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The Spectral Energy Distribution Of Fermi Bright Blazars

Abdo, A. A.; Ackermann, M.; Agudo, I.; Ajello, M.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Arkharov, A. A.; Axelsson, Magnus LU and Bach, U., et al. (2010) In Astrophysical Journal 716(1). p.30-70
Abstract
We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log nu-log nu F-nu representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation... (More)
We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log nu-log nu F-nu representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low-and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(ro), and optical to X-ray, alpha(ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (nu(S)(peak)) is positioned between 10(12.5) and 10(14.5) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(13) and 10(17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter gamma-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum gamma-ray sources, the correlation between nu(S)(peak) and gamma-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars. (Less)
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quasars: general, radiation mechanisms: non-thermal, galaxies: active, gamma rays: galaxies, BL Lacertae objects: general
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Astrophysical Journal
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716
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1
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30 - 70
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University of Chicago Press
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  • wos:000277960000002
  • scopus:77952931352
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0004-637X
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10.1088/0004-637X/716/1/30
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English
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2010-06-22 13:02:03
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@article{78256c9a-2707-4a32-baa2-2941ed2e87c1,
  abstract     = {We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray/gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log nu-log nu F-nu representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low-and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(ro), and optical to X-ray, alpha(ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (nu(S)(peak)) is positioned between 10(12.5) and 10(14.5) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(13) and 10(17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than 50% of known radio bright high energy peaked (HBL) BL Lacs are detected in the LBAS sample, only less than 13% of known bright FSRQs and LBL BL Lacs are included. This suggests that the latter sources, as a class, may be much fainter gamma-ray emitters than LBAS blazars, and could in fact radiate close to the expectations of simple SSC models. We categorized all our sources according to a new physical classification scheme based on the generally accepted paradigm for Active Galactic Nuclei and on the results of this SED study. Since the LAT detector is more sensitive to flat spectrum gamma-ray sources, the correlation between nu(S)(peak) and gamma-ray spectral index strongly favors the detection of high energy peaked blazars, thus explaining the Fermi overabundance of this type of sources compared to radio and EGRET samples. This selection effect is similar to that experienced in the soft X-ray band where HBL BL Lacs are the dominant type of blazars.},
  author       = {Abdo, A. A. and Ackermann, M. and Agudo, I. and Ajello, M. and Aller, H. D. and Aller, M. F. and Angelakis, E. and Arkharov, A. A. and Axelsson, Magnus and Bach, U. and Baldini, L. and Ballet, J. and Barbiellini, G. and Bastieri, D. and Baughman, B. M. and Bechtol, K. and Bellazzini, R. and Benitez, E. and Berdyugin, A. and Berenji, B. and Blandford, R. D. and Bloom, E. D. and Boettcher, M. and Bonamente, E. and Borgland, A. W. and Bregeon, J. and Brez, A. and Brigida, M. and Bruel, P. and Burnett, T. H. and Burrows, D. and Buson, S. and Caliandro, G. A. and Calzoletti, L. and Cameron, R. A. and Capalbi, M. and Caraveo, P. A. and Carosati, D. and Casandjian, J. M. and Cavazzuti, E. and Cecchi, C. and Celik, Oe. and Charles, E. and Chaty, S. and Chekhtman, A. and Chen, W. P. and Chiang, J. and Chincarini, G. and Ciprini, S. and Claus, R. and Cohen-Tanugi, J. and Colafrancesco, S. and Cominsky, L. R. and Conrad, J. and Costamante, L. and Cutini, S. and D'ammando, F. and Deitrick, R. and D'Elia, V. and Dermer, C. D. and de Angelis, A. and de Palma, F. and Digel, S. W. and Donnarumma, I. and do Couto e Silva, E. and Drell, P. S. and Dubois, R. and Dultzin, D. and Dumora, D. and Falcone, A. and Farnier, C. and Favuzzi, C. and Fegan, S. J. and Focke, W. B. and Forne, E. and Fortin, P. and Frailis, M. and Fuhrmann, L. and Fukazawa, Y. and Funk, S. and Fusco, P. and Gomez, J. L. and Gargano, F. and Gasparrini, D. and Gehrels, N. and Germani, S. and Giebels, B. and Giglietto, N. and Giommi, P. and Giordano, F. and Giuliani, A. and Glanzman, T. and Godfrey, G. and Grenier, I. A. and Gronwall, C. and Grove, J. E. and Guillemot, L. and Guiriec, S. and Gurwell, M. A. and Hadasch, D. and Hanabata, Y. and Harding, A. K. and Hayashida, M. and Hays, E. and Healey, S. E. and Heidt, J. and Hiriart, D. and Horan, D. and Hoversten, E. A. and Hughes, R. E. and Itoh, R. and Jackson, M. S. and Johannesson, G. and Johnson, A. S. and Johnson, W. N. and Jorstad, S. G. and Kadler, M. and Kamae, T. and Katagiri, H. and Kataoka, J. and Kawai, N. and Kennea, J. and Kerr, M. and Kimeridze, G. and Knoedlseder, J. and Kocian, M. L. and Kopatskaya, E. N. and Koptelova, E. and Konstantinova, T. S. and Kovalev, Y. Y. and Kovalev, Yu. A. and Kurtanidze, O. M. and Kuss, M. and Lande, J. and Larionov, V. M. and Latronico, L. and Leto, P. and Lindfors, E. and Longo, F. and Loparco, F. and Lott, B. and Lovellette, M. N. and Lubrano, P. and Madejski, G. M. and Makeev, A. and Marchegiani, P. and Marscher, A. P. and Marshall, F. and Max-Moerbeck, W. and Mazziotta, M. N. and McConville, W. and McEnery, J. E. and Meurer, C. and Michelson, P. F. and Mitthumsiri, W. and Mizuno, T. and Moiseev, A. A. and Monte, C. and Monzani, M. E. and Morselli, A. and Moskalenko, I. V. and Murgia, S. and Nestoras, I. and Nilsson, K. and Nizhelsky, N. A. and Nolan, P. L. and Norris, J. P. and Nuss, E. and Ohsugi, T. and Ojha, R. and Omodei, N. and Orlando, E. and Ormes, J. F. and Osborne, J. and Ozaki, M. and Pacciani, L. and Padovani, P. and Pagani, C. and Page, K. and Paneque, D. and Panetta, J. H. and Parent, D. and Pasanen, M. and Pavlidou, V. and Pelassa, V. and Pepe, M. and Perri, M. and Pesce-Rollins, M. and Piranomonte, S. and Piron, F. and Pittori, C. and Porter, T. A. and Puccetti, S. and Rahoui, F. and Raino, S. and Raiteri, C. and Rando, R. and Razzano, M. and Reimer, A. and Reimer, O. and Reposeur, T. and Richards, J. L. and Ritz, S. and Rochester, L. S. and Rodriguez, A. Y. and Romani, R. W. and Ros, J. A. and Roth, M. and Roustazadeh, P. and Ryde, F. and Sadrozinski, H. F. -W. and Sadun, A. and Sanchez, D. and Sander, A. and Parkinson, P. M. Saz and Scargle, J. D. and Sellerholm, A. and Sgro, C. and Shaw, M. S. and Sigua, L. A. and Siskind, E. J. and Smith, D. A. and Smith, P. D. and Spandre, G. and Spinelli, P. and Starck, J. -L. and Stevenson, M. and Stratta, G. and Strickman, M. S. and Suson, D. J. and Tajima, H. and Takahashi, H. and Takahashi, T. and Takalo, L. O. and Tanaka, T. and Thayer, J. B. and Thayer, J. G. and Thompson, D. J. and Tibaldo, L. and Torres, D. F. and Tosti, G. and Tramacere, A. and Uchiyama, Y. and Usher, T. L. and Vasileiou, V. and Verrecchia, F. and Vilchez, N. and Villata, M. and Vitale, V. and Waite, A. P. and Wang, P. and Winer, B. L. and Wood, K. S. and Ylinen, T. and Zensus, J. A. and Zhekanis, G. V. and Ziegler, M.},
  issn         = {0004-637X},
  keyword      = {quasars: general,radiation mechanisms: non-thermal,galaxies: active,gamma rays: galaxies,BL Lacertae objects: general},
  language     = {eng},
  number       = {1},
  pages        = {30--70},
  publisher    = {University of Chicago Press},
  series       = {Astrophysical Journal},
  title        = {The Spectral Energy Distribution Of Fermi Bright Blazars},
  url          = {http://dx.doi.org/10.1088/0004-637X/716/1/30},
  volume       = {716},
  year         = {2010},
}