The Deuterium Abundance and Nucleocosmochronology

We examine galactic chemical evolution models which reproduce the present-day and pre-solar values of deuterium starting with a primordial value which is consistent with a baryon-to-photon ratio of $3 imes 10^{-10}$. We consider various galactic chemical evolution models to determine the viability of significant deuterium destruction and which provide a consistent age of the galaxy at the time of the formation of the solar system and consequently its present day age from nuclear chronometers. These models generally require some amount of infall which we take with rates proportional to the gas mass as well as exponentially decreasing rates and some initial disk enrichment which we limit to the range of 0% to 30%. We present those models which give the observed pre-solar value and present-day value of D/H and which lead to a present-day gas fraction of $sigma = .05quad - quad .2$. These models result in a braod range for the age of galaxy between $9.8 - 21.6$ Gyrs.Comment: 16 pages, LateX, Figures available by anonymous ftp from ast1.spa.umn.edu in the directory pub with filename deutfig.ps, UMN-TH-1260/9