Relativistic hydrodynamic jets in the intracluster medium

Abstract: We have performed the first three-dimensional relativistic hydrodynamic simulations of extragalactic jets of pure leptonic and baryonic plasma compositions propagating into a hydrostatic intracluster medium environment. The numerical simulations use a general equation of state for a multi-component relativistic gas which closely reproduces the Synge equation of state for a relativistic perfect gas. We find that morphological and dynamical differences between leptonic and baryonic jets are much less evident than those between hot and cold jets. In all these models, the jets first propagate with essentially constant velocities within the core radius of the intracluster medium and then accelerate progressively so as to increase the jet advance velocity by a factor of between 1.2 and 1.6 at the end of simulations, depending upon the models. The temporal evolution of the average cavity pressure is not consistent with that expected by the extended theoretical model even if the average cavity pressure decreases as a function of time with a power-law. Our simulations produce synthetic radio images that are dominated by bright hot spots and appear similar to observations of the extended radio galaxies with collimated radio jets. These bright radio lobes would be visible as dark regions in X-ray images and are morphologically similar to observed X-ray cavities in the intracluster medium. This supports the expectation that the bow shock surrounding the head of the jet is important mechanism for producing X-ray cavities in the intracluster medium. Although there are quantitative differences among the models the total radio and X-ray intensity curves show qualitatively similar trends in all of them.