This week on HST

HST Programs: January 6 - January 12, 2014

Program Number Principal Investigator Program Title
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12893 Ronald L Gilliland, The Pennsylvania State University Study of Small and Cool Kepler Planet Candidates with High Resolution Imaging
12903 Luis C. Ho, Carnegie Institution of Washington The Evolutionary Link Between Type 2 and Type 1 Quasars
12934 Clive N. Tadhunter, University of Sheffield The importance warm outflows in the most rapidly evolving galaxies in the local Universe
12969 Peter Garnavich, University of Notre Dame Global Properties Are Not Enough: Probing the Local Environments of Type Ia Supernovae
12995 Christopher Johns-Krull, Rice University Testing Disk Locking in the Orion Nebula Cluster
13035 Sarah V. Badman, Lancaster University A unique opportunity to discover how energy is transported through Jupiter's magnetosphere
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13110 Andrew S. Fruchter, Space Telescope Science Institute The Astrophysics of the Most Energetic Gamma-Ray Bursts
13289 Boris T. Gaensicke, The University of Warwick RXJ0439.8-6809: the hottest pre-white dwarf, or the first double-degenerate supersoft X-ray source?
13293 Anne Jaskot, University of Michigan Green Pea Galaxies: Extreme, Optically-Thin Starbursts?
13306 Gillian Wilson, University of California - Riverside Is the Size Evolution of Massive Galaxies Accelerated in Cluster Environments?
13312 Danielle Berg, University of Minnesota - Twin Cities The Evolution of C/O in Low Metallicity Dwarf Galaxies
13332 Seth Redfield, Wesleyan University A SNAP Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
13334 Adam Riess, The Johns Hopkins University The Longest Period Cepheids, a bridge to the Hubble Constant
13335 Adam Riess, The Johns Hopkins University HST and Gaia, Light and Distance
13344 Adam Riess, The Johns Hopkins University A 1% Measurement of the Distance Scale with Perpendicular Spatial Scanning
13361 William P. Blair, The Johns Hopkins University Discovering and Characterizing the Young Supernova Remnant Population in M101
13364 Daniela Calzetti, University of Massachusetts - Amherst LEGUS: Legacy ExtraGalactic UV Survey
13402 Jean-Claude M. Gerard, Universite de Liege Remote sensing of the energy of Jovian auroral electrons with STIS: a clue to unveil plasma acceleration processes
13404 William M. Grundy, Lowell Observatory Mutual Orbits and Physical Properties of Binary Transneptunian Objects
13407 Crystal Martin, University of California - Santa Barbara COS Gas Flows: Challenging the Optical Perspective
13414 Mark R. Showalter, SETI Institute Reading the Record of Cometary Impacts into Jupiter's Rings
13435 Matteo Monelli, Instituto de Astrofisica de Canarias Multiple populations in external globular glusters: the Fornax dSph, the LMC, and the SMC
13442 R. Brent Tully, University of Hawaii The Geometry and Kinematics of the Local Volume
13449 Marla C. Geha, Yale University A Non-Universal Initial Mass Function in the Ultra-Faint Galaxy Coma Berenices
13452 Matthew Hayes, Observatoire Midi-Pyrenees Coupling the emission of ionizing radiation and Lyman alpha
13457 Kailash C. Sahu, Space Telescope Science Institute Accurate Mass Determination of the Nearby Old White Dwarf Stein 2051B through Astrometric Microlensing
13476 Nitya Kallivayalil, The University of Virginia Proper Motion and Internal Kinematics of the SMC: are the Magellanic Clouds bound to one another?
13483 Goeran Oestlin, Stockholm University eLARS - extending the Lyman Alpha Reference Sample
13496 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of MACSJ0416.1-2403
13501 Heather A. Knutson, California Institute of Technology Characterizing the Atmosphere of Benchmark Super-Earth HD 97658b

Selected highlights

GO 12943: The importance warm outflows in the most rapidly evolving galaxies in the local Universe

Artist's impression of the black hole and surrounding torus in an AGN
The peculiar nature of active galaxies was first discerned almost 100 years, when Edward A. Fath obtained a photographic spectrum on the Lick 36-inch of the nucleus of the the spiral galaxy, M77. Unlike most systems, which had star-like absorption line spectra, M77 (now more popularly known as NGC 1068) exhibited several strong emission lines that were also known to be present in gaseous nebulae. The emission was also concentrated near the galactic nucleus. We now know that these lines are due to hydrogen and ionised oxygen and nitrogen, generated by hot gas within a toroidal disk around a central supermassive black hole. There are still a number of significant questions concerning these active galactic nuclei (AGNs):
when do the black holes form? how are they fed? how do they evolve with time? and how do they affect the surrounding galaxy? In particular, does AGN evolution influence the formation of the bulge?
The present program focuses on the last issue, combining imaging with the wide-field camera on ACS with STIS long-slit spectroscopy to study gas outflows in a sample of ULIRGs (Ultra-Luminous InfraRed Galaxies). Analysis of the3se data will provide insight into how these flows contribute to the energy budget of the host galaxies.

GO 13334: The Longest Period Cepheids, a bridge to the Hubble Constant

ESO image of the material surrounding the long-period Cepheid, RS Puppis
Cepheid variable stars have been the prime extragalactic distance indicator since Henrietta Leavitt's discovery of the period-luminosity relation described by Cepheids in the Small Magellanic Cloud. It was Hubble's identification of Cepheids in NGC 6822 that finally established that at least some nebulae were island universes. Cepheids and the extragalactic distance scale figure largely in HST's history, notably through the Hubble Constant Program, one of the initial Key Projects. HST has since observed Cepheids in more than 30 galaxies. Establishing a Galactic sample with reliable distance determinations is obviously crucial to this process. Long period Cepheids, with pulsation periods in excess of 25 days, play a key role, since they are more luminous, easier to detect and can be observed with higher photometric accuracy in distant galaxies. The present program aims to add to the sample of well-observed Galactic Cepheids by using spatial scanning on WFC3 to determine accurate parallaxes for nine Cepheids at distances up to 4 kpc from the Sun. Spatial scanning enables astrometry to an acuracy of ~40 microarcseconds, offering the prospect of distances accurate to 4% for individual Cepheids, and an overall distance scal calibration accurate to ~1%.

GO 13496: HST Frontier Fields - Observations of MACSJ0416.1-2403

The Frontier Fields cluster, MACSJ0416.1-2403
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. Moreover, as intense concentrations of mass, galaxy clusters provide 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 builds on the highly successful CLASH program,which used 17-colour ACS/WFC3 images to map 25 galaxy clusters, tracing the mas profile and the dark matter distribution. in addition, the observations identified several lensed galaxies at redshifts that enter the JWST domaine, with the most distant object lying at a redshift z~11, within a few hundred million years of the Big Bang. The Frontier Fields program is a large-scale Director's Discretionary program that capitalises on the latter characteristic by targeting 4-6 strong-lensing galaxy clusters for very deep optical and near-infrared imaging. WFC3 and ACS will be used to observe the clusters, with simultaneous imaging obtained in parallel of a nearby "blank" field. Since the observations need to made at a specific orientation, they are being taken in two sets, ~6 months apart, alternating between detectors. MACSJ0416.1-2403 at z=0.396 is the second target, with the cluster being imaged with WFC3-IR and the nearby blank field with ACS.

GO 13501: Characterizing the Atmosphere of Benchmark Super-Earth HD 97658b

Artist's impression of the GJ 1214 system The first exoplanet, 51 Peg b, was discovered through radial velocity measurements in 1995. 51 Pegb was followed by a trickle, and then a flood of other discoveries, as astronomers realised that there were other solar systems radically different from our own, where "hot jupiters" led to short-period, high-amplitude velocity variations. Then, in 1999, came the inevitable discovery that one of those hot jupiters. HD 209458b, was in an orbit aligned with our line of sight to the star, resulting in transits. Since that date, the number of known transiting exoplanet systems has grown to more than 100 from ground-based observations, most detected through wide-field photometric surveys, while the high-sensitivity data provided by Kepler has added a further 1000+ systems. Among the most interesting are two "super-earths" - GJ 1214b, a ~6.5 Earth-mass companion to the nearby red dwarf, GJ 1214, in an orbit with period 1.58 days, semi-major axis 0.014 AU; aND HD 97658b, a ~6.4 Earth mass planet orbiting the K dwarf, HD 97658, with a period of 9.49 days and a semi-major axis of 0.0796 AU. GJ 1214b has been targeted by several previous HST programs; the present program is the first to target HD 97658b. The program will use scan mode to obtain time-resolved near-IR spectra of the planet during transit. The goal is to obtain data that will clearky distinguish between a large scaleheight, hydrogen-dominated atmosphere and a more compact, steam-dominated atmosphere.

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