Atomic carbon in southern hemisphere high-latitude clouds

We report the detection of atomic carbon in a sample of eight southern hemisphere high Galactic latitude molecular clouds, using the Antarctic Submillimeter Telescope and Remote Observatory. The 492 GHz (P-3(1) --> P-3(0)) transition of [C I] was detected in all of the clouds observed. The C/CO column density ratio ranges from 0.4 to 2.5 and is similar to the values previously measured in high-latitude clouds MBM 12 and HT) 210121. For all 10 high-latitude clouds observed in [C I], C/CO averages similar to 1.2 and decreases with increasing total gas column density N-H, as predicted by translucent cloud models. Quantitative comparison with chemical models of homogeneous clouds is unsatisfactory, however, and we conclude that the clumpy structure of clouds must be taken into account in order to interpret the data properly.