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The EDGES experiment has observed an absorption feature in the global 21 cmspectrum with a surprisingly large amplitude. These results can be explained bydecreasing the kinetic temperature of baryons, which could be achieved throughthe scattering between the baryons and cold dark matter particles. It seemsthat the most researched dark matter annihilation model is not able to explainsuch a large amplitude, since the interactions between the particles producedby the dark matter annihilation and the particles that have been present in theUniverse could increase the baryonic temperature. Recently, C. Feng and G.Holder have suggested that the large amplitude in the global 21 cm spectrumcould be produced by considering the possible excess of the early radioradiation. In this paper, we propose that the dark matter annihilation stillworks to explain the large amplitude observed by the EDGES experiment. Evenincluding the dark matter annihilation, the large absorption amplitude in theglobal 21 cm spectrum can be produced by considering the possible excess of theearly radio radiation.

Contributions of dark matter annihilation to the global 21cm spectrum observed by the EDGES experiment