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. Johnson; P. 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

doi:10.3847/1538-4357/835/2/288

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

Physics and Astronomy (Twin Cities)

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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 language	English (US)
Article number	288
Journal	Astrophysical Journal
Volume	835
Issue number	2
DOIs	https://doi.org/10.3847/1538-4357/835/2/288
State	Published - Feb 1 2017

Bibliographical note

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© 2017. The American Astronomical Society. All rights reserved..

Keywords

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

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Archambault, S., Archer, A., Benbow, W., Buchovecky, M., Bugaev, V., Cerruti, M., Connolly, M. P., Cui, W., Falcone, A., Alonso, M. F., Finley, J. P., Fleischhack, H., Fortson, L., Furniss, A., Griffin, S., Hütten, M., Hervet, O., Holder, J., Humensky, T. B., ... Zitzer, B. (2017). Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. Astrophysical Journal, 835(2), Article 288. https://doi.org/10.3847/1538-4357/835/2/288

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

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title = "Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS",

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.",

keywords = "BL Lacertae objects: general, galaxies: active, gamma rays: galaxies, magnetic fields",

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

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AU - Archambault, S.

AU - Archer, A.

AU - Benbow, W.

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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N2 - 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.

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.

KW - BL Lacertae objects: general

KW - galaxies: active

KW - gamma rays: galaxies

KW - magnetic fields

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UR - http://www.scopus.com/inward/citedby.url?scp=85011961389&partnerID=8YFLogxK

U2 - 10.3847/1538-4357/835/2/288

DO - 10.3847/1538-4357/835/2/288

M3 - Article

AN - SCOPUS:85011961389

SN - 0004-637X

VL - 835

JO - Astrophysical Journal

JF - Astrophysical Journal

IS - 2

M1 - 288

ER -

Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS

Abstract

Bibliographical note

Keywords

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