ELMAG: A Monte Carlo simulation of electromagnetic cascades on the extragalactic background light and in magnetic fields

Abstract

A Monte Carlo program for the simulation of electromagnetic cascades initiated by high-energy photons and electrons interacting with extragalactic background light (EBL) is presented. Pair production and inverse Compton scattering on EBL photons as well as synchrotron losses and deflections of the charged component in extragalactic magnetic fields (EGMF) are included in the simulation. Weighted sampling of the cascade development is applied to reduce the number of secondary particles and to speed up computations. As final result, the simulation procedure provides the energy, the observation angle, and the time delay of secondary cascade particles at the present epoch. Possible applications are the study of TeV blazars and the influence of the EGMF on their spectra or the calculation of the contribution from ultrahigh energy cosmic rays or dark matter to the diffuse extragalactic gamma-ray background. As an illustration, we present results for deflections and time delays relevant for the derivation of limits on the EGMF. Program summaryProgram title: ELMAG 1.01Catalogue identifier: AELK_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELK_v1_0.htmlProgram obtainable from: CPC Program Library, Queenʼs University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 4290No. of bytes in distributed program, including test data, etc.: 459 305Distribution format: tar.gzProgramming language: Fortran 95Computer: Any computer with Fortran 95 compilerOperating system: Any system with Fortran 95 compilerHas the code been vectorised or parallelised?: Yes, using the MPI versionRAM: 4 MbytesClassification: 11.3, 11.4Nature of problem: Calculation of secondaries produced by electromagnetic cascades on the extragalactic background light (EBL).Solution method: Monte Carlo simulation of pair production and inverse Compton scattering on EBL photons; two parametrisations from Ref. [1] can be chosen as EBL; weighted sampling of the cascading secondaries; recording of energy, observation angle and time delay of secondary particles at the present epoch.Restrictions: Deflections and time delays are calculated in the small-angle approximation.Running time: 400 seconds for 103 photons injected at redshift z=0.2 with energy E=100 TeV using one Intel(R) Core(TM) i7 CPU with 2.8 GHz.