BROAD-LINE RADIO GALAXIES OBSERVED WITH FERMI-LAT: THE ORIGIN OF THE GeV {gamma}-RAY EMISSION

Journal Article · Mon Oct 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/740/1/29; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21587423

Kataoka, J; Takahashi, Y; Maeda, K; Nakamori, T ^[1]; Stawarz, L ^[2]; Cheung, C C ^[3]; Hayashida, M; Digel, S W ^[4]; Grandi, P ^[5]; Burnett, T H ^[6]; Celotti, A ^[7]; Fegan, S J; Fortin, P ^[8]; Taylor, G B ^[9]; Tosti, G ^[10]; McConville, W ^[11]; Finke, J ^[12]; D'Ammando, F ^[13]

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1. Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)
2. Institute of Space and Astronautical Science, JAXA, Kanagawa 252-5210 (Japan)
3. National Academy of Sciences, Washington, DC 20001 (United States)
4. W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)
5. INAF-IASF Bologna, 40129 Bologna (Italy)
6. Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States)
7. Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34014 Trieste (Italy)
8. Laboratoire Leprince-Ringuet, Ecole Polytechnique, CNRS/IN2P3, Palaiseau (France)
9. Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131 (United States)
10. Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy)
11. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
12. Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)
13. IASF Palermo, 90146 Palermo (Italy)

We report on a detailed investigation of the {gamma}-ray emission from 18 broad-line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was found, however, in the considered data set. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicates that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high-accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found that none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broadband emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {>=}1% on average for BLRGs, whereas it is {<=}0.1% for Seyfert 1 galaxies.

• OSTI ID: 21587423
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 740; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
COSMIC RADIO SOURCES
DETECTION
ELECTROMAGNETIC RADIATION
EMISSION
GALAXIES
GAMMA DETECTION
GAMMA RADIATION
IONIZING RADIATIONS
JETS
RADIATION DETECTION
RADIATIONS
RADIO GALAXIES
SEYFERT GALAXIES