This week on HST


Hubble's 25th anniversary - April 24th, 2015


HST Programs: April 20 - April 26, 2015

Program Number Principal Investigator Program Title
13504 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of MACSJ1149.5+2223
13639 Matthew Bayliss, Harvard University Resolving Lyman-alpha Emission On Physical Scales < 270 pc at z > 4
13641 Peter Capak, California Institute of Technology A Detailed Dynamical And Morphological Study Of 5
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
13664 Susan D. Benecchi, Planetary Science Institute Origin and Composition of the Ultra-Red Kuiper Belt Objects
13671 Harald Ebeling, University of Hawaii Beyond MACS: A Snapshot Survey of the Most Massive Clusters of Galaxies at z>0.5
13689 Aleksandar M. Diamond-Stanic, University of Wisconsin - Madison How Compact is the Stellar Mass in Eddington-Limited Starbursts?
13692 William M. Grundy, Lowell Observatory Orbits and Physical Properties of Four Binary Transneptunian Objects
13694 Amanda R. Hendrix, Planetary Science Institute UV spectra of the icy Saturnian satellites: Understanding exogenic processes and NH3 in the system
13732 Anna Nierenberg, The Ohio State University Detecting dark matter substructure with narrow line lensing
13735 David J. Sand, Texas Tech University A New Dwarf Galaxy Associated with an Ultra-Compact High Velocity Cloud
13741 Thaisa Storchi-Bergmann, Universidade Federal do Rio Grande do Sul Constraining the structure of the Narrow-Line Region of nearby QSO2s
13749 David V. Bowen, Princeton University Baryon Structures Around Nearby Galaxies: Using an Edge-On Disk to Assess Inflow/Outflow Models
13750 John M. Cannon, Macalester College Fundamental Parameters of the SHIELD II Galaxies
13767 Michele Trenti, University of Melbourne Bright Galaxies at Hubble's Detection Frontier: The redshift z~9-10 BoRG pure-parallel survey
13775 Catherine Espaillat, Boston University Testing EUV Photoevaporation Models in Young Disks
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
13797 Alex V. Filippenko, University of California - Berkeley Early-Time UV Spectroscopy of Stripped-Envelope Supernovae: A New Window
13798 Carol A. Grady, Eureka Scientific Inc. A chemical inventory of Gas and Star-Grazing Exocomets in HD 172555
13799 Or Graur, New York University Constraining Type Ia Supernova Nucleosynthesis and Explosion Models Using Late-Time Photometry of SN2012cg
13800 C. Simon Jeffery, Armagh Observatory Heavy-metal, extreme chemistry and puzzling pulsation: ultraviolet clues to the formation of hot subdwarfs
13807 Paula Szkody, University of Washington Unprecedented Tracking of the Unique Dwarf Nova GW Lib from Largest Amplitude Outburst to Quiescent Pulsations
13856 Denija Crnojevic, Texas Tech University Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A
13859 Luca Fossati, Space Research Institute, Austrian Academy of Sciences Unveiling the circumstellar environment of the most extreme hot-Jupiters
14061 Francesco R. Ferraro, Universita di Bologna Exploring the MSP prenatal stage: the optical identification of a NS burster in Terzan 5.

Selected highlights

GO 13504: HST Frontier Fields - Observations of MACSJ1149.5+2223


The Frontier Fields cluster, MACSJ1149.5+2223
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. MACSJ1149.5+2223 at z=0.544 is the fourth target. The first epoch of observation were obtained in late 2014, with the cluster imaged with WFC3-IR and ACS obtaining obtain optical data on the nearby blank field. The second epoch observations being undertkane now switch cameras, with ACS on the cluster and WFC3-IR on the parallel field.

GO 13692: Orbits and Physical Properties of Four Binary Transneptunian Objects


Preliminary orbital determination for the KBO WW31, based on C. Veillet's analysis of CFHT observations; the linked image shows the improved orbital derivation, following the addition of HST imaging
The Kuiper Belt consists of icy planetoids that orbit the Sun within a broad band stretching from Neptune's orbit (~30 AU) to distance sof ~50 AU from the Sun (see David Jewitt's Kuiper Belt page for details). Over 500 KBOs (or trans-Neptunian objects, TNOs) are currently known out of a population of perhaps 70,000 objects with diameters exceeding 100 km. Approximately 2% of the known KBOs are binary (including Pluto, one of the largest known KBOs, regardless of whether one considers it a planet or not). This is a surprisingly high fraction, given the difficulties involved in forming such systems and the relative ease with which they can be disrupted. It remains unclear whether these systems formed from single KBOs (through collisions or 3-body interactions) as the Kuiper Belt and the Solar System have evolved, or whether they represent the final tail of an initial (much larger) population of primordial binaries. These issues can be addressed, at least in part, through deriving a better understanding of the composition of KBOs - and those properties can be deduced by measuring the orbital parameters for binary systems. The present proposal aims to use HST WFC3 observations to map the orbits of four binary systems. Those observations will be ued to determine the orbital period and semi-major axis and the total system mass, while the mid-infrared properties (measured by Spitzer) allow an assessment of the surface area/diameters; combining these measurements gives an estimate of the mean density.

GO 13798: A chemical inventory of Gas and Star-Grazing Exocomets in HD 172555


HST imaging of the debris disk in the beta Pictoris system
HD 172555 is a A5 star lying at distance of ~30 parsecs from the Sun in the southern constellation of Pavo. IRAS observations revealed that the star has excess raidation at mid-infrared wavelengths, and Spitzer observations confirmed the presence of a circumstellar debris disk. The space motions are consistent with membership of the Beta Pictoris moving group, a group of young stars generally characterised as ~12 million years old and including the M dwarf Gl 803 in addition to the eponymous system. The presence of not only debris disks, but also warps in the structure of those disks, strongly indicates the presence of planetary bodies in these young systems. Key questions remain, however, including the rate of gas depletion within the disks, the extent to gas survives as a function of radius within the debris disks and the abundance distribution of residual gaseous materials. The present program aims to search for and characterise the gas content of the HD 172555 disk. The Space Telescope Imaging Spectrograph (STIS) and the Cosmic Origins Spectrograph (COS) will be used to obtain ultraviolet spectra and near- and far-ultraviolet wavelengths, respectively. The wavelength range covered by the observations spans several key diagnostics, including absorption features due to neutral and ionised species, including carbon, aluminium and silicon.

GO 13856: Resolving the faint end of the satellite luminosity function for the nearest elliptical Cen A


A CTIO image of the active galaxy Centaurus A

Lying at a distance of 3.7 Mpc, Centaurus A is both the nearest elliptical galaxy and the nearest active galaxy to the Milky Way. Originally catalogued in 1826 by James Dunlop, the system (as the name suggests) was one of the first radio sources detected in the southern sky. Detailed optical imaging over the past 50 years have highlighted the presence of a substantial dust lane with embedded star formation. This strongly suggests that the system is a early-type elliptical or lenticular galaxy that has recently ingested asmoderately massive, gas-rich spiral companion. X-ray and radio observations have revealed extensive jet-like structures almost perpendicular to the disk, indicating the presence of a central black hole. The present observations, however, are focused not on Cen A itself, but on its immediate environs. Ground-based observations with the Magellan telescope have identified up to 15 candidate low-mass dwarf satellite companions. The present observations aim to use the Advanced Camera for Surveys on HST to investigate these candidates in more detail, and probe their likely mass and star formation history.

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