AI 中文总结
本研究通过含 krome 化学包的 p-gadget-3 模拟，结合半解析模型分析孤立及并合星系，明确 [CII] 是全局冷气体可靠示踪剂，其发射本质依赖星系演化历史，约 50% 来自分子气体。
AI 中文摘要
[CII] 发射是研究星系气体含量的有力工具，尤其适用于演化早期阶段。由于其低激发势，[CII] 158μm 谱线是光解区和巨分子云中中性气体的主要冷却剂，因此可作为星际介质所有相的示踪剂。然而，关于该发射所示踪气体的本质尚未达成共识。本研究旨在为 [CII] 发射的物理机制提供见解，并为未来观测提供预测。研究采用了使用包含 krome 化学包的 p-gadget-3 版本开展的四个预制备模拟，实现了一个后处理半解析模型以模拟 [CII] 发射，分析了一个孤立的银河系质量星系，以及三种并合构型：两个银河系质量星系的共转、反转和垂直并合。研究重现了基本关系，如 [CII] 光度与恒星形成率的 L[CII]-SFR 关系，其中并合会产生恒星形成单独无法示踪的额外 [CII] 发射分量；在宁静或星暴阶段，星系会偏离 L[CII]-SFR 关系。研究发现，[CII] 在全局尺度上是分子气体以及冷、暖相原子气体的可靠示踪剂，结果表明，无论构型如何，约 50% 的总 [CII] 发射由分子气体示踪，30%至40%由原子和电离氢示踪；研究还表明，[CII] 发射的本质强烈依赖于星系的演化历史，其中并合与星暴通过与分子氢的碰撞成为 [CII] 发射更高效的驱动因素。
英文摘要
[CII] emission is a powerful tool for studying the gas content in galaxies, especially at early stages of evolution. Given its low excitation potential, the [CII] 158 μm line is the main coolant of neutral gas in photodissociation regions and giant molecular clouds, hence a tracer of all phases of the interstellar medium. However, there is no consensus on what is the nature of the gas traced by this emission. We aim to provide insights into the physics of the [CII] emission and predictions for future observations. We used four pre-prepared simulations performed with a version of p-gadget-3, which includes the krome chemistry package. We implemented a postprocessing semi-analytical model to simulate the [CII] emission. We analysed an isolated Milky Way-mass-size galaxy, and three merger configurations: a co-rotating, counter-rotating, and perpendicular major mergers of two Milky Way-mass-size galaxies. We reproduce fundamental relations such as the [CII] luminosity and the star formation rate, L[CII]-SFR relation, in which mergers show an extra component for the [CII] emission not traced by the star formation alone. During quiescent or starburst stages, galaxies deviate from the L[CII]-SFR relation. We find that [CII] is a robust tracer of molecular gas, as well as atomic gas in both cold and warm phases on a global scale. Our results indicate that around 50 per cent of the total [CII] emission is traced by molecular gas, while 30 to 40 per cent is traced by atomic and ionised hydrogen regardless of the configuration. Our findings suggest that the nature of the [CII] emission depends strongly on the evolutionary history of galaxies, in which mergers and starbursts act as more efficient drivers of [CII] emission through collision with molecular hydrogen.
Comments14 pages, 12 figures, revised version submitted to Astronomy and Astrophysics
