This week on HST

HST Programs: March 24 - March 30, 2008

Program Number Principal Investigator Program Title Links
10852 Glenn Schneider, University of Arizona Coronagraphic Polarimetry with NICMOS: Dust grain evolution in T Tauri stars Abstract
10899 Matthew A. Malkan, University of California - Los Angeles Identifying z>7 galaxies from J-dropouts Abstract
11014 Albert Kong, Massachusetts Institute of Technology Primordial formation of close binaries in globular clusters with low density cores Abstract
11083 Patrick Cote, Dominion Astrophysical Observatory The Structure, Formation and Evolution of Galactic Cores and Nuclei Abstract
11113 Keith S. Noll, Space Telescope Science Institute Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution Abstract
11120 Daniel Wang, University of Massachusetts A Paschen-Alpha Study of Massive Stars and the ISM in the Galactic Center Abstract
11124 David V. Bowen, Princeton University The Origin of QSO Absorption Lines from QSOs Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11147 Rupali Chandar, Carnegie Institution of Washington The Origin of Diffuse UV Light from Spiral Disks Abstract
11153 Sangeeta Malhotra, Arizona State University The Physical Nature and Age of Lyman Alpha Galaxies Abstract
11161 Alicia M. Soderberg, California Institute of Technology Revealing the Explosion Geometry of Nearby GRB-SNe Abstract
11169 Michael E. Brown, California Institute of Technology Collisions in the Kuiper belt Abstract
11182 Konrad Kuijken, Universiteit Leiden The Mass of the Milky Way: Orbits for Leo I and Leo II: Second Epoch Imaging of Leo II Abstract
11195 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources Abstract
11196 Aaron S. Evans, State University of New York at Stony Brook An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe Abstract
11198 Anthony H. Gonzalez, University of Florida Pure Parallel Imaging in the NDWFS Bootes Field Abstract
11202 Leon Koopmans, Kapteyn Astronomical Institute The Structure of Early-type Galaxies: 0.1-100 Effective Radii Abstract
11210 George Fritz Benedict, University of Texas at Austin The Architecture of Exoplanetary Systems Abstract
11211 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11212 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries Abstract
11213 Gerard T. van Belle, California Institute of Technology Distances to Eclipsing M Dwarf Binaries Abstract
11216 John A. Biretta, Space Telescope Science Institute HST / Chandra Monitoring of a Dramatic Flare in the M87 Jet Abstract
11219 Alessandro Capetti, Osservatorio Astronomico di Torino Active Galactic Nuclei in nearby galaxies: a new view of the origin of the radio-loud radio-quiet dichotomy? Abstract
11220 Jeff Cooke, University of California - Irvine Mapping the FUV Evolution of Type IIn Supernovae Abstract
11300 Stefan Jordan, Astronomisches Rechen-Institut Heidelberg Mass and Radius of a Near-Chandrasekhar-limit magnetic white dwarf Abstract
11301 Ed Nelan, Space Telescope Science Institute /td> Dynamical Masses and Radii of Four White Dwarfs Abstract
11495 Carole A. Haswell, Open University The first direct detection of an extrasolar planetary stratosphere? /td> Abstract

Some selected highlights

GO 11169: Collisons in the Kuiper Belt

Visions of the Kuiper Belt The Kuiper Belt lies beyond the orbit of Neptune, extending from ~30 AU to ~50 AU from the Sun, and includes at least 70,000 objects with diameters exceeding 100 km. Setting aside Pluto, the first trans-Neptunian objects were discovered in the early 1990s. Most are relatively modest in size, with diameters of a few hundred km and photometric properties that suggested an icy composition, similar to Pluto and its main satellite, Charon. Over the last three years, however, a handful of substantially larger bodies have been discovered, with diameters of more than 1000 km; indeed, one object, Eris (2003 UB13), is slightly larger than Pluto (2320 km) and 25% more massive. We know the mass for Eris because it has a much lower mass companion, Dysnomia, which orbits Eris with a period of 16 days (see this recent press release ). Pluto, itself, has three companions: Charon, which is about 1/7th the mass of Pluto, and the much smaller bodies, Hydra and Nix, discovered from HST observations in early 2005. Observations of other Kuiper Belt Objects (KBOs), mainly using HST, reveal that a significant fraction are binary. This may indicate that the Kuiper Belt is a dangerous place to live, with frequent collisions between KBOs, leading to fragmentation and satellite formation. The present program aims to probe this issue through multi-wavelength observations of a substantial number of KBOs, sampling a broad range of properties.

GO 11195: Morphologies of the Most Extreme High-Redshift Mid-IR-luminous Galaxies II: The `Bump' Sources

HST images of interacting ultra-luminous IR galaxies Luminous infrared galaxies (LIRGs) are systems that have total luminosities exceeding 1011.4 LSun, with most of the energy emitted at wavelengths longward of 10 microns. Many (perhaps most) of these galaxies are interacting or merging disk galaxies, with the excess infrared luminosity generated by warm dust associated with the extensive star formation regions. Many systems also exhibit an active nucleus, and may be in the process of evolving towards an S0 or elliptical merger remnant. Until recently, very few candidate such systems were known at high redshifts; consequently, analyses and investigations of their origins had to rely on observations of low- and moderate-redshift analogues. The team leading this HST proposal have used a combination of mid-infrared (24 micron) and near-infrared observations to identify tens of candidates, and Spitzer follow-up spectroscopy has confirmed that many lie at redshifts 2 < z < 2.5. The sources appear to fall into two broad categories: thopse with bright 24-micron fluxes with power-law spectral energy distributions and SiO absorption at mid-IR wavelengths; and "bump" sources, with an SED that peaks near 1.6 microns (rest wavelength) and PAH absorption. The brighter sources were targeted in a Cycle 15 program; the present program uses NICMOS and WFPC2 to obtain high sensitivity, high angular-resolution observations of 22 of the "bymp" systems.

GO 11210: The Architecture of Exoplanetary Systems

Artist's impression of a young planetary system Immanuel Kant is generally credited with first proposing that the planets in the Solar System coalesced from a flat, rotating disk formed by the Solar Nebula. Direct confirmation of that process only came in the early 1990s, when millimetre-wave interferometers were able to detect molecular gas in Keplerian rotation around a handful of nearby young stars. Since then, there have been numerous other observations, including Hubble's images of proplyds (protoplanetary disks) in the Orion Cluster, and Hubble and Spitzer observations of edge-on disks in other young stars. One of the clear selling points of the Solar Nebula disk model is that it appears to offer a natural path to forming planets with coplanar orbits, matching (most of) our observations of the Solar System. On the other hand, as our knowledge of exoplanetary systems has accumulated over the last decade, it has become clear that dynamical interactions may play a very important role in the evolution of these systems. In particular, disk/planet interactions are generally regarded as responsible for the inward migration of gas giants to form hot Jupiters in <3 day period orbits. Planet-planet interactions could lead to significant changes in orbital inclination. Radial velocity planet searches are uncovering more and more multi-planet systems. This program focuses the high precision of HST's astrometric detectors, the Fine Guidance Sensors, on four of those systems. The aim is to complement the existing radial velocity measurements with sub-milliarcsecond precision astrometry, allowing determination of the true orbital paths - specifically, the relative inclination - of the low-mass objects in these systems.

GO 11213: Distances to Eclipsing M Dwarf Binaries

Artist's impression of a cool binary system Eclipsing binaries are stellar systems where the orbital plane lies in the line of sight, leading to the components undergoing mutual eclipses. These systems are extremely powerful probes of stellar properties, since (given the appropriate radial velocity measurements) they permit direct measurement of both stellar masses and radii. Accurate distances can also be derived from these systems. These results are particularly interesting for stars near the bottom of the main sequence, approaching the hydrogen buyrning limit. The present program aims to use the Fine Guidance Sensors on HST to determine sub-milliarcsecond trigonometric parallaxes for five M-dwarf binaries: YY Gem, GU Boo, CM Dra, NSVS0103 and TRES-HER0-R

Past weeks:
page by Neill Reid, updated 21/3/2008