The filling factor of intergalactic metals at redshift z=3

Observations of quasar absorption line systems reveal that the z=3 intergalactic medium (IGM) is polluted by heavy elements down to HI optical depths tau_HI 10^2 kpc. Galaxies in more massive haloes cannot possibly account for the observations as they are too rare for their outflows to cover a sufficiently large fraction of the volume. Galaxies need to enrich gas out to distances that are much greater than the virial radii of their host haloes. Assuming the metals to be well mixed on small scales, our modeling requires that the fractions of the simulated volume and baryonic mass that are polluted with metals are, respectively, >10% and >50% in order to match observations.