Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS

S. Archambault, A. Archer, W. Benbow, M. Buchovecky, V. Bugaev, M. Cerruti, M. P. Connolly, W. Cui, A. Falcone, M. Fernández Alonso, J. P. Finley, H. Fleischhack, L. Fortson, A. Furniss, S. Griffin, M. Hütten, O. Hervet, J. Holder, T. B. Humensky, C. A. JohnsonP. Kaaret, P. Kar, D. Kieda, M. Krause, F. Krennrich, M. J. Lang, T. T Y Lin, G. Maier, S. McArthur, P. Moriarty, D. Nieto, S. O'Brien, R. A. Ong, A. N. Otte, M. Pohl, A. Popkow, E. Pueschel, J. Quinn, K. Ragan, P. T. Reynolds, G. T. Richards, E. Roache, A. C. Rovero, I. Sadeh, K. Shahinyan, D. Staszak, I. Telezhinsky, J. Tyler, S. P. Wakely, A. Weinstein, T. Weisgarber, P. Wilcox, A. Wilhelm, D. A. Williams, B. Zitzer

Research output: Contribution to journalArticle

12 Citations (Scopus)

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+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.

Original languageEnglish (US)
Article number288
JournalAstrophysical Journal
Volume835
Issue number2
DOIs
StatePublished - Feb 1 2017

Fingerprint

blazars
cascades
electron-positron pairs
gamma rays
active galactic nuclei
magnetic field
electron
photons
exclusion
magnetic fields
deflection
confidence
field strength
angular distribution
scattering
microwaves
simulation

Keywords

  • BL Lacertae objects: general
  • galaxies: active
  • gamma rays: galaxies
  • magnetic fields

Cite this

Archambault, S., Archer, A., Benbow, W., Buchovecky, M., Bugaev, V., Cerruti, M., ... Zitzer, B. (2017). Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. Astrophysical Journal, 835(2), [288]. https://doi.org/10.3847/1538-4357/835/2/288

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; 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.

In: Astrophysical Journal, Vol. 835, No. 2, 288, 01.02.2017.

Research output: Contribution to journalArticle

Archambault, S, Archer, A, Benbow, W, Buchovecky, M, Bugaev, V, Cerruti, M, Connolly, MP, Cui, W, Falcone, A, Alonso, MF, Finley, JP, Fleischhack, H, Fortson, L, Furniss, A, Griffin, S, Hütten, M, Hervet, O, Holder, J, Humensky, TB, Johnson, CA, Kaaret, P, Kar, P, Kieda, D, Krause, M, Krennrich, F, Lang, MJ, Lin, TTY, Maier, G, McArthur, S, Moriarty, P, Nieto, D, O'Brien, S, Ong, RA, Otte, AN, Pohl, M, Popkow, A, Pueschel, E, Quinn, J, Ragan, K, Reynolds, PT, Richards, GT, Roache, E, Rovero, AC, Sadeh, I, Shahinyan, K, Staszak, D, Telezhinsky, I, Tyler, J, Wakely, SP, Weinstein, A, Weisgarber, T, Wilcox, P, Wilhelm, A, Williams, DA & Zitzer, B 2017, 'Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS', Astrophysical Journal, vol. 835, no. 2, 288. https://doi.org/10.3847/1538-4357/835/2/288
Archambault S, Archer A, Benbow W, Buchovecky M, Bugaev V, Cerruti M et al. Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. Astrophysical Journal. 2017 Feb 1;835(2). 288. https://doi.org/10.3847/1538-4357/835/2/288
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. / Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. In: Astrophysical Journal. 2017 ; Vol. 835, No. 2.
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AU - Buchovecky, M.

AU - Bugaev, V.

AU - Cerruti, M.

AU - Connolly, M. P.

AU - Cui, W.

AU - Falcone, A.

AU - Alonso, M. Fernández

AU - Finley, J. P.

AU - Fleischhack, H.

AU - Fortson, L.

AU - Furniss, A.

AU - Griffin, S.

AU - Hütten, M.

AU - Hervet, O.

AU - Holder, J.

AU - Humensky, T. B.

AU - Johnson, C. A.

AU - Kaaret, P.

AU - Kar, P.

AU - Kieda, D.

AU - Krause, M.

AU - Krennrich, F.

AU - Lang, M. J.

AU - Lin, T. T Y

AU - Maier, G.

AU - McArthur, S.

AU - Moriarty, P.

AU - Nieto, D.

AU - O'Brien, S.

AU - Ong, R. A.

AU - Otte, A. N.

AU - Pohl, M.

AU - Popkow, A.

AU - Pueschel, E.

AU - Quinn, J.

AU - Ragan, K.

AU - Reynolds, P. T.

AU - Richards, G. T.

AU - Roache, E.

AU - Rovero, A. C.

AU - Sadeh, I.

AU - Shahinyan, K.

AU - Staszak, D.

AU - Telezhinsky, I.

AU - Tyler, J.

AU - Wakely, S. P.

AU - Weinstein, A.

AU - Weisgarber, T.

AU - Wilcox, P.

AU - Wilhelm, A.

AU - Williams, D. A.

AU - Zitzer, B.

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AB - 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+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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KW - galaxies: active

KW - gamma rays: galaxies

KW - magnetic fields

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