Contributions of dark matter annihilation to the global 21cm spectrum observed by the EDGES experiment (1803.05803v4)

Abstract: The EDGES experiment has observed an absorption feature in the global 21 cm spectrum with a surprisingly large amplitude. These results can be explained by decreasing the kinetic temperature of baryons, which could be achieved through the scattering between the baryons and cold dark matter particles. It seems that the most researched dark matter annihilation model is not able to explain such a large amplitude, since the interactions between the particles produced by the dark matter annihilation and the particles that have been present in the Universe could increase the baryonic temperature. Recently, C. Feng and G. Holder have suggested that the large amplitude in the global 21 cm spectrum could be produced by considering the possible excess of the early radio radiation. In this paper, we propose that the dark matter annihilation still works to explain the large amplitude observed by the EDGES experiment. Even including the dark matter annihilation, the large absorption amplitude in the global 21 cm spectrum can be produced by considering the possible excess of the early radio radiation.