0 Assigned ID: 3164 ----- Attempting Submission 1 (Fri Mar 25 08:30:51 GMT 2022) ----- We propose to develop a new framework for measuring the absolute ages of globular clusters (GCs) and apply it to 7 metal-poor Milky Way (MW) GCs that have deep archival HST imaging. Preliminary calculations indicate that our new analysis techniques will lead to a factor of two reduction in the uncertainty of the ages of the oldest GCs. We will use the results of our analysis to (i) provide novel constraints on the stellar physics of metal-poor stars; (ii) examine the absolute ages of GCs and ultra-faint dwarf galaxies relative to cosmic reionization; and (iii) set a robust, cosmology-independent lower limit on the age of the Universe. The absolute ages of GCs anchor our understanding in a variety of contexts, from the chronology of the MW's formation to the connection between conditions in the interstellar medium and star cluster formation. While uncertainties in absolute ages have been relatively large (~1.5 Gyr or more), recent advances have provided an opportunity to significantly reduce these uncertainties. This will sharpen our view of the formation of star clusters and their connections to open questions in cosmology and galaxy formation. Using a Monte Carlo approach, we will create >10^5 isochrones that sample all relevant stellar physics uncertainties. We will fit the stellar models to the main sequence turnoff (MSTO) region of HST color-magnitude diagrams of 7 clusters. We will measure each cluster's absolute age, marginalized over all uncertainties in other parameters, and quantify how much each parameter contributes to each GC's age uncertainty. We will make all data and analysis products, including new stellar models, available to the community. Dr. Brian Chaboyer has extensive expertise in the creation of stellar evolution models and isochrones and pioneered the use of Monte Carlo techniques to estimate the uncertainty in ages of globular clusters. Dr. Chaboyer is the co-creator of the Dartmouth Stellar Evolution database (2007; 2008), which has been used extensively since its publication (over 1600 citations). Mr. Ying and Mr. Boudreaux are graduate students working with Dr. Chaboyer and have extensive experience with the Dartmouth stellar evolution code. Dr. Dan Weisz is an expert in resolved stellar populations, near field cosmology and the local distance scale. Dr. Michael Boylan-Kolchin is an expert in galaxy formation theory and its interface with cosmology. Drs. Boyian-Kolchin and Weisz have studied how precise stellar ages can be used to constrain cosmology models, including models of early dark energy. Stellar Populations and the Interstellar Medium Stellar Physics and Stellar Types 0 Regular false false false true false false SUPPORTED