High-Redshift Galaxy Surveys and the Reionization of the Universe

TL;DR

This paper reviews how star-forming galaxies in the early universe likely drove reionization, analyzing observational data and modeling uncertainties to support their role in providing the necessary ionizing photons.

Contribution

It offers a comprehensive analysis of galaxy contributions to reionization, addressing key uncertainties and demonstrating consistency with observational constraints.

Findings

Galaxies can produce sufficient ionizing photons at z~6-10.

Model uncertainties include escape fraction and luminosity function truncation.

Predicted ionizing emissivity aligns with observational data.

Abstract

Star-forming galaxies in the early universe provide us with perhaps the most natural way of explaining the reionization of the universe. Current observational results are sufficiently comprehensive, as to allow us to approximately calculate how the ionizing radiation from galaxies varies as a function of cosmic time. Important uncertainties in modeling reionization by galaxies revolve around the escape fraction and its luminosity and redshift dependence, a possible truncation of the galaxy luminosity function at the faint end, and an evolution in the production efficiency of Lyman-continuum photons with cosmic time. Despite these uncertainties, plausible choices for these parameters naturally predict a cosmic ionizing emissivity at z~6-10 whose evolution and overall normalization is in excellent agreement with that derived from current observational constraints. This strongly suggests that galaxies provide the necessary photons to reionize the universe.