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. What is not yet clear, however, is what fraction of the
volume needs to be enriched by metals and whether it suffices to enrich only
regions close to galaxies in order to reproduce the observations. We use gas
density fields derived from large cosmological simulations, together with
synthetic quasar spectra and imposed, model metal distributions to investigate
what enrichment patterns can reproduce the observed median optical depth of CIV
as a function of tau_HI. Our models can only satisfy the observational
constraints if the z=3 IGM was primarily enriched by galaxies that reside in
low-mass (m_tot<10^10 M_sun) haloes that can eject metals out to distances
>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.
