paper

Distribution and Kinematics of the Circum-nuclear Molecular Gas in the Seyfert 1 Galaxy NGC 3227

arXiv:astro-ph/9911487 · doi:10.1086/308703

Abstract

We present new interferometric observations of the 12CO(1-0), 12CO(2-1) and HCN (1-0) molecular line emission in NGC 3227 obtained with the IRAM Plateau de Bure interferometer (PdBI). We achieved an unprecedented angular resolution in the 12CO(2-1) line of about 0.6'' corresponding to only about 80pc at a distance of 17.3Mpc. The mapped 12CO emission is concentrated in the inner 8'' and accounts for 20% of the total 30m CO line flux. The 12CO emission is resolved into an asymmetric nuclear ring with a diameter of about 3''. The HCN line emission is mostly unresolved at our resolution of ~2.4'' and contains all of the single dish flux. We have decomposed the observed molecular gas motions into a circular and non-circular component revealing that about 80% of the gas in the circum-nuclear region exhibits pure circular rotation. We find evidence for bar streaming onto the nuclear ring and a redshifted emission knot on the ring perimeter. In the central arcsecond the gas shows apparent counter rotation. This behavior can be best explained by a warping of the inner molecular gas disk rather than gas motion in a nuclear bar potential. We detected molecular gas at a distance from the nucleus of only ~13pc with a velocity of about 75 km/s with respect to the systemic velocity and find that within the central arcsecond the rotation curve is rising again. This is the first time that millimetric CO-line emission has been detected interferometrically at such small distances to the nucleus of a Seyfert galaxy. These measurements indicate a lower limit on the enclosed mass of about 2x10^7 M_solar in the inner 15pc.

accepted for Ap.J. April issue, 54 pages, 22 figures

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