Quenching is a key topic in exploring the formation and evolution of galaxies. In this work, we study the quenching rate, i.e., the variation in the fraction of quenched galaxies per unit time, of the Illustris-1 simulation. By building the quenched fraction function $f(m,\rho, t)$ of each snapshot in the simulation, we derive an accurate form of quenching rate as $\Re_q=df(m,\rho,t)/dt$. According to the analytic expression of the quenching rate $\Re_q$, we split it into four components: mass quenching, environmental quenching, intrinsic mass quenching and intrinsic environmental quenching. The precise value and evolutions can be given via the formula of $\Re_q$. With this method, we analyze the Illustris-1 simulation. We find that quenched galaxies concentrate around $M_*\simeq10^{11}h^{-1}M_\odot$ and $\delta+1\simeq10^{3.5}$ at earlier times, and that the quenching galaxy population slowly shifts to lower stellar mass and lower overdensity regions with time. We also find that mass quenching dominates the quenching process in this simulation, in agreement with some previous analytical models. Intrinsic quenching is the second most important component. Environmental quenching is very weak, because it is possible that the pre- or postprocessing of environments disguises environmental quenching as intrinsic quenching. We find that our method roughly predict the actual quenching rate. It could well predict the actual amount of galaxies quenched by intrinsic quenching. However, it overestimates the amount of mass quenching galaxies and underestimates the amount of environmental quenching. We suggest that the reason is the nonlinearity of the environmental overdensity change and mass growth of the galaxy.

中文翻译：

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在 Illustris 模拟中估计星系淬火速率

淬火是探索星系形成和演化的关键课题。在这项工作中，我们研究了 Illustris-1 模拟的猝灭率，即单位时间内猝灭星系的分数的变化。通过构建模拟中每个快照的淬火分数函数 $f(m,\rho, t)$，我们得出淬火率的准确形式为 $\Re_q=df(m,\rho,t)/dt$。根据淬灭率$\Re_q$的解析表达式，我们将其分为四个部分：质量淬灭、环境淬灭、本征质量淬灭和本征环境淬灭。精确的值和演变可以通过 $\Re_q$ 的公式给出。使用这种方法，我们分析了 Illustris-1 模拟。我们发现淬火星系在早期集中在 $M_*\simeq10^{11}h^{-1}M_\odot$ 和 $\delta+1\simeq10^{3.5}$ 附近，并且随着时间的推移，猝灭星系群缓慢地转移到较低的恒星质量和较低的高密度区域。我们还发现，在该模拟中，质量淬火在淬火过程中占主导地位，这与之前的一些分析模型一致。本征淬火是第二重要的组成部分。环境淬火非常弱，因为环境的预处理或后处理可能将环境淬火伪装成内在淬火。我们发现我们的方法粗略地预测了实际的淬火速率。它可以很好地预测由本征猝灭而猝灭的星系的实际数量。然而，它高估了质量猝灭星系的数量，低估了环境猝灭的数量。