Thinking outside the halo: tracing the large-scale distribution of diffuse cosmic metals with semi-analytic models

With the installation of the Cosmic Origins Spectrograph on the Hubble Space Telescope, measurements of the metal content of the low redshift intergalactic medium (IGM) are now available. Using a new grid-based model for diffuse gas coupled to the SAGE semi-analytic model of galaxy formation, we examine the impact of supernova feedback on the pollution of the IGM. We consider different assumptions for the reheating and ejection of gas by supernovae and their dependence on galaxy circular velocity and gas surface density. Where metals are present, we find the most likely metallicity to be −1.5<log10(Z/Z⊙)<−1.0 at z=0, consistent with both observations and more sophisticated hydrodynamic simulations. Our model predicts that the regions of the IGM with the highest metallicities will be near galaxies with M⋆∼1010.5h−1M⊙ and in environments of densities ∼10× the mean. We also find that 90% of IGM metals at z=0 are ejected by galaxies with stellar masses less than 1010.33h−1M⊙