Gamma-Ray Astronomy and Baryonic Dark Matter

Recently, Dixon et al. have re-analyzed the EGRET data, finding astatistically significant diffuse $\gamma$-ray emission from the galactic halo.We show that this emission can naturally be explained within apreviously-proposed model for baryonic dark matter, in which $\gamma$-rays areproduced through the interaction of high-energy cosmic-ray protons with cold$H_2$ clouds clumped into dark clusters - these dark clusters supposedlypopulate the outer galactic halo and can show up in microlensing observations.Our estimate for the halo $\gamma$-ray flux turns out to be in remarkably goodagreement with the discovery by Dixon et al. We also address future prospectsto test our predictions.Comment: 9 pages, 1 figure included, to appear in ApJ 510, L103 (1999