Journal or Book Title
We mapped a 13 × 22 pc region in emission from 492 GHz [C I] and, for the first time, 551 GHz 13CO (5 → 4) in the giant molecular cloud M17SW. The morphologies of the [C I] and 13CO emission are strikingly similar. The extent and intensity of the [C I] and 13CO (5 → 4) emission is explained as arising from photodissociation regions on the surfaces of embedded molecular clumps. Modeling of the 13CO (5 → 4) emission in comparison to 13CO (1 → 0) indicates a temperature gradient across the cloud, peaking to at least 63 K near the M17 ionization front and decreasing to at least 20 K at the western edge of the cloud. We see no correlation between gas density and column density. The beam-averaged column density of C I in the core is 1 × 1018 cm-2, and the mean column density ratio N(C I)/N(CO) is about 0.4. The variations of N(C I)/N(CO) with position in M17SW indicate a similar clump size distribution throughout the cloud.
Howe, JE; Ashby, MLN; Bergin, EA; Chin, G; Erickson, NR; Goldsmith, PF; Harwit, M; Hollenbach, DJ; Kaufman, MJ; Kleiner, SC; Koch, DG; Neufeld, DA; Patten, BM; Plume, R; Schieder, R; Snell, Ronald L.; Stauffer, JR; Tolls, V; Wang, Z; Winnewisser, G; Zhang, YF; and Melnick, GJ, "Extended [C I] and (CO)-C-13 (5 -> 4) emission in M17SW" (2000). ASTROPHYSICAL JOURNAL. 641.