Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)
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)
Instituto de Astrofisica de AndalucIa, CSIC, 18080 Granada (Spain)
Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1042 (United States)
Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany)
Pulkovo Observatory, 196140 St. Petersburg (Russian Federation)
Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden)
Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy)
Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d'Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France)
Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy)
Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy)
Department of Physics, Center for Cosmology and Astro-Particle Physics, The Ohio State University, Columbus, OH 43210 (United States)
Instituto de AstronomIa, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)
Tuorla Observatory, University of Turku, FI-21500 Piikkioe (Finland)
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 {sub {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}{sub ro}, and optical to X-ray, {alpha}{sub ox}, spectral slopes) and from the {gamma}-ray spectral index. Our data show that the synchrotron peak frequency ({nu} {sup S} {sub peak}) is positioned between 10{sup 12.5} and 10{sup 14.5} Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10{sup 13} and 10{sup 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} {sup S} {sub 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.
Abdo, A A, et al. "THE SPECTRAL ENERGY DISTRIBUTION OF FERMI BRIGHT BLAZARS." Astrophysical Journal, vol. 716, no. 1, Jun. 2010. https://doi.org/10.1088/0004-637X/716/1/30
Abdo, A A, Ackermann, M, Ajello, M, Bechtol, K, Berenji, B, Agudo, I, Aller, H D, Aller, M F, Angelakis, E, Bach, U, Arkharov, A A, Axelsson, M, Baldini, L, Bellazzini, R, Ballet, J, Barbiellini, G, Bastieri, D, Baughman, B M, Benitez, E, & Berdyugin, A (2010). THE SPECTRAL ENERGY DISTRIBUTION OF FERMI BRIGHT BLAZARS. Astrophysical Journal, 716(1). https://doi.org/10.1088/0004-637X/716/1/30
Abdo, A A, Ackermann, M, Ajello, M, et al., "THE SPECTRAL ENERGY DISTRIBUTION OF FERMI BRIGHT BLAZARS," Astrophysical Journal 716, no. 1 (2010), https://doi.org/10.1088/0004-637X/716/1/30
@article{osti_21450887,
author = {Abdo, A A and Ackermann, M and Ajello, M and Bechtol, K and Berenji, B and Agudo, I and Aller, H D and Aller, M F and Angelakis, E and Bach, U and others},
title = {THE SPECTRAL ENERGY DISTRIBUTION OF FERMI BRIGHT BLAZARS},
annote = {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 {sub {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}{sub ro}, and optical to X-ray, {alpha}{sub ox}, spectral slopes) and from the {gamma}-ray spectral index. Our data show that the synchrotron peak frequency ({nu} {sup S} {sub peak}) is positioned between 10{sup 12.5} and 10{sup 14.5} Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10{sup 13} and 10{sup 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} {sup S} {sub 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.},
doi = {10.1088/0004-637X/716/1/30},
url = {https://www.osti.gov/biblio/21450887},
journal = {Astrophysical Journal},
issn = {ISSN 0004-637X},
number = {1},
volume = {716},
place = {United States},
year = {2010},
month = {06}}
Weekes, Trevor C.; Aharonian, Felix A.; Hofmann, Werner
HIGH ENERGY GAMMA-RAY ASTRONOMY: Proceedings of the 4th International Meeting on High Energy Gamma-Ray Astronomy, AIP Conference Proceedingshttps://doi.org/10.1063/1.3076692
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 588, Issue 1-2https://doi.org/10.1016/j.nima.2008.01.023
HIGH ENERGY GAMMA-RAY ASTRONOMY: Proceedings of the 4th International Meeting on High Energy Gamma-Ray Astronomy, AIP Conference Proceedingshttps://doi.org/10.1063/1.3076698
HIGH ENERGY GAMMA-RAY ASTRONOMY: 5th International Meeting on High Energy Gamma-Ray Astronomy, AIP Conference Proceedingshttps://doi.org/10.1063/1.4772332