Simulation of a Jet in a Galactic Wind
In the 1990ies, an ESO key project unified the up to then occasional evidence for absorption against the huge Lyman α emission line haloes of radio galaxies at high redshift (> 2). The results are published in Rob van Ojik et al. (1997). In short, almost all of the smaller sources have it, almost none of the larger ones, and it's not the Lyman α forest. The results have been confirmed recently by R.J. Wilman et al. (2004). Several explanations have been proposed. I summarised them in my recent paper which also contains these simulations. My suggestion is that the absorbers are due to a radiative bow shock by a galactic wind which preceeds the jet phase. In the larger sources, this thin shell is destroyed by the jet (sideways, the jet's cocoon accelerates the shell rendering the latter Rayleigh-Taylor instable). The hydrodynamic simulation (below) confirms the feasability of the model, which is well constrained by the observations. It requires the temperature in the proto-clusters of galaxies, which host the objects, to have a temperature of about a factor of ten less then present day clusters. This could not be confirmed directly by observations so far. If the onset of a galactic wind would be related to a starburst, this model would constitute a new hint of the starburst AGN connection.