Consistency of dark matter interpretations of the 3.5 keV X-ray line
  Tentative evidence of a 3.5 keV X-ray line has been found in the stacked
spectra of galaxy clusters, individual clusters, the Andromeda galaxy and the
galactic center, leading to speculation that it could be due to decays of
metastable dark matter such as sterile neutrinos. However searches for the line
in other systems such as dwarf satellites of the Milky Way have given negative
or ambiguous results. We reanalyze both the positive and negative searches from
the point of view that the line is due to inelastic scattering of dark matter
to an excited state that subsequently decays---the mechanism of excited dark
matter (XDM). Unlike the metastable dark matter scenario, XDM gives a stronger
signal in systems with higher velocity dispersions, such as galaxy clusters. We
show that the predictions of XDM can be consistent with null searches from
dwarf satellites, while the signal from the closest individual galaxies can be
detectable having a flux consistent with that from clusters. We discuss the
impact of our new fits to the data for two specific realizations of XDM.
