发表机构
Centro de Astrobiología (CAB), CSIC-INTA（天体生物学中心（CAB），西班牙国家研究委员会-国家航空航天技术研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过分析分子云G+0.693−0.027的同位素比例，揭示CMZ中存在冷宁静气体成分，且¹²C/¹³C比例高于公认值，支持银河中心由低化学处理气体补充的情景。
AI 中文摘要
银河中心分子区（CMZ）包含银河系大部分致密分子气体，但恒星形成率却低得出人意料。同位素比例是研究该气体局域物理条件和核合成历史的独特工具。本文总结了对分子云G+0.693−0.027开展的近期同位素研究：氘分馏（D/H比例）揭示出在温暖且湍流的CMZ中嵌有一个寒冷（运动温度T_kin≤30K）、相对宁静的气体成分，表明恒星形成的最早阶段可在这种极端环境中存续；还给出了从HC₃N和HC₅N得到的新¹²C/¹³C测量结果，包括首次对双取代¹³C同位素体的约束。通过天体化学模型校正同位素分馏后，推断出的元素比例（约37–48）超出了公认的CMZ假设值（约20），支持银河系中心由沿银河棒向内流动的化学处理程度较低的气体补充的情景。
英文摘要
The Central Molecular Zone (CMZ) contains most of the dense molecular gas in the Milky Way but forms stars at a surprisingly low rate. Isotopic ratios provide a unique tool to investigate both the local physical conditions and the nucleosynthetic history of this gas. I summarize recent isotopic studies toward the molecular cloud G$+$0.693$-$0.027. Deuterium fractionation (D/H ratios) reveals a cold ($T_{\rm kin}\lesssim30$ K), relatively quiescent gas component embedded within the otherwise warm and turbulent CMZ, indicating that the earliest stages of star formation can survive in this extreme environment. I also present new $^{12}$C/$^{13}$C measurements from HC$_3$N and HC$_5$N, including the first constraints from doubly substituted $^{13}$C isotopologues. After accounting for isotopic fractionation with astrochemical models, the inferred elemental ratio ($\sim37$--48) exceeds the canonical CMZ assumed value ($\sim$20), supporting a scenario in which the Galactic center is replenished by less chemically processed gas flowing inward along the Galactic bar.
Comments8 pages, 2 figures. Proceedings for the IAU Symposium 405 "Traversing the Galactic Center in Space and Time"
