This week on HST

HST Programs: December 16 - December 22, 2013

Program Number Principal Investigator Program Title
12883 Denis Grodent, Universite de Liege Unraveling electron acceleration mechanisms in Ganymede's space environment through N-S conjugate imagery of Jupiter's aurora
12892 Yue Shen, Carnegie Institution of Washington Imaging the Host Galaxies of Low-Redshift Quasars with Associated Absorbers
12995 Christopher Johns-Krull, Rice University Testing Disk Locking in the Orion Nebula Cluster
13046 Robert P. Kirshner, Harvard University RAISIN: Tracers of cosmic expansion with SN IA in the IR
13184 Jelle Kaastra, Space Research Organization Netherlands Deciphering AGN outflows: multiwavelength monitoring of NGC 5548
13229 Zolt Levay, Space Telescope Science Institute Hubble Heritage imaging of Comet ISON
13297 Giampaolo Piotto, Universita degli Studi di Padova The HST Legacy Survey of Galactic Globular Clusters: Shedding UV Light on Their Populations and Formation
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
13320 Fabien Grise, Instituto de Astrofisica de Canarias Unveiling the nature of ultraluminous X-ray sources via UV spectroscopy
13324 Davor Krajnovic, Astrophysikalisches Institut Potsdam Where cores are no more: assessing the role of dissipation in the assembly of early-type galaxies
13325 Claus Leitherer, Space Telescope Science Institute Pushing COS to the {Lyman-}Limit
13332 Seth Redfield, Wesleyan University A SNAP Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
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
13350 Andrew S. Fruchter, Space Telescope Science Institute How Low Can They Go? Detecting low luminosity supernova progenitors
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?
13389 Brian Siana, University of California - Riverside The Ultraviolet Frontier: Completing the Census of Star Formation at Its Peak Epoch
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
13438 William B. Sparks, Space Telescope Science Institute Probing the atmosphere of a transiting ocean world
13442 R. Brent Tully, University of Hawaii The Geometry and Kinematics of the Local Volume
13445 Joshua S. Bloom, University of California - Berkeley Absolute Calibration of the Extragalactic Mira Period-Luminosity Relation
13453 Michael Jura, University of California - Los Angeles The Elemental Compositions of Extrasolar Minor Planets
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
13489 John T. Stocke, University of Colorado at Boulder Accretion Physics in Nearby FR1 Galaxies
13501 Heather A. Knutson, California Institute of Technology Characterizing the Atmosphere of Benchmark Super-Earth HD 97658b
13517 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13613 C. S. Kochanek, The Ohio State University Dust to Dust: Monitoring the Evolution of the New Class of Self-Obscured Transients

Selected highlights

GO 13229: Hubble Heritage imaging of Comet ISON

HST image of Comet ISON, late April 2013
At least once every decade, the astronomical community gets excited by the discovery of a comet that offers the prospect of becoming a "comet of the century", developing a spectacular tail speading across the sky at sunset or sunrise. Unfortunately, while Comet McNaught put on a spectacular shows for the southern hemisphere in 2007, most of the predicted rivals of the Great Comets of 1680/1811/1882 have fizzled. The latest in line was Comet ISON which passed within 700,000 miles of the Sun in late November.The initial observations, when ISOn was out beyond jupietr's object, offered hope that this comet might be sufficiently active, but sufficiently well bound, to survive that close passage and emerge with a substantial tail on its return to the outer solar system. Numerous ground- and space-based tlescopes and probes were trained on ISON, and comet was well tracked in its approach to the immediate solar vicinity and its perihelion passage by the solar satellites, SOHO and STEREOA/B. As a sun-grazer, there was always a significant chance that the comet might break up close to perihelion, and that appears to have been what happened. The SOHO shows a well defined comet approaching perihelion, disappearing behind the central stop, and a ragged dust cloud emerging post-perihelion. ISON has not been since since it lef the STEREO field of view. The present Hubble observations, trained on where ISON is predicted to be, are aimed at determining whether any object of significant size survived.

GO 13332: A SNAPSHOT Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observation

A map of the Local Stellar Neighbourhood Understanding the nature and structure of gas within the interstellar medium is a key step towards understanding how material is recycled and how energetic processes, such as stellar winds and outflows, feed energy into the overall system. UV spectroscopy plays a key role in probing these effects: hot, background objects that produce relatively few intrinsic absorption features serve to map the the velocities and temperatures within the intervening gas along the line of sight. Observations of quasars are used to probe galaxy halos at moderate and high redshift; observations of hot stars provide similar information for gas in the Milky Way. The present program is using STIS to target stars within 100 parsecs of the Sun, studying the nearby interstellar medium. All of these stars have prior observations at far-UV wavelengths; the STIS data will cover the near-UV, surveying Fe II and Mg II absorption.This program builds on observations spanning 36 targets from Cycle 17.

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.

Past weeks:
page by Neill Reid, updated 14/10/2012
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