This week on HST

HST Programs: August 19 - August 25, 2013

Program Number Principal Investigator Program Title
12817 Richard J. Massey, University of Durham Longevity of dark matter substructure in Abell 3827
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12884 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies
12897 Marc W. Buie, Southwest Research Institute Pluto System Orbits in Support of New Horizons
12898 Leon Koopmans, Kapteyn Astronomical Institute Discovering the Dark Side of CDM Substructure
12902 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12904 Joel N. Bregman, University of Michigan The Galactic Fountain Meets The Accreting Halo
12911 Luigi R. Bedin, Osservatorio Astronomico di Padova A search for binaries with massive companions in the core of the closest globular cluster M4
12932 Francesco R. Ferraro, Universita di Bologna COSMIC-LAB: Hunting for optical companions to binary MSPs in Globular Clusters
12936 Edward B. Jenkins, Princeton University The Physical and Dynamical Properties of Gas that Molds the Fermi Bubbles
12961 Misty C. Bentz, Georgia State University Research Foundation A Cepheid Distance to NGC6814
12962 William B. Sparks, Space Telescope Science Institute Optical Line Emission Impact Polarization: SN1006
12969 Peter Garnavich, University of Notre Dame Global Properties Are Not Enough: Probing the Local Environments of Type Ia Supernovae
12971 Harvey B. Richer, University of British Columbia Completing the Empirical White Dwarf Cooling Sequence: Hot White Dwarfs in 47 Tucanae
13000 Sungryong Hong, National Optical Astronomy Observatory, AURA Impact of Environments on Lyman alpha Emitting Galaxies at High Redshift {z ~ 2.7}
13004 Margaret Meixner, The Johns Hopkins University The Life Cycle of Dust in the Magellanic Clouds: Crucial Constraints from Zn and Cr depletions
13021 Jacob L. Bean, University of Chicago Revealing the Diversity of Super-Earth Atmospheres
13042 Paul Denholm Dobbie, University of Tasmania Confirming the theoretical link between ultra-massive white dwarfs and heavy-weight intermediate mass stars.
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13057 Kailash C. Sahu, Space Telescope Science Institute Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing
13177 Marusa Bradac, University of California - Davis Spitzer UltRaFaint SUrvey {SURF'S Up}: Cluster Lensing and Spitzer Extreme Imaging Reaching Out to z~7
13364 Daniela Calzetti, University of Massachusetts - Amherst LEGUS: Legacy ExtraGalactic UV Survey
13386 Steven A. Rodney, The Johns Hopkins University Frontier Field Supernova Search
13505 Dan Milisavljevic, Harvard University SN 2012im/2013ek: A Supernova Double Take in NGC 6984
Selected highlights

GO 12880: The Hubble Constant: Completing HST's Legacy with WFC3


A GALEX image of Messier 106 (NGC 4258), one of the galaxies targeted in this program
The Hubble constant remains a key parameter in understanding cosmology and the evolution of the Universe. Refining measurements of H0 therefore still represents a vital means of probing the nature of dark energy. The present program aims to tackle this question by laying a firmer foundation to the SNe Ia distance scale. The WFC3 IR camera will be used to identify and characterise Cepheid variables in eight relatively nearby galaxies that have hosted Type Ia SNe. Cepheids have signficantly lower amplitude at near-infrared wavelengths, and the measured magnitudes are less subject to uncertainties due to foreground reddening and variations in metallicity. As a consequence, determining the mean apparent magnitude, and hence the period/apparent magnitude relation, is substantially more straightforward than at optical wavelengths. WFC3 has revolutionised this field by providing substantial greater areal coverage and higher precision photometry than NICMOS. Past observational program have targeted the Cepheids in the maser galaxy, NGC 4258, as well as Galactic Cepheids. The present program targets eight galaxies that have hosted Type Ia supernovae, offering the prospect of tying the SNe Ia scale directly to the Galaxy and to NGC 4258, avoiding the many intermediate steps of previous analyses. The aim is to reduce the level of systematics in determinations of H0 to the 1-2 percent level, setting signficantly stronger constraints on dark energy.
GO 12897: Pluto system orbits in support of New Horizons


Hubble Space Telescope images of the Pluto system, including the recently discovered moons, P4 and P5
Pluto, one of the largest members of the Kuiper Belt and, until recently, the outermost planet in the solar system, has been in the news over the last year or two. Besides the extended "planet"/"dwarf planet" debate, Pluto is the primary target of the New Horizons Mission. In 1978, James Christy discovered from analyses of photographic plates that Pluto has a relatively large companion moon, Charon, with a diameter of ~1200 km, or almost half that of Pluto itself. In 2005, Hubble observations led to the discovery of two small moons, christened Nix and Hydra. These two new moons are 5,000 fainter than Pluto itself, implying diameters as small as ~30-50 km if the surface composition is similar to Pluto itself. Over the past two years, a series of observations were taken in support of the New Horizons mission, using WFC3 to search for faint rings due to dust particles that might jeopardise the space craft and require a course correction. While no rings were detected unequivocally, two small satellite, christened "P4" and "P5", have been discovered. Both are significantly fainter than Nix and Hydra, and may well be as small as 10-13 km in size. There is also some evidence that might point to the presence of a debris ring within Charon's orbit. The present observations, again in support of New Horizons, will use WFC3 to push to even fainter magnitudes to both better characterise the P4 and P5 orbits and search for even fainter moons.
GO 13021: Revealing the Diversity of Super-Earth Atmospheres


Artist's impression of a planet in the GJ 1214 system
GJ 1214 is a 14th magnitude M4.5 dwarf that lies at a distance of ~13 parsecs from the Sun in the constellation of Ophiuchus. It's main claim to fame is that it has a confirmed planetary companion in an orbit with a period of 1.58 days and a mass of 6.55+/-0.98 earth masses. This super-Earth transits the parent star, allowing an accurate determination of its diameter as 2.64 times that of Earth. Transiting systems offer a potential gold-mine for extrasolar planetary studies, since not only is the diameter (and hence the average density) directly measureable form the eclipse depth, but the atmospheric composition can be probed through line absorption or re-radiated thermal flux. The results from these measurments can be used to test, and improve, theoretical models of extrasolar planets. These observations are best done from space: indeed, the only successful atmospheric observations to date have been with HST and Spitzer. The present program will use the WFC3/IR grisms to map the near-IR spectral energy distribution through several trasnits, searching for characteristic features due to water and (perhaps) methane.
GO 13364: LEGUS: Legacy ExtraGalactic UV Survey


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 of those 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, and the present program aims to capitalise on the past heritage of HST observations vby adding near-UV imaging for 50 nearby galaxies. The 50 targets are drawn from a catalogue of 400 systems within ~11 Mpc of the Milky Way, and have been selected to provide a fair sampling of the wide variety of galactic systems within that volume. The program will image star-forming regions in these systems in near-UV and blue wavelengths using the WFC3 UVIS channel with the F275W, F336W and F438W filters, supplemented by F55W and F81wW (V and IK) where necessary.
Past weeks:
Cycle 14 observations (from March 13 2006 to June 30 2006)
Cycle 15 observations (from July 1 2006)
Cycle 16 observations (from July 1 2007)
Cycle 17 observations (from July 13 2009)
Cycle 18 observations (from August 30 2010)
Cycle 19 observations (from October 3 2011)
Cycle 20 observations (from October 1 2012)