Cosmological constraints on TeV-scale dark matter subcomponents decaying between recombination and reionisation

TL;DR

This paper investigates how future 21-cm radio observations could better constrain TeV-scale decaying dark matter subcomponents, especially those decaying into neutrinos, by analyzing their effects on cosmological signals like the CMB and 21-cm line.

Contribution

It re-evaluates current CMB constraints and estimates the potential of future 21-cm observations to detect or limit decaying dark matter with lifetimes around 10^15 seconds.

Findings

21-cm signals could be more sensitive than CMB to certain dark matter decays.

Decays into neutrinos produce the strongest effects on cosmological observables.

Sensitivity depends mainly on the total electromagnetic energy injected, especially for very heavy dark matter.

Abstract

The Dark Ages and the Cosmic Dawn are an untapped well of information about the particle physics properties of dark matter, which may become accessible with future radio telescopes able to probe the 21-cm signal from atomic hydrogen. In this work we study the impact on cosmological observables of a dark matter subcomponent composed of TeV-scale particles that decay into electrons, photons or neutrinos with a lifetime shorter than the age of the universe. We re-evaluate constraints from the Cosmic Microwave Background (CMB) on these scenarios using the most recent data sets and estimate the sensitivity of future detections of the global 21-cm signal. Our main result is that the latter is potentially more sensitive to the effects of decaying dark matter with a lifetime $\tau \gtrsim 10^{15} \, \mathrm{s}$. This effect is strongest for the case of decays into neutrinos due to the different spectral distribution of the injected electromagnetic energy. For DM masses well above the TeV-scale, these differences become less pronounced and the sensitivity of both the CMB and the 21-cm signal depend primarily on the total amount of injected electromagnetic energy.