关于星系形成的第一性原理模拟：I。在盘状星系的高分辨率模拟中，我们应该如何选择恒星形成的标准？
Toward first-principle simulations of galaxy formation: I. How should we choose star formation criteria in high-resolution simulations of disk galaxies?
摘要：
我们进行了3维N体/SPH模拟研究如何质量分辨率和其他模型参数，如恒星形成效率参数，C* 和阈值密度，n影响银河系的气体/恒星盘在静态银河系的潜力结构。我们使用10^6 - 10^7个粒子来分辨冷的和致密的（T < 100 K & n_H > 100 cm^{-3}）相。我们发现，ISM的结构和年轻恒星的分布是敏感的假设的n。n = 100 cm^{-3}的高n值模型在ISM中产生clusterian多相位特征。年轻恒星分布在一个半质量高度为10 - 30 pc的薄盘中。在n = 0.1 cm^{-3}的低n模型中，发现恒星盘比高n模型厚好几倍，气体盘看起来比高n模型光滑。为了再现气盘的复杂结构，需要高分辨率的数值模拟。当我们调整C* 的值时，低n模型中模型星系的全局性质，如恒星形成历史，与高n模型中的相似，从而再现了表面气体密度和表面恒星形成率密度之间的观测关系。然而，我们强调，高n模型会自动重现关系，而不管C* 的值如何。ISM结构，相位分布，年轻恒星形成区的分布是非常相似的两个运行之间的C* 值相差15倍。我们还发现，从n_H ~1 cm^{-3}到n_H > 100 cm^{-3}的流动时间尺度约为局域动力学时间的5倍，且与C* 值无关。在高分辨率模拟中使用高n标准的恒星形成使得数值模型对恒星形成的建模非常不敏感。（节录）
英文摘要：
We performed 3-dimensional N-body/SPH simulations to study how mass resolution and other model parameters such as the star formation efficiency parameter, C* and the threshold density, nth affect structures of the galactic gaseous/stellar disk in a static galactic potential. We employ 10^6 - 10^7 particles to resolve a cold and dense (T < 100 K & n_H > 100 cm^{-3}) phase. We found that structures of the ISM and the distribution of young stars are sensitive to the assumed nth. High-nth models with nth = 100 cm^{-3} yield clumpy multi-phase features in the ISM. Young stars are distributed in a thin disk of which half-mass scale height is 10 - 30 pc. In low-nth models with nth = 0.1 cm^{-3}, the stellar disk is found to be several times thicker, and the gas disk appears smoother than the high-nth models. A high-resolution simulation with high-nth is necessary to reproduce the complex structure of the gas disk. The global properties of the model galaxies in low-nth models, such as star formation histories, are similar to those in the high-nth models when we tune the value of C* so that they reproduce the observed relation between surface gas density and surface star formation rate density. We however emphasize that high-nth models automatically reproduce the relation, regardless of the values of C*. The ISM structure, phase distribution, and distributions of young star forming region are quite similar between two runs with values of C* which differ by a factor of 15. We also found that the timescale of the flow from n_H ~1 cm^{-3} to n_H > 100 cm^{-3} is about 5 times as long as the local dynamical time and is independent of the value of C*. The use of a high-nth criterion for star formation in high-resolution simulations makes numerical models fairy insensitive to the modelling of star formation. (Abridged)
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