Exploring the FRI/FRII radio dichotomy with the Fermi satellite

Abstract: Misaligned Active Galactic Nuclei (MAGNs), i.e., radio galaxies and quasars with the jet not directly pointing at the observer, are a new class of GeV emitters. In low power radio galaxies (i.e., FRIs), gamma-rays are mainly produced in compact jet regions, although in at least one case, Centaurus A, high energy photons from the radio lobes have been also observed. The first localization of the gamma-ray dissipation zone in a high power radio galaxy (i.e., FRII) excludes major contributions from extended regions. The study of the FRII source 3C111 indicates that gamma-ray photons are produced in the jet. The site, coincident with the radio core, is estimated to be at a distance <~0.3 pc from the black hole. Although the place where high energy photons are produced is probably similar in FRIs and FRIIs, high power radio galaxies are rarer in the GeV sky. Our study of all the radio sources belonging to four complete radio catalogs (3CR, 3CRR, MS4, 2Jy) disfavors the idea that the paucity of FRIIs is due to their larger distance (and therefore to their faintness) and supports other possibilities, pointing to beaming/jet structural differences between FRIs and FRIIs.