Dynamical interactions and astrophysical effects of stable heavy neutrinos

Astrophysical consequences of the existence of any massive stable neutral lepton, and of heavy stable neutrinos in particular, are investigated. The extent to which heavy neutrinos may cluster gravitationally is studied, and it is suggested that heavy neutrinos might supply the dominant mass on large scales in galaxies and clusters of galaxies. The collapse of a gas consisting of nonrelativistic nondegenerate inert heavy neutrinos is analyzed, some specific simplified cases of collapse in which the neutrinos are treated as test particles are examined, and effects due to the self-gravity of the neutrinos are discussed. It is found that the ratio of heavy neutrinos to ordinary matter is preserved in any structures formed by dissipationless collapse and that the heavy neutrinos may dominate the total mass in such objects. Implications of these results are considered for galaxy formation, the masses of galaxies and clusters, and stellar structure and evolution.