论文标题
建立分子云种群：云合并的作用
Building the molecular cloud population: the role of cloud mergers
论文作者
论文摘要
我们研究了在移动网格代码中对银河系状星系的模拟中慢分子云合并的物理驱动因素，并确定了这些合并对银河系云种群的质量分布和星形形成效率的影响。我们发现，这些合并中有83％以低于5 km/s的相对速度出现，并且与大规模的原子气流有关，主要由（1）扩大由超新星爆炸引起的热，离子气体的气泡和（2）银河旋转。这些合并的主要效果是将分子质量汇总到高质量云中：合并占质量m> 2 x 10^6 msun云中包含的分子质量的50％以上。这些高质量云的密度更高，内部速度分散体和瞬时星形形成效率，其效率高于其未合并的低质量前体。因此，在我们的模拟星系中，平均瞬时星形形成效率，其合并率仅为每MYR的云的1％，比包含不合并的云层中的相似云中高25％。
We study the physical drivers of slow molecular cloud mergers within a simulation of a Milky Way-like galaxy in the moving-mesh code Arepo, and determine the influence of these mergers on the mass distribution and star formation efficiency of the galactic cloud population. We find that 83 per cent of these mergers occur at a relative velocity below 5 km/s, and are associated with large-scale atomic gas flows, driven primarily by (1) expanding bubbles of hot, ionised gas caused by supernova explosions and (2) galactic rotation. The major effect of these mergers is to aggregate molecular mass into higher-mass clouds: mergers account for over 50 per cent of the molecular mass contained in clouds of mass M > 2 x 10^6 Msun. These high-mass clouds have higher densities, internal velocity dispersions and instantaneous star formation efficiencies than their unmerged, lower-mass precursors. As such, the mean instantaneous star formation efficiency in our simulated galaxy, with its merger rate of just 1 per cent of clouds per Myr, is 25 per cent higher than in a similar population of clouds containing no mergers.
