Star Formation in Bright‐rimmed Clouds. I. Millimeter and Submillimeter Molecular Line Surveys

We present the results of the first detailed millimeter and submillimetermolecular line survey of bright rimmed clouds, observed at FCRAO in the CO(J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0)transitions, and at the HHT in the CO (J=2-1), HCO+ (J=3-2), HCO+ (J=4-3),H13CO+ (J=3-2), and H13CO+ (J=4-3) molecular line transitions. The source listis composed of a selection of bright rimmed clouds from the catalog of suchobjects compiled by Sugitani et al. (1991). We also present observations ofthree Bok globules done for comparison with the bright rimmed clouds. We findthat the appearance of the millimeter CO and HCO+ emission is dominated by themorphology of the shock front in the bright rimmed clouds. The HCO+ (J=1-0)emission tends to trace the swept up gas ridge and overdense regions which maybe triggered to collapse as a result of sequential star formation. Five of theseven bright rimmed clouds we observe seem to have an outflow, however only oneshows the spectral line blue-asymmetric signature that is indicative of infall,in the optically thick HCO+ emission. We also present evidence that in brightrimmed clouds the nearby shock front may heat the core from outside-in therebywashing out the normally observed line infall signatures seen in isolated starforming regions. We find that the derived core masses of these bright rimmedclouds are similar to other low and intermediate mass star forming regions.