外流气体的分子研究：速度相关的激波化学和EHV气体的特殊组成
A molecular survey of outflow gas: velocity-dependent shock chemistry and the peculiar composition of the EHV gas
摘要：
我们提出了一个由L1448-mm和IRAS 04166+2706提供动力的外流的分子调查，这两个源在它们的CO光谱中具有突出的翼和极高速（EHV）分量。两个流出的分子组成呈现出系统的变化与速度，我们分析通过划分流出在三个化学制度，其中两个与机翼组件和其他的超高压气体。对两种翼区的分析表明，H2 CO和CH 3OH等物种有利于低速气体，而SiO和HCN在最快的气体中更丰富。我们还发现，超高压制度是相对丰富的O-轴承物种，不仅检测到CO和SiO（已在其他地方报道），但也在SO，CH 3OH，和H2 CO（新报道），与HCO+的试探性检测。同时，EHV区域在含C分子如CS和HCN中相对较差。我们认为，这种成分上的差异是由于在超高压气体中较低的C/O比引起的。不同的化学成分的机翼和超高压制度表明，这两个外流成分有不同的物理起源。虽然现有的激波模型都不能解释所有观测到的特征，但用激波环境气体能更好地解释机翼部分。超高压气体的特殊成分可能反映了它的起源是来自原恒星或其周围圆盘的密集风。
英文摘要：
(Abridged) We present a molecular survey of the outflows powered by L1448-mm and IRAS 04166+2706, two sources with prominent wing and extremely high velocity (EHV) components in their CO spectra. The molecular composition of the two outflows presents systematic changes with velocity that we analyze by dividing the outflow in three chemical regimes, two of them associated with the wing component and the other the EHV gas. The analysis of the two wing regimes shows that species like H2CO and CH3OH favor the low-velocity gas, while SiO and HCN are more abundant in the fastest gas. We also find that the EHV regime is relatively rich in O-bearing species, as is not only detected in CO and SiO (already reported elsewhere), but also in SO, CH3OH, and H2CO (newly reported here), with a tentative detection in HCO+. At the same time, the EHV regime is relatively poor in C-bearing molecules like CS and HCN. We suggest that this difference in composition arises from a lower C/O ratio in the EHV gas. The different chemical compositions of the wing and EHV regimes suggest that these two outflow components have different physical origins. The wing component is better explained by shocked ambient gas, although none of the existing shock models explains all observed features. The peculiar composition of the EHV gas may reflect its origin as a dense wind from the protostar or its surrounding disk.
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