THE EFFECTS OF AN EARLY GALACTIC WIND ON THE EVOLUTION OF D, HE-3, AND Z

The predictions of the abundances of D and He-3 from big bang nucleosy nthesis (BBN) and recent observations of these two isotopes suggest th e need to develop new chemical evolution models. In particular, we exa mine the role of an early episode of massive star formation that would induce a strong destruction of D and a galactic wind. We discuss the ability of these models to match the observed local properties of the solar neighborhood such as the gas mass fraction, oxygen abundance, th e age-metallicity relation, and the present-day mass function. We also examine in detail the ability of the chemical evolution models discus sed to reproduce the apparent lack of low-mass, low-metallicity stars in the solar neighborhood, namely the G-dwarf distribution. Indeed, we find models which satisfy the above constraints while at the same tim e allowing for a large primordial D/H ratio as is reportedly measured in some quasar absorption systems at high z, without the overproductio n of heavy elements. The latter constraint is achieved by employing a simple dynamical model for a galactic wind.