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J.E. Howe, N.R. Erickson, R.L. Snell (UMass, Amherst), M.L.N. Ashby, E.A. Bergin, S.C. Kleiner, G.J Melnick, B.M. Patten, R. Plume, J.R. Stauffer, V. Tolls, Z. Wang, Y.F. Zhang (CfA), P.F. Goldsmith (Cornell U., NAIC), M. Harwit (Cornell U.), M.J. Kaufman (SJSU), D.A. Neufeld (JHU), D.G. Koch (NASA ARC), R. Schieder, G. Winnewisser (U. Köln), G. Chin (NASA GSFC)
Since its launch in December 1998, the Submillimeter Wave Astronomy Satellite has observed more than 50 Galactic molecular clouds, including dark clouds and star-forming GMC's, as well as other types of objects. We present results of observations of molecular cloud cores in emission lines from the J=5arrow4 rotational transition of 13CO and the 3P1arrow3P0 fine-structure transition of neutral carbon. We detect the 492 GHz [C~I] line in all cloud cores, with peak line temperatures (TA*) from a few tenth's of a Kelvin in some dark cloud cores to nearly 10 K in star-forming GMC's. We detect the 13CO(5arrow4) line in almost all cores except for a few cold dark cloud cores (TA* < 50 mK), with typical TA* in GMC cores of a few K up to 14 K towards Orion KL. We see a linear correlation of the integrated intensity of 13CO(5arrow4) and [C~I] emission, even though the critical density of the 13CO transition is two orders of magnitude greater than the [C~I] transition and the energy of the 13CO J=5 level is more than three times higher than the C0 3P1 level. Comparison of the SWAS observations with 13CO(1arrow0) emission from a subset of clouds observed with the FCRAO 14-m antenna shows an even tighter correlation of [C~I] integrated intensity with 13CO(1arrow0). We discuss these trends in the context of recent models of photon dominated regions, and derive physical conditions in the clouds using the SWAS and FCRAO observations together with LVG modeling of the cloud cores.
This work was supported by NASA's SWAS contract NAS5-30702 and NSF grant AST97-25951 to the Five College Radio Astronomy Observatory.
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