2000ApJ...539L..97S

We present a 17-point map of the M17SW cloud core in the 1₁₀⟶1₀₁ transition of ortho-H₂O at 557 GHz obtained with Submillimeter Wave Astronomy Satellite. Water emission was detected in 11 of the 17 observed positions. The line widths of the H₂O emission vary between 4 and 9 km.s^–1 and are similar to other emission lines that arise in the M17SW core. A direct comparison is made between the spatial extent of the H₂O emission and the ¹³CO J=5⟶4 emission; the good agreement suggests that the H₂O emission arises in the same warm, dense gas as the ¹³CO emission. A spectrum of the H₂¹⁸O line was also obtained at the center position of the cloud core, but no emission was detected. We estimate that the average abundance of ortho-H₂O relative to H₂ within the M17 dense core is approximately 1x10^–9, 30 times smaller than the average for the Orion core. Toward the H II region/molecular cloud interface in M17SW the ortho-H₂O abundance may be about 5 times larger than in the dense core.