AGN fueling: the observational point of view

Abstract

Observations at multiple wavelengths are reviewed to search for evidence for fueling mechanisms in galaxies, both for nuclear starbursts and AGN activity. Although it is undisputed that dynamical perturbations such as bars or tidal interactions accumulate gas in the central regions and sometimes trigger nuclear starbursts, the evidence remains scarce that these are necessary to fuel AGNs. Interpretations in terms of time-scales, feed-back, and black hole evolution are discussed. It is suggested that the AGN phase corresponds to the early-type phases of galaxies.