Ccs - a Tracer of Early Star Formation

We have conducted a survey of the CCS line toward 11 dark clouds and star-forming regions at 30 spatial resolution and 0.054 km s spectral resolution. Our results show that CCS can only be detected in quiescent clouds, not in active star-forming regions. The CCS distribution shows remarkable clumpy structure, and 25 clumps are identified in 7 clouds. The CCS clumps tend to exist around the higher density regions traced by NH emission or submillimeter continuum sources, and the distribution is not spherically symmetric. Variation of the CCS abundance was suggested as an indicator of the evolutionary status of star formation. However, we can only find a weak correlation between (CCS) and (H ), which suggests that the time scale for creating and destroying CCS may be very short compared to the lifetime of CCS. Therefore, we conclude that CCS clumps are unlikely to collapse into protostars, but rather transiently exist in the regions with density cm as the cloud evolves. As a result, CCS traces pre-protostellar cores in the very early stage of star formation or traces the envelope of pre-protostellar cores in the later stage.