This week on HST

HST Programs: September 20, 2010 - September 26, 2010

Program Number Principal Investigator Program Title
11548 S. Thomas Megeath, University of Toledo NICMOS Imaging of Protostars in the Orion A Cloud: The Role of Environment in Star Formation
11575 Schuyler D. Van Dyk, Jet Propulsion Laboratory The Stellar Origins of Supernovae
11579 Alessandra Aloisi, Space Telescope Science Institute The Difference Between Neutral- and Ionized-Gas Metal Abundances in Local Star-Forming Galaxies with COS
11591 Jean-Paul Kneib, Laboratoire d'Astrophysique de Marseille Are Low-Luminosity Galaxies Responsible for Cosmic Reionization?
11593 Michael C. Liu, University of Hawaii Dynamical Masses of the Coolest Brown Dwarfs
11598 Jason Tumlinson, Space Telescope Science Institute How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos
11600 Benjamin Weiner, University of Arizona Star formation, extinction and metallicity at 0.7
11605 Travis Stuart Barman, Lowell Observatory Obtaining the Missing Links in the Test of Very Low Mass Evolutionary Models with HST
11619 Adam Gabriel Jensen, Wesleyan University Definitive ISM Abundances through Low-mass X-ray Binaries as Lighthouses
11692 J. Christopher Howk, University of Notre Dame The LMC as a QSO Absorption Line System
11696 Matthew A. Malkan, University of California - Los Angeles Infrared Survey of Star Formation Across Cosmic Time
11700 Michele Trenti, University of Colorado at Boulder Bright Galaxies at z>7.5 with a WFC3 Pure Parallel Survey
11702 Hao-Jing Yan, The Ohio State University Search for Very High-z Galaxies with WFC3 Pure Parallel
11721 Richard S. Ellis, California Institute of Technology Verifying the Utility of Type Ia Supernovae as Cosmological Probes: Evolution and Dispersion in the Ultraviolet Spectra
11728 Timothy M. Heckman, The Johns Hopkins University The Impact of Starbursts on the Gaseous Halos of Galaxies
11734 Andrew J. Levan, The University of Warwick The hosts of high redshift gamma-ray bursts
11735 Filippo Mannucci, Osservatorio Astrofisico di Arcetri The LSD project: dynamics, merging and stellar populations of a sample of well-studied LBGs at z~3
11787 Edmund Nelan, Space Telescope Science Institute Dynamical Masses and Radii of Four White Dwarf Stars
12018 Andrea H. Prestwich, Smithsonian Institution Astrophysical Observatory Ultra-Luminous x-Ray Sources in the Most Metal-Poor Galaxies
12042 James C. Green, University of Colorado at Boulder COS-GTO: Pluto
12166 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies
12210 Adam S. Bolton, University of Utah SLACS for the Masses: Extending Strong Lensing to Lower Masses and Smaller Radii
12215 Nancy R. Evans, Smithsonian Institution Astrophysical Observatory Searching for the Missing Low-Mass Companions of Massive Stars
12217 Philip Lucas, University of Hertfordshire Spectroscopy of faint T dwarf calibrators: understanding the substellar mass function and the coolest brown dwarfs
12234 Wesley Fraser, California Institute of Technology Differentiation in the Kuiper belt: a search for silicates on icy bodies.
12245 Mark R. Showalter, SETI Institute Orbital Evolution and Stability of the Inner Uranian Moons
12256 Sean A. Farrell, University of Leicester The Ultraviolet and Optical Counterparts of the Intermediate Mass Black Hole Candidate ESO 243-49 HLX-1
12292 Tommaso L. Treu, University of California - Santa Barbara SWELLS: doubling the number of disk-dominated edge-on spiral lens galaxies
12311 Giampaolo Piotto, Universita di Padova Multiple Stellar Populations in Galactic Globular Clusters
12312 Harold A. Weaver, The Johns Hopkins University Applied Physics Laboratory Hubble Investigation of 103P/Hartley 2 in Support of NASA's DIXI Mission
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale

Selected highlights

GO 11593: Dynamical Masses of the Coolest Brown Dwarfs

Epsilon Indi Bab, the binary brown dwarf companion of the nearby K dwarf Brown dwarfs are objects that form like stars, but lack sufficient mass to drive the central temperature above a few million degrees, and therefore never succeed in igniting core hydrogen fusion. Discovered almost 15 years ago, these objects initially have surface temperatures of ~3,500K, but cool rapidly and move through spectral types M, L and T. Following their discovery, considerable theoretical attention has focused on the evolution of their intrinsic properties, particularly the details of the atmospheric changes in the evolution from type L to type T and beyond. This transition marks the emergence of methane as a dominant absorber at near-infrared wavelengths. Current models suggest this transition occurs at ~1400-1200K, and that the spectral changes are at least correlated with, and perhaps driven by, the distribution and properties of dust layers ("clouds"). The overall timescales associated with this process remains unclear. Mass is a crucial factor in mapping those changes, but mass is also the most difficult quantity to measure in a reliable fashion. The present proposal aims to tackle this issue through astrometry of ultracool binary systems, deriving the orbits and hence dynamical masses. Initially designed for ACS, the current observations are being made with WFPC2, and the binary system SDSSJ092615.38+584720.9 will be imaged in the coming week.

GO 11600: Star formation, extinction and metallicity at 0.7

ACS images of a section of the GOODS fields The Great Observatories Origins Deep Survey, originated as a Cycle 12 HST Treasury program, 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 in Ursa Major and the Chandra Deep Field-South in Fornax. Initially, the program combined deep optical/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. These two fields have become among the most studied celestial regions. In addition to deep HST data at optical and near-infrared wavelengths (both fields have been covered by NICMOS), the fields have been covered at X-ray wavelengths by Chandra (obviously) and XMM-Newton, and ground-based imaging and spectroscopy using numerous telescopes, including the Kecks, Gemini, Surbaru and the ESO VLT. Part of the GOODS South field was covered by the WFC3 Early Release Science observations (see ), and both fields are also covered partially by one of the three Multi-Cycle Treasury programs allocated time in Cycle 18-20. The present program is using the G141 grism on the WFC3 IR camera to conduct a spectroscopic survey of part of the GOODS-North field. The data will enable the identification of H-alpha+[N II] emission from galaxies at redshifts 0.7 < z < 1.5, and thereby set constraints on star formation at those redshifts.

GO 11598: How Galaxies Acquire their Gas: A Map of Multiphase Accretion and Feedback in Gaseous Galaxy Halos

A computer simulation of galactic gas accretion and outflow Galaxy formation, and the overall history of star formation within a galaxy, clearly demands the presence of gas. The detailed evolution therefore depends on how gas is accreted, recycled, circulated through the halo and, perhaps, ejected back into the intergalactic medium. Tracing that evolutionary history is difficult, since gas passes through many different phases, some of which are easier to detect than others. During accretion and, probably, subsequent recycling, the gas is expected to be reside predominantly at high temperatures. The most effective means of detecting such gas is through ultraviolet spectroscopy, where gas within nearby systems can be detected as absorption lines superimposed on the spectra of more distant objects, usually quasars. The present program is using the Cosmic Origins Spectrograph to observe z>1 QSOs that lie at small angular separations from SDSS galaxies at redshifts between z=0.15 and 0.35. The sightlines run through the halos of the galaxies, and the QSOs therefore provide a pencilbeam backlight that probes hot gas in the foreground systems.

GO 12311: Multiple Stellar Populations in Galactic Globular Clusters

NGC 2808, a globular cluster with multiple stellar populations Globular clusters are remnants of the first substantial burst of star formation in the Milky Way. With typical masses of a few x 105 solar masses, distributed among several x 106 stars, the standard picture holds that these are simple systems, where all the stars formed in a single starburst and, as a consequence, have the same age and metallicity. Until recently, the only known exception to this rule was the cluster Omega Centauri, which is significantly more massive than most clusters and has both double main sequence and a range of metallicities among the evolved stars. Omega Cen has been joined by several additional clusters, including NGC 2808, which shows evidence for three distinct branches to the main sequence. The origin of this feature is remains uncertain, but it may be significant that NGC 2808 is also one of the more massive clusters, and might therefore be able to survive several burst of star formation (or, conversely, be the product of a multi proto-globular merger). Evidence for multiple populations has also been found in other clusters, including NGC 1851, 47 Tucanae and NGC 6752 - all relatively massive clusters. The present program aims to use high-precision UV (F275W) and far-red (F814W) WFC3 observations of those clusters, together with M4 and M22, to probe the detailed structure along the main sequence.

Past weeks:
page by Neill Reid, updated 12/11/2010