This week on HST

HST Programs: January 5 - January 11, 2015

Program Number Principal Investigator Program Title
13026 Andrew J. Levan, The University of Warwick XMM-Newton Target of Opportunity of Tidal Disruption Events
13419 John Bally, University of Colorado at Boulder The First Ultraviolet Survey of Orion Nebula's Protoplanetary Disks and Outflows
13459 Tommaso L. Treu, University of California - Los Angeles The Grism Lens-Amplified Survey from Space {GLASS}
13462 Brian E. Wood, Naval Research Laboratory Tracking the Winds of Red Giants from the Star to the ISM
13504 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of MACSJ1149.5+2223
13517 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13644 Xiaohui Fan, University of Arizona CIII] Emission in z=5.7 Galaxies: A Pathfinder for Galaxy Spectroscopy in the Reionization Era
13646 Ryan Foley, University of Illinois at Urbana - Champaign Understanding the Progenitor Systems, Explosion Mechanisms, and Cosmological Utility of Type Ia Supernovae
13652 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs: Plugging the last gaps
13657 Jeyhan Kartaltepe, National Optical Astronomy Observatory, AURA Probing the Most Luminous Galaxies in the Universe at the Peak of Galaxy Assembly
13686 Adam Riess, The Johns Hopkins University The Longest Period Cepheids, a bridge to the Hubble Constant
13695 Benne W. Holwerda, Sterrewacht Leiden STarlight Absorption Reduction through a Survey of Multiple Occulting Galaxies (STARSMOG)
13704 Steven G. Parsons, Valparaiso University Testing the single degenerate channel for supernova Ia
13710 Philip A. Rosenfield, Universita degli Studi di Padova Constraining Models of Evolved UV-Bright Stars in the M31 Bulge
13711 Abhijit Saha, National Optical Astronomy Observatory, AURA Establishing a Network of Next Generation SED standards with DA White Dwarfs
13724 Todd J. Henry, Georgia State University Research Foundation Pinpointing the Characteristics of Stars and Not Stars --- VERSION 2014.1021
13748 Luigi R. Bedin, Osservatorio Astronomico di Padova Astrometric search for Planets in the closest Brown Dwarf Binary system Luhman 16AB
13752 John Henry Debes, Space Telescope Science Institute An autopsy of dead planetary systems with COS
13754 Jeremy J. Drake, Smithsonian Institution Astrophysical Observatory The first mass and angular momentum loss measurements for a CV-like binary
13755 Jenny E. Greene, Princeton University The Hosts of Megamaser Disk Galaxies (II)
13760 Derck L. Massa, Space Science Institute Filling the gap --near UV, optical and near IR extinction
13761 Stephan Robert McCandliss, The Johns Hopkins University High efficiency SNAP survey for Lyman alpha emitters at low redshift
13763 S. Thomas Megeath, University of Toledo WFC3 Spectroscopy of Faint Young Companions to Orion Young Stellar Objects
13764 Eric S. Perlman, Florida Institute of Technology The Physics of the Jets of Powerful Radio Galaxies and Quasars
13767 Michele Trenti, University of Cambridge Bright Galaxies at Hubble's Detection Frontier: The redshift z~9-10 BoRG pure-parallel survey
13773 Rupali Chandar, University of Toledo H-alpha LEGUS: Unveiling the Interplay Between Stars, Star Clusters, and Ionized Gas
13776 Michael D. Gregg, University of California - Davis Completing The Next Generation Spectral Library
13790 Steven A. Rodney, The Johns Hopkins University Frontier Field Supernova Search
13793 Rebecca A A Bowler, Royal Observatory Edinburgh Unveiling the merger fraction, sizes and morphologies of the brightest z ~ 7 galaxies
13813 Sean A. Farrell, University of Sydney Mapping the Broad-band Spectrum of a New Candidate Intermediate Mass Black Hole
13824 Wolfgang E Kerzendorf, University of Toronto SN 2011fe - tackling the Type Ia progenitor puzzle through extremely late time photometry
13829 William B. Sparks, Space Telescope Science Institute The ice plumes of Europa
13846 Todd Tripp, University of Massachusetts - Amherst The COS Absorption Survey of Baryon Harbors (CASBaH): Probing the Circumgalactic Media of Galaxies from z = 0 to z = 1.5
13853 Stephen Bradley Cenko, NASA Goddard Space Flight Center UV Spectroscopy of Newly Discovered Tidal Disruption Flares
13868 Dale D. Kocevski, Colby College Are Compton-Thick AGN the Missing Link Between Mergers and Black Hole Growth?
13876 Howard E. Bond, The Pennsylvania State University HST Observations of Astrophysically Important Visual Binaries
13938 Thomas R. Ayres, University of Colorado at Boulder Alpha Centauri at a Crossroads
14040 David Jewitt, University of California - Los Angeles Unique Hubble Investigation of a Newly Discovered Main Belt Comet

Selected highlights

GO 13652: The frequency and chemical composition of rocky planetary debris around young white dwarfs: Plugging the last gaps

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 typcail targets0, 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 presentSNAPSHOT program aims to cap pervious investigations by targeting white dwarfs with cooling ages of 5-25 Myrs and 100-300 Myrs: models suggest that planetary collisions should be frequent at the younger ages, when the parent stars have just completed extensive mass loss on the AGB.

GO 13686: 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 outlined by variables 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 13773: H-alpha LEGUS: Unveiling the Interplay Between Stars, Star Clusters, and Ionized Gas

UGC 4305 = Holmberg II - Arp 268, one of the star-forming galaxies targeted by LEGUS
Understanding the global architecture of star formation is a key step towards understanding the morphological evolution of galaxies and the characteristics of the underlying stellar populations. HST has devoted extensive resources to observations of nearby galaxies over its lifetime, including detailed surveys of a handful of systems, notably the PHAT survey of M31, with the enhanced imaging capabilities made available following SM4. Most programs, however, have focused on optical, far-red and, to a lesser extent, near-infrared wavelengths. While those observations provide high-quality colour-magnitude data that enable an exploration of relatively mature populations, they are less effective at probing active star-formation sites populated by young, high-mass stars. Those regions are most prominent at ultraviolet wavelengths. The HST LEGUS capitalises on the past heritage of HST observations by adding near-UV imaging for 50 nearby galaxies, drawn from a catalogue of 400 systems within ~11 Mpc of the Milky Way. They have been selected to provide a fair sampling of the wide variety of galactic systems within that volume. LEGUS itself is imaging star-forming regions at near-UV and blue wavelengths using the WFC3 UVIS channel with the F275W, F336W and F438W filters, supplemented by F55W and F814W (V and I) where necessary. The present program builds on that foundation by adding WFC3 narrow-band (F657N) H-alpha imaging of 32 galaxies from the sample.

GO 14040: Unique Hubble Investigation of a Newly Discovered Main Belt Comet

Asteroid 596-Scheila, the prototype main-belt coment, imaged by Peter Lake in December, 2010
The term 'comet" is generally associated with low-mass, volatile-rich solar system objects that spend most of their life at very lage distances from the Sun, plunging only rarely into the inner regions where they acquire extended tails due to outgassing. Sometimes those obejcts are captured into short-period, eccentric orbits, leading to rapid depletion of the volatile content in rapidly-successive perihelion passages. However, recent years have seen growing evidence of another class of cometes exist: comets with near-circular orbits that place them between Mars and Jupiter, within the realm of the Main Belt of asteroids. The objects include the asteroids Scheila, which underwent an outburst in late 2010, 1979 OW7/1996 N2 and the Pan-STARRs discoveries 2006 VW139, imaged during an outburst; and Main Belt Comet 2013-P5. The initial hypothesis was that these bursts of activity might represent the effect of collisions, but the presence of multiple episodes in some objects suggests that an intrinsic origin is possible. The asteroid P/2014 S4 was identified (by Pan-STARRs observations) as a possible MBC in September 2014, and initial follow-up HST observations showed significant variation in the structure of the "coma" over an interval of only 2 weeks. The present HST program builds on those results by using high-resolution visual imaging with Wide-Feld Camera 3 to monitor the progression of the outburst and probe the underlying physical nature of the event.

Past weeks:
page by Neill Reid, updated 11/11/2014
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