On the interaction of jets with the dense medium of the early universe

In recent years, radio galaxies have been found at redshifts above five. They differ in higher radio power and emission line characteristics from sources nearby. To understand these centers of proto-galaxy-clusters, hydrodynamic jets with cooling were simulated. After validation of the 3D code NIRVANA by comparison with literature simulations, an adiabatic 2D parameter study in the relevant regime (density contrast jet/medium eta=10^{-2}-10^{-5} was performed. Characteristic cocoon shape and broadenings were found. The radial expansion can be analytically approximated by a spherical blast wave with constant energy injection. In a non-equilibrium simulation the bow shock cooled to 10^4 K during jet propagation time (external density 1 ccm. After global cooling and compression, the bow shock turned into a big absorber which fragmented, and should form stars in typically 10^4 globular clusters of 10^6 solar masses. Filamentation and fragmentation was confirmed at high resolution. Absorbers in far-off radio galaxies and globular cluster excesses in nearby CD galaxies can be explained that way. With literature parameters fo Cygnus~A, a 3D simulation, for the first time with counter-jet, was performed. The bow shock shows two clearly separated phases, also evident in observation. Basic jet parameters have been derived. The simulation shows characteristic X-ray features (rings) which were identified and interpreted in two sources (M87).