2002A&A...386L...1K

A radiative hydrodynamic simulation for a typical, powerful high redshift radio galaxy is presented. The jet is injected at one third the speed of light into a 10000 times denser, homogeneous medium. In the beginning of the simulation, the bow shock consists of a spherical shell that is similar to a spherical blast wave. This shell cools radiatively down to ≃10⁴K, providing after 6x10⁶yrs a neutral column of 3.8x10²¹cm^–2 around the whole system. The shell starts to fragment and forms condensations. This absorbing screen will cover a smaller and smaller fraction of the radio source, and therefore the emission line region, and eventually form stars in typically 10⁴ globular clusters of 10⁶M_☉. Approximately 10⁹M_☉ are entrained into the radio cocoon. This gas, cooling and illuminated from the radio source, could be the emission line gas observed in high redshifted radio galaxies and radio loud quasars. The neutral column behind the bow shock can account for the absorption found in almost all of the small sources. The globular cluster excess of ≃10⁴ systems found in present day brightest cluster galaxies (BCGs), which are believed to be the vestiges of these objects, is consistent with the presented scenario.