Nonthermal Particles and Radiation Produced by Cluster Merger Shocks

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Show simple item record Berrington, Robert C. Dermer, Charles D. 2020-01-31T15:19:47Z 2020-01-31T15:19:47Z 9/10/2003
dc.identifier.citation Berrington, R. C., & Dermer, C. D. (2003). Nonthermal particles and radiation produced by cluster merger shocks. The Astrophysical Journal, 594(2), 709. en_US
dc.description.abstract We have developed a numerical model for the temporal evolution of particle and photon spectra resulting from nonthermal processes at the shock fronts formed in merging clusters of galaxies. Fermi acceleration is approximated by injecting power-law distributions of particles during a merger event, subject to constraints on maximum particle energies. We consider synchrotron, bremsstrahlung, Compton, and Coulomb processes for the electrons, nuclear, photomeson, and Coulomb processes for the protons, and knock-on electron production during the merging process. The broadband radio through γ-ray emission radiated by nonthermal protons and primary and secondary electrons is calculated both during and after the merger event. Using ROSAT observations to establish typical parameters for the matter density profile of clusters of galaxies, we find that typical merger shocks are weak and accelerate particles with relatively soft spectra. We consider the prospects for detecting nonthermal radio and γ-ray emission from clusters of galaxies and implications for the origin of ultra–high-energy cosmic rays and the diffuse γ-ray background. Our results suggest that only a few of the isotropically distributed unidentified EGRET sources are due to shocks formed in cluster mergers and that only a minor contribution to the diffuse extragalactic γ-ray background can originate from cluster merger shocks. Cluster merger shocks can accelerate protons to ≲1019 eV for the standard parameters considered here. We predict that GLAST will detect several cluster mergers, and depending on the mean magnetic fields in the intracluster medium, the Low Frequency Array could detect anywhere from several to several hundred. en_US
dc.format.mimetype application/pdf
dc.relation.isversionof en_US
dc.relation.isversionof en_US
dc.subject acceleration of particles en_US
dc.subject galaxies: clusters: general en_US
dc.subject methods: numerical en_US
dc.subject shock waves en_US
dc.subject X-rays: galaxies: clusters en_US
dc.title Nonthermal Particles and Radiation Produced by Cluster Merger Shocks en_US
dc.type Article en_US
dc.rights.holder (c) 2003. The American Astronomical Society

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