CONSTRAINTS ON DECAYING NEUTRINOS FROM THE FAR-ULTRAVIOLET EXTRAGALACTIC BACKGROUND LIGHT

We consider light neutrinos as dark matter candidates, concentrating on those proposed by Sciama, with rest energies near 30 eV and decay lifetimes of (2 +/- 1) x 10(23) S. Using equations developed by Wesson, Valle, & Stabell for the visible extragalactic background light, and assuming that the neutrinos are clustered in galactic halos similar to that around our own Galaxy, we show that their decay would be capable of significant contributions to the far-ultraviolet background. Observations in this region by Martin & Bowyer limit the possible mass of the neutrino halos to 2 x 10(11) M., which is less than the required galactic ''missing mass.'' In order to form galatic halos of mass 5 x 10(11) M., such neutrinos would have to decay with lifetimes of at least 3 x 10(23) s to be consistent with the observations. Sciama's proposal remains marginally viable, but more observational data will test it and similar neutrino models critically.