, studies of the creation, growth and motions of these layers has been limited to theoretical analyses; the ACS/HRC images will provide the first empirical measurements of the aerosols responsible for the high haze.

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 10592: An ACS survey of a complete sample of luminous infrared galaxies

A NICMOS image of the interacting LIRG, NGC 6090

Luminous infrared galaxies (LIRGs) have total luminosities that exceed 1011.4 LSun, with most of the energy emitted at wavelengths longward of 10 microns. Many (perhaps most) of these galaxies are interacting or merging disk galaxies, with the excess infrared luminosity generated by warm dust associated with the extensive star formation regions. Many systems also exhibit an active nucleus, and may be in the process of evolving towards an S0 or elliptical merger remnant. The present program surveys a total of 88 such systems from the IRAS Revised Bright Galaxy Sample, imaging each system with the ACS using the F439W (B) and F814W (I) filters. The observations will probe
  • the distribution of star formation activity and the presence of bars and bridges, funneling gas towards active regions
  • the relationship between star formation and AGN activity
  • the overall structural properties of the LIRGS as a function of luminosity and environment
Over the next week, observations are scheduled of NGC 6390, UGC 8335 and NGC 6786

GO 10610: Astrometric masses of extrasolar planets and brown dwarfs

An artist's impression of the planets circling the M dwarf, Gl 876

The overwhelming majority of extrasolar planetary systems have been identified through radial velocity monitoring, and the detection of the reflex motion of the parent star as it orbits the common center of mass of the system. Just as radial velocities measure the stellar "wobble" introduced along the line of sight, so high precision astrometry can be used to measure motion in the plane of the sky. Combining these data gives the full three-dimensional motions of the system, and a direct measure of the mass of the planetary companion. The Fine Guidance Sensors on HST are the only system currently capable of making observations at the required sub-milliarcscond accuracy, and has already been used for astrometry of four systems, including the M dwarf Gl 876. The current GO program pursues observations of six planetary hosts, and FGS observations of three targets, HD 136118, HD 145675 (14 Her) and HD 168443, are scheduled over the next week.

GO 10775: An ACS Survey of Galactic Globular Clusters

HST 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 clusters Palomar 1, NGC 1261, NGC 6838, NGC 3201, NGC 5904 and NGC 104 (47 Tucanae) are scheduled over the next week.

page by Neill Reid, updated 8/3/2006