Seyfert galaxies and the cosmic γ-ray diffuse background

Three active galaxies, generally classified as Seyferts, have been discovered recently to be powerful, low energy γ-ray sources. The similarity between their spectral characteristics and those of the cosmic background at γ-ray energies suggests that these objects could make a significant contribution to this diffuse flux. This contribution has been assessed using two different number densities of γ-ray-emitting Seyfert galaxies based on optical and X-ray data. The comparison of the estimated and measured diffuse γ-ray background intensities is used to gain a deeper understanding of the metabolism of Seyfert galaxies.