Decay of massive photinos and gravitinos and keV X-ray background

Abstract

The contributions of the decay of supersymmetry-breaking photinos and gravitinos with masses of a few keV to the X-ray background and of neutrinos with mass about 20 eV to the UV background are discussed, using the Coma cluster of galaxies as an example. Assuming a cluster mass of 10 to the 48th g, the cluster is found to contain about 10 to the 80th neutrinos with lifetimes about 10 to the 25th sec producing UV photons of energy about 10 eV, in rough agreement with Apollo 17 UV--spectrometer observations (Henry et al., 1978) at 130 nm. The number of photinos and gravitinos (with lifetimes 10 to the 23rd sec) in the cluster is estimated as 10 to the 77th, corresponding to an X-ray luminosity of 10 to the 46th erg/sec. This mechanism has the advantage that it lowers the amount of hot intergalactic gas required in the general X-ray background model, thus reducing the conflict with the gas limit imposed by the primordial deuterium abundance.