Star formation in bright-rimmed clouds. I. Millimeter and submillimeter molecular surveys.
DE VRIES C.H., NARAYANAN G. and SNELL R.L.
Abstract (from CDS):
We present the results of the first detailed 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), H13CO+ (J=1⟶0), and N2H+ (J=1⟶0) transitions, and at the Heinrich Hertz Telescope 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 list is composed of a selection of bright-rimmed clouds from the catalog of such objects compiled by Sugitani et al. 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. 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.
ISM: Clouds - ISM: Molecules - Radio Lines: ISM - Stars: Formation - Stars: Pre-Main-Sequence