The Molecular Gas in the Circumnuclear Region of Seyfert Galaxies

Subarcsecond IRAM Plateau de Bure millimeter interferometric observations of the 12CO (2-1) line emission in the Seyfert 1 galaxy NGC 3227 and in the Seyfert 2 galaxy NGC 1068 have revealed complex kinematic systems in the inner 100-300 pc that are not consistent with pure circular motion in the host galaxies. Modeling of these kinematic systems with elliptical orbits in the plane of the host galaxy (representing gas motion in a bar potential) is a possible solution but does not reproduce all the features observed. A better description of the complex kinematics is achieved by circular orbits that are tilted out of the plane of the host galaxy. This could indicate that the thin circumnuclear gas disk is warped. In the case of NGC 1068, the warp model suggests that at a radius of ~70 pc, the gas disk is oriented edge-on, providing material for the obscuration of the active galactic nucleus. The position-velocity diagrams show rising rotation curves at r ≤ 13 pc and an indication for large enclosed masses of ≥2 × 107 M☉ for NGC 3227 and ≥108 M☉ for NGC 1068 within the central 25 pc.

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