This week on HST

HST Programs: December 3 - December 9, 2007

Program Number Principal Investigator Program Title Links
10787 Jane Charlton, The Pennsylvania State University Modes of Star Formation and Nuclear Activity in an Early Universe Laboratory Abstract
10798 Leon Koopmans, Kapteyn Astronomical Institute Dark Halos and Substructure from Arcs & Einstein Rings Abstract
10815 Thomas M. Brown, Space Telescope Science Institute The Blue Hook Populations of Massive Globular Clusters Abstract
10829 Paul Martini, The Ohio State University Secular Evolution at the End of the Hubble Sequence Abstract
10889 Roelof de Jong, Space Telescope Science Institute The Nature of the Halos and Thick Disks of Spiral Galaxies Abstract
10890 Arjun Dey, National Optical Astronomy Observatories Morphologies of the Most Extreme High-Redshift Mid-IR-Luminous Galaxies Abstract
10907 Scott F. Anderson, University of Washington New Sightlines for the Study of Intergalactic Helium: A Dozen High-Confidence, UV-Bright Quasars from SDSS/GALEX Abstract
10915 Julianne Dalcanton, University of Washington ACS Nearby Galaxy Survey Abstract
11002 Peter Eisenhardt, Jet Propulsion Laboratory A Census of LIRGs in Clusters of Galaxies in the First Half of the Universe from the IRAC Shallow Survey Abstract
11080 Daniela Calzetti, University of Massachusetts Exploring the Scaling Laws of Star Formation Abstract
11082 Christopher Conselice, Univ. of Nottingham NICMOS Imaging of GOODS: Probing the Evolution of the Earliest Massive Galaxies, Galaxies Beyond Reionization, and the High Redshift Obscured Universe Abstract
11084 Dan Zucker, Institute of Astronomy, Cambridge Probing the Least Luminous Galaxies in the Local Universe Abstract
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11122 Bruce Balick, University of Washington Expanding PNe: Distances and Hydro Models Abstract
11124 David V. Bowen, Princeton University The Origin of QSO Absorption Lines from QSOs Abstract
11128 David Bradley Fisher, University of Texas at Austin Time Scales Of Bulge Formation In Nearby Galaxies Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11142 Lin Yan, California Institute of Technology Revealing the Physical Nature of Infrared Luminous Galaxies at 0.3 Abstract
11157 Joseph H. Rhee, University of California - Los Angeles NICMOS Imaging Survey of Dusty Debris Around Nearby Stars Across the Stellar Mass Spectrum Abstract
11169 Michael E. Brown, California Institute of Technology Collisions in the Kuiper belt Abstract
11178 William M. Grundy, Lowell Observatory Probing Solar System History with Orbits, Masses, and Colors of Transneptunian Binaries Abstract
11197 Peter Garnavich, University of Notre Dame Sweeping Away the Dust: Reliable Dark Energy with an Infrared Hubble Diagram 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
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11309 Jacob L. Bean, University of Texas at Austin Chemical Composition of an Exo-Neptune Abstract
11312 Graham Smith, University of Birmingham The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2 Abstract
11361 Keith Noll, Space Telescope Science Institute Hubble Heritage Observations of Mars at 2007 Opposition Abstract

Some selected highlights

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

GO 11312: The Local Cluster Substructure Survey (LoCuSS): Deep Strong Lensing Observations with WFPC2

Combined optical and X-ray (Chandra) image of a lensing galaxy cluster Gravitational lensing supplies a powerful method of tracing the mass distribution in galaxy clusters; at the same time, the amplified the light from background galaxies provides a means of probing the early stages of galaxy formation. These measurements are particularly effective when X-ray imaging data are also available, allowing direct measurement of the mass density and distribution of the hot intracluster medium. This snapshot proposal aims to use the Wide Field Camera on ACS to observe the central regions of low redshift (0.15 < z < 0.3) clusters with the requisite Chandra observations. The HST images will allow the resolution of lensed arcs in the cluster cores (due to strong lensing) and characterisation of weak-lensing distortions of the image profiles of faint background galaxies. The frequency and detailed distribution (size, multiplicity, redshifts) of the strong lens systems sets strong constraints on the total mass content, and its structure, in the central regions of low-redshift clusters. Those results, in turn, constrain cluster evolution, and offer insight into likely schemes for studying dark energy at higher redshifts.

GO 11361: Hubble Heritage Observations of Mars at 2007 Opposition

HST images of Mars oppositions over the last decade Mars lies at an average distance of 228 million kilometres, or 1.52 AU, from the Sun, and has an orbital period of 687 days. As a result, it comes into opposition with Earth (i.e. the Sun, Earth and Mars lie along a straight line) once every 780 days, or approximately every 2 years. At that time, Mars makes its closest approach, but the actual distance varies significantly from opposition to opposition since the Martian orbit has significant eccentricity (e=0.093, as compared with e=0.007 for Earth). HST has been systematically observing Mars at opposition since February 1995, 15 months after WFPC2 was installed in Servicing Mission 1. At that time, the planet lay at a distance of 101 million kilometres from Earth and subtended a diameter less than 14 arcseconds. Succeeding oppositions were at increasingly smaller separations, until the opposition of August 28 2003, when Mars was only 55.8 million miles away with an angular diameter of 25.1 arcseconds, its closest approach since 57,617 BCE (but we won't have to wait quite so long - Mars passes even closer on August 28 2287). As in past years, HST will take a series of images of Mars as it approaches opposition, which, this year, will be at 19:47 UT (2:47 pm EST) on Christmas Eve. At that time, Mars will lie at a distance of 88.2 million kilometres with a diameter of 15.2 arcseconds.

Past weeks:
page by Neill Reid, updated 7/11/2007