Observational evidence for AGN feedback in early-type galaxies

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell PublishingA major amendment in recent models of hierarchical galaxy formation is the inclusion of so-called active galactic nucleus (AGN) feedback. The energy input from an active central massive black hole is invoked to suppress star formation in early-type galaxies at later epochs. A major problem is that this process is poorly understood, and compelling observational evidence for its mere existence is still missing. In search for signatures of AGN feedback, we have compiled a sample of 16 000 early-type galaxies in the redshift range 0.05 200 km s ) and roughly evenly distributed between star formation and AGN at intermediate and low (σ