N ov 2 00 5 Early Cosmic Chemical Evolution : Relating the Origin of a Diffuse Intergalactic Medium and the First Long - Lived Stars

Nucleosynthetic signatures in common between the gas responsible for the high redshift Lyman α forest and a subsample of extremely metal poor stars are found. A simple mass loss model of chemical evolution with physically motivated parameters provides a consistent picture in which the gas is identified with that lost by supernova-driven winds during the first generation of star formation. Substantial mass loss occurs which can account for a diffuse IGM with up to 80% of the total baryon content and a peak [C-O/H] abundance of ∼ −2.9. This mass loss component differs from one produced later during galaxy formation and evolution that contributes to a circum-galactic medium (CGM). The CGM was shown earlier to have a mass of ∼ 10% of all baryons and peak [Fe/H]∼ −1.