franco_vazza"Cosmological simulation of radio synchrotron bridge between
pre-merging galaxy clusters" by K. Nishiwaki, Brunetti, myself and Gheller
This paper investigates a possible formation scenario for the emission in a radio "bridge" observed with LOFAR, in between two clusters which still have to merge (usually this emission is found **after** the merger as it is believed to be the result of the dissipated turbulent energy injected during the merger).
But by following the process in detail with Lagragian tracers and MHD cosmological simulations (ENZO code) we show the emission can actually be produced also before !
If a modest amount of mildly relativistic electrons was already present in the region, as a result of the previous injections by AGN, star winds and previous shocks, than the turbulence developing during the merger can actually do Fermi II re-acceleration on the same electrons, and make them radio visible again.
The final simulated radio spectra, once compared with the latest constraints by LOFAR observations, allows to further constrains the parameters of the model (essentially , the little known amplification of magnetic fields on scales poorly resolved by the simulation).
Ages ago we did an ENZO simulation of the same system, to show that this scenario might work, but just relying on the timely analysis of turbulence at each snapshots, and not directly evolving the ageing of electrons with Lagrangian tracers, as instead K. Nishiwaki just accurately did in this paper.