Buoyant bubbles of relativistic plasma in galaxy cluster cores plausibly play a key role in conveying the energy from a supermassive black hole to the intracluster medium (ICM). While the amount of energy supplied by the bubbles to the ICM is set by energy conservation, the physical mechanisms involved in coupling the bubbles and the ICM are still being debated. A team of researchers from the Max Planck Institute for Astrophysics (MPA) and the University of Oxford argues that internal waves might be efficient in extracting energy from the bubbles and distributing it over large masses of the ICM.

Figure 1. Chandra X-ray image of the Perseus cluster. The bubbles appear as dark (X-ray dim) regions in this image. “Active” bubbles (radius ∼ 7 kpc) are marked with black dashed circles. They are surrounded by quasi-spherical weak shocks (radius ∼ 14 kpc), shown by yellow circles. The outer bubble, to the north-west from the centre, has the “horizontal” and “vertical” (radial) sizes L ∼ 25 kpc and h ∼ 7 kpc, respectively.