Rapid onset of the 21-cm signal suggests a preferred mass range for dark matter particle

TL;DR

The paper uses the recent 21-cm signal detection to constrain dark matter particle masses, finding a preferred range that challenges cold dark matter models and supports warm dark matter scenarios.

Contribution

It introduces a novel method to set both lower and upper bounds on dark matter particle mass using the 21-cm signal, specifically applying it to a warm dark matter model.

Findings

Warm dark matter particle mass is constrained to about 7.3 keV.

Cold dark matter cannot reproduce the observed 21-cm signal.

Results provide bounds for fuzzy dark matter and sterile neutrino models.

Abstract

We are approaching a new era to probe the 21-cm neutral hydrogen signal from the period of cosmic dawn. This signal offers a unique window to the virgin Universe, e.g., to study dark matter models with different small-scale behaviours. The EDGES collaboration has recently published the first results of the global 21-cm spectrum. We demonstrate that such a signal can be used to set, unlike most observations concerning dark matter, both lower and upper limits for the mass of dark matter particles. We study the 21-cm signal resulting from a simple warm dark matter model with a sharp-$k$ window function calibrated for high redshifts. We tie the PopIII star formation to Lyman-alpha and radio background production. Using MCMC to sample the parameter space we find that to match the EDGES signal, a warm dark matter particle must have a mass of $7.3^{+1.6}_{-3.3}$ keV at 68\% confidence interval. This translates to $2.2^{+1.4}_{-1.7} \times 10^{-20}$ eV for fuzzy dark matter and $63^{+19}_{-35}$ keV for Dodelson-Widrow sterile neutrinos. Cold dark matter is unable to reproduce the signal due to its slow structure growth.