The large-scale structure of giant molecular clouds: SWAS observations of [C I] 3P1 → 3P0 and 13CO J = 5 → 4 emission Original Research Article

The Submillimeter Wave Astronomy Satellite (SWAS) is a NASA Small Explorer class mission designed to search for H2O and O2 emission in molecular clouds, and to investigate the large-scale structure of these clouds via mapping of the 3P1 → 3P0 transition of neutral atomic carbon (C I) and the J = 5 → 4 transition of 13CO. In this paper we will demonstrate the superb ability of SWAS to obtain maps of the physical conditions (i.e. density and temperature) in molecular clouds over scales much larger than have been previously possible. We will also show how, over large scales, the [C I] emission is consistent with that predicted by models of Photodissociation Regions (PDRs). Finally, we will briefly describe how the low-resolution [C I] observations can be used to infer clump sizes, even when the clumps are smaller than the beam.