Impacts of new small-scale N-body simulations on dark matter annihilations constrained from cosmological 21-cm line observations

We revisit constraints on annihilating dark matter based on the cosmological global 21 cm signature observed by EDGES. For this purpose, we used the numerical data of the latest N-body simulation for the first time performed by state-of-the-art standard in order to estimate the boost factor at high redshifts (z = 10-100), which enhances the annihilation of dark matter in course of structure formations. By taking into account to what fraction injected energy from dark matter annihilation contributes to ionization, excitation, and heating of intergalactic medium during dark ages, we estimated how large the global 21 cm absorption can be. In the thermal freeze-out scenario, we find that the dark matter masses mDM < 15 GeV and mDM < 3 GeV have been excluded at 95% C.L. for the modes into bb over bar and e+e-, respectively, which are obtained independently of any uncertainties in local astrophysics such as observationally-fitted density profiles of dark matter halos.

Automated summary

Constraints on annihilating dark matter are revisited based on the cosmological global 21 cm signature observed by EDGES. By estimating the boost factor at high redshifts and taking into account the energy injected from dark matter annihilation, the study excludes dark matter masses below 15 GeV and 3 GeV at 95% confidence level for certain modes in the thermal freeze-out scenario.