This week on HST


HST Programs: February 23 - March 1, 2015

Program Number Principal Investigator Program Title
13331 Laurent Pueyo, Space Telescope Science Institute Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive
13498 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of MACSJ0717.5+3745
13643 Gaspard Duchene, University of California - Berkeley Imaging the tenuous dusty atmosphere of edge-on protoplanetary disks
13650 Kevin France, University of Colorado at Boulder The MUSCLES Treasury Survey: Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems
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
13677 Saul Perlmutter, University of California - Berkeley See Change: Testing time-varying dark energy with z>1 supernovae and their massive cluster hosts
13679 Lorenz Roth, Royal Institute of Technology Europa's Water Vapor Plumes: Systematically Constraining their Abundance and Variability
13699 Nicolas Martin, Universite de Strasbourg I Fellowship of the Andromeda Dwarf Galaxies: A Census of their Extended Star Formation Histories
13724 Todd J. Henry, RECONS Institute Pinpointing the Characteristics of Stars and Not Stars --- VERSION 2014.1021
13732 Anna Nierenberg, The Ohio State University Detecting dark matter substructure with narrow line lensing
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
13779 Sangeeta Malhotra, Arizona State University The Faint Infrared Grism Survey (FIGS)
13788 Aida H. Wofford, CNRS, Institut d'Astrophysique de Paris COS Views of Local Galaxies Approaching Primeval Conditions
13790 Steven A. Rodney, The Johns Hopkins University Frontier Field Supernova Search
13800 C. Simon Jeffery, Armagh Observatory Heavy-metal, extreme chemistry and puzzling pulsation: ultraviolet clues to the formation of hot subdwarfs
13805 Kurt D. Retherford, Southwest Research Institute Io's Atmosphere Silhouetted in Transit by Jupiter Lyman-alpha
13809 Jessica R. Lu, University of Hawaii The IMF and Internal Kinematics of the Massive Young Star Cluster, Westerlund 1
13826 Massimo Robberto, Space Telescope Science Institute The Orion Nebula Cluster as a Paradigm of Star Formation
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
13876 Howard E. Bond, The Pennsylvania State University HST Observations of Astrophysically Important Visual Binaries
13940 Matthew Brorby, University of Iowa X-RAYS FROM GREEN PEA ANALOGS
14050 Laura Kreidberg, University of Chicago Exploring the Frontiers of Exoplanet Atmosphere Dynamics with NASA's Great Observatories

Selected highlights

GO 13679: Europa's Water Vapor Plumes: Systematically Constraining their Abundance and Variability


The HST imaging of a potential water plume around Europa's south pole superimposed on an image of the satellite
Europa is the smallest, and the most intriguing, of the four Galilean satellites of Jupiter. With a diameter of 3139 km, Europa is almost twice the size of Earth's moon and significantly larger than Mercury. In 1957, Gerard Kuiper commented that both infrared spectroscopy and the optical colours and albedo suggested that Jovian satellite II (Europa) is covered "by H2O snow". Images taken by the Voyager space probes in the late 1970s (see left) reveal a smooth surface, with only a handful of craters larger than a few kilometres. These features are consistent with a relatively young, icy surface. Subsequent detailed investigations by the Galileo satellite strongly suggest that a substantial body of liquid water, heated by tidal friction, underlies a 5 to 50 km thick icy crust. The presence of this subterranean (subglacial?) ocean clearly makes Europa one of the two most interesting astrobiology targets in the Solar System. Most recently, analysis of observations taken by the Space Telescope imaging Spectrograph (STIS) on Hubble indicated the presence of an extended cloud of Lyman-alpha emission near the polar regions while Europa was furthest in its orbit from Jupiter, strongly suggesting that Europa's oceans may be vaporising into space.Follow-up observations on two further occasions earlier in 2014 failed to detect any emission, suggesting that the emission is either sporadic or periodic; in the latter case, the emission might be related to the location of Europa within its orbit and the consequent tidal strain imposed by Jupiter.The present program is conducting a methodical series of observations designed to image Europa at a range of orbital locations. STIS is being used to search for H and O auroral emissions at UV wavelengths and will aim to map the distribution of emission at different phases of the Europan orbit.

GO 13677: Fellowship of the Andromeda Dwarf Galaxies: A Census of their Extended Star Formation Histories


M31, the Andromeda spiral galaxy, and its companiosn - from the PANDAS survey
M31, the Andromeda galaxy, is the nearest large spiral system to the Milky Way (d ~ 700 kpc), and, with the Milky Way, dominates the Local Group. The two galaxies are relatively similar, with M31 likely the larger system; thus, Andromeda provides the best opportunity for a comparative assessment of the structural properties of the Milky Way. Like the Milky Way, Andromeda has a number of satellite galaxy companions. At present, some 31 systems have been identified, the majority from the Pan Andromeda Archaeological Survey (PANDAS), a wide-field survey utilising ground-based imaging data. The four most prominent satellites are the dwarf ellipticals NGC 147, NGC 185, NGC 205 and M32; most of the remaining systems are dwarf spheroidals, with absolute visual magnitudes between MV<\sub> =-10 and -6 and masses less than 108 MSun. The present program aims to probe the star formation history of these systems. The Advanced Camera for Surveys (ACS) will be used to obtain deep V (F606W) and I(F814W) imaging of the 19 dwarf spheroidals that currently lack any HST data; the structure of the red giant branch and horizontal branch in the resultant colour-magnitude diagrams will map the metallicity and age of the component stellar populations.
GO 13940: X-rays from Green Pea analogs


A montage of green pea galaxies discovered by the Galaxy Zoo project
Standard Big Bang cosmology includes an epoch of reionisation, when hydrogen gas in the intergalactic medium is\ionised, reducing the line-of-sight opacity and ending thed ark ages. Among the candidates for carrying out that ionisation are X-ray sources, particularly high-mass X-ray binaries in compact, low-metallicity dwarf galaxies.Studying those galaxies directly is not possible, so the present program aims to investigate the potential of this diea through observations of local analogues. The Sloan Digital Sky Survey, conducted from Apache Point Observatory from the 1990s through the early years of this century, has provided a treasure trove of information of galaxies at low and moderate redshifts. One of the interesting discoveries originating from SDSS was the identiication of "green pea" galaxies - compact objects whose combined images have a greenish hue, originally uncovered by citizen scientists as part of the Galaxy Zoo project. Closer inspection shows that these are gas-rich galaxies lying at relatively low redshifts, 0.1 < z < 0.36, with the green-tinged hue partly stemming from the presence of strong oxygen ([O III]) emission. A subset of those systems ar being targeted in the present program for imaging at red and ultraviolet wavelengths with WFC3 (F606W and F336W filters). The goal is to determine the prevalence of super star clusters, and hence the likelihood for high-mass X-ray binaries in those systems.

GO 13809: The IMF and Internal Kinematics of the Massive Young Star Cluster, Westerlund 1


The massive, reddedened open star cluster, Westerlnd 1
Westerlund 1 is a massive, young star cluster that lies somewhere between 3.5 and 5 kpc from the Sun in the constellation Ara in the general direction of the Galactic Centre. The cluster was discovered just over 50 years ago by Bengt Westerlund, but has only been subject to detailed scrutiny in more recent years since interstellar material along the line of sight leads to foreground absorption of around 14 magnitudes at optical wavelengths. Detailed investigations became possible as near-infrare astronomy came of age in the 1990s. These show that Westerlund 1 has an age of 4-5 Myrs, comparable with the Orion Nebula Cluster but probably singificantly more massive. The cluster includes several O stars within an extremely compact region. As a result, it presents an opportunity to examine how the star formation mioght be influenced by such an extreme environment. In particular, is there any evidence for changes in the IMF? The present proposal is using the WFC3-IR camera to obtain deep, multi-band images at two epochs. The initial observations were obtained in March 2013, during Cycle 20. With a 2 year baseline, the second epoch data will not only permit the identification of cluster members with masses as low as ~0.1 MSun, but will also enable astrometry of sufficient accuracy to constrain the internal cluster kinematics.

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