Misaligned external gas acquisition boosts central black hole activities

TL;DR

This study finds that misaligned external gas acquisition, indicated by differences in gas and star kinematic angles, enhances AGN activity, especially in high-luminosity cases, suggesting external gas interactions fuel black hole growth.

Contribution

First observational evidence linking gas-stellar kinematic misalignment to increased AGN activity, highlighting external gas accretion as a key fueling mechanism.

Findings

AGN fraction increases with gas-stellar kinematic misalignment in blue/green galaxies.

High luminosity AGN fraction correlates with larger $ riangle PA$, low luminosity does not.

External gas interactions likely facilitate gas inflow and black hole fueling.

Abstract

One important question in active galactic nucleus (AGN) is how gas is brought down to the galaxy center. Both internal secular evolution (torque induced by non-axisymmetric 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 ($\Delta PA\equiv|PA_{\mathrm{gas}}-PA_{\mathrm{star}}|$) between ionized gas ($PA_{\mathrm{gas}}$) and stellar disks ($PA_{\mathrm{star}}$) in blue and green galaxies, meanwhile this fraction remains roughly constant for red galaxies. Also the high luminosity AGN fraction increases with $\Delta PA$ while the low luminosity AGN fraction is independent with $\Delta PA$. These observational results support a scenario in which the interaction between accreted and pre-existing 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 $\Delta PA$.