Models and observations of the millimeter and submillimeter molecular line emission of bright -rimmed clouds
We present the results of a comparison of new millimeter and submillimeter molecular line survey of bright-rimmed clouds, observed at FCRAO in the CO (J = 1 → 0), C18O (J = 1 → 0), HCO+ (J = 1 → 0), H 13CO+ (J = 1 → 0), and N 2H+ (J = 1 → 0) transitions, 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), and at the CSO in the HCO+ (J = 4 → 3) and H13CO+ (J = 4 → 3) molecular line transitions with synthetic observations of a hydrodynamic shock driven triggered star formation model. We also present observations of three Bok globules done for comparison with the bright-rimmed clouds. We find that the appearance of the millimeter CO and HCO+ emission is dominated by the morphology 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 may be triggered to collapse as a result of sequential star formation. The morphologies of the observed bright-rimmed cloud are in good agreement with the our modeled emission. Five of the seven bright-rimmed clouds we observe seem to have an outflow, however only one shows the spectral line blue-asymmetric signature that is indicative of infall, in the optically thick HCO+ emission. We also present evidence that in bright-rimmed clouds the nearby shock front may heat the core from outside-in thereby washing out the normally observed line infall signatures seen in isolated star forming regions. We find that the derived core masses of these bright-rimmed clouds are similar to other low and intermediate mass star forming regions.