ON THE GALACTIC EVOLUTION OF D AND HE-3

The determined abundances of primordial He-4 and Li-7 provide a basis with which to test the standard model of big bang nucleosynthesis in c onjunction with the other two light-element isotopes D and He-3, also produced in the big bang. Overall, consistency in the standard big ban g nucleosynthesis model is best achieved for a baryon-to-photon ratio of typically 3 x 10(-10) for which the primordial value of D is 5 time s greater than the present observed abundance and about 3 times greate r than the presolar value. We consider various models for the chemical evolution of the Galaxy to test the feasibility for the destruction o f D without the overproduction of He-3 and overall metallicity. Models which are capable of achieving this goal include ones with a star for mation rate proportional to the gas mass fraction or an exponentially decreasing star formation rate. We discuss the effect of parameters th at govern the initial mass function and of surviving fractions of He-3 in stars between one and three solar masses.