MASSIVE NEUTRINOS AND DARK HALOS AROUND GALAXIES

In this paper we investigate the hypothesis that hot massive neutrinos can be the main dark matter component of galactic halos. The consiste ncy of the cosmological nu's phase space density with the properties o f the dark matter halos of dwarf galaxies sets an upper limit to the n eutrino mass m(nu) (Tremaine & Gunn 1973; TG). Here we apply the TG ar gument to a very large sample (1100 objects) of high quality rotation curves of normal spirals, and calculate reliable upper limits to the n eutrino mass. Unlike previous works, our estimate is distance independ ent and holds for different Hubble Types and for the whole luminosity range. We find that, in order to be clustered on galaxy halo scales, n u's should be so massive as to violate the cosmological constraint <Om ega(nu) less than or equal to 1. Thus, we conclude that hot neutrinos do not play a relevant role on galactic scales.