Cosmic Chemical Evolution with an Early Population of Intermediate Mass
  Stars
  We explore the consequences of an early population of intermediate mass stars
in the 2 - 8 M\odot range on cosmic chemical evolution. We discuss the
implications of this population as it pertains to several cosmological and
astrophysical observables. For example, some very metal-poor galactic stars
show large enhancements of carbon, typical of the C-rich ejecta of low-mass
stars but not of supernovae; moreover, halo star carbon and oxygen abundances
show wide scatter, which imply a wide range of star-formation and
nucleosynthetic histories contributed to the first generations of stars. Also,
recent analyses of the 4He abundance in metal-poor extragalactic H II regions
suggest an elevated abundance Yp \simeq 0.256 by mass, higher than the
predicted result from big bang nucleosynthesis assuming the baryon density
determined by WMAP, Yp = 0.249. Although there are large uncertainties in the
observational determination of 4He, this offset may suggest a prompt initial
enrichment of 4He in early metal-poor structures. We also discuss the effect of
intermediate mass stars on global cosmic evolution, the reionization of the
Universe, the density of white dwarfs, as well as SNII and SNIa rates at high
redshift. We also comment on the early astration of D and 7Li. We conclude that
if intermediate mass stars are to be associated with Population III stars,
their relevance is limited (primarily from observed abundance patterns) to low
mass structures involving a limited fraction of the total baryon content of the
Universe.
