AI 中文总结
研究对银河系中心分子云 G+0.693 中 MgS 等金属硫化物进行探测，通过模拟低速激波对 MgS 化学过程建模，分析相关反应、时间尺度及耗尽因子，发现 Mg 大多锁定在尘埃颗粒中，首次分析 MgS 化学，为后续研究提供参考。
AI 中文摘要
对银河系中心分子云 G+0.693 中硫化镁（MgS）和硫化钠（NaS）的探测是星际介质中金属硫化物的首次探测，但关于其形成关键反应的信息匮乏。本文通过模拟低速激波通过来对 MgS 化学过程建模以恢复近期在 G+0.693 处测量的丰度。分析了其形成和破坏的主导反应、相关化学时间尺度及恢复观测丰度所需的耗尽因子。用 SiS 作为 MgS 的代理构建初始化学网络，通过量子化学计算研究反应放热性。运行三相模型模拟 G+0.693 的演化和物理条件。结果表明元素 Mg 需 1000 的耗尽因子才能恢复观测到的 MgS 丰度，意味着超过 99.9%的 Mg 被锁定在尘埃颗粒中。气相中 MgH 和 S 之间的中性-中性反应是形成 MgS 的主导反应。这项工作是对金属硫化物 MgS 化学的首次分析，表明 Mg 主要以硅酸盐形式大量掺入尘埃颗粒，但关键 MgS 形成反应还需更多实验室和/或理论研究以获得更可靠约束，未来任务如 PRIMA 将有助于了解星际尘埃颗粒中金属硫化物的含量。
英文摘要
The detection of magnesium sulphide (MgS) and sodium sulphide (NaS) towards the Galactic Center molecular cloud G+0.693 constitutes the first detection of metal sulphides in the interstellar medium (ISM). However, there is scarce information about the key reactions (either in the gas phase or on grains) involved in their formation. In this paper, we model the chemistry of MgS simulating the passage of a low-velocity shock to recover the abundances recently measured towards G+0.693. Through this chemical modelling, we analyse the dominant reactions involved in the formation and destruction of this molecule, their associated chemical time-scales, and the depletion factor needed to recover the observed abundances. We build the initial chemical network of MgS by using SiS as a proxy for this metal sulphide, and we investigate the exothermicity of these and additional, uniquely proposed reactions through quantum chemical computations. We run a three-phase model (initial translucent cloud, cloud collapse phase and shock interaction stage) that mimics the evolution and physical conditions of G+0.693. Our results show that a depletion factor of 1000 is required for elemental Mg to recover the observed abundances of MgS. This implies that potentially more than 99.9% of Mg is locked in dust grains. The dominant reaction leading to the formation of MgS is the neutral-neutral reaction between MgH and S in the gas phase. This work represents the first analysis of the chemistry of the metal-sulphide MgS and suggests that Mg is largely incorporated into dust grains, most likely in the form of silicates. However, additional laboratory and/or theoretical studies of the key MgS formation reactions are essential to obtain more reliable constraints. Future missions, such as PRIMA, will provide insights into the amount of metal-sulphides locked into interstellar dust grains.
CommentsThe title of previous version was incorrect. In this new version the content of the paper remains unchanged; only the arXiv title has been modified. Accepted in A&A
