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2009•The Astrophysical JournalOpen access

FERMIOBSERVATIONS OF TeV-SELECTED ACTIVE GALACTIC NUCLEI

A. A. Abdo, M. Ackermann, Marco Ajello, W. B. Atwood, M. Axelsson, L. Baldini, Jean Jacques Ballet, Guido Barbiellini, Matthew G. Baring, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, E. D. Bloom, E. Bonamente, A. W. Borgland, J. Bregeon, A. Brez, Monica Brigida, P. Bruel, T. H. Burnett, G. A. Caliandro, R. A. Cameron, P. A. Caraveo, J. M. Casandjian, E. Cavazzuti, Claudia Cecchi, Ozlem Celik, Alexandre Chekhtman, Chi Chiu Cheung, J. Chiang, S. Ciprini, R. Claus, J. Cohen-Tanugi, L. R. Cominsky, Janet M. Conrad, S. Cutini, Alessandro De Angelis, F. de Palma, Giuseppe Di Bernardo, E. do Couto e Silva, Persis S. Drell, A. Drlica-Wagner, R. Dubois, D. Dumora, C. Farnier, C. Favuzzi, S. Fegan, J. Finke, Warren B. Focke, P. Fortin, L. Foschini, M. Frailis, Y. Fukazawa, S. Funk, P. Fusco, F. Gargano, D. Gasparrini, Neil A. Gehrels, S. Germani, G. Giavitto, B. Giebels, N. Giglietto, Paolo Giommi, F. Giordano, T. Glanzman, G. Godfrey, I. A. Grenier, M.-H. Grondin, J. E. Grove, Lucas Guillemot, S. Guiriec, Y. Hanabata, M. Hayashida, Elizabeth A. Hays, D. Horan, R. E. Hughes, M. Jackson, G. Jóhannesson, Anthony S. Johnson, Robert P. Johnson, W. Neil Johnson III, T. Kamae, Hideaki Katagiri, J. Kataoka, N. Kawai, Matthew T. Kerr, Jürgen Knödlseder, M. Kocian, M. Kuss, J. Landé, L. Latronico, Marianne Lemoine-Goumard, Francesco Longo, F. Loparco, B. Lott, M. N. Lovellette, P. Lubrano, G. M. Madejski, Andrey P. Makeev, Mario Nicola Mazziotta, W. McConville, J. E. McEnery, C. Meurer, P. F. Michelson, W. Mitthumsiri, Tsunefumi Mizuno, A. A. Moiseev, C. Monte, Maria Elena Monzani, Aldo Morselli, Igor V. Moskalenko, S. Murgia, P. L. Nolan, Jay P. Norris, E. Nuss, T. Ohsugi, N. Omodei, E. Orlando, Jonathan F. Ormes, Masanori Ozaki, D. Paneque, J. Panetta, D. Parent, V. Pelassa, Monica Pepe, M. Pesce-Rollins, Frederic Piron, T. A. Porter, S. Rainò, R. Rando, M. Razzano, A. Reimer, Olaf Reimer, T. Reposeur, L. C. Reyes, S. Ritz, Lynn Rochester, A. Y. Rodriguez, M. Roth, F. Ryde, Hartmut F.-W. Sadrozinski, David A. Sanchez, A. Sander, P. M. Saz Parkinson, J. D. Scargle, Terry LeRoy Schalk, A. Sellerholm, Carmelo Sgro', M. S. Shaw, E. J. Siskind, David A. Smith, Patrick D. Smith, Gloria Spandre, Paolo Spinelli, Mark S. Strickman, D. J. Suson, H. Tajima, Hiromitsu TAKAHASHI, T. Takahashi, Takaaki Tanaka, Yasuyuki Tanaka, J. B. Thayer, J. G. Thayer, D. J. Thompson, Luigi Tibaldo, Diego F. Torres, Gino Tosti, A. Tramacere, Y. Uchiyama, T. Usher, V. Vasileiou, N. Vilchez, V. Vitale, A. P. Waite, Pengfei Wang, B. L. Winer, K. S. Wood, T. Ylinen, Marcus Ziegler

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Abstract

We report on observations of TeV-selected active galactic nuclei (AGNs) made during the first 5.5 months of observations with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope ( Fermi ). In total, 96 AGNs were selected for study, each being either (1) a source detected at TeV energies (28 sources) or (2) an object that has been studied with TeV instruments and for which an upper limit has been reported (68 objects). The Fermi observations show clear detections of 38 of these TeV-selected objects, of which 21 are joint GeV–TeV sources, and 29 were not in the third EGRET catalog. For each of the 38 Fermi -detected sources, spectra and light curves are presented. Most can be described with a power law of spectral index harder than 2.0, with a spectral break generally required to accommodate the TeV measurements. Based on an extrapolation of the Fermi spectrum, we identify sources, not previously detected at TeV energies, which are promising targets for TeV instruments. Evidence for systematic evolution of the γ-ray spectrum with redshift is presented and discussed in the context of interaction with the extragalactic background light.

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What this paper is about

We report on observations of TeV-selected active galactic nuclei (AGNs) made during the first 5.5 months of observations with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope ( Fermi ). In total, 96 AGNs were selected for study, each being either (1) a source detected at TeV energies (28 sources) or (2) an object that has been studied with TeV instruments and for which an upper limit has been reported (68 objects). The Fermi observations show clear detections of 38 of these TeV-selected objects, of which 21 are joint GeV–TeV sources, and 29 were not in the third EGRET catalog. For each of the 38 Fermi -detected sources, spectra and light curves are presented. Most can be described with a power law of spectral index harder than 2.0, with a spectral break generally required to accommodate the TeV measurements. Based on an extrapolation of the Fermi spectrum, we identify sources, not previously detected at TeV energies, which are promising targets for TeV instruments. Evidence for systematic evolution of the γ-ray spectrum with redshift is presented and discussed in the context of interaction with the extragalactic background light.

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Available abstract

We report on observations of TeV-selected active galactic nuclei (AGNs) made during the first 5.5 months of observations with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope ( Fermi ). In total, 96 AGNs were selected for study, each being either (1) a source detected at TeV energies (28 sources) or (2) an object that has been studied with TeV instruments and for which an upper limit has been reported (68 objects). The Fermi observations show clear detections of 38 of these TeV-selected objects, of which 21 are joint GeV–TeV sources, and 29 were not in the third EGRET catalog. For each of the 38 Fermi -detected sources, spectra and light curves are presented. Most can be described with a power law of spectral index harder than 2.0, with a spectral break generally required to accommodate the TeV measurements. Based on an extrapolation of the Fermi spectrum, we identify sources, not previously detected at TeV energies, which are promising targets for TeV instruments. Evidence for systematic evolution of the γ-ray spectrum with redshift is presented and discussed in the context of interaction with the extragalactic background light.

Key concepts: Physics, Fermi Gamma-ray Space Telescope, Astrophysics, Context (archaeology), Telescope, Redshift, Astronomy, Spitzer Space Telescope

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