On bars, bulges, and the fueling of active galactic nuclei

Both the fueling of a central black hole and the buildup of bulges are-at least theoretically-facilitated by nonaxisymmetric potentials. It is argued here that the recently established surface brightness division between bulge-dominated galaxies that dominate the local type 2 active galactic nucleus (AGN) luminosity function and disk-dominated galaxies that host (at best) weak AGNs can be understood in terms of a simple bar-instability criterion.