GALACTIC EVOLUTION OF D AND 3 He INCLUDING STELLAR PRODUCTION OF 3 He

New stellar models which track the production and destruction of He (and D) have been evolved for a range of stellar masses (0:65 M=M 100), metallicities (0:01 Z=Z 1) and initial (main sequence) He mass fractions (10 5 X3;MS 10 ). Armed with the He yields from these stellar models we have followed the evolution of D and He using a variety of chemical evolution models with and without infall of primordial or processed material. Production of new He by the lower mass stars overwhelms any reasonable primordial contributions and leads to predicted abundances in the presolar nebula and/or the present interstellar medium in excess of the observationally inferred values. This result, which obtains even for zero primordial D and He, and was anticipated by Rood, Steigman & Tinsley (1976), is insensitive to the choice of chemical evolution model; it is driven by the large He yields from low mass stars. In an attempt to ameliorate this problem we have considered a number of non-standard models in which the yields from low mass stars have been modi ed. Although several of these non-standard models may be consistent with the He data, they may be inconsistent with observations of C/C, O and, most seriously, the super-He rich planetary nebulae (Rood, Bania & Wilson 1992). Even using the most extreme of these non-standard models (Hogan 1995), we obtain a generous upper bound to pre-galactic He: X3P 3:2 10 5 which, nonetheless, leads to a stringent lower bound to the universal density of nucleons.