Neutrinos, galactic dark matter and flat rotation curves

Degenerate or partially degenerate density distributions of neutrinos do not give rise to flat rotation curves. If the galactic dark matter chiefly consists of neutrinos they would have to be isothermal. Such a halo of thermal neutrinos would, however, dissipates on time scales substantially shorter than typical galaxy ages. Comparison with other forms of dark matter is also made and sensitivity to inclusion of baryons in the core is also studied. 19 refs. (author)