HST this week: 105



This week on HST


HST Programs: April 15 - April 21, 2013

Program Number Principal Investigator Program Title
12177 Pieter van Dokkum, Yale University 3D-HST: A Spectroscopic Galaxy Evolution Treasury
12445 Sandra M. Faber, University of California - Santa Cruz Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey -- GOODS-North Field, Late Visits of SNe Search
12468 Keith S. Noll, NASA Goddard Space Flight Center How Fast Did Neptune Migrate? A Search for Cold Red Resonant Binaries
12529 Alicia M. Soderberg, Harvard University What Powers Nature's Most Luminous Supernovae?
12813 Brian Schmidt, Australian National University Network of 13 high precision STIS spectrophotometric standards for ground based surveys
12860 Xiaohui Fan, University of Arizona Detecting Sources of Early IGM Enrichment
12870 Boris T. Gaensicke, The University of Warwick The mass and temperature distribution of accreting white dwarfs
12877 Igor D. Karachentsev, Russian Academy of Sciences, Special Astrophysical Obs. Exposing the Maffei Group
12879 Adam Riess, The Johns Hopkins University A 1% Measurement of the Distance Scale with Perpendicular Spatial Scanning
12899 Danny Steeghs, The University of Warwick Emission line imaging of the bipolar shell in the Helium Nova V445 Puppis
12928 Alaina L. Henry, Oak Ridge Associated Universities Gaseous outflows from low mass galaxies: Understanding local laboratories for high redshift star formation
12929 Judith L. Provencal, University of Delaware COS Observations of Pulsating DB White Dwarfs
12930 Carrie Bridge, California Institute of Technology WISE Discovered Ly-alpha Blobs at High-z: The missing link?
12965 David Ehrenreich, Observatoire de Geneve Properties and dynamics of the upper atmosphere of the hot-Neptune GJ 436b
12970 Michael C. Cushing, University of Toledo Completing the Census of Ultracool Brown Dwarfs in the Solar Neighborhood using HST/WFC3
12972 Christopher R. Gelino, Jet Propulsion Laboratory In Search of the Coldest Atmospheres: Identifying Companions to the Latest WISE Brown Dwarfs
12975 Simon J. Lilly, Eidgenossiche Technische Hochschule (ETH) Do winds transport magnetic fields out of high redshift galaxies?
12990 Adam Muzzin, Sterrewacht Leiden Size Growth at the Top: WFC3 Imaging of Ultra-Massive Galaxies at 1.5 < z < 3
12994 Anthony H. Gonzalez, University of Florida A Lensing Study of IDCS J1426.5+3508: A Massive Galaxy Cluster at z=1.75
12995 Christopher Johns-Krull, Rice University Testing Disk Locking in the Orion Nebula Cluster
13003 Michael D. Gladders, University of Chicago Resolving the Star Formation in Distant Galaxies
13020 Edward F. Guinan, Villanova University A Comprehensive COS Study of the Magnetic Dynamos, Rotations, UV Irradiances and Habitability of dM Stars with a Broad Span of Ages
13022 Edo Berger, Harvard University Staring into the Beasts' Lair: HST Observations of the Host Galaxies of Pan-STARRS Ultra-luminous Supernovae
13024 John S. Mulchaey, Carnegie Institution of Washington A Public Snapshot Survey of Galaxies Associated with O VI and Ne VIII Absorbers
13033 Jason Tumlinson, Space Telescope Science Institute COS-Halos: New FUV Measurements of Baryons and Metals in the Inner Circumgalactic Medium
13036 Richard Mushotzky, University of Maryland Hubble Observations of Kepler-Monitored AGN - GO orbits
13051 Jonathan D. Nichols, University of Leicester Long term observations of Saturn's northern auroras
13057 Kailash C. Sahu, Space Telescope Science Institute Detecting and Measuring the Masses of Isolated Black Holes and Neutron Stars through Astrometric Microlensing

Selected highlights

GO 12177: 3D-HST: A Spectroscopic Galaxy Evolution Treasury


Part of the GOODS/Chandra Deep Field South field, as imaged by HST
One of the exciting new capabilities offered by the post-SM4 Hubble Telescope is multi-object, low-resolution, near-infrared spectroscopy, using the two grisms available on the IR channel of Wide-Field Camera 3. These observations provide an important avenue for complementing wide-field imaging surveys. In particular, the present program aims to build on the extensive database currently being accumulated as part of the CANDELS Multi-Cycle Treasury program. CANDELS, itself, rests on past HST Treasury programs, and will provide multi-tiered imaging of five fields. 3D-HST will supplement portions of four fields (GOODS-south, AEGIS, the UDS and COSMOS fields) with WFC3/G141 and ACS/G800L grism data. The spectroscopic data will provide important additional information on the galaxy redshift distribution, and on the star formation characteristics in the redshift range 1 < z < 3.5. The data should also be useful in identifying quasars at high redshifts, potentially extending beyond z~6.

GO 12468: How Fast Did Neptune Migrate? A Search for Cold Red Resonant Binaries


Preliminary orbital determination for the KBO WW31, based on C. Veillet's analysis of CFHT observations; the linked image shows the improved orbital derivation, following the addition of HST imaging
The Kuiper Belt consists of icy planetoids that orbit the Sun within a broad band stretching from Neptune's orbit (~30 AU) to distance sof ~50 AU from the Sun (see David Jewitt's Kuiper Belt page for details). Over 500 KBOs (or trans-Neptunian objects, TNOs) are currently known out of a population of perhaps 70,000 objects with diameters exceeding 100 km. Approximately 2% of the known TNOs are binary (including Pluto, one of the largest known TNOs, regardless of whether one considers it a planet or not). TNOs are grouped within three broad classes: resonant objects, whose orbits are in mean motion resonance with Neptune, indicating capture; scattered objects, whose current orbits have evolved through gravitational interactions with Neptune or other giant planets; and classical TNOs, which are on low eccentricity orbits beyond Neptune, with no orbital resonance with any giant planet. The latter class are further sub-divided into "hot" and "cold" objects, depending on whether the orbits have high or low inclinations with respect to the ecliptic. Cold, classical TNOs show relatively uniform characteristics, including red colours, high albedos and an extremely high binary fraction (>30%). They are believed to have formed in situ, and were therefore in place to experience the range of gravitational interactions as the giant planets migrated to their present location. As that migration occurred, subsets are expected to have been trapped in transitory resonance orbits. The present proposal aims to use HST to complete a photometric survey of all known resonant TNOs, with the goal of identifying the proportion of cold classical TNOs that have been captured. The relative number of such objects can be used to constrain models for Neptune's orbital migration in the early Solar System.

GO 12929: COS Observations of Pulsating DB White Dwarfs


The surface-temperature map on a pulsating white dwarf (Figure by Mike Montgomery U. Texas group)
White dwarfs are compact, electron-degenerate remnants that represent the final evolutionary stage for stars less massive than ~7 Msun. White dwarfs emerge from planetary nebulae with extremely high surface temperatures, but with no central energy source, they simply cool like a brick. As they cool, the spectral energy distribution and the spectral characteristics evolve with time. Most white dwarfs have thin hydrogen envelopes, and are therefore have strong Balmer-series absorption lines in the optical at temperatuers above ~8,000 degrees (DA white dwarfs). A sizeable minority, however, have helium envelopes, and spetra dominated by helium lines; these are DB white dwarfs. Both DA and DB white dwarfs evolve through regions of atmospheric instability as they cool - instability strips, analagous to those populated by Cepheids and RR Lyraes in the hydrogen-burning regime. White dwarfs undergo non-radial pulsations are high-order gravity modes, driven by opacity variations in the stellar interior. In the case of DB white dwarfs, the region falls near surface temperatures of ~19,000K. Determing accurate effective temperatures is crucial to constraining the models developed for these highly compact objects. The present program aims to use UV spectra obtaiend with' the Cosmic Origins Spectrograph to refine temperatures for 6 pulsating DB white dwarfs.

GO 12965:Properties and dynamics of the upper atmosphere of the hot-Neptune GJ 436b


Artist's impression of the exo-Neptune in orbit around Gliese 436
Gliese 436 is an early-type M dwarf (spectral type M2.5) with a mass approximately 40% that of the Sun lying at a distance of ~10 parsecs. In August 2004, the Lick/Carnegie planet search team (led by Geoff Marcy and Paul Butler) announced the discovery of a ~22 Earth-mass planet in a 2.64 day orbit around this star. Unlike most "hot jupiters", this "hot Neptune", one of the first such objects discovered, is on an elliptical orbit, e=0.16, which, with a semi-major axis of 0.0278 AU, brings it within 3.5 million kilometres of the central star. Gl 436 is significantly cooler than the Sun, with a surface temperature close to ~3400 degrees Kelvin; even so, the "surface" temperatures on Gl 436b are expected to reach ~740 K (~370 C). In May of 2007, a team led by F. Pont demonstrated that Gl 436b transits the parent star. The initial ground-based observations allowed them to derive a diameter approximately 4 times that of Earth, directly comparable with Uranus and Neptune. Follow-up observations with NICMOS and FGS on HST and with IRAC on Spitzer refined the radius measurement to 4.9 Earth radii. This provides key insight into the likely origins of Gl 436b, since combining the diameter with the measured mass gives the mean density, and, by inference, the likely composition. For Gl 436b, the indications are that the planet is a displaced "ice giant". The present program aims to probe the atmospheric structure by using STIS to searching for Lyman alpha absorption that might be the signature of evaporation driven by stellar irradiation.

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