Active galactic nuclei and the gamma-ray cosmic diffuse background

Number-flux relations at gamma-ray energies (0.3-20 MeV) for active galactic nuclei have been computed, starting from their X-ray luminosity function and making different assumptions on the spectral shape and cosmological evolution of these sources. The resulting contribution to the cosmic diffuse emission has then been compared to the measured intensity and spectrum of the extragalactic background, in order to derive quantitative constraints on the population properties of active galactic nuclei. Upper limits on the gamma-ray luminosity evolution have thus been derived as a function of the assumed spectral properties. These constraints are discussed in the context of the capabilities of the future gamma-ray astronomy missions SIGMA and GRO, whose expected results in this field have been quantitatively estimated.