Most galaxies comparable to or larger than the mass of the Milky Way host hot, X-ray emitting atmospheres and central radio sources. Hot atmospheres and radio jets and lobes are the ingredients of radio-mechanical active galactic nucleus (AGN) feedback. About half of the most massive early type galaxies harbour multi-phase filamentary gas, which appears to result from the thermally unstable cooling of their hot atmospheres. We will present recent results based on radio and X-ray observations, which indicate that in massive early type galaxies the central radio sources are mostly switched on. We will show that for galaxies with thermally unstable hot atmospheres, the mechanical jet power correlates strongly with the Bondi accretion power. Further investigating the dependence of jet power on individual quantities in the Bondi formula, such as the supermassive black hole mass and the specific entropy of the gas at the Bondi radius, we find a very tight correlation between the jet power and black hole mass and, although poorly constrained, a hint of an anti-correlation between jet power and entropy. The results indicate that at least for thermally unstable systems, the jet power is set primarily by the supermassive black hole mass. The fact that we only see a strong correlation for thermally unstable atmospheres suggests that the black holes producing the jets and lobes are fed by cooling gas from the galactic atmospheres. It appears that once the atmosphere becomes thermally unstable, the cooling gas feeds the black holes in the centres of all galaxies at a similar jet-to-Bondi power ratio, possibly indicating a key universal property of black hole accretion in early-type galaxies. Importantly, since the central black hole mass of X-ray luminous early-type galaxies correlates with the total mass of the host halo, more massive systems undergoing thermally unstable cooling will naturally have larger jet powers.
Norbert Werner is a professor and the leader of the High-Energy Astrophysics research group in the Department of Theoretical Physics and Astrophysics at Masaryk University. He earned his PhD at SRON Netherland's Institute for Space Research and Utrecht University in 2008, where he mainly worked on the physics and chemical enrichment of the hot gas permeating clusters of galaxies and the cosmic web. Then he spent 8 years at Stanford University, mainly studying the influence of supermassive black holes on the hot gaseous haloes, investigating the faint and mysterious outskirts of galaxy cluster, and working on preparations for the science with the Japanese ASTRO-H/Hitomi satellite. Between 2016 and 2020 he was the leader of the MTA-ELTE Lendulet Hot Universe research group in Budapest, where he helped to initiate the development of CubeSats to detect gamma-ray bursts. Together with his team he continues his research activities at Masaryk University and acts as the scientific coordinator for the UV space telescope named QUVIK, which is a candidate for a Czech national science satellite.