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Pre-Cometary Ice Composition from Hot Core Chemistry

机译：热核化学的赛前冰成分

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Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same pre-biotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere.
机译：位于恒星形成区域周围的赛前冰包含的分子是益生元化合物或益生元前体。由于冰芯在这些位置附近升华，因此对热芯进行分子线调查可提供有关冰的成分的信息。我们将静水压热核模型与复杂的化学反应网络相结合，以计算分子，离子和自由基随时间变化的丰度。该模型考虑了冰和气相之间的相互作用。它应用于发生高质量恒星形成的猎户座热核，以及应用于太阳质量双星原恒星系统IRAS 16293-2422。我们的计算表明，在热核阶段结束时，两个恒星形成位点都会产生相同的益生元CN分子。但是，在Orion热核中，这些分子以较大的丰度形成。将计算值与从观测线数据中得出的丰度进行比较，需要化学未处理的分子云作为热核演化的初始状态。因此，似乎这些物体是在比以前认为的年轻得多的云阶段形成的。这意味着，在形成热核之前，年轻云层的冰相不包含大量的含CN分子。在热核中合成的益生元分子在气相和竞争前的冰中引起化学富集。人们认为这种丰富化是地球和其他地方生命形成的重要外星方面。

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