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E. M. Gregersen (Caltech), N. J. Evans (UT-Austin)
We have observed 17 starless cores selected from Ward-Thompson et al.\ (1994) in the HCO+ J=3-2 line. Six of these cores have line asymmetries indicative of collapse. The excess of blue-skewed profiles over red-skewed profiles is similar to that seen in Class 0 and I sources. The observed line profiles share the same linewidths and peak temperatures as those predicted from young sources in evolutionary models, but the blue/red ratios, like those of more advanced sources, are higher than models predict. This fact, combined with the large spatial extent of the infall signature, suggests that we are observing cores undergoing inward motions. We have also divided these starless cores into two groups based on the continuum photometry of Ward-Thompson et al.\ and our HCO+ data. We find stronger HCO+ emission among the cores detected in the submillimeter and all the blue-skewed line profiles are in this group. This supports the suggestion of Ward-Thompson et al.\ that these are the pre-protostellar cores.
The author(s) of this abstract have provided an email address for comments about the abstract: emg@astro.caltech.edu