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 nucleosynthesis (BBN) and recent observations of these two isotopes suggest the need to develop new chemical evolution models. In particular, we examine 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, the age-metallicity relation, and the present-day mass function. We also examine in detail the ability of the chemical evolution models discussed 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 time allowing for a large primordial D/H ratio as is reportedly measured in some quasar absorption systems at high z, without the overproduction of heavy elements. The latter constraint is achieved by employing a simple dynamical model for a galactic wind.