0 Assigned ID: 1399 ----- Attempting Submission 1 (Fri Mar 01 04:46:24 GMT 2013) ----- HST Phase I Proposal 1399 (cstars_apt) successfully submitted. ----- Attempting Submission 3 (Fri Mar 01 19:29:18 GMT 2013) ----- HST Phase I Proposal 1399 (cstars_apt) successfully submitted. ----- Attempting Submission 4 (Sat Mar 02 00:12:55 GMT 2013) ----- Intermediate age stellar populations dominate the light from high-redshift galaxies. Many of the stars in this age range end their lives as carbon-rich asymptotic giant branch stars (carbon stars), a luminous but poorly constrained stage of stellar evolution. Population synthesis codes currently depend on models of carbon star evolution, which have been calibrated over a limited range of parameters. Carbon stars may account for up to 40% of the bolometric luminosity in high-redshift galaxies and recent studies have shown that the uncertainty in the contribution of carbon stars to integrated galaxy light can cause galactic mass and age estimates to change by a factor of 2. Here we propose to significantly improve this calibration over a much larger range of galactic environments by performing an archival HST study of the resolved carbon star populations throughout the nearby Universe (within ~4 Mpc). Carbon stars are relatively easily identified in color-magnitude diagrams, allowing us to determine their luminosity and relative number densities. We have identified a sample of 40 galaxies with sufficiently deep HST photometry to determine accurate star formation histories and compare the properties of the carbon stars to the properties (e.g., age, metallicity, star formation rate) of the underlying populations. Our study will result in an empirical calibration of carbon stars that can be used to place much needed constraints on stellar evolution models and thereby improve our understanding of galaxy evolution. RESOLVED STELLAR POPULATIONS 12 Medium false false 0.0 0.0 false false false SUPPORTED