This week on HST


HST Programs: September 1 - September 7, 2014

Program Number Principal Investigator Program Title
12937 Dennis Zaritsky, University of Arizona Direct Confirmation of Intracluster Stars as SN Ia Progenitors
12969 Peter Garnavich, University of Notre Dame Global Properties Are Not Enough: Probing the Local Environments of Type Ia Supernovae
13281 Sebastiano Cantalupo, University of California - Santa Cruz Illuminating the Dark Phases of Galaxy-Formation with the Help of a z=2.4 Quasar
13298 Richard M. Plotkin, University of Michigan Radio-quiet Quasars with Extremely Weak Emission Lines: a New Perspective on Quasar Unification
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
13323 Adam F. Kowalski, NASA Goddard Space Flight Center Taking the Temperature of Explosive Stellar Flares
13331 Laurent Pueyo, Space Telescope Science Institute Confirmation and characterization of young planetary companions hidden in the HST NICMOS archive
13332 Seth Redfield, Wesleyan University A SNAP Survey of the Local Interstellar Medium: New NUV Observations of Stars with Archived FUV Observations
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
13365 Martin A Cordiner, Catholic University of America Probing the nature of small-scale structure towards rho Oph stars: A new avenue in diffuse interstellar band research
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
13410 Cristina Pallanca, Universita di Bologna COSMIC-LAB: a BSS orbiting a NS? The companion to the supermassive NS in NGC6440.
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
13442 R. Brent Tully, University of Hawaii The Geometry and Kinematics of the Local Volume
13448 Andrew J. Fox, Space Telescope Science Institute - ESA The Closest Galactic Wind: UV Properties of the Milky Way's Nuclear Outflow
13483 Goeran Oestlin, Stockholm University eLARS - extending the Lyman Alpha Reference Sample
13496 Jennifer Lotz, Space Telescope Science Institute HST Frontier Fields - Observations of MACSJ0416.1-2403
13513 Julia Comerford, University of Colorado at Boulder A Pilot Search for Spatially Offset AGN in Galaxy Merger Remnants
13515 Breanna Binder, University of Washington The Effect of Intermediate-Luminosity Transients on the X-ray Luminosity Functions of Spiral Disks
13517 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
13626 Arlin Crotts, Columbia University in the City of New York Light Echoes and Environment of SN 2014J in M82
13633 John R. Spencer, Southwest Research Institute A Kuiper Belt Object for the New Horizons Mission
13926 Zolt Levay, Space Telescope Science Institute Hubble Heritage Observations of LBN 67

Selected highlights

GO 13323: Taking the Temperature of Explosive Stellar Flares


Artist's impression of a flaring low-mass star.
One of the major surprises delivered by the Einstein X-ray Observatory in the 1980s was the high level of chromospheric activity present in cool, late-type dwarfs. Proportionately low-mass dwarfs are significantly more active than (and often as luminous as) solar-type stars, and are frequently subject to high energy flares and outbursts. This was surprising since these cool dwarfs are fully convective, and are therefore incapable of supporting the rotational dynamo that is believed to power magnetic activity in sun-like stars. In the succeeding 30+ years, subsequent observatories, notably Chandra and HST, with increasingly sensitive X-ray and UV detectors have pushed observations to fainter flux limits and lower luminosity stars. Those observations demonstrate that activity persists through spectral class M and is even present among ultracool L dwarfs, probably powered through shear dynamos maintained by convective motions. Theoretical modeling had lagged behind these observational results, and the current models are not able to reproduce the hot blackbody emission that is detected in most stellar flares. The present program aims to tackle this problem by using the Cosmic Origins Spectrograph to obtain near-UV spectra of the nearby dM4e dwarf, GJ 1243. This star falls within the Kepler survey field, and extensive monitoring has shown that it has a high frequency of moderate level flares. Simultaneous ground-based observations will allow characterisation of variations across the full UV-optical-far-red spectrum.

GO 13442: The Geometry and Kinematics of the Local Volume


The galaxies within the Local Group
The Milky Way Galaxy is a member of a relatively sparse set of galaxies known as the Local Group. Fifty-four members are currently catalogued within ~1.5 Mpc., with the overwhelming majority being dwarf systems. The Milky Way and M31 are the two dominant members, with M33 the only other spiral system. Moving beyond the Local Group, we encounter five further galaxy groups within ~3 Mpc: the M81 group, the Canes I group, the Maffei group, the Sculptor group and the NGC 5128 group ( see this link ). Beyond them lies the Virgo supercluster. HST is well suited to mapping the distance distribution of the inner groups: the high sensitivity of the Advanced Camera for Surveys and Wide-Field Camera 3 combined with the unparalleled angular resolution enables resolution of the most luminous stars; constructing the colour-magnitude provides access to a number of distance indicators, including the tip of the first red giant branch (RGB). Red giants have completed the core hydrogen-burning main-sequence stage of evolution and have moved to burning hydrogen in an inner shell. The maximum luminosity in this pahse, and hence the location of the tip of the RGB, is set when the core reaches a sufficiently high temperature to ignite helium burning, the so-called helium flash. At that point, hydrogen shell-burning is extionguished, the star contracts and moves onto the horizontal branch. The present program is part of a series of HST programs that are targetting galaxies within 4 Mpc. with the ultimate aim of developing a detailed map of the local universe.

GO 13496: HST Frontier Fields - Observations of MACSJ0416.1-2403


The Frontier Fields cluster, MACSJ0416.1-2403
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. MACSJ0416.1-2403 at z=0.396 is the second target: at the first epoch, the cluster was imaged with WFC3-IR, with ACS obtaining optical data on the nearby blank field; the second epoch observations switch cameras, with ACS on the cluster and WFC3-IR on the parallel field.

GO 13626: Light Echoes and Environment of SN 2014J in M82


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 lumunisuty, 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 (d~3.5 Mpc). 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 supernoa reached maximum at V~10.5 in early February and has since declined to fainter than 14th magnitude at visual wavelengths. The current program aims to probe the immediate environments of the supernova by searching for evidence of light echoes - reflections of the original explosion produced by interstellar features in the vicinity of the supernova.

Past weeks:
page by Neill Reid, updated 26/8/2014
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