CO Line Observations of the Bar and Nucleus of the Barred Spiral Galaxy M83

Abstract CO (J = 1 – 0) line observations of the bar and nucleus of the intermediate barred spiral galaxy M83 were made with the 45-m telescope of the Nobeyama Radio Observatory with a 16″-beam. The observed area was 210″ × 60″(3.8 kpc × 1.1 kpc), which covered the optical bar. A ridge of CO emission is found on the leading edge of the bar and is traced by straight dust lanes. In the mapped field, about 40 % of the CO line flux is concentrated within a radius of 0.4 kpc around the center of the galaxy. The velocity field suggests a noncircular motion of the gas, which is consistent with the prediction by the theoretical models for barred spiral galaxies. The CO line profiles suggest that the rotation curve rises steeply in the nucleus and that the velocity dispersion is 50–100 km s–1 around the nucleus.