Ionizing radiation from z=4-10 galaxies

TL;DR

This study uses high-resolution cosmological simulations to analyze the escape of ionizing radiation from galaxies between redshifts 4 and 10, revealing high escape fractions at early times and their implications for cosmic reionization.

Contribution

It provides the first detailed simulation-based analysis of ionizing photon escape fractions across a broad galaxy mass range during reionization, including dust effects and evolution over time.

Findings

Escape fraction at z=10.4 is about 80% and decreases over time.

Dust absorption is correlated with metallicity and unlikely to hinder UV output significantly.

Results support reionization driven by low-luminosity dwarf galaxies.

Abstract

We compute the escape of ionizing radiation from galaxies in the redshift interval z=4-10, i.e., during and after the epoch of reionization, using a high-resolution set of galaxies, formed in fully cosmological simulations. The simulations invoke early, energetic feedback, and the galaxies evolve into a realistic population at z=0. Our galaxies cover nearly four orders of magnitude in masses (10^{7.8}-10^{11.5}\msun) and more than five orders in star formation rates (10^{-3.5}-10^{1.7}\msun\yr^{-1}), and we include an approximate treatment of dust absorption. We show that the source-averaged Lyman-limit escape fraction at z=10.4 is close to 80% declining monotonically with time as more massive objects build up at lower redshifts. Although the amount of dust absorption is uncertain to 1-1.5 dex, it is tightly correlated with metallicity; we find that dust is unlikely to significantly impact the observed UV output. These results support reionization by stellar radiation from low-luminosity dwarf galaxies and are also compatible with Lyman continuum observations and theoretical predictions at z\sim3-4.