Fuelling active galactic nuclei

Abstract

We suggest that most nearby active galactic nuclei are fed by a series of small-scale, randomly oriented accretion events. Outside a certain radius these events promote rapid star formation, while within it they fuel the supermassive black hole. We show that the events have a characteristic time-evolution. This picture agrees with several observational facts. The expected luminosity function is broadly in agreement with that observed for moderate-mass black holes. The spin of the black hole is low, and aligns with the inner disc in each individual feeding event. This implies radio jets aligned with the axis of the obscuring torus, and uncorrelated with the large-scale structure of the host galaxy. The ring of young stars observed about the Galactic Centre are close to where our picture predicts that star formation should occur. © 2007 The Authors. Journal compilation © 2007 RAS.