Signatures of clumpy dark matter in the global 21 cm background signal

TL;DR

This paper investigates how self-annihilating dark matter, including neutralinos and light dark matter, affects the 21cm background signal by altering hydrogen and helium ionization and heating, with potential detectable deviations at high redshifts.

Contribution

It provides a detailed analysis of the impact of dark matter annihilation and substructures on the 21cm signal, highlighting the conditions under which these effects could be observed.

Findings

Dark matter annihilation can cause up to ~20 mK deviations in the 21cm signal at z=30.

Substructures within dark matter halos significantly enhance the annihilation effects.

Detectability of these effects requires reducing systematics below 20 mK at 50 MHz.

Abstract

We examine the extent to which the self-annihilation of supersymmetric neutralino dark matter, as well as light dark matter, influences the rate of heating, ionisation and Lyman-alpha pumping of interstellar hydrogen and helium and the extent to which this is manifested in the 21cm global background signal. We fully consider the enhancements to the annihilation rate from DM halos and substructures within them. We find that the influence of such structures can result in significant changes in the differential brightness temperature. The changes at redsfhits z<25 are likely to be undetectable due to the presence of the astrophysical signal; however, in the most favourable cases, deviations in the differential brightness temperature, relative to its value in the absence of self-annihilating DM, of up to ~20 mK at z=30 can occur. Thus we conclude that, in order to exclude these models, experiments measuring the global 21cm signal, such as EDGES and CORE, will need to reduce the systematics at 50 MHz to below 20 mK.