Towards a Bullet-proof test for indirect signals of dark matter
  Merging galaxy clusters such as the Bullet Cluster provide a powerful testing
ground for indirect detection of dark matter. The spatial distribution of the
dark matter is both directly measurable through gravitational lensing and
substantially different from the distribution of potential astrophysical
backgrounds. We propose to use this spatial information to identify the origin
of indirect detection signals, and we show that even statistical excesses of a
few sigma can be robustly tested for consistency--or inconsistency--with a dark
matter source. For example, our methods, combined with already-existing
observations of the Coma Cluster, would allow the 3.55 keV line to be tested
for compatibility with a dark matter origin. We also discuss the optimal
spatial reweighting of photons for indirect detection searches. The current
discovery rate of merging galaxy clusters and associated lensing maps strongly
motivates deep exposures in these dark matter targets for both current and
upcoming indirect detection experiments in the X-ray and gamma-ray bands.
