Halo dark clusters of brown dwarfs and molecular clouds

Abstract

The discovery of Massive Astrophysical Compact Halo Objects (MACHOs) in microlensing experiments makes it compelling to understand their physical nature, as well as their formation mechanism. Within the present uncertainties, brown dwarfs are a viable candidate for MACHOs, and the present paper deals with this option. According to a recently proposed scenario, brown dwarfs are clumped along with cold molecular clouds into dark clusters -- in several respects similar to globular clusters -- which form in the outer part of the galactic halo. Here, we analyze the dynamics of these dark clusters and we address the possibility that a sizable fraction of MACHOs can be binary brown dwarfs. Moreover, we point out that Ly-$\alpha$ absorption systems naturally fit within the present picture.

arXiv commentLatex file. To appear in Astrophysical Journal

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• Does Transparent Hidden Matter Generate Optical Scintillation?
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• Rotating baryonic dark halos
• CMB as a possible new tool to study the dark baryons in galaxies
• Searching for Galactic hidden gas through interstellar scintillation: Results from a test with the NTT-SOFI detector
• Virial clouds explaining the observed rotational asymmetry in the galactic halos
• Seeing the halo rotation of nearby spiral galaxies using Planck data
• Globular Clusters as Candidates for Gravitational Lenses to Explain Quasar-Galaxy Associations