用SOFIA上的GREAT仪器发现星际巯基自由基（SH）
Discovery of interstellar mercapto radicals (SH) with the GREAT instrument on SOFIA
摘要：
我们报告的星际巯基自由基的第一次检测，获得沿视线的亚毫米连续源W 49 N。我们用SOFIA上的GREAT仪器观测了L1接收机上边带中的1383 GHz π 3/2 J = 5/2 - 3/2 λ双峰。由此产生的光谱揭示了SH吸收的材料本地W 49 N，以及在前景气体，与W 49 N无关，这是位于沿视线。对于相对于当地静止标准速度在37 - 44 km/s范围内的前景物质，我们推断总SH柱密度约为2.6 E+12 cm-2，对应于相对于H2的约7 E-9丰度，并产生SH/H2S丰度比约为0.13。观测到的SH/H2S丰度比远小于标准模型对湍流耗散区和激波中SH和H2S生成的预测值，这表明吸热中性-中性反应SH + H2 -> H2S + H必须随着被认为在扩散分子云中产生CH+和SH+的离子-中性反应而增强。
英文摘要：
We report the first detection of interstellar mercapto radicals, obtained along the sight-line to the submillimeter continuum source W49N. We have used the GREAT instrument on SOFIA to observe the 1383 GHz Doublet Pi 3/2 J = 5/2 - 3/2 lambda doublet in the upper sideband of the L1 receiver. The resultant spectrum reveals SH absorption in material local to W49N, as well as in foreground gas, unassociated with W49N, that is located along the sight-line. For the foreground material at velocities in the range 37 - 44 km/s with respect to the local standard of rest, we infer a total SH column density ~ 2.6 E+12 cm-2, corresponding to an abundance of ~ 7 E-9 relative to H2, and yielding an SH/H2S abundance ratio ~ 0.13. The observed SH/H2S abundance ratio is much smaller than that predicted by standard models for the production of SH and H2S in turbulent dissipation regions and shocks, and suggests that the endothermic neutral-neutral reaction SH + H2 -> H2S + H must be enhanced along with the ion-neutral reactions believed to produce CH+ and SH+ in diffuse molecular clouds.
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