Evidence for a Galactic gamma ray halo
  We present quantitative statistical evidence for a $\gamma$-ray emission halo surrounding the Galaxy. Maps of the emission are derived. EGRET data were analyzed in a wavelet-based non-parametric hypothesis testing framework, using a model of expected diffuse (Galactic + isotropic) emission as a null hypothesis. The results show a statistically significant large scale halo surrounding the center of the Milky Way as seen from Earth. The halo flux at high latitudes is somewhat smaller than the isotropic gamma-ray flux at the same energy, though of the same order (O(10^(-7)--10^(-6)) ph/cm^2/s/sr above 1 GeV). 
D. D. Dixon, D. H. Hartmann, E. D. Kolaczyk, J. Samimi, R. Diehl, G.   Kanbach, H. Mayer-Hasselwander, and A. W. Strong