Extragalactic Gamma-ray Background Radiation from Beamed and Unbeamed Active Galactic Nuclei

The origin of the extragalactic gamma-ray background (EGRB) radiation has been a mystery in astrophysics for a longtime. Recently the Fermi gamma-ray satellite (Fermi) has revealed that similar to 22% of the unresolved EGRB would be explained by blazars,which are one population of beamed active galactic nuclei (AGNs). The remaining similar to 78% of the unresolved EGRB is still unknown. We estimate the contribution of gamma-ray loud radio galaxies,which are misaligned radio loud AGNs recently detected by Fermi, to EGR Busing the radio luminosity function of radio-loud AGNs with the correlation between the radio and gamma-ray luminosities. We find that similar to 25% of the unresolved EGRB will be explained by gamma-ray loud radio galaxy population. We also discuss further about the origin of EGRB by comparing the Fermi EGRB data with our studies on various AGN populations' contribution to EGRB, which are radio quiet AGNs, blazars, and gamma-ray loud radio galaxies.