Metal enrichment of the intergalactic medium

Abstract

I demonstrate by means of high-resolution cosmological simulations, which include modelling of a two-phase interstellar medium, that the dominant mechanism for transporting heavy elements from protogalaxies into the intergalactic medium (IGM) is the merger mechanism as discovered by Gnedin & Ostriker. Direct ejection of the interstellar gas by supernovae plays only a minor role in transporting metals into the IGM: for a realistic cosmological scenario only a small fraction of all metals in the IGM is delivered by the supernova-driven winds, while most of the metals in the IGM are transported by the merger mechanism. As a result, the metallicity distribution in the IGM is highly inhomogeneous, in agreement with studies of the QSO metal absorption systems, and the predicted metallicity distribution of Lyman alpha absorbers as a function of their column density is in excellent agreement with the observational data.