Astrophysics from the 21-cm background

TL;DR

This paper reviews how the 21-cm background reveals early Universe astrophysics, including ionization, heating sources, and the potential of current models to inform about high-redshift cosmic conditions.

Contribution

It provides a comprehensive review of the astrophysical processes encoded in the 21-cm background and explores the sensitivity of signals to various cosmological parameters.

Findings

Global 21-cm signal is sensitive to ionization and heating history.

Power spectrum variations reflect different astrophysical source models.

Current predictions help constrain early Universe conditions.

Abstract

This chapter describes the astrophysics encoded by the 21-cm background. We begin with a brief introduction to the radiative transfer and ionization chemistry relevant to the high-z intergalactic medium. Then, we will provide a review of the most plausible sources of ionization and heating in the early Universe. Finally, we will explore a variety of current 21-cm predictions, and illustrate the sensitivity of the global 21-cm signal and power spectrum to parameters of interest.