发表机构
Leiden University; University of Bonn; University College London; National Radio Astronomy Observatory; University of Virginia; Max-Planck-Institut für Astronomie（莱顿大学; 波恩大学; 伦敦大学学院; 美国国家射电天文台; 弗吉尼亚大学; 马克斯·普朗克天文学研究所）
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UCLCHEM化学模型分析NGC 253星系中心分子区含硫物种行为，可区分受激、激波后及宁静气体，为研究河外恒星形成区分子发射起源提供有效方法。
AI 中文摘要
含硫（S）物种在银河系恒星形成区中普遍存在，从致密冷核到原恒星活动相关的外流和激波区域均有分布。近期一项观测研究调查了NGC 253星系中心分子区（CMZ）含硫物种的起源，发现硫发射与正在形成的恒星存在关联，但需要对这些观测开展更广泛的建模，以确定硫发射的确切起源（如激波或热蒸发）。本研究利用化学建模，探究含硫物种在星暴星系NGC 253更极端环境中的行为，以及它们如何帮助深化对外部星系致密恒星形成气体相关发射的理解。研究采用气尘时变化学模型UCLCHEM，对NGC 253星系CMZ物理条件下的静态暖云与C型激波进行建模，将观测到的丰度及丰度比与模型输出的丰度进行比较。结果发现，根据模型类型（激波、激波后或静态云），含硫物种达到的最高丰度存在显著差异，因此可利用含硫物种的观测丰度区分受激气体、激波后气体或宁静（非受激）气体；研究还确认了基于观测的发射起源结论，包括未分辨发射的情况，将巨分子云（GMC）尺度观测与化学建模进行比较，是研究和约束河外恒星形成区分子发射起源的有效方法，含硫物种可用于区分星际介质（ISM）的不同组分类型（受激/激波后/宁静气体）。
英文摘要
Sulphur(S)-bearing species are ubiquitous in Galactic star-forming regions, from dense cold cores to outflows and shocks linked to protostellar activity. A recent observational study investigated the origin of S-bearing species towards the central molecular zone (CMZ) of NGC 253 and showed that Sulphur emission is linked to the presence of forming stars. However, more extensive modelling of these observations are required to determine the exact origin of the Sulphur emission (e.g. shock or thermal evaporation). Using chemical modelling, we examine how S-bearing species behave in the more extreme environment of the starburst galaxy NGC 253, and more generally, how they can help us improve our understanding of the emission linked with the dense star-forming gas in external galaxies. We use the gas-grain time-dependent chemical model UCLCHEM to model static warm clouds and C-type shocks under the physical conditions found in the CMZ of NGC 253. We compare observed abundances and abundance ratios to the modelled output abundances. We found that depending on the model type (shock, post-shock or static cloud), the highest abundance reached by the S-bearing species varies significantly. Hence, we can use their observed abundances of S-bearing species to distinguish between shocked, post-shocked or a quiescent (non-shocked) gas. We also confirm observationally-based conclusions on their emission origins, including in the case of unresolved emission. Comparing GMC-scale observations with chemical modelling is a powerful method to investigate and constrain the origin of molecular emission towards extragalactic star-forming regions. Sulphur-bearing species are useful to distinguish between different types of ISM components (shocked/post-shocked/quiescent gas).
Comments19 pages, 18 figures; To be published in A&A
