DENSE CLUMPS AND CANDIDATES FOR MOLECULAR OUTFLOWS IN W40

Abstract

We report the results of the 12CO (J = 3?2) and HCO+ (J = 4?3) observations of the W40 H ii region with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope (HPBW ? 22?) to search for molecular outflows and dense clumps. We found that the velocity field in the region is highly complex, consisting of at least four distinct velocity components at VLSR ? 3, 5, 7, and 10 km s?1. The ?7 km s?1 component represents the systemic velocity of cold gas surrounding the entire region, and causes heavy absorption in the 12CO spectra over the velocity range 6 ? VLSR ? 9 km s?1. The ?5 and ?10 km s?1 components exhibit high 12CO temperature (?40 K) and are found mostly around the H ii region, suggesting that these components are likely to be tracing dense gas interacting with the expanding shell around the H ii region. Based on the 12CO data, we identified 13 regions of high velocity gas, which we interpret as candidate outflow lobes. Using the HCO+ data, we also identified six clumps and estimated their physical parameters. On the basis of the ASTE data and near-infrared images from 2MASS, we present an updated three-dimensional model of this region. In order to investigate molecular outflows in W40, the SiO (J = 1?0, v = 0) emission line and some other emission lines at 40 GHz were also observed with the 45 m telescope at the Nobeyama Radio Observatory, but they were not detected at the present sensitivity.