Solving the Mystery of Dark Matter with XMM-Newton

The sterile neutrino is a dark matter candidate that emits an Xray throughradiative decay. We initiated the first dedicated Xray search for dark matter,deriving new constraints on sterile neutrinos from Suzaku data on the Ursa Minordwarf spheroidal galaxy, and a marginal detection of a sterile neutrino line at2.5 keV in the extreme dark matter dwarf spheroidal Willman 1. This tentativedetection can only be tested with XMMNewton EPIC. We propose 75100 ksecobservations (including offset pointings) of Willman 1, as well as Segue 1 andUrsa Major II. Confirmation by XMMNewton would be of incomparable astrophysicalimportance, pointing the way to new physics, and implying that future Xrayspectroscopic missions will directly map the dark distribution and its evolution. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]