On Bars, Bulges and Fuelling of Active Galactic Nuclei

Both fuelling of a central black hole and the build-up of bulges are – at least theoretically – facilitated by non-axisymmetric potentials. It is argued here that the recently established surface brightness division between bulge-dominated galaxies that dominate the local type 2 AGN luminosity function, and disk-dominated galaxies that host (at best) weak AGN can be understood in terms of a simple bar-instability criterion.