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

The presence of metals in hot cluster gas and in Ly-alpha absorbers, as wellas the mass-metallicity relation of observed galaxies, suggest that galaxieslose a significant fraction of their metals to the intergalactic medium (IGM).Theoretical studies of this process have concentrated on metal removal bydynamical processes or supernova-driven winds. Here, we investigate theenrichment of the IGM by the expulsion of dust grains from galaxies byradiation pressure. We use already completed cosmological simulations, to whichwe add dust assuming that most dust can reach the equilibrium point betweenradiation pressure and gravitational forces. We find that the expulsion of dustand its subsequent (partial) destruction in the IGM can plausibly account forthe observed level of C and Si enrichment of the z=3 IGM. At low-z, dustejection and destruction could explain a substantial fraction of the metals inclusters, but it cannot account for all of the chemical species observed. Dustexpelled by radiation pressure could give clusters a visual opacity of up to0.2-0.5 mag in their central regions even after destruction by the hotintracluster medium; this value is interestingly close to limits and claimedobservations of cluster extinction. We also comment on the implications of ourresults for the opacity of the general IGM. Finally, we suggest a possible`hybrid' scenario in which winds expel gas and dust into galaxy halos butradiation pressure distributes the dust uniformly through the IGM.Comment: 5 emulateapj pages including 3 figures. Accepted by ApJ Letter