论文标题
太空中的生命种子（Solis）V。甲醇和乙醛在Protostellar喷气驱动冲击L1157-B0和B1中
Seeds of Life in Space (SOLIS) V. Methanol and acetaldehyde in the protostellar jet-driven shocks L1157-B0 and B1
论文作者
论文摘要
目的：过去，原始冲击的观察能够对甲酰胺（NH2CHO）的形成途径设置约束，从而利用其观察到的空间分布并与天体化学模型预测进行了比较。在这项工作中，我们遵循相同的策略来研究乙醛（CH3CHO）的情况。方法：为此，我们使用了大型程序索利斯框架中使用IRAM-NOEMA干涉仪获得的数据来对甲醇（CH3OH）和乙醛线发射中的L1157蓝光流出沿L1157蓝光流出沿L1157 Blueshift的流出进行成像。结果：我们成像了六个CH3OH和八个CH3CHO线，覆盖了最高30 K的上层能量。这两个物种都追踪B0分子腔以及北部B1部分，即最年轻的冲击（1000年）发生的区域。 CH $ _3 $ OH和CH $ _3 $ CHO排放峰朝B1B团块峰值，在那里我们测量了以下列密度和相对丰度：1.3 x 10^16 cm-2和6.5 x 10-6（甲醇），以及7 x 10^10^13^13 cm-2 cm-2和3.5 x 10-8 x 10-8（乙醛）。我们对观察到的CH3OH线进行了非LTE LVG分析：发射气体的平均动力学温度和密度分别为TKIN = 90 K，NH2 = 4 x 10^5 cm-3。 CH3OH和CH3CHO丰度比B1b的比例为190，在整个B0-B1结构中的变化少于一个因子3。结论：天体化学模型预测与观察到的甲醇和乙醛空间分布的比较不允许区分乙醛是在谷物地幔上形成的，还是在气相上形成的气相，作为其气相的形成，是由乙基自由基（CH3CH2）主导的，它以ATOMIC OXEG的反应为主导。在年轻冲击中观察到乙醛，例如10^2年龄，或/和/和/和/和/和/和/和/和//和乙基的频率目前尚不可用的乙基自由基是为了解决问题。
Aim: In the past, observations of protostellar shocks have been able to set constraints on the formation route of formamide (NH2CHO), exploiting its observed spatial distribution and comparison with astrochemical model predictions. In this work, we follow the same strategy to study the case of acetaldehyde (CH3CHO). Method: To this end, we used the data obtained with the IRAM-NOEMA interferometer in the framework of the Large Program SOLIS to image the B0 and B1 shocks along the L1157 blueshifted outflow in methanol (CH3OH) and acetaldehyde line emission. Results: We imaged six CH3OH and eight CH3CHO lines which cover upper level energies up to 30 K. Both species trace the B0 molecular cavity as well as the northern B1 portion, i.e. the regions where the youngest shocks (1000 yr) occurred. The CH$_3$OH and CH$_3$CHO emission peaks towards the B1b clump, where we measured the following column densities and relative abundances: 1.3 x 10^16 cm-2 and 6.5 x 10-6 (methanol), and 7 x 10^13 cm-2 and 3.5 x 10-8 (acetaldehyde). We carried out a non-LTE LVG analysis of the observed CH3OH line: the average kinetic temperature and density of the emitting gas are Tkin = 90 K and nH2 = 4 x 10^5 cm-3, respectively. The CH3OH and CH3CHO abundance ratio towards B1b is 190, varying by less than a factor 3 throughout the whole B0-B1 structure. Conclusions: The comparison of astrochemical model predictions with the observed methanol and acetaldehyde spatial distribution does not allow to distinguish whether acetaldehyde is formed on the grain mantles or rather on the gas-phase, as its gas-phase formation, dominated by the reaction of ethyl radical (CH3CH2) with atomic oxygen, is very fast. Observations of acetaldehyde in younger shocks, e.g. 10^2 yr old, or/and of the ethyl radical, whose frequencies are not presently available, are necessary to settle the issue.
