This week on HST

HST Programs: January 25 - January 31, 2016

Program Number Principal Investigator Program Title
13646 Ryan Foley, University of Illinois at Urbana - Champaign Understanding the Progenitor Systems, Explosion Mechanisms, and Cosmological Utility of Type Ia Supernovae
13702 Sally Oey, University of Michigan Mapping the LyC-Emitting Regions of Local Galaxies
13740 Daniel Stern, Jet Propulsion Laboratory Clusters Around Radio-Loud AGN: Spectroscopy of Infrared-Selected Galaxy Clusters at z>1.4
13757 Saurabh W. Jha, Rutgers the State University of New Jersey The Progenitor System of a Peculiar Thermonuclear White-Dwarf Supernova
13760 Derck L. Massa, Space Science Institute Filling the gap --near UV, optical and near IR extinction
13763 S. Thomas Megeath, University of Toledo WFC3 Spectroscopy of Faint Young Companions to Orion Young Stellar Objects
13765 Bradley M Peterson, The Ohio State University A Cepheid-Based Distance to the Benchmark AGN NGC 4151
13783 George G. Pavlov, The Pennsylvania State University Thermal evolution of old neutron stars
13856 Denija Crnojevic, Texas Tech University Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A
14038 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of Abell 370
14071 Sanchayeeta Borthakur, The Johns Hopkins University How are HI Disks Fed? Probing Condensation at the Disk-Halo Interface
14076 Boris T. Gaensicke, The University of Warwick An HST legacy ultraviolet spectroscopic survey of the 13pc white dwarf sample
14084 Seth Redfield, Wesleyan University Connecting Earth with its Galactic Environment: Probing Our Interstellar Past Along the Historical Solar Trajectory
14089 Paul A. Wilson, CNRS, Institut d'Astrophysique de Paris Far-UV observations of H, C, N and O in exocomets of Beta Pic
14098 Harald Ebeling, University of Hawaii Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5
14102 Claus Leitherer, Space Telescope Science Institute The II Zw 40 Supernebula: 30 Doradus on Steroids
14110 David Kent Sing, University of Exeter Charaterizing the atmosphere of the enlarged Neptune-mass planet HAT-P-26b
14118 Luigi R. Bedin, Osservatorio Astronomico di Padova The end of the White Dwarf Cooling Sequences of Omega Centauri
14134 Swara Ravindranath, Space Telescope Science Institute Spectral Diagnostics for the Reionization Era: Exploring the Semi-Forbidden CIII] Emission in Low Metallicity Green Pea Galaxies
14141 Guy Worthey, Washington State University NGSL Extension 1. Hot Stars and Evolved Stars
14163 Mickael Rigault, Humboldt Universitat zu Berlin Honing Type Ia Supernovae as Distance Indicators, Exploiting Environmental Bias for H0 and w.
14172 Brendan Bowler, University of Texas at Austin Imaging Accreting Protoplanets in the Young Cluster IC 348
14189 Adam S. Bolton, University of Utah Quantifying Cold Dark Matter Substructure with a Qualitatively New Gravitational Lens Sample
14193 Catherine Espaillat, Boston University Footprints of the Magnetosphere: the Star- Disk Connection in T Tauri Stars
14206 Adam Riess, The Johns Hopkins University A New Threshold of Precision, 30 micro-arcsecond Parallaxes and Beyond
14212 Karl Stapelfeldt, NASA Goddard Space Flight Center A Snapshot Imaging Survey of Spitzer-selected Young Stellar Objects in Nearby Star Formation Regions*.t23
14216 Robert P. Kirshner, Harvard University RAISIN2: Tracers of cosmic expansion with SN IA in the IR
14227 Casey Papovich, Texas A & M University The CANDELS Lyman-alpha Emission At Reionization (CLEAR) Experiment
14234 Joshua D. Simon, Carnegie Institution of Washington The Lowest Luminosity Star-Forming Galaxy
14241 Daniel Apai, University of Arizona Cloud Atlas: Vertical Cloud Structure and Gravity in Exoplanet and Brown Dwarf Atmospheres
14251 Amy E. Reines, National Optical Astronomy Observatory, AURA The Structures of Dwarf Galaxies Hosting Massive Black Holes
14259 Denija Crnojevic, Texas Tech University Resolved halo substructures beyond the Local Group: the assembly histories of NGC 253 and NGC 5128
14262 Knud Jahnke, Max-Planck-Institut fur Astronomie, Heidelberg Are the fastest growing black holes at z=2 caused by major galaxy mergers?
14327 Saul Perlmutter, University of California - Berkeley See Change: Testing time-varying dark energy with z>1 supernovae and their massive cluster hosts
14465 Jonathan Charles Tan, University of Florida Peering to the Heart of Massive Star Birth
14474 David Jewitt, University of California - Los Angeles Comet P/2010 V1 fragmentation event

Selected highlights

GO 14076: An HST legacy ultraviolet spectroscopic survey of the 13pc white dwarf sample

Artist's impression of a comet spiralling in to the white dwarf variable, G29-38
During the 1980s, one of the techniques used to search for brown dwarfs was to obtain near-infrared photometry of white dwarf stars. Pioneered by Ron Probst (KPNO), the idea rests on the fact that while white dwarfs are hot (5,000 to 15,000K for the typical targets), they are also small (Earth-sized), so they have low luminosities; consequently, a low-mass companion should be detected as excess flux at near- and mid-infrared wavelengths. In 1988, Ben Zuckerman and Eric Becklin detected just this kind of excess around G29-38, a relatively hot DA white dwarf that also happens to lie on the WD instability strip. However, follow-up observations showed that the excess peaked at longer wavelengths than would be expected for a white dwarf; rather, G 29-38 is surrounded by a dusty disk. Given the orbital lifetimes, those dust particles must be regularly replenished, presumably from rocky remnants of a solar system. G 29-38 stood as a lone prototype for almost 2 decades, until a handful of other dusty white dwarfs were identified from Spitzer observations within the last couple of years.In subsequent years, a significant number of DA white dwarfs have been found to exhibit narrow metallic absorption lines in their spectra. Those lines are generally attributed to "pollution" of the white dwarf atmospheres. Given that the diffusion time for metals within the atmospheres is short (tens to hundreds of years), the only reasonable means of maintaining such lines in ~20% of the DA population is to envisage continuous accretion from a surrounding debris disk. The Cosmic Origins Spectrograph (COS) is an ideal instrument for probing the abundance of trace elements in white dwarfs atmospheres: more than 70 systems have been observed, with detection rates running at around 50%. The present program is using COS to refine the statistics by targeting a volume-limited sample of 37 white dwarfs within 13 parsecs of the Sun. This sample is sufficient to provide an estimate of the overall occurence of accreting systems.

GO 14216: RAISIN2: Tracers of cosmic expansion with SN IA in the IR

The first supernova discovered by the Pan-STARRs survey
Supernovae are the most spectacular form of stellar obituary. In recent years, these celestial explosions have acquired even more significance through the use of Type Ia supernovae as distance indicators in mapping the `dark energy' acceleration term of cosmic expansion. However, while there are well-established models for the two main types of supernovae (runaway fusion on the surface of a white dwarf in a binary system for Type Ia, or detonation of the core in Type II), some uncertainties remain as to the uniformity of the events. Moreover, as the sample of known supernova has grown, so has the range of photometric systems and the methods used to fit the light curve and account for the ever-present uncertainites inroduced by dust absorption. Consequently, the potential remains for systematic bias in distance estimates due both to intrinsic differences and to measurement errors. The present program builds on a Cycle 21 program, and aims to minimise these systematics by compiling standard sequences of observations, primarily in the Y, J, and H filters, of supernovae at redshifts between z~0.3 and 0.5. Focusing on those wavelengths minises the effects, and hence the uncertainties, due to dust absorption. The supernovae themselves are drawn from the Pan-STARRS survey, with the WFC3-IR camera on HST employed to obtain the photometry.

GO 14241: Cloud Atlas: Vertical Cloud Structure and Gravity in Exoplanet and Brown Dwarf Atmospheres

Ground-based imaging the the very low-mass brown dwarf binary, 2MASS1207
Recent years have seen the discovery of numerous extrasolar planets. Initially, most were discovered through radial velocity monitoring; more recently the superb photometric properties of the Kepler mission have led to the discovery of numerous transiting systems. Lagging behind in numbers, but offering the greatest prospect for probing physical conditions, is direct imaging. A handful of systems with resolved planetary companions have been discovered, most notably the multi-planet system around the nearby A-type star, HR 8799, and 2MASS1207B, the planetary-mass wide companion to the brown dwarf, 2MASS1207A, a member of the TW Hydrae association. These systems are expected to have gross properties that are similar to the Solar System gas giants, particularly atmospheric cloud structure. but they are much more massive and therefore have higher gravities. The present program aims to gain insight into their structure by comparing resolved exoplanets and higher mass, but similar temperature, brown dwarfs. Observations of isolated brown dwarfs have shown evidence for systematic variations in brightness, possibly due to dust within the atmosphere forming clouds, perhaps giving the dwarf's surface a banded appearance, similar to Jupiter. The clouds themselves may appear and disappear over relatively short timescales, leading to photometric variations at particular wavelengths. Past programs have used both Spitzer and HST to monitor spectral variability in a number of systems. The present program will use Wide-field Camera 3 to obtain time-series near-infrared grism spectra of ten brown dwarfs and high-mass exoplanets. Variations in those spectra map the atmospheric cloud structure in each system, and those variations can be examined for correlations with the mass/gravity of the parent object.

GO 14474: Comet P/2010 V1 fragmentation event

Comet P/2010 V1 Ikeya-Murakami shortly after its disovery in 2010
Comet P/2010 V1 is a member of the family of short period comets that live in the inner Solar System. Discovered near perihelion in 2010 by the Japanese astronomers Kaoru Ikeya and Shigeki Murakami, the comet has an orbital period of 5.49 years, an orbital ecentricity of 0.49 and comes within 1.58 AU of the Sun at perihelion. Shortly after its discovery, the comet was observed to undergo significant brightening, suggesting a major burst of activity. The comet was recovered in late December 2015, and observations revealed that the system had fragmented, with 4 components identified from deep ground-based observations by early January. The present program aims to take advantage of Hubble's unparalleled resolution at optical wavelengths and probe the number and size distribution of the fragments, with the aim of setting constraints on the likely mechanism driving this disruptive event.

Past weeks:
page by Neill Reid, updated 23/12/2014
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