Determination of density structure in dark clouds from CS observations

We present CS J = -1-0 and J = 2-1 observations of the three dark clouds TMC-1, L134 N, and B335. The J = 2-1 CS lines toward L134 N and B335 are self-absorbed; there is no evidence for self-absorption in the J = 1-0 lines of L134 N and B335, nor evidence for self-absorption in the CS lines in TMC-1. The isotopic species, C/sup 34/S, has also been detected in all three clouds, indicating optical depths much greater than 1 in the C/sup 32/S lines. Maps of these three clouds have been obtained in the J = 1-0 CS transition because this transition is optically thinner and is less complicated by self-absorption. These observations have shown that B335 is centrally condensed and TMC-1 and L134 N are fragmented into two or more condensations. These condensations have densities greater than 10/sup 4/ cm/sup hyphen3/ and masses between 2 and 10 M/sub sun/. The intrinsic CS line width of these condensations is 0.3-0.4 km s /sup -1/ and can be explained by turbulence near the sound speed for a 10-15 K gas. The structure we observe in these clouds may be indicative of an early evolutionary phase of star formation.