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We present methods to assess whether gamma-ray excesses towards Milky Waydwarf galaxies can be attributed to astrophysical sources rather than to darkmatter annihilation. As a case study we focus on Reticulum II, the dwarf whichshows the strongest evidence for a gamma-ray signal in Fermi data. Dark mattermodels and those with curved energy spectra provide good fits to the data,while a simple power law is ruled out at 97.5% confidence. We compare RetII'sspectrum to known classes of gamma-ray sources and find a useful representationin terms of spectral curvature and the energy at which the spectral energydistribution peaks. In this space the blazar classes appear segregated from theconfidence region occupied by RetII. Pulsars have similar gamma-ray spectra toRetII but we show that RetII is unlikely to host a pulsar population detectablein gamma rays. Tensions with astrophysical explanations are stronger whenanalyzing 6.5 years of Pass 7 than with the same amount of Pass 8 data, wherethe excess is less significant. These methods are applicable to any dwarfgalaxy which is a promising dark matter target and shows signs of gamma-rayemission along its line of sight.

Astrophysical explanations of suspected dark matter signals in dwarf galaxies