Simulating the transport of relativistic electrons and magnetic fields injected by radio galaxies in the intracluster medium

open4siAcknowledgements. We are grateful to the anonymous referee for their helpful comments on the first draft of this work. The authors gratefully acknowledge the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for supporting this project by providing computing time through the John von Neumann Institute for Computing (NIC) on the GCS Supercomputer JUWELS at Jülich Supercomputing Centre (JSC), under projects “stressicm” and projects no. 11823, 10755 and 9016 as well as hhh44. F.V. acknowledges financial support from the European Union’s Horizon 2020 program under the ERC Starting Grant “MAGCOW”, no. 714196. D.W. is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 441694982. M.B. acknowledges support from the Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy – EXC 2121 “Quantum Universe” – 390833306. We also acknowledge the usage of online storage tools kindly provided by the Inaf Astronomica Archive (IA2) initiave (http://www.ia2.inaf.it) and of the Cosmological Calculator by N. Wrigth (http://www.astro.ucla.edu/~wright/CosmoCalc.html). We gratefully acknowledge helpful scientific discussions with M. Brienza and E. Vardoulaki, concerning details of radio observations of radio galaxies.Radio galaxies play an important role in the seeding of cosmic rays and magnetic fields in galaxy clusters. Here, we simulate the evolution of relativistic electrons injected into the intracluster medium by radio galaxies. Using passive tracer particles added to magnetohydrodynamical adaptive-mesh simulations, we calculated the evolution of the spectrum of relativistic electrons, taking into account energy losses and re-acceleration mechanisms associated with the dynamics of the intracluster medium. Re-acceleration can occur at shocks via diffusive shock acceleration, and in turbulent flows via second-order Fermi re-acceleration. This study confirms that relativistic electrons from radio galaxies can efficiently fill the intracluster medium over scales of several hundreds of Myr and that they create a stable reservoir of fossil electrons that remains available for further re-acceleration by shock waves and turbulent gas motions. Our results also show that late evolution of radio lobes and remnant radio galaxies is significantly affected by the dynamics of the surrounding intracluster medium. Here, the diffusive re-acceleration couples the evolution of relativistic particles to the gas perturbations. In the near future, deep radio observations, especially at low frequencies, will be able to probe such mechanisms in galaxy clusters.openVazza F.; Wittor D.; Brunetti G.; Bruggen M.Vazza F.; Wittor D.; Brunetti G.; Bruggen M