标题： 非平衡冷却速率对于碰撞冷却的富金属气体 显示英文标题

标题： Non-equilibrium cooling rate for a collisionally cooled metal-enriched gas

摘要： 我们给出了无尘气体在宽广温度（$10 K\le T\le 10^8 K$）和金属丰度（$10^{-4} Z_\odot \le Z \le 2 Z_\odot$）范围内碰撞控制的非平衡（时变）冷却速率的一致性计算结果。我们确认，在 $10^2 \simlt T\simlt 10^4$ K 和 $Z\simlt 10^{-3} Z_\odot$ 温度下，分子氢主导冷却过程。我们发现，在 $T\sim (4-5)\times 10^3$ K 附近，H$_2$对冷却速率的贡献在金属丰度范围 $Z\simlt 10^{-2} Z_\odot$ 内激发了热不稳定性。等压冷却速率通常低于等容冷却速率，因为相关的气体密度增加既促进了更有效的氢重新结合，又使精细结构能级的分布达到平衡。 等体冷却使电离分数在$T\simlt10^4$K时保持相当高：在$T\simeq 10^3$K和$Z\simlt 0.1 Z_\odot$时高达$\sim0.01$，且在更高金属丰度下更高，而等压冷却则低至少一个数量级。 尽管电离分数有所增加，但分子氢（通过 H$^-$ 形成）的气相形成速率随着金属丰度的增加而降低，因为更高的金属丰度缩短了演化时间。 为了模拟超新星遗迹的演化，我们将自洽的冷却速率实现到多维并行代码ZEUS-MP中，并将其与之前发表的使用表格冷却速率的类似模型进行比较。 我们发现两种描述之间存在显著差异，例如，在星际介质中喷出的金属混合方面可能表现出这种差异。 显示英文摘要

摘要： We present self-consistent calculations of non-equilibrium (time-dependent) cooling rates for a dust-free collisionally controlled gas in wide temperature ($10 K\le T\le 10^8 K$) and metallicity ($10^{-4} Z_\odot \le Z \le 2 Z_\odot$) ranges. We confirm that molecular hydrogen dominates cooling at $10^2 \simlt T\simlt 10^4$ K and $Z\simlt 10^{-3} Z_\odot$. We find that the contribution from H$_2$ into cooling rate around $T\sim (4-5)\times 10^3$ K stimulates thermal instability in the metallicity range $Z\simlt 10^{-2} Z_\odot$. Isobaric cooling rates are generally lower than isochoric ones, because the associated increase of gas density leads to both more efficient hydrogen recombination and equilibration of the fine-structure level populations. Isochoric cooling keeps the ionization fraction remains quite high at $T\simlt10^4$ K: up to $\sim0.01$ at $T\simeq 10^3$ K and $Z\simlt 0.1 Z_\odot$, and even higher at higher metallicity, contrary to isobaric cooling where it at least an order of magnitude lower. Despite this increase in ionization fraction the gas-phase formation rate of molecular hydrogen (via H$^-$) lowers with metallicity, because higher metallicity shorttens the evolution time. We implement our self-consistent cooling rates into the multi-dimensional parallel code ZEUS-MP in order to simulate evolution of a supernova remnant, and compare it with an analogous model with tabulated cooling rates published in previous works. We find significant differences between the two descriptions, which may appear, e.g., in mixing of the ejected metals in the circumstellar medium.