Can the extragalactic gamma-ray background be explained by AGN?

Abstract. Very high energy gamma-rays from blazars traversing cosmological distances through the meta-galactic radiation eld can convert into electron-positron pairs in photon-photon collisions. The converted gamma-rays initiate electromagnetic cascades driven by inverse-Compton scattering with microwave background photons. Using a model for the time-dependent meta-galactic radiation eld consistent with currently available far-infrared to optical data, the cascade contributions by faint, unresolved sources like blazars and FRI galaxies have been calculated. We come to the conclusion that depending on what is known so far about AGN, they are not able to produce the total extragalactic ux detected by EGRET. A test for the model will be the upcoming observations with FERMI. It would also be helpful to detect a signal above 100 GeV where the gamma-ray ux declines to 107GeV sr1 cm2 s1