Dark Baryons in Galactic Halos

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As is well known, most of the baryons are observationally unaccounted. Moreover, certain recent developments suggest that dark baryons are mostly locked up in galactic halos - which are anyway dominated by nonbaryonic dark matter - and a sizable fraction of them consists of gas clouds. While a priori various forms of baryonic dark matter in galaxies can be conceived, observational constraints rule out most of the possibilities, leaving brown dwarfs and cold gas clouds mostly made of H₂ as the only viable candidates. So, it looks natural to suppose that baryonic dark matter in galaxies is accounted for by dark clusters made of brown dwarfs and cold H₂ clouds. We discuss a realistic dark cluster formation mechanism. We also discuss various ramifications of the dark cluster scenario in question, paying particular attention to its observational implications.