This week on HST

HST Programs: November 28, 2011 - December 4, 2011

Program Number Principal Investigator Program Title
11704 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12041 James C. Green, University of Colorado at Boulder COS-GTO: Io Atmosphere/STIS
12060 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-South Field, Non-SNe-Searched Visits
12099 Adam Riess, The Johns Hopkins University Supernova Follow-up for MCT
12101 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12177 Pieter van Dokkum, Yale University 3D-HST: A Spectroscopic Galaxy Evolution Treasury
12190 Anton M. Koekemoer, Space Telescope Science Institute WFC3/IR Spectroscopy of the Highest Redshift Black Hole Candidates
12246 Christopher W. Stubbs, Harvard University Weak Lensing Mass Calibration of SZ-Selected Clusters
12247 Nial R. Tanvir, University of Leicester Identifying and studying gamma-ray bursts at very high redshifts
12248 Jason Tumlinson, Space Telescope Science Institute How Dwarf Galaxies Got That Way: Mapping Multiphase Gaseous Halos and Galactic Winds Below L*
12253 Douglas Clowe, Ohio University Gravity in the Crossfire: Revealing the Properties of Dark Matter in Bullet-like Clusters
12257 Leo Girardi, Osservatorio Astronomico di Padova The Nature of Multiple Main Sequence Turn-offs and Dual Red Clumps in Magellanic Cloud Star Clusters
12283 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey {WISP}: A Survey of Star Formation Across Cosmic Time
12286 Hao-Jing Yan, University of Missouri - Columbia Hubble Infrared Pure Parallel Imaging Extragalactic Survey {HIPPIES}
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12328 Pieter van Dokkum, Yale University 3D-HST: A Spectroscopic Galaxy Evolution Treasury Part 2
12378 Andrew J. Levan, The University of Warwick The differing environments of dark gamma-ray bursts
12448 Arlin Crotts, Columbia University in the City of New York Towards a Detailed Understanding of T Pyx, Its Outbursts and Shell
12471 Dawn K. Erb, University of Wisconsin - Milwaukee The Bottom of the Iceberg: Faint z~2 Galaxies and the Enrichment of the IGM
12474 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs
12475 Seth Redfield, Wesleyan University Cool Star Winds and the Evolution of Exoplanetary Atmospheres
12488 Mattia Negrello, Open University SNAPshot observations of gravitational lens systems discovered via wide-field Herschel imaging
12506 Adam L. Kraus, University of Hawaii A Precise Mass-Luminosity-Temperature Relation for Young Stars
12515 Dougal Mackey, Australian National University Probing the outer limits of a galactic halo - deep imaging of exceptionally remote globular clusters in M31
12519 Raghvendra Sahai, Jet Propulsion Laboratory Newly Discovered LMC Preplanetary Nebulae as Probes of Stellar Evolution
12526 Katherine Anne Alatalo, University of California - Berkeley Mapping Recent Star Formation and Dust in NGC 1266, a Local Example of AGN-driven Feedback
12533 Crystal Martin, University of California - Santa Barbara Escape of Lyman-Alpha Photons from Dusty Starbursts
12546 R. Brent Tully, University of Hawaii The Geometry and Kinematics of the Local Volume
12553 Johan P. U. Fynbo, University of Copenhagen, Niels Bohr Institute Detecting the stellar continuum of the galaxy counterparts of three z>2 Damped Lyman-alpha Absorbers
12568 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12581 Julia Christine Roman-Duval, Space Telescope Science Institute A Direct CO/H2 Abundance Measurement in Diffuse and Translucent LMC and SMC Molecular Clouds
12585 Sara Michelle Petty, University of California - Los Angeles Unveiling the Physical Structures of the Most Luminous IR Galaxies Discovered by WISE at z>1.6
12591 Elena Gallo, University of Michigan A Chandra/HST census of accreting black holes and nuclear star clusters in the local universe
12601 Laurent Lamy, Observatoire de Paris - Section de Meudon HST STIS/ACS observations of the aurorae of Uranus during active solar wind conditions
12613 Knud Jahnke, Max-Planck-Institut fur Astronomie, Heidelberg Are major galaxy mergers a significant mechanism to trigger massive black hole growth at z=2?
12686 Stephen Bradley Cenko, University of California - Berkeley Sw J2058+05: A Possible Second Relativistic Tidal Disruption Flare

Selected highlights

GO 11704: The Ages of Globular Clusters and the Population II Distance Scale

Hubble Heritage image of the globular cluster, M15
Globular clusters are the oldest structures within the Milky Way that are directly accessible to observation. They are relatively simple systems, with relatively simple colour-magnitude diagrams (albeit with some complexities adduced from recent HST observations, see GO 11233 ). Matching those CMDs against theoretical models allows us to set constraints on the age of the oldest stars in the Galaxy, and hence on the age of the Milky Way and the epoch of galaxy formation. However, the accuracy of those age determinations rest crucially on the accuracy of the cluster distance determinations. The clusters themselves lie at distances of several kpc at best, and tens of kpc at worst; thus, direct trigonometric parallax measurements must await microacrsecond astrometric missions. The classical method of deriving distances is main sequence fitting - using nearby stars, with similar chemical abundances and accurate parallax measurements, to map out the main sequence in absolute units, and then scaling the cluster data to fit. The problem with this method is that metal-poor subdwarfs are rare, so even Hipparcos was only able to obtain accurate distances to a handful of stars. The present program aims to improve the distance measurements by using the Fine Guidance Sensors on HST to determine sub-millarcsecond trigonometric parallaxes to 9 subdwarfs, almost doubling the sample available for MS fitting.

GO 12246: Weak Lensing Mass Calibration of SZ-Selected Clusters

The ACS optical/far-red image of the galaxy cluster, Abell 2218, revealing an extensive number of lensed arcs
The overwhelming majority of galaxies in the universe are found in clusters. As such, these systems offer an important means of tracing the development of large-scale structure through the history of the universe. Galaxy clusters can be identified at moderate redshifts by searching for signatures of the Sunyaev-Zeldovich effect: high energy electrons in the hot intercluster medium interact with radiation from the cosmic microwave background to distort the microwave spectrum. The South Pole Telescope is a 10-metre microwave/millimetre telescope located at Amundsen-Scott South Pole Station on the Antarctiva high plateau, close to the geographic South Pole. That telescope has been used to search for galaxy clusters. As intense mass concentrations, these systems are highly efficient gravitational lenses, capable of concentrating and magnifying light from background high redshift galaxies to allow detailed spectropic investigations of star formation in the early universe. Hubble imaging has already revealed lensed arcs and detailed sub-structure within a handful of rich clusters. At the same time, the lensing characteristics provide information on the mass distribution within the lensing cluster. The present program aims to use the Wide Field Camera on the Advanced Camera for Surveys to obtain 2x2 mosaic images of a unfiromly selected sample of high mas clusters in the redshift range 0.58 < z < 0.88. The HST data will be analysed for weak lensing signatures that can be combined with X-ray, IR and optical observations to constrain the mass estimates for these clusters.

GO 12378: The different environments of dark gamma-ray bursts

The life-cycle of agamma-ray burst
Gamma ray bursts are events that tap extraordinary energies (1045 to 1047 joules) in remarkably short periods of time. Several thousands bursts have been detected over the last 30+ years, and analyses indicate that they can be divided into two classes with durations longer or shorter than 2 seconds. The short bursts appear to release more high energy radiation, so the two subsets are known as long/soft and short/hard bursts. The long/soft bursts appear to originate in the collapse of very massive stars, while the short/hard bursts are coalescing binary systems (probably pairs of neutron stars or black holes). The first optical counterpart to a gamma ray burst was identified in 1998, allowing confirmation of their extragalactic nature, and, since then, more than 60 bursts have been detected at X-ray wavelengths, and half that number detected at either optical or radio wavelengths; all of these detections are long/soft bursts. In the past decade, optical counterparts have been detected for many of these sources, allowing not only direct study of their characteristics, but also investigations of the properties of the underlying host galaxies. Some sources, however, do not appear to generate optical counetrparts, perhaps because the optical emission is suppressed due to substantial local dust obscuration. The absence of those data has hampered previous attempts to match those sources, and their environments, against GRBs with optical counetrparts. The present program aims to circumvent this issue by using Chandra observations to obtain accurate positions for the X-ray counterparts of such sources, and then match that astrometry against deep visual (F606W) and near-infrared (F160W) HST WFC3 images.

GO 12475: Cool Star Winds and the Evolution of Exoplanetary Atmospheres

The solar corona
All stars lose mass although, in the best 1984 tradition, some lose mass more equally than others. With growing evidence for the near-ubiquity of planetary systems, increasing attention is being devoted to how mass loss varies from star to star, and how varying mass loss rates might affect the conditions on planets orbiting within the habitable zone of that system. On Earth, we have direct experience of the impact of mild solar variability, where coronal mass ejections can lead to spectracular auroral displays and satellite disruption; more energetic outbursts on other stars could lead to significant erosion of the outer atmosphere, and perhaps radiation-induced mutation of hypothetical life forms. The present proposal aims to probe one aspect of this subject by using the Space Telescope Imaging Spectrograph (STIS) to probe mass loss rates in a sample of four late-type dwarfs thata re known to ahve planetary companions. All four of these stars are known to haver ealtively low mass-loss rates. High resolution ultraviolet spectra will be used to search for emission due to Mg II and Fe II, characteristic of stellar winds; in addition, lower resolution spectra will be used to search for Lyman-alpha absorption due to hydrogen within the putative stellar winds.

Past weeks:
page by Neill Reid, updated 28/11/2011