The enrichment of "fossil" radio electrons by multiple radio galaxies in clusters and in the cosmic web
Radio observations show that a volume-filling distribution of fossil relativistic electrons is needed to understand the emergence of diffuse radio emissions in cluster of galaxies (e.g. radio halos or radio relics), because such electrons are the necessary “seeds” used by Fermi I and II re-acceleration mechanisms to power radio emission. Radio galaxies are a viable candidate for the continuous seeding of such electrons in cosmic structures, but they are a difficult ingredient for modern numerical simulations as their modelling encompasses a challenging range of scales. I will present recent developments and results in the numerical simulation of this process, which potentially allows us to connect the visible an invisible activity of radio galaxies in crowded cosmic environments, and help us better constraining AGN energetics and duty cycle.