Prof. Nicole Nesvadba

How do supermassive black holes suppress star formation in their host galaxies? This question is at the heart of the AGN feedback hypothesis, and is still unanswered after two decades of intense observational and theoretical work. Most studies focus on gas removal in the host galaxies of very powerful AGN as a main feedback mode, however, observations clearly show that outflows alone are insufficient to understand AGN feedback. Meanwhile, alternative scenarios do exist which even challenge the basic assumption of a physical connection between the AGN energy output and low star formation rates in galaxies. As a consequence, in spite of the current popularity of the AGN feedback hypothesis, its central prediction -- the direct physical link between the energy injection by the AGN and star formation -- remains a subject of considerable controversy. In this talk, I will discuss the observational and theoretical evidence that AGN do impact star formation in their host galaxies, within a scenario that includes outflows as well as turbulence induced by the deposition of AGN energy in the surrounding gas. I will focus on radio AGN activity -- often considered a rare phenomenon, but actually ubiquitous in the cores of massive galaxies with Mstellar >= 10**11 Msun -- which provides us with a particularly clean environment to investigate the distribution of AGN kinetic energy in the surrounding multiphase gas, and its impact on star formation. I will also illustrate how detailed observations of the gas and stellar content in massive galaxies combined with with hydrodynamic simulations can pave the way towards a physical understanding of the energy transfer that is at the core of the AGN feedback hypothesis.