MOLECULAR GAS AND THE NUCLEAR STAR CLUSTER IN IC 342: SUFFICIENT INFLOW FOR RECURRING STAR FORMATION EVENTS?

摘要

We present high spatial resolution (1″.2) millimeter-interferometric observations of the ~(12)CO (2-1) line emission in the central 300 pc of the late-type spiral galaxy IC 342. The data, obtained with the Owens Valley Radio Observatory, allow first-time detection of a molecular gas disk that coincides with the luminous young stellar cluster in the nucleus of IC 342. The nuclear CO disk has a diameter of ～30 pc and a molecular gas mass of M_(H_2) ～ 2 x 10~5 Solar mass. It connects via two faint CO bridges to the well-known 100 pc diameter circumnuclear gas ring. Analysis of the gas kinematics shows that the line of nodes in the inner 15 pc is offset by about 45° from the major kinematic axis, indicating noncircular motion of the gas within a few parsecs of the dynamical center of IC 342. Both the morphology and the kinematics of the CO gas indicate ongoing inflow of molecular gas into the central few parsecs of IC 342. We infer a gas inflow rate between 0.003 and 0.14 Solar mass yr~(-1), based on the observed surface density of the nuclear gas disk and estimates of the radial velocities of the surrounding gas. Inflow rates of this order can support repetitive star formation events in the nucleus of IC 342 on timescales much smaller than a Hubble time.