Search for magnetically broadened cascade emission from blazars with veritas
Archambault, S. Archer, A. Benbow, W. Buchovecky, M. Bugaev, V. Cerruti, M. Connolly, M. P. Cui, W. Falcone, A. Alonso, M. Fernández
Archambault, S.
Archer, A.
Benbow, W.
Buchovecky, M.
Bugaev, V.
Cerruti, M.
Connolly, M. P.
Cui, W.
Falcone, A.
Alonso, M. Fernández
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Publication Date
2017-02-02
Keywords
Externally hosted open access publications with University of Galway authors, galaxies: active, gamma rays: galaxies, magnetic fields, extragalactic background light, active galactic nuclei, gamma-ray observations, large-area telescope, pair halos, cosmic voids, tev blazars, fields, radiation, universe
Type
journal article
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Citation
Archambault, S. Archer, A.; Benbow, W.; Buchovecky, M.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Falcone, A.; Alonso, M. Fernández; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Griffin, S.; Hütten, M.; Hervet, O.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; Moriarty, P.; Nieto, D.; O’Brien, S.; Ong, R. A.; Otte, A. N.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Sadeh, I.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Weisgarber, T.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Zitzer, B. (2017). Search for magnetically broadened cascade emission from blazars with veritas. The Astrophysical Journal 835 (2),
Abstract
We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron-positron pairs, which then interact with cosmic microwave background photons via inverse-Compton scattering to produce gamma-rays. Due to the deflection of the electron- positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadened emission from 1ES 1218 vertical bar 304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around 10(-14) G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES. 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission.
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Publisher
American Astronomical Society