Gas Dynamics in the Non-barred Seyfert Galaxy NGC 4501

Abstract

We report high resolution interferometer observations of the central 5 kpc region of NGC 4501. The observations were carried out in CO line using the Nobeyama Millimeter Array (NMA). The CO major features are (1) a nuclear concentration which consists of double peaks, (2) spiral arms. The feature (1) has a low star-forming efficiency, which might be due to low gas- to-dynamical mass ratio. The central double peaks are located on the root of optical spiral arms in a HST image. The spiral arms are extending out from the nuclear region, and they show systematic non-circular motions. They seem to be associated with the HST spiral dust lanes and may be linked to the central double peaks. We calculated gas cloud orbits in a stellar spiral potential, and could explain the observed CO spiral arms and non-circular motion in the arms. In a stellar spiral potential, two mechanisms of angular momentum transfer are possible — galactic spiral shocks in orbit-crowding regions, and gravitational torques exerted by the stellar spirals. We found that the galactic shock is dominant. These mechanisms lead to gas inflow which possibly explains the central-condensed double peaks in NGC 4501.KeywordsDouble PeakGravitational TorqueSpiral Density WaveAngular Momentum TransferSpiral Galaxy NGC4501These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.