Discovery of a Nuclear Gas Bar Feeding the Active Nucleus in Circinus

We report the discovery of gas inflow motions towards the active nucleus of the Circinus galaxy caused by the non-axisymmetric potential of a nuclear gas bar. Evidence for dust associated with the bar comes from the HST/NICMOS H −K color map, whereas the streaming motions along the gas bar are seen in the velocity field of the H2S(1)(1–0) emission line. The gas bar is about 100pc long with a visual extinction in excess of 10mag. Indication for the gaseous nature of this bar comes from the lack of a stellar counterpart even in the K band where the extinction is greatly reduced. We also use the NICMOS emission line images (Paα, [Sivi], and [Fe ii]) to study the innermost region of the ionization cones and the nuclear star forming activity. We discuss the possible relationship of these components with the gaseous bar. Subject headings: Galaxies: individual: Circinus – galaxies: nuclei – galaxies: active – galaxies: Seyfert – galaxies: kinematics and dynamics – infrared: galaxies