Thermal and chemical evolution of the primordial clouds in warm dark matter models with keV sterile neutrinos in one-zone approximation

Abstract

We follow the evolution of the baryonic top-hat overdensity in a single-zone approximation. Our goal is to juxtapose the evolution of the gas temperature in the primordial clouds in the lambda cold dark matter model and the warm dark matter model with keV sterile neutrinos and to check the effects of their decays, into one X-ray photon and one active neutrino, on the structure formation. We find that, in all the cases we have examined, the overall effect of sterile dark matter is to facilitate the cooling of gas and to reduce the minimal mass of the halo able to collapse. Hence, we conclude that X-rays from the decays of dark matter in the form of sterile neutrinos can help the early collapse of gas clouds and the subsequent star formation.