Determination of dark matter type by X-ray sources statistics
  The current cosmological model includes cold dark matter, which consists of
massive nonrelativistic particles. There are also some observational and
theoretical evidences for warm dark matter. The existence of warm DM can be
examined by measuring of the galaxy clusters density profiles and accurate
counting of dwarf galaxies. In this work I suppose that DM haloes are well
traced by X-ray gas in clusters, groups, pairs and even single galaxies. The
type of DM is inspected with the Xgal sample of 5021 X-ray emitting galaxies
observed by XMM-Newton. The selection bias of this sample is also analyzed.
