On the origin of the diffuse X-ray background

Abstract

The possibility that the diffuse X-ray background (XRB) could have been generated by the infall of baryons into the potential wells of dark matter is investigated within the framework of a hot dark matter (neutrino)-dominated universe. The XRB spectrum is fitted with the thermal bremsstrahlung kernel, and constraints on the nature of the infall and properties of the X-ray emitting gas are derived. The results indicate that around xi = 5 infall results in the formation of high-density knots with a hot plasma phase constituting 1 percent or less of the baryonic content of the universe. These dense regions can be regarded as the progenitors of present-day galaxies. Constraints are also derived for forms of dark matter other than neutrinos