1999ApJ...524...65T

Seyfert nuclei are typical active galactic nuclei (AGNs) in the local universe, which are thought to be powered by gas accretion onto a supermassive black hole (SMBH). The dynamical effect exerted either by nonaxisymmetric gravitational potential (such as a stellar bar) or by interaction with other galaxies has been often considered to cause the efficient gas fueling. However, recent systematic studies for large samples of Seyfert nuclei have shown that (1) Seyfert nuclei do not prefer barred galaxies as their hosts, and (2) only ≃10% of Seyfert galaxies have companion galaxies. These findings again raise the question: ``What is important in the fueling of nuclear activity?'' Here we suggest that an alternative fueling mechanism, the minor-merger-driven (i.e., mergers between a gas-rich disk galaxy and a bound, less-massive satellite galaxy) fueling appears consistent with almost all important observational properties of Seyfert galaxies. Nucleated (i.e., either an SMBH or a dense nuclear star cluster) galaxies and satellites seem necessary to ensure that the gas in the host disk is surely fueled into the very inner region (e.g., {Lt}1 pc). Taking account that local quasars may be formed by major mergers between/among galaxies, we propose that all the AGNs in the local universe were made either by minor or by major mergers.