Cylindrical model for the dark matter halo of disk galaxies

Abstract: A cylindrical model for the dark matter halo of disk galaxies is developed. At the center of the cylinder, in the plane perpendicular to the long axis, the rotation curve is constant for distances much less than the cylinder length and Keplerian at much greater distances. The rotation curve is equivalent to the spherical truncated flat (TF) profile, a model derived empirically from the radial velocity dispersion of the Milky Way dark halo. It is shown that an isothermal, self-gravitating cylinder of length 89 kpc can account for the observed radial velocity dispersion of the Milky Way dark halo with less mass than the NFW profile. Moreover, a cylindrical model of the Milky Way dark halo is consistent with free-streaming neutrinos of mass 1.1 eV.