SIMBAD references

Recent suggestions that buoyant radio emitting cavities in the intracluster medium (ICM) can cause significant reheating of cooling flows are re-examined when the effects of the intracluster magnetic field are included. Expansion of the cavity creates a tangential field in the ICM surrounding the cavity, and this field can suppress instabilities that mix the ICM and the radio source. Onset of instability can be delayed for ∼10⁸ yr, and calculation of the subsequent turbulent cascade shows that actual reheating of the ICM may be delayed for up to ∼5x10⁸ yr. These results may explain why the relic radio cavities remain as intact entities at times ≥10⁸ yr, and the delay in injection of energy from the radio source into the ICM may mean that the role of radio sources in reheating cooling flows should be re-examined. In addition, the existence of relic radio cavities may also imply that the particle content of radio source lobes is primarily electrons and protons rather than electrons and positrons.