Computer Simulations of Cosmic Reionization

TL;DR

This paper reviews the observational constraints and physical processes involved in cosmic reionization, emphasizing advances in computer simulations that model the ionization of intergalactic gas by early cosmic sources.

Contribution

It provides a comprehensive overview of recent progress in numerical modeling of cosmic reionization, highlighting the convergence towards a general understanding and remaining challenges.

Findings

Significant progress in radiative transfer simulations

Converged models of the reionization process

Remaining unsolved problems in numerical cosmology

Abstract

The cosmic reionization of hydrogen was the last major phase transition in the evolution of the universe, which drastically changed the ionization and thermal conditions in the cosmic gas. To the best of our knowledge today, this process was driven by the ultra-violet radiation from young, star-forming galaxies and from first quasars. We review the current observational constraints on cosmic reionization, as well as the dominant physical effects that control the ionization of intergalactic gas. We then focus on numerical modeling of this process with computer simulations. Over the past decade, significant progress has been made in solving the radiative transfer of ionizing photons from many sources through the highly inhomogeneous distribution of cosmic gas in the expanding universe. With modern simulations, we have finally converged on a general picture for the reionization process, but many unsolved problems still remain in this young and exciting field of numerical cosmology.