Gamma rays from a baryonic dark halo

A recent re-analysis of EGRET data by Dixon et al [1] has led to the discovery of a statistically significant diffuse gamma-ray emission from the galactic halo. We show that this emission can naturally be accounted for within a previously-proposed model for baryonic dark matter, according to which dark clusters of brown dwarfs and cold self-gravitating H-2 clouds populate the outer galactic halo and can show up in microlensing observations. Basically, cosmic-ray protons in the galactic halo scatter on the clouds clumped into dark clusters, giving rise to the observed gamma-ray flux. We derive maps for the corresponding intensity distribution, which turn out to be in remarkably good agreement with those obtained by Dixon et al [1]. We also address future prospects to test our predictions