Constraints on sterile neutrino dark matter from XMM-Newton observations of M33

Using archival XMMNewton 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 0.55?keV more intense than 10-610-5?erg?s-1. 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 110?keV mass range.