Massive neutrinos and ultraviolet astronomy

Massive neutrinos (or photinos) dominating galactic halos may decay into less massive particles by emitting ultraviolet photons. The lifetime for this process can be calculated from particle physics in a model-dependent way. The observed ultraviolet background constrains this lifetime to exceed about 1024 seconds. If the photon energy exceeds 13.6 eV, the existence of HI structures from the galactic plane imposes a similar constraint. The existence of Si IV and C IV in the halos of our own and other galaxies could be due to approx. 50 eV photons emitted by neutrinos or photinos of rest-mass approx. 100 eV if their lifetime approx. 1027 seconds. This lifetime could be in agreement with the theoretical value for 100 eV particles. (Auth.)