标题： 猎户座巴尔PDR中的氘化学 - 以CH2D+为主角的“温暖”化学 显示英文标题

标题： Deuterium chemistry in the Orion Bar PDR - "warm" chemistry starring CH2D+

摘要： 气相分子中的氘同位素分馏水平通常与寒冷区域（如前恒星核心）相关联。 在热环境中（如热核或热冠状物）也观察到显著的同位素分馏比值，据信这些是由围绕尘埃颗粒的冰质包层蒸发产生的，因此是早期冷环境（无论是气相还是颗粒表面化学）的残留产物。 最近在猎户座巴尔（Orion Bar）的一个特征温度为70K的团块中检测到DCN，表明高氘同位素分馏也可以在PDRs中被探测到。 因此，猎户座巴尔的团块似乎是一个研究氘同位素分馏的良好环境，特别是在温热气体中，这使得在不同温度范围内验证化学模型成为可能，在这种温度范围内，主导的分馏过程被认为与在冷气体（<20K）中不同。 我们旨在详细观测研究猎户座巴尔PDR中发生的化学过程，以了解DCN是否由冰质包层蒸发产生，或者是否是涉及CH2D+前体离子（其能存活于比普通H2D+前体更高的温度）的暖气体相化学的结果。 利用APEX和IRAM 30米望远镜，我们针对猎户座巴尔的两个团块选择了特定的氘化物种进行观测。 我们在猎户座巴尔PDR的一个团块中确认了DCN的探测，并发现了两种新的氘化分子（DCO+和HDCO）。 HCN和H2CO显示出显著的氘同位素分馏，但HCO+的分馏较低。 我们还给出了其他与氘化学相关的分子的上限值。 ... 我们提供了证据表明，由CH2D+驱动的温暖氘化学正在团块中起作用。 显示英文摘要

摘要： High levels of deuterium fractionation in gas-phase molecules are usually associated with cold regions, such as prestellar cores. Significant fractionation ratios are also observed in hot environments such as hot cores or hot corinos, where they are believed to be produced by the evaporation of the icy mantles surrounding dust grains, and thus are remnants of a previous cold (either gas-phase or grain surface) chemistry. The recent detection of DCN towards the Orion Bar, in a clump at a characteristic temperature of 70K, has shown that high deuterium fractionation can also be detected in PDRs. The Orion Bar clumps thus appear as a good environment for the observational study of deuterium fractionation in luke-warm gas, allowing to validate chemistry models in a different temperature range, where dominating fractionation processes are predicted to be different than in cold gas (< 20K). We aimed at studying observationally in detail the chemistry at work in the Orion Bar PDR, to understand if DCN is produced by ice mantle evaporation, or is the result of warm gas-phase chemistry, involving the CH2D+ precursor ion (which survives higher temperatures than the usual H2D+ precursor). Using the APEX and the IRAM 30m telescopes, we targetted selected deuterated species towards two clumps in the Orion Bar. We confirmed the detection of DCN and detected two new deuterated molecules (DCO+ and HDCO) towards one clump in the Orion Bar PDR. Significant deuterium fractionations are found for HCN and H2CO, but a low fractionation in HCO+. We also give upper limits for other molecules relevant for the deuterium chemistry. (...) We show evidence that warm deuterium chemistry driven by CH2D+ is at work in the clumps.