Mechanical heating by active galaxies

Jets and winds are significant channels for energy loss from accreting black holes. These outflows mechanically heat their surroundings, through shocks as well as gentler forms of heating. We discuss recent efforts to understand the nature and distribution of mechanical heating by central active galactic nuclei (AGN) in clusters of galaxies, using numerical simulations and analytic models. Specifically, we will discuss whether the relatively gentle 'effervescent heating' mechanism can compensate for radiative losses in the central regions of clusters, and account for the excess entropy observed at larger radii. J. Binney (2005 Phil. Trans. R. Soc. A, 363, 739749, doi: 10. 1098/rsta.2004.1520) discusses the possible role of violent, episodic heating by AGN in clusters.