The AGNs and the extragalactic gamma ray background

The first part of this paper describes the identification of γ-ray AGNs. The database of cosmic γ-rays above 100 MeV from the SAS-2 satellite has been analysed to identify γ-ray emissions from 11 quasars, 3 BL Lac Objects and 1 radiogalaxy. Further investigations of the relationship between their γ-ray fluxes in different energy regions (>100 MeV and 35-100 MeV) and the relationship between their γ-ray fluxes and their redshifts, support that the sources detected are genuine extragalactic objects.

The second part of this paper describes the determination of the contribution from AGNs to the extragalactic γ-ray background. The SAS-2 γ-ray data have been employed to determine the functional relationships between the absolute γ-ray luminosities L_γ and the absolute optical luminosities of quasars and

Seyfert galaxies. From these, their contribution to the extragalaxtic γ-ray background can be derived. We have shown that quasars (B<20) and Seyfert (Type 1 and 1.5) galaxies together contribute to a substantial part (about 59%) of the diffuse γ-ray background in the 35-100 MeV range. Therefore we conclude that the extragalactic γ-ray background is likely to be generated by active galaxies such as quasars and Seyfert galaxies.