A SCENARIO FOR A BARYONIC DARK HALO

The recent observations of microlensing events in the LMC by the MACHO and EROS collaborations suggest that an important fraction of the galactic halo is in the form of Massive Halo Objects (MHO) of about 0.1 M.. Here, we argue that the galactic halo is mainly baryonic and that besides MHO also H-2 molecular clouds may significantly contribute to it. We propose a scenario in which dark clusters of MHO and/or H2 molecular clouds form in the halo at galactocentric distances larger than approximately 10 - 20 kpc, since there we expect less collisions among proto globular cluster clouds and a smaller UV radiation flux. Cosmic ray protons may induce a significant gamma-ray flux in H-2 molecular clouds. Our calculation gives an upper bound to this flux which is below present detectability.