Enrichment of the Intergalactic Medium by Radiation Pressure–driven Dust Efflux

Abstract

The presence of metals in hot cluster gas and in Lyα absorbers, as well as the mass-metallicity relation of observed galaxies, suggest that galaxies lose a significant fraction of their metals to the intergalactic medium (IGM). Theoretical studies of this process have concentrated on metal removal by dynamical processes or supernova-driven winds. Here we investigate the enrichment of the IGM by the expulsion of dust grains from galaxies by radiation pressure. We use already completed cosmological simulations to which we add dust, assuming that most dust can reach the equilibrium point between radiation pressure and gravitational forces. We find that the expulsion of dust and its subsequent (partial) destruction in the IGM can plausibly account for the observed level of C and Si enrichment of the z=3 IGM. At low z, dust ejection and destruction could explain a substantial fraction of the metals in clusters, but it cannot account for all of the chemical species observed. Dust expelled by radiation pressure could give clusters a visual opacity of up to 0.2-0.5 mag in their central regions, even after destruction by the hot intracluster medium; this value is interestingly close to limits and claimed observations of cluster extinction. We also comment on the implications of our results for the opacity of the general IGM. Finally, we suggest a possible ``hybrid'' scenario in which winds expel gas and dust into galaxy halos but in which radiation pressure distributes the dust uniformly through the IGM.