Interaction of the outflow and quiescent gas in Orion - HCO(+) aperture synthesis maps

The authors present high-resolution (17arcsec) aperture synthesis maps of HCO⁺ J = 1-0 emission at 89 GHz in the Orion molecular cloud obtained with the Hat Creek millimeter interferometer. The low spatial frequencies of the brightness distribution, which are not sampled by the interferometer, were derived from single-dish data taken with the Onsala 20 m telescope. The HCO⁺ maps probe the interaction of an outflow from IRc2 with quiescent gas. Four components, with different distributions, kinematics, and chemistry, can be identfied in the HCO⁺ maps. (1) The quiescent molecular ridge, which is located just outside the expanding ring, or "doughnut", of gas inferred from SO observations. (2) A compact component centered near IRc2. (3) A high-velocity bipolar outflow. It is argued that IRc2 is the source of the outflow. (4) An extended outflow, which consists largely of ambient gas which has been swept up by the high-velocity outflow.