A snapshot of the oldest active galactic nuclei feedback phases

Active galactic nuclei inject large amounts of energy into their host galaxies and surrounding environment, shaping properties evolution1,2. In particular, active-galactic-nuclei jets inflate cosmic-ray lobes, which can rise buoyantly as light ‘bubbles’ in the medium3, displacing heating encountered thermal gas thus halting its spontaneous cooling. These bubbles have been identified a wide range systems4,5. However, due to short synchrotron lifetime electrons, most advanced phases evolution remained observationally unconstrained, preventing us from fully understand coupling with external medium, active feedback. Simple subsonic hydrodynamic models6,7 predict that pressure gradients, naturally present around rising bubbles, transform them toroidal structures, resembling mushroom clouds stratified atmosphere. The way timescales on these tori will eventually disrupt depend various factors including magnetic fields plasma viscosity8,9. Here we report observations below 200 MHz, sensitive oldest radio-emitting particles, showing late multiple generations galaxy group unprecedented level detail. bubbles’ buoyancy power efficiently offset radiative cooling intragroup medium. still not thoroughly mixed gas, after hundreds million years, probably under action fields. LOFAR reveal bubbles. bubble offsets while prevent mixing between