The 21-cm forest as a simultaneous probe of dark matter and cosmic heating history

TL;DR

This paper proposes using the 21-cm forest's one-dimensional power spectrum as a novel method to simultaneously constrain dark matter properties and cosmic heating history during the epoch of reionization, enhancing observational feasibility.

Contribution

It introduces a new approach to break degeneracies between dark matter models and heating effects using the 21-cm forest power spectrum, enabling simultaneous constraints.

Findings

The method can distinguish between different dark matter particle masses.

It enhances sensitivity to the Universe's heating history.

Potential for upcoming SKA observations to constrain early Universe properties.

Abstract

The absorption features in spectra of high-redshift background radio sources, caused by hyperfine structure lines of hydrogen atoms in the intervening structures, are known collectively as the 21-cm forest. They provide a unique probe of small-scale structures during the epoch of reionization, and can be used to constrain the properties of the dark matter (DM) thought to govern small-scale structure formation. However, the signals are easily suppressed by heating processes that are degenerate with a warm DM model. Here we propose a probe of both the DM particle mass and the heating history of the Universe, using the one-dimensional power spectrum of the 21-cm forest. The one-dimensional power spectrum measurement not only breaks the DM model degeneracy but also increases the sensitivity, making the probe actually feasible. Making 21-cm forest observations with the upcoming Square Kilometre Array has the potential to simultaneously determine both the DM particle mass and the heating level in the early Universe, shedding light on the nature of DM and the first galaxies.