Constraints on decaying dark matter from XMM-Newton observations of M31

Abstract

We derive constraints on the parameters of the radiatively decaying dark matter (DM) particle, using the XMM-Newton EPIC spectra of the Andromeda galaxy (M31). Using the observations of the outer (5-13 arcmin) parts of M31, we improve the existing constraints. For the case of sterile neutrino DM, combining our constraints with the latest computation of abundances of sterile neutrinos in the Dodelson-Widrow (DW) scenario, we obtain the lower mass limit m s < 4 keV, which is stronger than the previous one m s < 6 keV, obtained recently by Asaka, Laine & Shaposhnikov. Comparing this limit with the most recent results on Lyman α forest analysis of Viel et al. (m s > 5.6 keV), we argue that the scenario in which all the DM is produced via the DWmechanism is ruled out.We discuss, however, other production mechanisms and note that the sterile neutrino remains a viable candidate for DM, either warm or cold. © 2008 The Authors. Journal compilation © 2008 RAS.