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from 4 - Extragalactic and Cosmology
Published online by Cambridge University Press: 04 August 2010
We discuss several recent observational results according to which a significant fraction of the Galactic dark matter halo may exist in the form of dense self-gravitating clumps of H2.
We model the large scale mass distribution in the Milky Way and derive in a self-consistent way the associated gravitational potential. The basic constraint in our model is that the shape of the gaseous Galactic halo, observable from synchrotron radiation, γ-rays, soft X-ray background and from H I lines with high-velocity dispersion needs to be explained by the mass distribution.
The resulting mass model has a flat rotation curve. In the solar vicinity surface density, volume density and gravitational acceleration Kz are consistent with all known constraints. We find that the distributions of HI gas and dark matter are closely related to each other. Furthermore, the mass distribution implies a co-rotation of disk and halo for radii R > 5 kpc.
Our analysis supports strongly the hypothesis, that the gaseous halo of the Milky Way traces dark matter in the form of dense self-gravitating H2 condensations as indicated from an analysis of the γ-ray background observed with EGRET (Shchekinov et al., these proceedings). In addition we find evidence for an extended non-baryonic dark matter halo, which co-exists with the baryonic component. We derive for the Milky Way a baryonic mass fraction of 12% in close agreement with cosmological predictions.
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