Mass, metal, and energy feedback in cosmological simulations

Abstract

Using GADGET-2 cosmological hydrodynamic simulations including an observationally constrained model for galactic outflows, we investigate how feedback from star formation distributes mass, metals, and energy on cosmic scales from z = 6 0. We include instantaneous enrichment from Type II supernovae (SNe), as well as delayed enrichment from Type Ia SNe and stellar [asymptotic giant branch (AGB)] mass loss, and we individually track carbon, oxygen, silicon and iron using the latest yields. Following on the success of the momentum-driven wind scalings, we improve our implementation by using an on-the-fly galaxy finder to derive wind properties based on host galaxy masses. By tracking wind particles in a suite of simulations, we find: (1) wind material re-accretes on to a galaxy (usually the same one it left) on a recycling time-scale that varies inversely with galaxy mass (e.g. <1 Gyr for L * galaxies at z = 0). Hence, metals driven into the intergalactic medium by galactic superwinds cannot be assumed to leave their galaxy forever. Wind material is typically recycled several times; the median number of ejections for a given wind particle is 3, so by z = 0 the total mass ejected in winds exceeds 0.5 b .