10673( 1) - 04/05/05 12:30 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 10673 Version: 1 Check-in Date: 05-Apr-2005 16:30:24 1.Proposal Title: A Reevaluation of the Cepheid Distance Scale from a Homogeneous Analysis of 22 Galaxies Observed with WFPC2 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle 4. Parallel Pointing Tolerance AR 14 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Dr. Douglas C. Leonard California Institute of Technology CoI: Dr. Nial R. Tanvir University of Hertfordshire N CoI: Dr. Shashi Kanbur University of Massachusetts N ------------------------------------------------------------------------------------ 6. Abstract 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. ------------------------------------------------------------------------------------ 10673( 1) - 04/05/05 12:30 - [ 2] Summary Form for Proposal 10673 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category AR ------------------------------------------------------------------------------------------------------------------------------------