This week on HST


HST Programs: October 29 - November 4, 2012

Program Number Principal Investigator Program Title
12228 Glenn Schneider, University of Arizona Probing for Exoplanets Hiding in Dusty Debris Disks: Inner {<10 AU} Disk Imaging, Characterization, and Exploration
12444 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-North Field, Middle Visits of SNe Search
12458 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12471 Dawn K. Erb, University of Wisconsin - Milwaukee The Bottom of the Iceberg: Faint z~2 Galaxies and the Enrichment of the IGM
12497 Sungryong Hong, National Optical Astronomy Observatory, AURA Constraining Stellar Feedback : A Census of Shock-ionized Gas in Nearby Starbursts Galaxies.
12564 Roeland P. van der Marel, Space Telescope Science Institute Proper Motions along the Sagittarius Stream: Constraining Milky Way Parameters and Dark Halo Shape
12569 Sylvain Veilleux, University of Maryland Ionized and Neutral Outflows in the QUEST QSOs
12581 Julia Christine Roman-Duval, Space Telescope Science Institute - ESA A Direct CO/H2 Abundance Measurement in Diffuse and Translucent LMC and SMC Molecular Clouds
12587 Miriam Garcia, Instituto de Astrofisica de Canarias Winds of very low metallicity OB stars: crossing the frontier of the Magellanic Clouds
12612 John T. Stocke, University of Colorado at Boulder Probing Weak Intergalactic Absorption with Flaring Blazar Spectra
12669 Luigi R. Bedin, Osservatorio Astronomico di Padova Exploring the Bottom End of the White Dwarf Cooling Sequence in the Open Cluster NGC6819
12685 Dean C. Hines, Space Telescope Science Institute Enabling Dark Energy Science for JWST and Beyond
12812 Zolt Levay, Space Telescope Science Institute Hubble Heritage
12813 Brian Schmidt, Australian National University Network of 13 high precision STIS spectrophotometric standards for ground based surveys
12870 Boris T. Gaensicke, The University of Warwick The mass and temperature distribution of accreting white dwarfs
12873 Beth Biller, Max-Planck-Institut fur Astronomie, Heidelberg Search for Planetary Mass Companions around the Coolest Brown Dwarfs
12879 Adam Riess, The Johns Hopkins University A 1% Measurement of the Distance Scale with Perpendicular Spatial Scanning
12893 Ronald L Gilliland, The Pennsylvania State University Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging
12902 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12930 Carrie Bridge, California Institute of Technology WISE Discovered Ly-alpha Blobs at High-z: The missing link?
12940 Philip Massey, Lowell Observatory The Unevolved Massive Star Content of the Magellanic Clouds
12941 Ian William Stephens, University of Illinois at Urbana - Champaign Probing Isolated Massive Star Formation in the LMC
12972 Christopher R. Gelino, Jet Propulsion Laboratory In Search of the Coldest Atmospheres: Identifying Companions to the Latest WISE Brown Dwarfs
12975 Simon J. Lilly, Eidgenossiche Technische Hochschule (ETH) Do winds transport magnetic fields out of high redshift galaxies?
12978 Daniel E. Welty, University of Chicago Properties of Diffuse Molecular Gas in the Magellanic Clouds
12995 Christopher Johns-Krull, Rice University Testing Disk Locking in the Orion Nebula Cluster
13010 Fabio Bresolin, University of Hawaii A precise calibration of the zero point of the cosmic distance scale from late-type eclipsing binaries in the LMC
13029 Alex V. Filippenko, University of California - Berkeley A Snapshot Survey of the Sites of Recent, Nearby Supernovae
13031 William M. Grundy, Lowell Observatory Testing Collisional Grinding in the Kuiper Belt
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13102 Michael McDonald, Massachusetts Institute of Technology Zooming in on the Starburst at the Core of the Phoenix Cluster
13179 Robert P. Kirshner, Harvard University Ultraviolet Spectra of the Exceptional SN 2009ip

Selected highlights

GO 12228: Probing for Exoplanets Hiding in Dusty Debris Disks: Inner <10 AU Disk Imaging, Characterization, and Exploration


HST-ACS image of the disk surrounding the nearby M dwarf, AU Mic
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 disk structure is affected by massive bodies (i.e. planets and asteroids), which, through dynamical interactions and resonances, can produce rings and asymmetries. Over the past decade, HST and Spitzer have provided complementary information on this subject, with Spitzer measuring thermal radiation from circumstellar dust and HST providing high-resolution mapping of debris disks in reflected light. Most recently, HST ACS coronagraphic imaging have revealed the presence of a planetary object within the disk of the nearby A star, . Planetary companions to the young (60 Myr-old) F star, HR 8799, have also been imaged by both ground-based telescopes and HST. The ACS coronagraph was associated with the High Resolution Camera, which is no longer functioning; nor is NICMOS. However, coronagraphy is still possible using the occulting bar on the Space Telescope Imaging Spectrograph (STIS). The present program aims to expand the catalogue of imaged exoplanets to other nearby young stars that are known to harbour debris disks. The present set of observations targets the young, nearby M dwarf, AU Mic (or Gliese 803).

GO 12444: Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-North Field, Middle Visits of SNe Search


Part of the GOODS/Chandra Deep Field South field, as imaged by HST
CANDELS is one of three Multi-Cycle Treasury Program, whose observations will be executed over the next three HST Cycles. It builds on past investment of both space- and ground-based observational resources. In particular, it includes coverage of the two fields of the Great Observatory Origins Deep Survey (GOODS), centred on the northern Hubble Deep Field (HDF) in Ursa Major and the Chandra Deep Field-South in Fornax. In addition to deep HST data at optical and near-infrared wavelengths, the fields have been covered at X-ray wavelengths by Chandra (obviously) and XMM-Newton; at mid-infrared wavelengths with Spitzer; and ground-based imaging and spectroscopy using numerous telescopes, including the Kecks, Surbaru and the ESO VLT. This represents an accumulation of almost 1,000 orbits of HST time, and comparable scale allocations on Chandra, Spitzer and ground-based facilities. The CANDELS program is capitalising on this large investment, with new observations with WFC3 and ACS on both GOODS fields, and on three other fields within the COSMOS, EGS and UDS survey areas (see this link for more details). The prime aims of the program are twofold: reconstructing the history of galaxy formation, star formation and nuclear galactic activity at redshifts between z=8 and z=1.5; and searching for high-redshift supernovae to measure their properties at redshifts between z~1 and z~2. The program incorporates a tiered set of observations that complement, in areal coverage and depth, the deep UDF observations, while the timing of individual observations will be set to permit detection of high redshift SNe candidates, for subsequent separate follow-up. The present observations form part of the SNe detection sequence for the GOODS-North field.

GO 12879: A 1% Measurement of the Distance Scale with Perpendicular Spatial Scanning


HST WFPC2 image of NGC 4639, one of the Cepheid-rich spiral galaxies used to calibrate SNe Ia
The cosmic distance scale and dark energy are two key issues in modern astrophysics, and HST has played a vital role in probing both. On the one hand, HST has been involved in cosmic distance measurements since its inception, largely through the H0 Key Project, which used WFPC2 to identify and photometer Cepheids in 31 spiral galaxies at distances from 60 to 400 Mpc. On the other, HST is the prime instrument for investigating cosmic acceleration by searching for and following Type Ia supernovae at moderate and high redshift. These two cosmological parameters are directly related, and recent years have seen renewed interest in improving the accuracy of H0 with the realization that such measurements, when coupled with the improved constraints from the Cosmic Microwave Background, provide important constraints on cosmic acceleration and the nature of Dark Energy. Previous HST programs have focused on identifying and measuring light curves for cepheids in external galaxies (eg GO 10802 , GO 11570 ) or quantifying the effects of variations in intrinsic stellar parameters, such as metallicity (eg GO 10918 , GO 11297 ). The present program focuses on the Galactic Cepheids that form the foundation for the whole distance ladder, employing a revived version of an old technique to determine accurate astrometry, and hence trigonometric parallaxes and reliable distances. The technique is drift-scanning - tracking HST during the observation so that stars form trails on the detector. This mode of observations was available in the early years of HST's operations, and has been revived primarily as a means of obtaing high signal-to-noise grism spectroscolpic data of stars hosting transiting exoplanets. However, the same technique can be used in imaging mode, and the extended trails allow multiple measurements of position differences for stars in the field. The net result is a significant improvement in the relative precision of the final astrometry. The present program targets 11 Galactic cepheids and aims for astrometric accuracies of 20 micro-arcseconds.

GO 12893: Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging

The Kepler satellite Kepler is a NASA Discovery-class mission, designed to search for extrasolar planets by using high-precision photometric observations to detect transits. Launched on 7 March 2009, Kepler continuously monitors ~100,000 (mainly) solar-type stare within a ~100 square degree region in Cygnus. The mission has been an astounding success. Ground-based observations have successfully detected a couple of dozen transiting planets (e.g. HD 209458); almost 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, with a smattering of neptune-sized "super-Earths". Kepler, in contrast, has so far identified 1,790 exoplanet host stars and a total of 2,321 transiting exoplanets. More significantly, the exquisite precision of Kepler's photometric observations enables it to detect the 0.01% transit signature of earth analogues in these systems. 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 detector to allow high photometric accuracy. As a result, faint eclipsing stellar binaries will contribute to the source counts. Moreover, since the target field is (intentionally) within the Milky Way, there is a significant potential for unresolved stars within the (relatively broad) Kepler psf to increase the total signal, and hence dilute the depth of transits, giving the appearance of a smaller diameter exoplanet. This program is using the high spatial resolution imaging provided by HST to study a subset of the Kepler Earth-like candidates to assess the potential of this effect.

Past weeks:
page by Neill Reid, updated 14/10/2012
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