Kinematics and Morphology of the Resolved Narrow Line Region in NGC 4151

Abstract

A complement of HST narrow band images, STIS slitless and long-slit spectra have been employed to probe the morphology, kinematics, dynamics, and ionization structure of the near-nuclear region in NGC 4151. The images illustrate the inner biconical cloud distribution which exhibits recessional velocities relative to the nucleus to the NE and approaching velocities to the SW of the nucleus. The STIS spectra of the NLR map the velocity field from 1.2 kpc to within 13 pc (H _° = 75 km s^-1 Mpc^-1) of the nucleus. We find evidence for at least two kinematic cloud populations. One is characterized by Low Velocities and Low Velocity Dispersions (LVLVD clouds: ∣v∣ < 400 km s^-1, and Δ v < 130 kms^-1). These clouds extend through the NLR and may be gravitationally associated with the host galaxy. Another component is characterized by High Velocities and High Velocity Dispersions (HVHVD clouds:400 < ∣v∣ ≲ 1700 km s^-1, Δv ≥ 130 km s^-1).This set of clouds is located within 1.1″ (∼ 70 pc) of the nucleus and has radial velocities which are too high to be gravitational in origin, show no strong correlation with the knots in the radio jet, but are consistent with wind driven outflow.