The extent of intergalactic metal enrichment from galactic winds during the Cosmic Dawn

Abstract

ABSTRACT One of the key processes driving galaxy evolution during the Cosmic Dawn is supernova feedback. This likely helps regulate star formation inside of galaxies, but it can also drive winds that influence the large-scale intergalactic medium. Here, we present a simple semi-analytic model of supernova-driven galactic winds and explore the contributions of different phases of galaxy evolution to cosmic metal enrichment in the high-redshift (z ≳ 6) Universe. We show that models calibrated to the observed galaxy luminosity function at z ∼ 6–8 have filling factors $\sim 1{{\%}}$ at z ∼ 6 and $\sim 0.1{{\%}}$ at z ∼ 12, with different star formation prescriptions providing about an order of magnitude uncertainty. Despite the small fraction of space filled by winds, these scenarios predict an upper limit to the abundance of metal-line absorbers in quasar spectra at $z \gtrsim 5$ which is comfortably above that currently observed. We also consider enrichment through winds driven by Pop III star formation in minihalos. We find that these can dominate the total filling factor at $z \gtrsim 10$ and even compete with winds from normal galaxies at z ∼ 6, at least in terms of the total enriched volume. But these regions have much lower overall metallicities, because each one is generated by a small burst of star formation. Finally, we show that Compton cooling of these supernova-driven winds at $z \gtrsim 6$ has only a small effect on the cosmic microwave background.