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Поисковые слова: merging galaxies
HST this week: 308


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This week on HST

HST Programs: November 3 - November 9, 2008

HST resumed operations on the side B electronics on the CU/SDF (Command Unit/Science Data Formatter) on 23 October 2008. WFPC2 calibration measurements and on-sky observations restarted on October 25th, and the ACS/SBC was brought on line later that week.

Program Number Principal Investigator Program Title Links
11103 Harald Ebeling, University of Hawaii A Snapshot Survey of The Most Massive Clusters of Galaxies Abstract
11113 Keith S. Noll, Space Telescope Science Institute Binaries in the Kuiper Belt: Probes of Solar System Formation and Evolution Abstract
11130 Luis Ho, Carnegie Institution of Washington AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II Abstract
11151 Gregory J. Herczeg, California Institute of Technology Evaluating the Role of Photoevaporation of Protoplanetary Disk Dispersal Abstract
11158 R. Michael Rich, University of California - Los Angeles HST Imaging of UV emission in Quiescent Early-type Galaxies Abstract
11175 Sandra M. Faber, University of California - Santa Cruz UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence 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
11203 Kevin Luhman, The Pennsylvania State University A Search for Circumstellar Disks and Planetary-Mass Companions around Brown Dwarfs in Taurus Abstract
11212 Filling the Period Gap for Massive Binaries Douglas R. Gies, Georgia State University Research Foundation Abstract
11218 Howard E. Bond, Space Telescope Science Institute Snapshot Survey for Planetary Nebulae in Globular Clusters of the Local Group Abstract
11289 Jean-Paul Kneib, Laboratoire d'Astronomie Spatiale SL2S: The Strong Lensing Legacy Survey Abstract
11681 William B. Sparks, Space Telescope Science Institute A Search for Ultraviolet Emission Filaments in Cool Core Clusters Abstract
11789 George Fritz Benedict, University of Texas at Austin An Astrometric Calibration of Population II Distance Indicators Abstract
11901 Filling the Period Gap for Massive Binaries Douglas R. Gies, Georgia State University Research Foundation Abstract
11945 Asteroseismology of Extrasolar Planet Host Stars Ron Gilliland, Space Telescope Science Institute Abstract

Some selected highlights

GO 11130: AGNs with Intermediate-mass Black Holes: Testing the Black Hole-Bulge Paradigm, Part II

Schematic diagram of an active galactic nucleus Active galaxies are characterised by bright, compact nuclei that are the source of strong emission lines due highly ionised material. These phenomena are generally believed to arise in hot gas in an accretion disk, centred on a massive (>106 solar mass) hole; indeed, detailed kinematics for a handful of objects have confirmed the presence of a compact, massive object in the core. Most active galactic nuclei (AGNs) are found in spiral galaxies that possess at least a moderately prominent bulge. The present aims to determine whether AGNs exist within later-type spirals, with less prominent bulge components. At the same time, the proposers hope to probe the lower mass limit for black hole formation, specifically testing whether significant numbers of intermediate-mass (~105 colar mass) black holes form. To eamine this issue, this proposal targets lower luminosity galaxies, using WFPC2 to obtain I-band (F814W) images of AGNs selected from SDSS spectroscopy. Those images will be used to characterise the nuclear morphology and determine bulge/disk ratios.

GO 11175: UV Imaging to Determine the Location of Residual Star Formation in Galaxies Recently Arrived on the Red Sequence

Galaxy mergers and the red sequence

The overwhelming majority of galaxies are found in clusters. Observations show that almost all well-defined cluster systems at low and moderate redshift have a significant population of elliptical galaxies which have red colours, indicative of old stellar populations and minimal current star formation. The elliptical galaxies outline a distinct sequence in the colour-magnitude (or colour-mass) diagram, the so-called red sequence. Over the last few years, there has been considerable interest in understanding the origins of this sequence: how did the ellipticals form (most theories envisage mergers of gas-rich systems at moderate redshifts)? when did star formation cease in these galaxies (most galaxies in clusters at redshifts 1.5 < z < 3 seem to have active star formation)? are there environmentally-dependent effects? This proposal aims to address some of these questions through WFPC2 BVI and ACS/SBC observations of a number of low-redshift (0.04 < z < 0.10) galaxies that appear to have only recently arrived on the red sequence. The WFPC2 data will provide detailed morphologies, while the SBC ultraviolet imaging will be ued to search for traces of residual star formation.

GO 11196: An Ultraviolet Survey of Luminous Infrared Galaxies in the Local Universe

A NICMOS image of the interacting LIRG, NGC 6090 Luminous infrared galaxies (LIRGs) have total luminosities that exceed 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. These two programs build on a previous ACS survey of 88 systems from the IRAS Revised Bright Galaxy Sample (GO 10592) in the F439W and F814W passbands. Program GO 11196 is using the ACS/SBC and WFPC2 to obtain far- (F140LP) and near- (F218W) UV imaging of 27 galaxies; GO 11235 concentrates on near-infrared H-band NICMOs NIC2 imaging of the galaxy cores. Combined with the previously obtained B- and I-band data, these observations will probe
  • the distribution of star formation activity and the presence of bars and bridges, funneling gas towards active regions
  • the age distribution of star clusters
  • the relationship between star formation and AGN activity
  • correlations between near-infrared emission and the mid-IR structures identified from Spitzer IRAC imaging;
  • the presence of coherent structure, bars or bridges, that might funnel gas into the nuclei;
  • the overall structural properties of the LIRGS as a function of luminosity and environment
The observations will also provide a detailed UV images for a reference sample of nearby galaxies. Observations of several interacting system are scheduled for this week.

GO 11789: An Astrometric Calibration of Population II Distance Indicators

Measuring trigonometric parallax Trigonometric parallax measurement remains the fundamental method of determining distances to astronomical objects. The best ground-based parallax measurements can achieve accuracies of ~1 milliarcsecond, comparable with the typical accuracies achieved by the ESA Hipparcos astrometric satellite. This level of accuracy allows us to obtain reliable distances and luminosities for main sequence stars, subgiants, red giants and even a number of metal poor subdwarfs. However, with an effective distance limit of 100-150 parsecs, the sampling volume includes less than a handful of rarer, shorter-lived celestial objects. In particular, there are no RR Lyraes or Cepheids, two of the principal calibrators in the extragalactic distance scale. There is only one instrument currently available that can achieve astrometry of higher accuracy - the Fine Guidance Sensors (FGS) on HST. The present team used the FGS to measure a parallax of 3.82+/10.2 milliarseconds for RR Lyrae, the nearest star of its type. this corresponds to a distance of 262 parsecs. The present program aims to improve the calibration by extending observations to four more relatively nearby RR Lyraes (XZ Cyg, UV Oct, RZ Cep and SU Dra) and two Pop II Cepheids (Kappa Pav and VY Pyx).
Past weeks:
page by Neill Reid, updated 1/10/2008