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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{sup −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.

Authors:
;  [1]; ;  [2]; ;  [3];  [4];  [5]; ;  [6];  [7];  [8]; ;  [9];  [10];  [11]; ;  [12];  [13];  [14] more »; « less
  1. Physics Department, McGill University, Montreal, QC H3A 2T8 (Canada)
  2. Department of Physics, Washington University, St. Louis, MO 63130 (United States)
  3. Fred Lawrence Whipple Observatory, Harvard-Smithsonian Center for Astrophysics, Amado, AZ 85645 (United States)
  4. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States)
  5. School of Physics, National University of Ireland Galway, University Road, Galway (Ireland)
  6. Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907 (United States)
  7. Department of Astronomy and Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802 (United States)
  8. Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA), CC 67—Suc. 28, (C1428ZAA) Ciudad Autónoma de Buenos Aires (Argentina)
  9. DESY, Platanenallee 6, D-15738 Zeuthen (Germany)
  10. School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
  11. Department of Physics, California State University—East Bay, Hayward, CA 94542 (United States)
  12. Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, CA 95064 (United States)
  13. Department of Physics and Astronomy and the Bartol Research Institute, University of Delaware, Newark, DE 19716 (United States)
  14. Physics Department, Columbia University, New York, NY 10027 (United States)
Publication Date:
OSTI Identifier:
22663913
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 835; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANGULAR DISTRIBUTION; BL LACERTAE OBJECTS; COMPARATIVE EVALUATIONS; COMPTON EFFECT; DETECTION; ELECTRONS; EMISSION; GALAXIES; GALAXY NUCLEI; GAMMA RADIATION; MAGNETIC FIELDS; PHOTONS; POSITRONS; RELICT RADIATION; SIMULATION; SPECTRA; TEV RANGE; VISIBLE RADIATION

Citation Formats

Archambault, S., Griffin, S., Archer, A., Bugaev, V., Benbow, W., Cerruti, M., Buchovecky, M., Connolly, M. P., Cui, W., Finley, J. P., Falcone, A., Alonso, M. Fernández, Fleischhack, H., Hütten, M., Fortson, L., Furniss, A., Hervet, O., Johnson, C. A., Holder, J., Humensky, T. B., E-mail: elisa.pueschel@ucd.ie, E-mail: weisgarber@physics.wisc.edu, and and others. Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. United States: N. p., 2017. Web. doi:10.3847/1538-4357/835/2/288.
Archambault, S., Griffin, S., Archer, A., Bugaev, V., Benbow, W., Cerruti, M., Buchovecky, M., Connolly, M. P., Cui, W., Finley, J. P., Falcone, A., Alonso, M. Fernández, Fleischhack, H., Hütten, M., Fortson, L., Furniss, A., Hervet, O., Johnson, C. A., Holder, J., Humensky, T. B., E-mail: elisa.pueschel@ucd.ie, E-mail: weisgarber@physics.wisc.edu, & and others. Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS. United States. doi:10.3847/1538-4357/835/2/288.
Archambault, S., Griffin, S., Archer, A., Bugaev, V., Benbow, W., Cerruti, M., Buchovecky, M., Connolly, M. P., Cui, W., Finley, J. P., Falcone, A., Alonso, M. Fernández, Fleischhack, H., Hütten, M., Fortson, L., Furniss, A., Hervet, O., Johnson, C. A., Holder, J., Humensky, T. B., E-mail: elisa.pueschel@ucd.ie, E-mail: weisgarber@physics.wisc.edu, and and others. Wed . "Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS". United States. doi:10.3847/1538-4357/835/2/288.
@article{osti_22663913,
title = {Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS},
author = {Archambault, S. and Griffin, S. and Archer, A. and Bugaev, V. and Benbow, W. and Cerruti, M. and Buchovecky, M. and Connolly, M. P. and Cui, W. and Finley, J. P. and Falcone, A. and Alonso, M. Fernández and Fleischhack, H. and Hütten, M. and Fortson, L. and Furniss, A. and Hervet, O. and Johnson, C. A. and Holder, J. and Humensky, T. B., E-mail: elisa.pueschel@ucd.ie, E-mail: weisgarber@physics.wisc.edu and and others},
abstractNote = {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{sup −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.},
doi = {10.3847/1538-4357/835/2/288},
journal = {Astrophysical Journal},
number = 2,
volume = 835,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2017},
month = {Wed Feb 01 00:00:00 EST 2017}
}