This week on HST


HST Programs: November 7, 2011 - November 13, 2011


Program Number Principal Investigator Program Title
11616 Gregory J. Herczeg, Max-Planck-Institut fur extraterrestrische Physik The Disks, Accretion, and Outflows {DAO} of T Tau stars
12101 Marc Postman, Space Telescope Science Institute Through a Lens, Darkly - New Constraints on the Fundamental Components of the Cosmos
12167 Marijn Franx, Universiteit Leiden Resolving the Matter of Massive Quiescent Galaxies at z=1.5-2
12185 Jenny E. Greene, Princeton University The Hosts of Megamaser Disk Galaxies
12192 James T. Lauroesch, University of Louisville Research Foundation, Inc. A SNAPSHOT Survey of Interstellar Absorption Lines
12196 David J. Radburn-Smith, University of Washington Disk Truncations: Probing Galaxy Formation at the Limits
12275 Bart P. Wakker, University of Wisconsin - Madison Measuring gas flow rates in the Milky Way
12281 Mark Clampin, NASA Goddard Space Flight Center STIS Coronagraphic Imaging of the Kuiper Belt Surrounding the HR 8799 Planetary System.
12283 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey {WISP}: A Survey of Star Formation Across Cosmic Time
12320 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale
12324 C. S. Kochanek, The Ohio State University The Temperature Profiles of Quasar Accretion Disks
12378 Andrew J. Levan, The University of Warwick The differing environments of dark gamma-ray bursts
12461 Adam Riess, The Johns Hopkins University Supernova Follow-up for MCT
12464 Kevin France, University of Colorado at Boulder Project MUSCLES: Measuring the Ultraviolet Spectral Characteristics in Low-mass Exoplanetary Systems
12469 Pilar Ruiz-Lapuente, Universidad de Barcelona High-Precision Proper Motion Measurements of the Stars in the Field of SN 1572 with WFC3/UVIS
12471 Dawn K. Erb, University of Wisconsin - Milwaukee The Bottom of the Iceberg: Faint z~2 Galaxies and the Enrichment of the IGM
12474 Boris T. Gaensicke, The University of Warwick The frequency and chemical composition of rocky planetary debris around young white dwarfs
12475 Seth Redfield, Wesleyan University Cool Star Winds and the Evolution of Exoplanetary Atmospheres
12481 Carrie Bridge, California Institute of Technology WISE-Selected Lyman-alpha Blobs: An Extreme Dusty Population at High-z
12488 Mattia Negrello, Open University SNAPshot observations of gravitational lens systems discovered via wide-field Herschel imaging
12515 Dougal Mackey, Australian National University Probing the outer limits of a galactic halo - deep imaging of exceptionally remote globular clusters in M31
12525 William C. Keel, University of Alabama Giant Ionized Clouds Around Local AGN - Obscuration and History
12528 Philip Massey, Lowell Observatory Probing the Nature of LBVs in M31 and M33: Blasts from the Past
12533 Crystal Martin, University of California - Santa Barbara Escape of Lyman-Alpha Photons from Dusty Starbursts
12550 Daniel Apai, University of Arizona Physics and Chemistry of Condensate Clouds across the L/T Transition - A SNAP Spectral Mapping Survey
12553 Johan P. U. Fynbo, University of Copenhagen, Niels Bohr Institute Detecting the stellar continuum of the galaxy counterparts of three z>2 Damped Lyman-alpha Absorbers
12568 Matthew A. Malkan, University of California - Los Angeles WFC3 Infrared Spectroscopic Parallel Survey WISP: A Survey of Star Formation Across Cosmic Time
12569 Sylvain Veilleux, University of Maryland Ionized and Neutral Outflows in the QUEST QSOs
12570 Sylvain Veilleux, University of Maryland Deep FUV Imaging of Cool Cores in Galaxy Clusters
12571 Peter Lundqvist, Stockholm University The Crab Halo
12590 Casey Papovich, Texas A & M Research Foundation Galaxy Assembly at High Densities: HST Dissection of a Cluster at z=1.62
12594 Edmund Nelan, Space Telescope Science Institute The White Dwarf Mass-Radius Relation Based on Dynamical Masses: STIS Observations of Close Double Degenerates
12601 Laurent Lamy, Observatoire de Paris - Section de Meudon HST STIS/ACS observations of the aurorae of Uranus during active solar wind conditions
12616 Linhua Jiang, Arizona State University Near-IR Imaging of the Most Distant Spectroscopically-Confirmed Galaxies in the Subaru Deep Field
12746 Albert Kong, National Tsing Hua University Close binary populations in metal-rich globular clusters

Selected highlights

GO 12275: Measuring gas flow rates in the Milky Way


A map of the high velocity cloud systems surrounding the Milky Way (B. Wakker, U. Wisconsin).
The stellar components of the Milky Way Galaxy are well known: the disk, the central bulge and the old, metal-poor stellar halo. However, the Milky Way is also surrounded by a halo of hot, gas that is itself embedded within a much more tenuous corona of even hotter, ionised gas. Within that structure lie high velocity clouds. Originally discovered in the 1930s as absorption features in stellar spectra, these clouds have velocities that differ significantly from the rotational velocity along that line of sight, and they are generally believed to be undergoing infall into the Galaxy. The origin and nature of these systems remains uncertain, with some favouring a Galactic origin, driven by star formation and feedback between disk and halo, and others supporting their origin within the warm-hot intergalactic medium. HVCs are not self luminous, so indirect methods need to be applied to examine their characteristics. The most effective is to identify stars that lie behind individual systems and, as with their discovery in the 1930s, search the stellar spectra for signature absorption lines produced by material within the cloud. Many, indeed most, of the key absorption features lie at ultraviolet wavelengths, a spectral region that has been opened up with the installation of the Cosmic Origins Spectrograph on HST. Detailed information is currently available for only five HVCs. The present program is using active galactic nuclei (AGNs) as background light sources to probe most of the remaining known HVCs within the Milky Way.

GO 12283: WISP - A Survey of Star Formation Across Cosmic Time


A region of massive star formation
Star formation is the key astrophysical process in determining the overall evolution of galactic systems, the generation of heavy elements, and the overall enrichment of interstellar and intergalactic material. Tracing the overall evolution through a wide redshift range is crucial to understanding how gas and stars evolved to form the galaxies that we see around us now. The present program builds on the ability of HST to carry out parallel observations, using more than one instrument. While the Cosmic Origins Spectrograph is focused on obtaining ultraviolet spectra of unparalleled signal-to-noise, this program uses the near-infrared grisms mounted on the Wide-Field Camera 3 infrared channel to obtain low resolution spectra between 1 and 1.6 microns of randomly-selected nearby fields. The goal is to search for emission lines characteristic of star-forming regions. In particular, these observations are capable of detecting Lyman-alpha emission generated by star formation at redshifts z > 5.6. A total of up to 40 "deep" (4-5 orbit) and 20 "shallow" (2-3 orbit) fields will be targeted in the course of this observing campaign.

GO 12571: The Crab halo


The Crab Nebula
Messier 1, the Crab Nebula, represents one of astronomy's iconic images. The remnant of a bright supernova observed in 1054 by Arabian and Chinese astronomers, the Crab was first recorded in 1731 by the English astronomer, John Bevis, thirt-seven years before Messier compiled his catalogue of non-comets. The energy source for the gaseous emission is the neutron star that lies in the centre of nebulosity, and was one of the first pulsars to be identified. The Crab is also a source of high energy emission, including radiation at X-ray and gamma ray wavelengths. Overall, this system plays a crucial role in aiding our understanding of post-supernova evolutionary processes. However, there are still some notable undertainties in the detailed processes within even this system. As an example, the observed total mass contained within the pulsar and the surrounding nebula is only about half that expected based on theoretical models for the progenitor mass, and the total energy currently measured is only a few percent of that predicted by supernova models. One means of explaining the discrepancy would be the presence of a substantial halo of high velocity, hot gas enveloping the system. The present HST program aims to test this hypothesis through using the Cosmic Origins Spectrograph to measure the profile of the C IV 1550 Angstrom line, and use those data to constrain the presence of a fast-moving gaseous shell surrounding the system.

GO 12601: HST STIS/ACS observations of the aurorae of Uranus during active solar wind conditions


Nicmos image of aurorae on Uranus
The atmospheres of the gas giant planets in the solar system are dynamic entities that can exhibit dramatic changes over a variety of timescales. In addition to changes within the atmospheres themselves, due the formation and dissipation of storms, these systems can exhibit auroral activity. Planetary aurorae are stimulated by the influx of charged particles from the Sun, which travel along magnetic field lines and funnel into the atmosphere near the magnetic poles. Aurorae therefore require that a planet has both a substantial atmosphere and a magnetic field. Aururae are common phenomena on Earth, sometimes visible at magnetic latitudes more than 40 degrees from the pole, and have also been seen on Jupiter, Saturn, Uranus and Neptune. Indeed, the Jovian and Saturnian aurorae were the target of a concentrated HST imaging campaign during the 2007 International Heliophysical Year (see Program GO 10862 ). The Uranian aurorae are less intense, and were first detected by Voyager 2 during its flyby in 1986. At that time, Uranus was oriented almost pole-on to Earth, allowing observations of only one hemisphere. Now, 25 years later, Uranus has completed more than a quarter of its 84-year-period orbit, and passed through the equator-on ring plane crossing in May-August of 2007 (see Program GO 10870 ). . As a result, we now have clear access to both the northern and southern polar regions. The present program aims to take advantage of this access to monitor auroral activity by using the ACS Solar Blind Camera to image Uranus at ultraviolet wavelenths, and use STIS to obtain FUV spectra that will cover emission by hydrogen Lyman alpha and by molecular hydrogen in the Lyman bands.

Past weeks:
page by Neill Reid, updated 10/11/2011