This week on HST

HST Programs: January 29 - February 4, 2007

HST plans to resume science observations with NICMOS and WFPC2. Observations are scheduled to start on February 3.

Program Number Principal Investigator Program Title Links
10792 Matthias Dietrich, The Ohio State University Research Foundation Quasars at Redshift z=6 and Early Star Formation History Abstract
10802 Adam Riess, Space Telescope Science Institute SHOES-Supernovae, HO, for the Equation of State of Dark energy Abstract
10822 Reginald Dufour, Rice University CIII] Imagery of Planetary Nebulae Abstract
10927 Wei-Chun Jao, Georgia State University The Weight-Watcher Program for Subdwarfs Abstract
10929 Todd Henry, Georgia State University Research Foundation Calibrating the Mass-Luminosity Relation at the End of the Main Sequence Abstract

Some selected highlights

GO 10802: SHOES-Supernovae, HO, for the Equation of State of Dark energy

WFPC2 image of NGC 4639, one of the spirals targeted in this program The cosmic distance scale and dark energy are two key issues in modern astrophysics, and HST has played a vital role in probing both. On the one hand, HST has been involved in cosmic distance measurements since its inception, largely through the H0 Key Project, which used WFPC2 to identify and photometer Cepheids in 31 spiral galaxies at distances from 60 to 400 Mpc. On the other, HST is the prime instrument for investigating cosmic acceleration by searching for and following Type Ia supernovae at moderate and high redshift. These two cosmological parameters are directly related, and recent years have seen renewed interest in improving the accuracy of H0 with the realization that such measurements, when coupled with the improved constraints from the Cosmic Microwave Background, provide important constraints on cosmic acceleration and the nature of Dark Energy. The present HST program was designed to combine observations that tackle both questions. The recent failure of the ACS Wide-Field Camera means that it will no longer be possible to search for new high-redshift supernovae. However, NICMOS is satill available to observe known Cepheids in several Key Project spirals that have hosted Type Ia supernovae. The near-infrared data will provide more accurate distance estimates for those galaxies, tying together the Cepheid and SN Ia distance scales.

GO 10822: CIII] Imagery of Planetary Nebulae

NGC 2392 - the Eskimo nebula Planetary nebulae are celestial gravestones, marking the deaths of intermediate mass stars. Those stars have ascended the first giant branch; ignited helium and either settled onto either the horizontal branch or red clump, or traversed Cepheid tracks; initiated double shell-burning along the asymptotic giant branch and developed the pulsations that characterise red giant variables, such as Miras. Those pulsations culminate in the ejection of the outer atmosphere and the formation of a planetary nebula, illuminated by the rapidly cooling proto-white dwarf that is the stellar core. Planetary nebulae provide important information on how stars return processed material to the interstellar medium. The aim of the present proposal is to use WFPC2 to image several planetaries in a narrow passband that includes the 1909 Angstrom emission line due to forbidden C III. Comparing these observations with [O III] 5007 data will provide an additional means of probing the C/O abundance ratio in these objects.

Past weeks:
page by Neill Reid, updated 28/1/2007