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B.A. Biller (Swarthmore College), T.T. Helfer (National Radio Astronomy Observatory)
In an earlier survey of CS(J=2--1) emission in the plane of the Milky Way, Helfer & Blitz (1997) found that emission from this high dipole moment molecule was more commonly detected in the Galactic plane than in solar-neighborhood Giant Molecular Clouds, albeit at a weaker level than in starforming cores in GMCS. Here, we present observations of CS(J=3--2) and CS(J=2--1) from twenty-one pc-scale ``features'' along nine lines of sight in the first quadrant of the Milky Way plane. Using a Large Velocity Gradient (LVG) radiative transfer model of the observed line temperatures, we derive moderate (log n(H2) cm-3 = 3--5) densities for the features. The moderate densities suggest that these features are not cloud cores; they may instead be similar to the envelopes around starforming cores. For one line of sight that was specially selected for strong molecular emission, we derive a density of log n(H2) cm-3 = 5.4; this special position appears to be the only core candidate in our sample. We also present interferometric observations of one of the cloud features; these observations place limits on the size scale of the emitting region.
The author(s) of this abstract have provided an email address for comments about the abstract: beth@merlin.swarthmore.edu