Fermi Large Area Telescope observations of misaligned active galactic nuclei

Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope for 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII radio sources consisting of two FRII radio galaxies and two steep spectrum radio quasars. The broad line FRI radio galaxy 3C 120 is reported here as a γ -ray source for the first time. The analysis is based on directional associations of LAT sources with radio sources in the 3CR, 3CRR, and MS4 (collectively referred to as 3C-MS) catalogs. Seven of the eleven LAT sources associated with 3C-MS radio sources have spectral indices larger than 2.3 and, except for the FRI radio galaxy NGC 1275 that shows possible spectral curvature, are well described by a power law. No evidence for time variability is found for any sources other than NGC 1275. The γ-ray luminosities of FRI radio galaxies are significantly smaller than those of the BL Lac objects detected by the LAT, whereas the γ -ray luminosities of the FRII sources are quite similar to those of FSRQs, which could reflect different beaming factors for the γ -ray emission. A core dominance (CD) study of the 3CRR sample indicates that sources closer to the jet axis are preferentially detected with the Fe r m i LAT, insofar as the γ -ray-detected misaligned AGNs have larger CD at a given average radio flux. The results are discussed in view of the AGN unification scenario.