Constraints on sterile neutrino dark matter from XMM--Newton observation
  of M33
  Using archival XMM-Newton observations of the diffuse and unresolved
components emission in the inner disc of M33 we exclude the possible
contribution from narrow line emission in the energy range 0.5-5 keV more
intense than 10^{-6}-10^{-5} erg/s. Under the hypothesis that sterile neutrinos
constitute the majority of the dark matter in M33, we use this result in order
to put constraints on their parameter space in the 1-10 keV mass range.
