Galactic wind shells and high redshift radio galaxies

On the nature of associated absorbers

Astrophysics Group, Cavendish Laboratory, Cambridge CB3 0HE, UK e-mail: M.Krause@mrao.cam.ac.uk

Received: 19 August 2004
Accepted: 15 March 2005

Abstract

A jet is simulated on the background of a galactic wind headed by a radiative bow shock. The wind shell, which is due to the radiative bow shock, is effectively destroyed by the impact of the jet cocoon, thanks to Rayleigh-Taylor instabilities. Associated strong HI absorption, and possibly also molecular emission, in high redshift radio galaxies which is observed preferentially in the smaller ones may be explained by that model, which is an improvement of an earlier radiative bow shock model. The model requires temperatures of ≈10⁶ K in the proto-clusters hosting these objects, and may be tested by high resolution spectroscopy of the Lyα line. The simulations show that – before destruction – the jet cocoon fills the wind shell entirely for a considerable time with intact absorption system. Therefore, radio imaging of sources smaller than the critical size should reveal the round central bubbles, if the model is correct.