High Resolution CO Images of Seyfert Galaxies

Abstract

Summary The Berkeley-Illinois-Maryland millimeter array has been used to image the CO (J=1−0) emission of three Seyfert galaxies, NGC 3227, NGC 7469 and NGC 5033, selected for their strong single-dish CO detections. Extensive u-v coverage was obtained for all three galaxies resulting in 2″-3″resolution. The CO emission in NGC 3227 and NGC 7469 appears as compact structures centered on the active nuclei, containing substantial fractions (∼ 80% and ∼ 50%) of the single-dish flux. In NGC 3227, 10% of the CO flux detected by the interferometer is contained within the ionized narrow line region. The unresolved molecular gas concentrations in the nucleus of NGC 3227 imply a CO mass of 6.5 × 10⁷ M_⊙ concentrated within a diameter ≍ 50 pc. The CO emission in NGC 5033 is not detected at this resolution, implying a CO structure size of 20″-60″(1.2-3.6 kpc). Continuum emission at 2.7mm is not detected in any of the three galaxies. In the center of NGC 7469, the H₂ mass is comparable to the dynamical mass. Kinematic studies of the detected gas reveal a rotational motion of the gas in NGC 3227 and NGC 7469, allowing identification of the gas in NGC 7469 with a nuclear starburst. These data are consistent with the idea that interactions between galaxies cause gas to concentrate in their nuclei thereby feeding starburst and Seyfert activity.