Simulazioni numeriche di restarting radio galaxies

The goal of this thesis is to study the physical properties and morphology of a plasma jet associated with a radio galaxy when its characterized by a restart activity. This happens when the Active Galactic Nucleus (AGN) stops to fuel the expansion of the jet for a certain time, to then restart to supply again energy to the plasma. The focus will split into low-powered and high-powered radio galaxies to see if the restart influences their morphology. Then the results obtained will be compared to the observation of the sources of Centaurus A (for the low-powered radio galaxies) and 3C388 (for the high-powered restarting radio galaxies) to study if the simulations can describe these particular cases. To do so, the relativistic magneto-hydrodynamic equations (RMHD) will be solved using the PLUTO code with the computation power of the OCCAM supercomputer of C3S. The initial parameters will then be set to obtain a low-powered source of the Fanaroff-Riley I class (FRI) for the first case (case A) and a high-powered FRII source for the second one (case B). The simulations, before applying any restart, show that the choice of the parameters is correct as the sources described by the data, for both cases A and B, are the ones expected. The results obtained for case A shows a morphology compatible with the one observed for Centaurus A, with the presence of a warmspot that gives the source a dual FRI-FRII morphology. While, for the latter, it has been discovered that to observe a morphology similar to the one of 3C388 (a Double Double Radio Galaxy, DDRG) it is needed a precise timing of the restart, otherwise the source will be a standard FRII. Moreover, it has been observed that even with the correct restart the morphology of a DDRG is a temporary phase.