2012MNRAS.427.1482G

By simulating jet-inflated bubbles in cooling flows with the PLUTO hydrodynamic code we show that mixing of high entropy shocked jet's material with the intra-cluster medium (ICM) is the major heating process perpendicular to the jets' axis. Heating by the forward shock is not significant. The mixing is very efficient in heating the ICM in all directions, to distances of ∼ 10kpc and more. Although the jets are active for a time period of only 20Myr, the mixing and heating near the equatorial plane, as well as along the symmetry axis, continues to counter radiative cooling for times of >rsim 10⁸ yr after the jets have ceased to exist. We discuss some possible implications of the results. (i) The vigorous mixing is expected to entangle magnetic field lines, hence to suppress any global heat conduction in the ICM near the centre. (ii) The vigorous mixing forms multi-phase ICM in the inner cluster regions, where the coolest parcels of gas will eventually cool first, flow inwards and feed the active galactic nucleus to set the next jet-activity episode. This further supports the cold feedback mechanism. (iii) In cases where the medium outside the region of r ∼ 10kpc is not as dense as in groups and clusters of galaxies, like during the process of galaxy formation, the forward shock and the high pressure of the shocked jets' material might expel gas from the system.