CO emission from Centaurus A

Abstract

CO(2-1) emission has been detected along the major axis of the dust lane in Centaurus A out to a distance of 2-arcmin from the active nucleus. The derived radial distribution of molecular gas (H2) is centrally peaked with a scale length of about 1.5 kpc and is similar to that expected from a small Sc galaxy. The total H2 mass is about a billion solar masses, comparable to the mass of atomic gas. The molecular gas appears to be concentrated mostly at inner radii, while the atomic gas is found predominantly at larger radii. At current linear resolution of 1 kpc, infalling molecular gas near the nucleus could not be detected; the kinematics of the CO emission from the nuclear region is consistent with circular rotation. The systematic velocity of the molecular disk is found to be 547 km/s, similar to previous values determined for Centaurus A from H I and H II regions in the disk, and to recent values for stars in the elliptical component, indicating that, if it were to be considered as a disk galaxy-elliptical galaxy merger system, Centaurus A would be well relaxed.