Probing the nature of dark matter with cosmic x rays: Constraints from “dark blobs” and grating spectra of galaxy clusters

Abstract

Gravitational lensing observations of galaxy clusters have identified dark matter blobs with remarkably low baryonic content. We use such a blob to probe the particle nature of dark matter with x-ray observations. From these observations we improve the most conservative constraints from the Milky Way halo on a particular dark matter candidate, the sterile neutrino, by an order of magnitude. We also study high resolution x-ray grating spectra of a cluster of galaxies. Based on these conservative constraints obtained from cosmic x-ray observations alone, the low mass (${m}_{s}\ensuremath{\lesssim}10\text{ }\text{ }\mathrm{keV}$) and low mixing angle (${sin}^{2}(2\ensuremath{\theta})\ensuremath{\lesssim}{10}^{\ensuremath{-}6}$) sterile neutrino is still a viable dark matter candidate.