@article{f346120f78194df499040106e10f1626,
title = "Probing intergalactic magnetic fields with simulations of electromagnetic cascades",
abstract = "We determine the effect of intergalactic magnetic fields on the distribution of high-energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-ray-induced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called {"}Large Sphere Observer{"} method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left- and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the Q-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the S-statistics. Both methods provide a quantitative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths B10-15 G and magnetic coherence lengths Lc100 Mpc. We show that the S-statistics has a better performance than the Q-statistics when assessing magnetic helicity from the simulated halos.",
author = "{Alves Batista}, Rafael and Andrey Saveliev and G{\"u}nter Sigl and Tanmay Vachaspati",
note = "Funding Information: R.A.B. acknowledges the financial support from the John Templeton Foundation. The work of A.S. has been supported by the Deutscher Akademischer Austauschdienst e.V. (DAAD) funded by the Bundesministerium fur Bildung und Forschung (BMBF) and the European Union (EU) Marie Curie Actions. A.S. would like to thank Arizona State University (ASU) for the hospitality during his stay. Furthermore, A.S. is grateful to the Helmholtz Alliance for Astroparticle Physics (HAP) and the Collaborative Research Center SFB 676 Particles, Strings and the Early Universe for providing generous travel funds which were important for the collaboration leading to this work. T.V. is supported by United States Department of Energy (DOE), Office of High Energy Physics, under Award number #DE-SC0013605 at ASU. T.V. is grateful to the Institute for Advanced Study, Princeton for hospitality while this work was being done. Special thanks go to Andrew J. Long for his ideas and discussions which helped to complete this work and to the Nordic Institute for Theoretical Physics (NORDITA) in Stockholm for organizing the workshop Origin, Evolution, and Signatures of Cosmological Magnetic Fields during which important aspects of this work have been discussed. Publisher Copyright: {\textcopyright} 2016 American Physical Society.",
year = "2016",
month = oct,
day = "10",
doi = "10.1103/PhysRevD.94.083005",
language = "English (US)",
volume = "94",
journal = "Physical Review D",
issn = "2470-0010",
publisher = "American Physical Society",
number = "8",
}