OBSERVATIONS OF LARGE-SCALE [C-I] EMISSION FROM S140

We have mapped the large-scale distribution of the 492 GHz [C I] 3P1 --> 3P0 and 220 GHz (CO)-C-13 J = 2 --> 1 lines across the S140 molecular cloud. The observations employed the University of Texas Gaussian Focal Reducer on the Caltech Submillimeter Observatory telescope to produce a high surface accuracy off-axis telescope with a 3' beam. The [C I] emission covers a greater-than-or-equal-to 8 by approximately 10 pc region which closely matches the extent of the S140 molecular cloud as seen in (CO)-C-13. The line shapes of [C I] and (CO)-C-13 are also quite similar. Typical column densities of C0 are approximately 15 times those of (CO)-C-13. In this source, the neutral carbon emission most likely arises in the photon-dominated surface layers of molecular clumps. The layer in which C0 is the dominant form of gaseous carbon contains greater-than-or-equal-to 20% of all the neutral material in the extended cloud. The ratio of the [C I] 3P1 --> 3P0 to CO J = 2 --> 1 cooling integrated over the cloud is approximately 1.3, similar to the global value of this ratio in our Galaxy and to the value in the inner 100 pc of IC 342 and M82.