We have observed the 1_(10)-1_(01) pure rotational transitions of both H_2~(16)O and H_2~(18)O toward Sagittarius B2 using the Submillimeter Wave Astronomy Satellite. The spectra thereby obtained show a complex pattern of absorption and—in the case of H_2~(16)O—emission, with numerous features covering a wide range of LSR velocities (-130 to 130 km s~(-1)) and representing absorption both in gas associated with Sgr B2 as well as by several components of foreground gas along the line of sight. The ortho-water abundance derived for the absorbing foreground gas is ～6 x 10~(-7) relative to H_2.
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机译：我们已经用亚毫米波天文学卫星观测到H_2〜（16）O和H_2〜（18）O向射手座B2的1_（10）-1_（01）纯旋转跃迁。由此获得的光谱显示出复杂的吸收模式，在H_2〜（16）O的情况下，具有多种特征，涵盖了大范围的LSR速度（-130至130 km s〜（-1）），并表现出吸收与Sgr B2有关的气体以及沿视线的前景气体的几种成分。相对于H_2，吸收前景气体的原水丰度约为〜6 x 10〜（-7）。
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