Orion热芯中的防冻剂-首次在Orion-KL中检测到乙二醇
Antifreeze in the hot core of Orion - First detection of ethylene glycol in Orion-KL
摘要：
它们的化学成分的比较显示，一阶，彗星和星际丰度之间有很好的协议。然而，一种复杂的含氧有机分子，乙二醇（CH $_{2}$ OH）$_{2}$，似乎偏离了这种相关性，因为它不容易在星际介质中检测到，虽然它被证明是相当丰富的其他含氧物种在彗星海尔-波普。因此，乙二醇与相关分子乙醇醛CH $_{2}$ OHCHO和乙醇CH $_{3}$ CH $_{2}$ OH一起，在星际冰和彗星冰的比较以及彗星物质形成的任何讨论中，都是关键物质。在这里，我们专注于分析乙二醇在最近的和最好的研究热核心样区域，猎户座KL。我们使用ALMA干涉数据，因为高空间分辨率的观测使我们能够减少线混淆问题，相对于单碟观测，因为不同的分子预计将表现出不同的空间分布。此外，需要大的光谱带宽，因为需要许多单独的跃迁来安全地检测大的有机分子。混淆和连续体减法是主要问题，并已小心处理。我们在Orion-KL中检测到乙二醇的aGg'构象异构体。发射是紧凑的，峰值朝向靠近主连续峰的热芯，西南约2”;这种分布明显不同于其他含O物质。假设光学细线和当地的热力学平衡，我们推导出的旋转温度为145 K和柱密度为4.6 10 $^{15}$ cm $^{-2}$。对gGg'构象异构体的柱密度的限制低五倍。
英文摘要：
Comparison of their chemical compositions shows, to first order, a good agreement between the cometary and interstellar abundances. However, a complex O-bearing organic molecule, ethylene glycol (CH$_{2}$OH)$_{2}$, seems to depart from this correlation because it was not easily detected in the interstellar medium although it proved to be rather abundant with respect to other O-bearing species in comet Hale-Bopp. Ethylene glycol thus appears, together with the related molecules glycolaldehyde CH$_{2}$OHCHO and ethanol CH$_{3}$CH$_{2}$OH, as a key species in the comparison of interstellar and cometary ices as well as in any discussion on the formation of cometary matter. We focus here on the analysis of ethylene glycol in the nearest and best studied hot core-like region, Orion-KL. We use ALMA interferometric data because high spatial resolution observations allow us to reduce the line confusion problem with respect to single-dish observations since different molecules are expected to exhibit different spatial distributions. Furthermore, a large spectral bandwidth is needed because many individual transitions are required to securely detect large organic molecules. Confusion and continuum subtraction are major issues and have been handled with care. We have detected the aGg' conformer of ethylene glycol in Orion-KL. The emission is compact and peaks towards the Hot Core close to the main continuum peak, about 2" to the south-west; this distribution is notably different from other O-bearing species. Assuming optically thin lines and local thermodynamic equilibrium, we derive a rotational temperature of 145 K and a column density of 4.6 10$^{15}$ cm$^{-2}$. The limit on the column density of the gGg' conformer is five times lower.
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