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 gal actic 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 b esides MHO also H-2 molecular clouds may significantly contribute to i t. We propose a scenario in which dark clusters of MHO and/or H2 molec ular clouds form in the halo at galactocentric distances larger than a pproximately 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 c louds. Our calculation gives an upper bound to this flux which is belo w present detectability.