Dynamics of the Narrow‐Line Region in the Seyfert 2 Galaxy NGC 1068

Abstract

We present dynamical models based on a study of high-resolution long-slit spectra of the narrow-line region (NLR) in NGC 1068 obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST). The dynamical models consider the radiative force due to the active galactic nucleus (AGN), gravitational forces from the supermassive black hole (SMBH), nuclear stellar cluster, and galactic bulge, and a drag force due to the NLR clouds interacting with a hot ambient medium. The derived velocity profile of the NLR gas is compared to that obtained from our previous kinematic models of the NLR, using a simple biconical geometry for the outflowing NLR clouds. The results show that the acceleration profile due to radiative line driving is too steep to fit the data and that gravitational forces alone cannot slow the clouds down, but with drag forces included, the clouds can slow down to the systemic velocity over the range 100-400 pc, as observed. However, we are not able to match the gradual acceleration of the NLR clouds from ~0 to 100 pc, indicating the need for additional dynamical studies.