This week on HST


HST Programs: February 17 - February 23, 2014

Program Number Principal Investigator Program Title
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
13113 C. S. Kochanek, The Ohio State University ENERGY DEPENDENT X-RAY MICROLENSING AND THE STRUCTURE OF QUASARS
13282 You-Hua Chu, University of Illinois at Urbana - Champaign A Search for Surviving Companions of Type Ia Supernovae in the Large Magellanic Cloud
13293 Anne Jaskot, University of Michigan Green Pea Galaxies: Extreme, Optically-Thin Starbursts?
13297 Giampaolo Piotto, Universita degli Studi di Padova The HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations and Formation
13309 Yicheng Guo, University of California - Santa Cruz UV Snapshot of Low-redshift Massive Star-forming Galaxies: Searching for the Analogs of High-redshift Clumpy Galaxies
13324 Davor Krajnovic, Astrophysikalisches Institut Potsdam Where cores are no more: assessing the role of dissipation in the assembly of early-type galaxies
13330 Bradley M Peterson, The Ohio State University Mapping the AGN Broad Line Region by Reverberation
13331 Laurent Pueyo, Space Telescope Science Institute Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive
13335 Adam Riess, The Johns Hopkins University HST and Gaia, Light and Distance
13343 David Wittman, University of California - Davis Probing Dark Matter with a New Class of Merging Clusters
13346 Thomas R. Ayres, University of Colorado at Boulder Advanced Spectral Library II: Hot Stars
13352 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13364 Daniela Calzetti, University of Massachusetts - Amherst LEGUS: Legacy ExtraGalactic UV Survey
13390 Nathan Smith, University of Arizona A Time-Lapse Movie of the Kinematics Across the Carina Nebula with ACS
13391 Nathan Smith, University of Arizona WFC3-IR Imaging of Dense, Embedded Outflows from Intermediate-Mass Protostars in Carina
13392 Ben E. K. Sugerman, Goucher College Six in One Blow: Reconstructing the Circumstellar Environments of Supernovae in NGC 6946 with Light Echoes
13395 Theodore R. Gull, NASA Goddard Space Flight Center Constraining the evolutionary state of the hot, massive companion star and the wind-wind collision region in Eta Carinae
13398 Christopher W. Churchill, New Mexico State University A Breakaway from Incremental Science: Full Characterization of the z<1 CGM and Testing Galaxy Evolution Theory
13406 Alain Lecavelier des Etangs, CNRS, Institut d'Astrophysique de Paris Hydrogen, Deuterium and Nitrogen in the Beta Pictoris disk
13409 Richard Mushotzky, University of Maryland Hubble Observations of Kepler-Monitored Seyfert Is
13412 Tim Schrabback, Universitat Bonn, Argelander Institute for Astronomy An ACS Snapshot Survey of the Most Massive Distant Galaxy Clusters in the South Pole Telescope Sunyaev-Zel'dovich Survey
13413 Kartik Sheth, Associated Universities, Inc. Star formation and Dissolution Across Dynamically Distinct Environments in NGC 1097
13428 Christopher R. Gelino, Jet Propulsion Laboratory Characterizing the Ultra-cold Brown Dwarf WD 0806-661B
13459 Tommaso L. Treu, University of California - Santa Barbara The Grism Lens-Amplified Survey from Space {GLASS}
13469 Howard E. Bond, The Pennsylvania State University Tol 26 and the EGB 6 Class of Planetary-Nebula Nuclei: What Happens to a Companion Star when a PN is Ejected?
13482 Britt Lundgren, University of Wisconsin - Madison The Evolving Gas Content of Galaxy Halos: A Complete Census of MgII Absorption Line Host Galaxies at 0.7 < z < 2.5
13483 Goeran Oestlin, Stockholm University eLARS - extending the Lyman Alpha Reference Sample
13485 Bo Reipurth, University of Hawaii The HH 24 Jet Complex: Collimated and Colliding Jets from a Newborn Multiple Stellar System
13517 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time

Selected highlights

GO 13282: A Search for Surviving Companions of Type Ia Supernovae in the Large Magellanic Cloud


Combined HST and Chnadra imaging of the supernova remnant SNR 0509-67.5 in the LMC
Type Ia supernovae are generally believed to be produced by the explosive deflagration of white dwarf star that exceeds the Chandrasekhar due to accretion from a binary companion, either a hydrogen-burning main-sequence/red giant star or another degenerate. In double degenerate systems, the white dwarfs merge and explode; in the single degenerate mode, the non-degenerate companion is likely to survive, albeit in a stripped, ablated form. Besides providing crucial information on stellar evolution and how stars enrich the interstellar medium, Type Ia supernovae have acquired global importance in recent years through their use as distance indicators. Indeed, these objects played a crucial role in identifying dark energy and the accelerating universe. In that context, it is important to obtain a better udnerstanding of the underlying mechanism and the distribution of intrinsic properties of these exploding stars.Relatively nearby supernovae that can be probed in detail are therefore crucial to the large mapping of the cosmic flow. The present program aims to probe whether the double degenerate or single degenerate mode of formation is more important by using HST imaging to search for survivors in a sample of nine supernova remnants in the LMC. If the double degenerate mechanism is the dominant mechanism, then few survivors of the progenitor explosion will be found.

GO 13330: Mapping the AGN Broad Line Region by Reverberation


Simulations of the appearance and velocity structure within an AGN disk (see Keith Horne's web page).
Active galaxies (AGNs) are generally luminous systems, characterised by the presence of strong nuclear emission lines of numerous species including H, He I, He II, and Fe, Ca, O, C and S over a range of ionisations. These features originate from gas clouds in the nuclear regions, with the energy supplied through accretion onto a central massive black hole. The high-temperature, rapidly-rotating gas clouds nearest the central engine are responsible for producing broad emission lines (hence, the "Broad Line Region"). The structure of the BLR can be discerned using a technique known as reverberation mapping: variations in the accretion rate lead to fluctuations in luminosity; those variations lead, in turn, to variations in the photoionisation of the BLR, and corresponding changes in spectral line strengths and velocities; monitoring those changes, and correlating them with the photometric variability of the central source, measures the light travel time from nucleus to BLR gas, and hence maps the size of the BLR. The present prorgam will use the Cosmic Origins Spectrograph to undertake systematic monitoring of the nuclear regions of the Seyfert I galaxy, NGC 5548. The observatons are spread over the next 6 months, with one orbit per day for 179 days.

GO 13406: Hydrogen, Deuterium and Nitrogen in the Beta Pictoris disk


The extended disk around Beta Pictoris
It is now well established that planet formation occurs within circumstellar disks.The past decade has seen the identification of many examples of such phenomena around young stars, notably through infrared observations by the Spitzer space telescope and ground-based data from millimetre-wave interferometers.. The general indications are that the planet-formation process occurs rapidly, with the disks largely dissipating within 10-15 million years of formation. Key questions that remain, however, include the rate of gas depletion within the disks, the extent to gas survives within the debris disks and the abundance distribution of any residual gaseous materials. Most examples of circumstellar disks are found in stars in young star-forming associations, but there are a number among isolated, young stars in the Solar neighbourhood. The most extensively studied system is beta Pictoris, an A star at a distance of ~ 19 parsecs and an estimated age of ~10-20 million years. The disk was originally discovered in the early 1980s and has since been observed extensively from both the ground and space, including coronagraphic observations with STIS and direct imaging with WFPC2, ACS and WFC3 on HST. The present program aims to build on those past observations by using the Cosmic Origins Spectrograph to probe the gas content of the system, specifically searching for ulrtaviolet signatuers of neutral hydrogen, deuterium and nitrogen.

GO 13428: Characterizing the Ultra-cold Brown Dwarf WD 0806-661B


The stellar menagerie: Sun to Jupiter, via brown dwarfs
Brown dwarfs are objects that form in the same manner as stars, by gravitational collapse within molecular clouds, but which do not accrete sufficient mass to raise the central temperature above ~2 million Kelvin and ignite hydrogen fusion. As a result, these objects, which have masses less than 0.075 MSun or ~75 M<\sub>Jup, lack a sustained source of energy, and they fade and cool on relatively short astronomical (albeit, long anthropological) timescales. Following their discovery over a decade ago, considerable observational and theoretical attention has focused on the evolution of their intrinsic properties, particularly the details of the atmospheric changes. At their formation, most brown dwarfs have temperatures of ~3,000 to 3,500K, comparable with early-type M dwarfs, but they rapidly cool, with the rate of cooling increasing with decreasing mass. As temperatures drop below ~2,000K, dust condenses within the atmosphere, molecular bands of titanium oxide and vanadium oxide disappear from the spectrum to be replaced by metal hydrides, and the objects are characterised as spectral type L. Below 1,300K, strong methane bands appear in the near-infrared, characteristics of spectral type T. At present, the coolest T dwarfs known have temperatures of ~650 to 700K. At lower temperatures, other species, notably ammonia, are expected to become prominent, and a number of efforts have been undertaken recently to find examples of these "Y" dwarfs. One approach that has long-standing success is to look for companions to stars already known to lie near the Sun; the first ultracool M dwarfs (VB 8, VB 10), the first L dwarf (GD 165B) and the first T dwarf (Gl 229B) were all discovered through this method of fortunate association. The present program targets a ~Y2 dwarf that, like GD 165B and Gl 229B, happens to be a companion of a white dwarf in the Solar neighbourhood. The obejct was found seredipitously from multi-epoch Spitzer data. WFC3 on HST will be used to obtain photometry at near-infrared wavelengths. be used

Past weeks:
page by Neill Reid, updated 7/2/2014
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