Where do the 3.5 keV photons come from? A morphological study of the
  Galactic Center and of Perseus
  We test the origin of the 3.5 keV line photons by analyzing the morphology of
the emission at that energy from the Galactic Center and from the Perseus
cluster of galaxies. We employ a variety of different templates to model the
continuum emission and analyze the resulting radial and azimuthal distribution
of the residual emission. We then perform a pixel-by-pixel binned likelihood
analysis including line emission templates and dark matter templates and assess
the correlation of the 3.5 keV emission with these templates. We conclude that
the radial and azimuthal distribution of the residual emission is incompatible
with a dark matter origin for both the Galactic center and Perseus; the
Galactic center 3.5 keV line photons trace the morphology of lines at
comparable energy, while the Perseus 3.5 keV photons are highly correlated with
the cluster's cool core, and exhibit a morphology incompatible with dark matter
decay. The template analysis additionally allows us to set the most stringent
constraints to date on lines in the 3.5 keV range from dark matter decay.
