Assigned ID: 420 ----- Submission 1 (Fri Jan 21 21:49:42 GMT 2005) ----- One of the most valuable datasets in the HST archive is the collection of repeated images of nearby galaxies obtained in an effort to determine H_0 through the analysis of Cepheid variable stars. With total exposure times of ~18 orbits for each galaxy, the combined frames in V- and I-band are also among the deepest HST images ever obtained of individual galaxies, and represent a largely unexploited wellspring of photometric data for additional investigations. We propose to carry out a homogeneous analysis of all images obtained with the WFPC2 for Cepheid studies, and make available to the community the complete catalog of photometric measurements of all point- and extended-sources detected in the final, processed frames. With 100,000 objects typically detected per target galaxy, the final catalog will contain two-color photometry of over 2 million objects. The scope and accessibility of the catalog will facilitate an array of scientific investigations, including comparative studies of the star formation history and stellar content of spiral galaxies, planetary nebula, OB associations, stellar populations and abundances, supergiant stars, and young stellar clusters. Our own goal with the dataset is to produce a uniform, objective recalibration of the Cepheid distance scale using rigorous, quantitative methods of analysis developed by our group to permit the automated selection of Cepheid candidates from the thousands of objects detected and photometered.

COSMOLOGY 12 160000.00 Budget to be split over two years. false 0.0 false false true false false SUPPORTED