This week on HST


HST Programs: March 27 - April 02, 2006

Program number
Principal Investigator
Program title
Links
10166 William Borucki, NASA Ames Research Center ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field
Abstract
10478 Edmund Nelan, Space Telescope Science Institute Dynamical Masses and Radii of Four White Dwarf Stars
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
10501 Rupali Chandar, The Johns Hopkins University Extending the Heritage: Clusters, Dust, and Star Formation in M51
Abstract
10504 Richard Ellis, California Institute of Technology Characterizing the Sources Responsible for Cosmic Reionization
Abstract
10507 Denis Grodent, Universite de Liege High resolution imaging of Jupiter's diffuse auroral emissions inside and outside the main oval during solar minimum.
Abstract
10514 Keith Noll, Space Telescope Science Institute Kuiper Belt Binaries: Probes of Early Solar System Evolution
Abstract
10519 Janet Simpson, NASA Ames Research Center Testing the Stellar Coalescence and Accretion Disk Theories of Massive Star Formation with NICMOS
Abstract
10524 Francesco Ferraro, Universita di Bologna Blue Stragglers: a key stellar population to probe internal cluster dynamics
Abstract
10525 Suzanne Hawley, University of Washington Characterizing the Near-UV Environment of M Dwarfs: Implications for Extrasolar Planetary Searches and Astrobiology
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
10536 Raghvendra Sahai, Jet Propulsion Laboratory What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey
Abstract
10547 Edward Fitzpatrick, Villanova University A SNAP Program to Obtain Complete Wavelength Coverage of Interstellar Extinction
Abstract
10556 David Turnshek, University of Pittsburgh Neutral Gas at Redshift z=0.5
Abstract
10575 Goran Ostlin, Stockholm University Lyman alpha morphology of local starburst galaxies
Abstract
10582 Gregory Sivakoff, The University of Virginia Probing The Galaxy-wide Globular Cluster - Low Mass X-ray Binary Connection in Early-type Galaxies
Abstract
10584 Andreas Zezas, Smithsonian Institution Astrophysical Observatory The link between X-ray source and stellar populations in M81
Abstract
10591 Arjun Dey, National Optical Astronomy Observatories, AURA ACS observations of the galaxies in a giant Ly-alpha nebula at z~2.7
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
10596 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: A Test of the Black Hole-Bulge Paradigm
Abstract
10605 Evan Skillman, University of Minnesota - Twin Cities Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies
Abstract
10610 George Benedict, University of Texas at Austin Astrometric Masses of Extrasolar Planets and Brown Dwarfs
Abstract
10617 John Biretta, Space Telescope Science Institute HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet
Abstract
10622 Andrew Dolphin, University of Arizona ACS Photometric Calibration from Faint Standards
Abstract
10775 Ata Sarajedini, University of Florida An ACS Survey of Galactic Globular Clusters
Abstract
10776 Matt Mountain, Space Telescope Science Institute HST/ACS Mosaic of M82
Abstract

Some selected highlights


GO 10166: ACS and WFPC2 Stellar Photometry in the Kepler Mission Target Field

The Kepler satellite

Kepler, a NASA Discovery mission, is designed to search for extrasolar planets by using high-precision photometric observations to detect transits. Scheduled for launch in June 2008, Kepler will continuously monitor ~100,000 (mainly) so lar-type stare within a ~100 square degree region in Cygnus. Ground-based observations have successfully detected several transiting planets (e.g. HD 209458); all are "hot jupiters", gas giants on short-period orbits which produce a photometric dip of ~10-2 with a periopd of a few days. In contrast, Kepler aims at detecting terrestrial planets within the habitable zone, and therefore must detect photometric transit signatures at the 10-4 level that last for 2-16 hours and recur on timescales of 1-2 years. This is a challenging task.
A subset of stellar binaries provide one of the main sources of confusion in searching for planetary transits, since "grazing" transits can mimic the planetary signature. This is particularly an issue with Kepler, since the optical system is designed to provide a broad psf, spreading the stellar flux over a large area on the detetcor to allow high photometric accuracy. As a result, faint eclipsing stellar binaries will contribute to the source counts. This program is using the high spatial resolution imaging provided by HST to study a small subset of the full Kepler target field to assess the likely statistical impact of these false positives.

GO 10487: A Search for Debris Disks in the Coeval Beta Pictoris Moving Group

WFPC2 image of Beta Pic's disk

Over the last few years, there has been growing recognition of the presence of a number of young stellar associations, each consisting of 20-50 stars, within the Solar Neighbourhood. Beta Pictoris (or Gl 219), a relatively young (~20 Myrs old) A5 dwarf, lying at a distance of just under 20 parsecs form the Sun, is the `flagship' member of one of those groups.. The IRAS satellite originally singled out this A star as unusual, detecting significant excess radiation over the expected photospheric fluxes at mid-infrared wavelengths; Smith & Terrile (1984) used ground-based coronagraphic observations to show that this was due re-radiation from a substantial debris disk. A further 30 stars are associated with this young group, with spectral types ranging from A to late M. Several of these stare are known to also have dusty disks, including the binary HR 7329 (A0 + M7) and the nearby active M1 dwarf, AU Mic (Gl 803). The present proposal aims to extend the sample, using the ACS/HRC in coronagraphic mode to search for debris disks around 21 members of the moving group.

GO 10536: What Are Stalled Preplanetary Nebulae? An ACS SNAPshot Survey

K-band image of IRAS0937+1212, also known as Frosty Leo (ESO ground-based image)

Most stars are expected to terminate their life as hydrogen burning objects by traversing the asympotic giant branch (AGB) and expelling their outer atmosphere to form a planetary nebula (PN). Mass loss from the giant star is generally expected to be spherically symmetric, but many known planetaries are strikingly asymmetric in shape. Previous observations, primarily with HST, have shown that the asymmetries develop very early in the transition from AGB to PN; roughly half of the targets from a morphologically-unbiased sample prove to have either bipolar or multipolar morphologies, with the origin as yet undetermined (although binarism is a suspect). Those observations also identified a peculiar class of PN, with the prototype being IRAS0937+1212, or "Frosty Leo". These are very dusty systems, with IRAS F(60-micron)/F(25-micron) flux ratios exceeding 1, with moderately large post-AGB ages (~10,000 years), but relatively cool central stars. The suggestion is that these systems have "stalled" in their evolution towards the PN phase due to backfall of material onto the central star, essentially replenishing some of the mass loss. This proposal aims to obtain greater insight into this process by imaging 100 dusty (F(60)/F(25) > 1) PN candidates using the F606W and F814W passbands on ACS.

GO 10605: Quantifying Star Formation and Feedback: The M81 Group Dwarf Galaxies

The M81 galaxy group

The M81 group is a loose collection of approximately 20 galaxies centred on the interacting pair M81, a spiral, and M82, the well-known starburst galaxy. The group lies at a distance of ~4 Mpc, and was targeted for Cepheid observations as part of the HST H0 Key Project.
This program will use ACS to survey 10 group members, chosen to span a factor of ~150 in luminosity, ~1000 in star formaton rate and a factor of 3 in metallicity. The ACS F555W and F814W (V, I) images will be used to study the recent star formation history, probing the last 500 Myrs with a time-resolution acccuracy of 5-10%. The goal is to investigate the extent and efficiency of feedback mechanisms in the ISM, notably examining the fraction of star formation triggered by feedback, the relative numbers of clusters and associations, and the role played by feedback from previous star formation episodes.

GO 10584: The link between X-ray source and stellar populations in M81

The combined UV/X-ray image of M81

M81, the main spiral galaxy in the M81 group, is itself the subject of a separate HST program, also using ACS. The aim here is to characterise the nature of the X-ray sources detected in deep Chandra observations, with the specific aim of separating high-mass and low-mass X-ray binaries (HMXRBs and LMXRBs). As one might expect, HMXRBs are expected to be associated with young stellar populations (high mass stars); LMXRBs are generally believed to consist of either a neutron star or black hole which is accreting matter from a lower-mass companion (main-sequence star, red giant or white dwarf) that fills its Roche lobe. LMXRBs are therefore likely to be present in somewhat older stellar populations than the HMXRBS. This proposal aims to quantify this issue through a detailed survey of M81.


Past weeks:
page by Neill Reid, updated 28/3/2006