Fueling Nuclear Star Clusters: Gas Dynamics in the Central 100pc

摘要

Our high resolution observations of the 12CO line emission in the central 300 pc of two late type galaxies IC 342 and NGC 6946 revealed the presence of abundant molecular material in the form of central gas disks with diameters of ~ 30 pc. These nuclear gas disks appear to coincide with star formation at the very center. Analysis of the gas kinematic in the nuclear gas disk of IC 342 finds evidence for non-circular motion. If interpreted as gas inflow to the center of IC342, crude estimates of the inflow rate are sufficiently high to replenish the fuel supply for future star formation events. We infer a gas inflow rate between 0.003 and 0.14 M 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. The distribution and kinematics of the CO(2-1) line emission in NGC6946 were recently mapped with the PdBI interferometer at 0.6 resolution. The observed molecular gas properties are in agreement with the inner 200pc long NIR bar feeding the ongoing nuclear star formation.