Author(s): A. Abdo A., Ackermann M., Ajello M., Baldini L., Ballet J., Barbiellini G., Bastieri D., Bechtol K., Bellazzini R., Berenji B., D. Blandford R., Bruel P., M. Casandjian J., Cohen-Tanugi J., J. Fegan S., Fortin P., A. Grenier I., Guillemot L., Guiriec Sylvain, Horan D., Kn¨odlseder J., Lemoine-Goumard M., Lott B., Nuss E., Parent D., Pelassa V., Piron F., Sanchez D., Tibaldo L., Vilchez N.
(Article) Published:
The Astrophysical Journal / The Astrophysical Journal Letters, vol. 720 p.912-922 (2010)
Links openAccess full text : 
Ref HAL: in2p3-00530049_v1
Ref Arxiv: 1007.1624
DOI: 10.1088/0004-637X/720/1/912
Ref. & Cit.: NASA ADS
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126 citations
Abstract:
Analysis is presented on 15 months of data taken with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope for 11 non-blazar AGNs, including 7 FRI radio galaxies and 4 FRII radio sources consisting of 2 FRII radio galaxies and 2 steep spectrum radio quasars. The broad line FRI radio galaxy 3C 120 is reported here as a gamma-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 gamma-ray luminosities of FRI radio galaxies are significantly smaller than those of BL Lac objects detected by the LAT, whereas the gamma-ray luminosities of FRII sources are quite similar to those of FSRQs, which could reflect different beaming factors for the gamma-ray emission. A core dominance study of the 3CRR sample indicate that sources closer to the jet axis are preferentially detected with the Fermi-LAT, insofar as the gamma-ray--detected misaligned AGNs have larger core dominance at a given average radio flux. The results are discussed in view of the AGN unification scenario.
Comments: 28 pages, 8 figures, 2 tables. Accepted for publication in The Astrophysical Journal