Reionization and Cosmic Dawn: theory and simulations

TL;DR

Recent advances in simulations and observations have refined our understanding of cosmic reionization timing, but the nature of early sources remains elusive; upcoming 21-cm observations promise a new era of detailed astrophysical insights.

Contribution

The paper reviews recent progress in modeling and constraining cosmic dawn and reionization, emphasizing the role of simulations and upcoming 21-cm observations.

Findings

Reionization timing constrained to within dz ~ 1.

Current constraints from Planck and high-redshift quasars.

Future 21-cm observations will enable detailed astrophysical insights.

Abstract

We highlight recent progress in the sophistication and diversification of cosmic dawn and reionization simulations. The application of these modeling tools to current observations has allowed us narrow down the timing of reionization, which we now know to within dz ~ 1 for the bulk of reionization. The strongest constraints come from the optical depth to the CMB measured with the {\it Planck} satellite and the first detection of ongoing reionization from the spectra of the z=7.1 QSOs ULASJ1120+0641. However, we still know virtually nothing about the astrophysical sources during the first billion years. The revolution in our understanding will be led by upcoming interferometric observations of the cosmic 21-cm signal. The properties of the sources and sinks of UV and X-ray photons are encoded in the 3D patterns of the signal. The development of Bayesian parameter recovery techniques, which tap into the wealth of the 21-cm signal, will soon usher in an era of precision astrophysical cosmology.