The long-term effect of radio sources on the intracluster medium

Abstract

We have performed three-dimensional hydrodynamical simulations of FR II radio sources in β-profile cooling-flow clusters. The effects of cooling of the cluster gas were incorporated into a modified version of the ZEUS-MP code. The simulations followed not only the active phase of the radio source, but also the long-term behaviour for up to 2 Gyr after the jets of the radio source were switched off. We find as expected that the radio source has a significant effect on the cooling flow while it is active; however, we also find that the effects of the radio source on the cluster are long-lived. A buoyancy-driven convective flow is established as the remnants of the radio source rise through the cluster dragging material from the cluster core. Although the central Mpc of the cluster reverts to having a cooling flow, this asymmetric convective flow is able to remove the cool gas accumulating at the cluster core and indeed there is a net outflow persisting for time-scales of approximately an order of magnitude longer than the time for which the source is active or longer. The convective flow may also provide a mechanism to enhance the metallicity of the cluster gas at large cluster radii.