This week on HST


HST Programs: February 10 - February 16, 2014

Program Number Principal Investigator Program Title
12880 Adam Riess, The Johns Hopkins University The Hubble Constant: Completing HST's Legacy with WFC3
12903 Luis C. Ho, Carnegie Institution of Washington The Evolutionary Link Between Type 2 and Type 1 Quasars
13286 Ryan Foley, University of Illinois at Urbana - Champaign Understanding the Progenitor Systems, Explosion Mechanisms, and Cosmological Utility of Type Ia Supernovae
13297 Giampaolo Piotto, Universita degli Studi di Padova The HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations and Formation
13302 J. Michael Shull, University of Colorado at Boulder COS Spectra of High-Redshift AGN: Probing Deep into the Rest-Frame Ionizing Continuum and Broad Emission Lines
13309 Yicheng Guo, University of California - Santa Cruz UV Snapshot of Low-redshift Massive Star-forming Galaxies: Searching for the Analogs of High-redshift Clumpy Galaxies
13330 Bradley M Peterson, The Ohio State University Mapping the AGN Broad Line Region by Reverberation
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
13338 Kevin B. Stevenson, University of Chicago Confirming a Sub-Earth-Sized Exoplanet in the Solar Neighborhood
13346 Thomas R. Ayres, University of Colorado at Boulder Advanced Spectral Library II: Hot Stars
13352 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13364 Daniela Calzetti, University of Massachusetts - Amherst LEGUS: Legacy ExtraGalactic UV Survey
13374 Dougal Mackey, Australian National University Extremely faint, diffuse satellite systems in the M31 halo: exceptional star clusters or tiny dwarf galaxies?
13398 Christopher W. Churchill, New Mexico State University A Breakaway from Incremental Science: Full Characterization of the z<1 CGM and Testing Galaxy Evolution Theory
13399 Asantha Cooray, University of California - Irvine Spatially Resolved WFC3/Grism Spectral Line Imaging of Gravitational Lensed Herschel-selected Luminous Dusty Starbursts
13408 Jon Mauerhan, University of California - Berkeley Constraining the Physical Properties of LBV Nebulae in the Galactic Center Environment
13412 Tim Schrabback, Universitat Bonn, Argelander Institute for Astronomy An ACS Snapshot Survey of the Most Massive Distant Galaxy Clusters in the South Pole Telescope Sunyaev-Zel'dovich Survey
13428 Christopher R. Gelino, Jet Propulsion Laboratory Characterizing the Ultra-cold Brown Dwarf WD 0806-661B
13445 Joshua S. Bloom, University of California - Berkeley Absolute Calibration of the Extragalactic Mira Period-Luminosity Relation
13448 Andrew J. Fox, Space Telescope Science Institute - ESA The Closest Galactic Wind: UV Properties of the Milky Way's Nuclear Outflow
13457 Kailash C. Sahu, Space Telescope Science Institute Accurate Mass Determination of the Nearby Old White Dwarf Stein 2051B through Astrometric Microlensing
13459 Tommaso L. Treu, University of California - Santa Barbara The Grism Lens-Amplified Survey from Space {GLASS}
13465 Thomas R. Ayres, University of Colorado at Boulder Alpha Cen: Climbing out of a Coronal Recession? {year 3 continuation}
13467 Jacob L. Bean, University of Chicago Follow The Water: The Ultimate WFC3 Exoplanet Atmosphere Survey
13472 Wendy L. Freedman, Carnegie Institution of Washington The Hubble Constant to 1%? STAGE 4: Calibrating the RR Lyrae PL relation at H-Band using HST and Gaia Parallax Stars
13482 Britt Lundgren, University of Wisconsin - Madison The Evolving Gas Content of Galaxy Halos: A Complete Census of MgII Absorption Line Host Galaxies at 0.7 < z < 2.5
13609 David Jewitt, University of California - Los Angeles Investigating the Trigger Mechanism for Newly Discovered Main Belt Comet P/2013 P5
13612 David Jewitt, University of California - Los Angeles Hubble Investigation of the First Known, Multi-Fragment Main Belt Comet: P/2013 R3
13620 William B. Sparks, Space Telescope Science Institute Probing the atmosphere of a transiting ocean world: are there ice fountains on Europa?
13621 Ariel Goobar, Stockholm University The closest reddened Type Ia supernova in the HST life time
13623 Zolt Levay, Space Telescope Science Institute Hubble Heritage observations of NGC 2174 for HST 24th anniversary

Selected highlights

GO 13445: Absolute Calibration of the Extragalactic Mira Period-Luminosity Relation


The spiral galaxy, NGC 4258, as imaged by GALEX
Defining a reliable cosmic distance scale remains one of the most important tasks facing modern cosmologists. 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. Cepheids are not the only pulsating variables that can serve as distance indicators, however: RR Lyraes serve as distance indicators for old populations; and pulsating red giant variables offer an alternatiev in intermediate-age populations. Most long period variable stars (LPVs) are red giants on the asymptotic giant branch (AGB). These are intermediate mass stars, between ~1.5 and ~7 solar masses, that are powered by hydrogen and helium shell-burning. The interactions between the two energy sources lead to instabilities that can generate substantial pulsations, with periods from ~50 to ~500 days. Mira, or omicron Ceti, is the Galactic prototype for this type of variable, and numerous LPVs have been identified throughout the Milky Way and in the neighbouring Small and Large Magellanic Clouds. The LMC and SMC variables show a clear period-luminosity relation, particularly at near-infrared wavelengths, with longer period stars having higher intrinsic luminosities. This P-L relation, while not as well established for classical cepheids, allows LPVs to contribute to measurements of the extragalactic distance scale, particularly since miras are more luminous than Cepheids at inreared wavelengths. The present program aims to capitalise on these characteristics by using the WFC3 IR camera to search for mira variables in NGC 4258, a spiral galaxy that hosts several megamaser sources that enable accuate distance measurements. The aim is to use these miras to define a period-luminosity relation that can serve as a reference point for measuring distances to more distant galaxies.

GO 13459: The Grism Lens-Amplified Survey from Space {GLASS}


HST imaging of the galaxy cluster MACS0717.5-3745
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. Hubble is currently undertaking deep imaging observations of up to 6 galaxy clusters as part of the Frontier Fields Director's Time program (GO 13495). The present program supplements those visual and near-infrared data by adding imaging spectrophotometry at near-infrared wavelengths, using the low-resolution G102 and G141 grisms on the WFC3-IR camera. In all, the program targets 10 clusters drawn from both the Frontier Fields sample and from the larger-scale (but less deep) multicolour CLASH program. The goal is to identify and characterise galaxies at relatively high redshifts, close to the epoch of reionisation. The grism data should provide low-resolution spectra for 150-200 galaxies at redshifts z>6, with the potential to detect Lyman alpha emission at redshifts up to z~8.5. The present observations target the Frontier Fields cluster, MACS0717.5+3745.

GO 13620: Probing the atmosphere of a transiting ocean world: are there ice fountains on Europa?


An image of Europa taken by Voyage 2 in 1979
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, stongly suggesting that Europa's oceans may be vaporising into space. The present HST program also aims to search for outgassing, but in this by looking for absorption features against the smooth background light of Juptier while Europa is in transit. This DD program follows upon GO 134338, using STIS in time-tag mode to search from transient features in th far-UV, and applying coronagraphy at near-UV wavelengths to look for dust signatures.

GO 13621: The closest reddened Type Ia supernova in the HST life time


Image of the recent supernova in M82, Jan 24th (Katzman Automated Imaging Telescope/LOSS)
Type Ia supernovae are generally believed to be produced by the explosive deflagration of white dwarf star that exceeds the Chandrasekhar due to accretion from a binary companion, either a hydrogen-burning main-sequence/red giant star or another degenerate. Besides providing crucial information on stellar evolution and how stars enrich the interstellar medium, Type Ia supernovae have acquired global importance in recent years through their use as distance indicators. Indeed, these objects played a crucial role in identifying dark energy and the accelerating universe. In that context, it is important to understand the distribution of intrinsic properties of these exploding stars, and whether those properties, particularly luminosity, correlate with other parameters, such as metallicity. Relatively nearby supernovae that can be probed in detail are therefore crucial to the large mapping of the cosmic flow. Astronomers were therefore delighted with the discovery of a type Ia supernova in the relatively nearby starburst galaxy, M82. This object, designated SN2014J, was discovered on January 21st by a group of UCL undergraduates and their lecturer in a series of short exposures taken as a quick test as clouds closed in on London's Mill Hill Observatory. The supernova is expected to reach maximum around February 2nd, at which time the supernova is expected to reach ~10th magnitude. As the second closest Type Ia of recent years (SN 1993J in M81 was at a similar distance), this object has attracted significant attention, despite the substantial line of sight reddening. The current program will use WFC3 to obtain a time series of UV images, probing the intrinsic luminosity and v ariations as ejecta permeate the surrounding environment.

Past weeks:
page by Neill Reid, updated 7/2/2014
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