Misaligned External Gas Acquisition Boosts Central Black Hole Activities

One important question in active galactic nuclei (AGN) is how gas is brought down to the galaxy center. Both internal secular evolution (torque induced by nonaxisymmetric galactic structures such as bars) and external processes (e.g., mergers or interactions) are expected to redistribute the angular momentum (AM) and transport gas inward. However, it is still under debate whether these processes can significantly affect AGN activities. Here we for the first time report that AGN fraction increases with the difference of kinematic position angles (ΔPA ≡ ∣PA gas − PA star ∣) between ionized gas (PA gas ) and stellar disks (PA star ) in blue and green galaxies, meanwhile this fraction remains roughly constant for red galaxies. Also, the high luminosity AGN fraction increases with ΔPA, while the low luminosity AGN fraction is independent of ΔPA. These observational results support a scenario in which the interaction between accreted and preexisting gas provides the AM loss mechanism, thereby the gas inflow fuels the central BH activities, and the AM loss efficiency is positively correlated with the ΔPA.