Intergalactic heating by Lyman-alpha photons including hyperfine structure corrections

TL;DR

This paper investigates how Lyman-alpha photons influence intergalactic heating during Cosmic Dawn, emphasizing the importance of hyperfine structure corrections and concluding that CMB heating is negligible.

Contribution

It introduces hyperfine structure corrections into models of Lyman-alpha photon interactions affecting intergalactic heating during Cosmic Dawn.

Findings

Hyperfine structure significantly affects hydrogen heating rates.

CMB heating of neutral hydrogen is negligible.

Heating time scales are extremely long, around 10^27 seconds.

Abstract

Lyman-alpha photons from the first radiating sources in the Universe play a pivotal role in 21-cm radio detections of Cosmic Dawn and the Epoch of Reionization. Comments are provided on the effect of the hyperfine structure of hydrogen on the rate of heating or cooling of the Intergalactic Medium. It is shown that heating of the still neutral hydrogen by the Cosmic Microwave Background is negligible, with a characteristic heating time of 1e27 s/ (1+z) at redshift z.