The molecular cloud ring in NGC 1068

The Owens Valley Millimeter Interferometer has been used to map the CO emission in the nucleus of NGC 1068 at 6-arcsec resolution (500 pc). Approximately 50 percent of the total CO emission within the central 6 kpc is contained in a ring (or arms) at R = 0.9 - 2.4 kpc near the outer edge of the inner disk, where IR observations have shown a high rate of massive star formation. The CO kinematics indicate mean circular and expansion velocities of 164 and 71 km/s, respectively for the ring assuming a major axis position angle of 55 deg. (For a major axis PA = 82 deg, the circular velocity is 185 km/s and the expansion velocity is less than 20 km/s.) The mass of molecular clouds within this region is approximately 4 x 10 to the 9th solar mass. It is proposed that the ring has formed of gas collected by the action of a central stellar bar; the infall of this gas may have been triggered by a close encounter of merger with another galaxy.