This week on HST

HST Programs: November 17 - November 23, 2008

Program Number Principal Investigator Program Title Links
10877 Weidong Li, University of California - Berkeley A Snapshot Survey of the Sites of Recent, Nearby Supernovae Abstract
10880 Henrique Schmitt, Naval Research Laboratiry The host galaxies of QSO2s: AGN feeding and evolution at high luminosities Abstract
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
11201 Nitya Kallivayalil, Harvard University Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images 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
11612 Kris Davidson, University of Minnesota - Twin Cities Eta Carinae's Continuing Instability and Recovery - the 2009 Event Abstract
11704 Brian Chaboyer, Dartmouth College The Ages of Globular Clusters and the Population II Distance Scale Abstract
11901 Douglas R. Gies, Georgia State University Research Foundation Filling the Period Gap for Massive Binaries Abstract
11956 Keith Noll, Space Telescope Science Institute Hubble Heritage Abstract

Some selected highlights

GO 10877: A Snapshot Survey of the Sites of Recent, Nearby Supernovae

A recent supernova in M100 Supernovae mark the (spectacular) evolutionary endpoint for a subset of stellar systems. Standard models predict that they originate from massive stars and (probably) close binaries with a compact (WD, neutron star) component, but there are still some questions remaining over whether we fully understand the range of possible progenitors. The last decade has seen the development of a number of large-scale programs, usually using moderate-sized telescopes, that are dedicated to monitoring (relatively nearby galaxies, searching for new supernovae. This program obtains follow-up images of recent supernovae, concentrating on systems within 20 Mpc of the Milky Way. The observations are taken well after maximum, with the aim of using the high spatial resolution of WFPC2 to identify the fading remnant and perhaps determine its origin.

GO 11201: Systemic and Internal motions of the Magellanic Clouds: Third Epoch Images

The Large Magellanic Cloud (upper left) with the Small Magellanic Cloud (right) and the (foreground) Galactic globular cluster47 Tucanae The Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) are the most massive satellites of the Milky Way galaxy. The orbital motions of these systems can be used to probe the mass distribution of Milky Way, and backtracking the orbits can shed light on how the three systems have interacted, In particular, the well known Magellanic Stream, stretching between the two Clouds, is thought to be a product either of interactions between the Clouds, or of ram-stripping of gas from the LMC on its last passage through the Plane of the Milky Way. The present program builds on observations obtained at two epochs with the now-defunct (but perhaps soon to be revived) ACS High Resolution Camera (ACS/HRC). The previous programs targeted known QSOs lying behind the Clouds; the QSOs serve as fixed reference points for absolute astrometry of the numerous foreground LMC/SMC stars. First epoch observations were made in late 2002 (GO 9462), with the follow-up imaging in late 2004 (GO 10130). The tangential motions of the Clouds amount to only a few milliarcseconds, but the high spatial resolution and high stability of HST imaging makes such measurements possible, even with only a 2-year baseline. Surprisingly, the initial results suggest that the 3-D motions of both clouds are much higher than expected, suggesting either that the LMC/SMC/MW is either dynamically very young, or unbound. The present program will use WFPC2 to obtain third-epoch data in the same fields, providjng a crucial test of the initial results

GO 11704: The Ages of Globular Clusters and the Population II Distance Scale

Hubble Heritage image of the globular cluster, M15 Globular clusters are the oldest structures within the Milky Way that are directly accessible to observation. They are relatively simple systems, with relatively simple colour-magnitude diagrams (albeit with some complexities adduced from recent HST observations, see GO 11233 ). Matching those CMDs against theoretical models allows us to set constraints on the age of the oldest stars in the Galaxy, and hence on the age of the Milky Way and the epoch of galaxy formation. However, the accuracy of those age determinations rest crucially on the accuracy of the cluster distance determinations. The clusters themselves lie at distances of several kpc at best, and tens of kpc at worst; thus, direct trigonometric parallax measurements must await microacrsecond astrometric missions. The classical method of deriving distances is main sequence fitting - using nearby stars, with similar chemical abundances and accurate parallax measurements, to map out the main sequence in absolute units, and then scaling the clusetr data to fit. The problem with this method is that metal-poor subdwarfs are rare, so even Hipparcos was only able to obtain accurate distances to a handful of stars. The present program aims to improve the distance measurements by using the Fine Guidance Sensors on HST to determine sub-millarcsecond trigonometric parallaxes to 9 subdwarfs, almost doubling the sample available for MS fitting.

Past weeks:
page by Neill Reid, updated 1/10/2008