) Chinese Journal ofAstronomy and Astrophysics

Abstract Preliminary investigation of GALEX images of the diffuse ultraviolet background radiation suggests that part of the diffuse background represents red-shifted Lyman α recom-bination radiation from the intergalactic medium, which in turn would require, to maintain the observed high degree of ionization of the intergalactic medium, that the non-baryonic dark matter decay with the emission of an ionizing photon. Techniques for verifying this and for treating the data are described in some detail. Key words: techniques: ultraviolet – cosmology: diffuse backgroun