We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 1_(10) → 1_(01) transition of ortho-H_2O at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, ρ Oph A, NGC 2024, CRL 2591, W3, W3OH, Mon R2, and W33 and was not detected in TMC-1, L134N, and B335. We also present a small map of the H_2O emission in S140. Observations of the H_2~(18)O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-H_2O relative to H_2 in the giant molecular cloud cores was found to vary between 6 x 10~(-10) and 1 x 10~(-8). Five of the cloud cores in our sample have previous H_2O detections; however, in all cases the emission is thought to arise from hot cores with small angular extents. The H_2O abundance estimated for the hot core gas is at least 100 times larger than in the gas probed by SWAS. The most stringent upper limit on the ortho-H_2O abundance in dark clouds is provided in TMC-1, where the 3 σ upper limit on the ortho-H_2O fractional abundance is 7 x 10~(-8).
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机译：我们提出亚毫米波天文学卫星（SWAS）的观测结果，表明在557 GHz下邻氢H_2O向12个分子云核的1_（10）→1_（01）跃迁。在NGC 7538，ρOph A，NGC 2024，CRL 2591，W3，W3OH，Mon R2和W33中检测到水排放，而在TMC-1，L134N和B335中未检测到水排放。我们还展示了S140中H_2O排放的小图。朝向S140和NGC 7538观察到H_2〜（18）O谱线，但未检测到发射。在巨分子云核中，邻H_2O相对于H_2的丰度在6 x 10〜（-10）和1 x 10〜（-8）之间变化。我们的样本中有五个云核心具有以前的H_2O检测值。但是，在所有情况下，都认为发射是由角度范围较小的热芯引起的。热核气体的H_2O丰度比SWAS探测的气体至少高100倍。在TMC-1中提供了暗云中邻H_2O丰度的最严格上限，其中邻H_2O分数丰度的3σ上限为7 x 10〜（-8）。
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