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 long time. Recently the Fermi gamma-ray
satellite (Fermi) has revealed that ~22% of the unresolved EGRB would be
explained by blazars, which are one population of beamed active galactic nuclei
(AGNs). The remaining ~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 EGRB using the radio luminosity
function of radio-loud AGNs with the correlation between the radio and
gamma-ray luminosities. We find that ~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.
