We review the progress in modeling the galaxy population in hydrodynamical simulations of the ΛCDM cosmogony. State-of-the-art simulations now broadly reproduce the observed spatial clustering of galaxies; the distributions of key characteristics, such as mass, size, and SFR; and scaling relations connecting diverse properties to mass. Such improvements engender confidence in the insight drawn from simulations. Many important outcomes, however, particularly the properties of circumgalactic gas, are sensitive to the details of the subgrid models used to approximate the macroscopic effects of unresolved physics, such as feedback processes. We compare the outcomes of leading simulation suites with observations, and with each other, to identify the enduring successes they have cultivated and the outstanding challenges to be tackled with the next generation of models. Our key conclusions include the following:▪Realistic galaxies can be reproduced by calibrating the ill-constrained parameters of subgrid feedback models. Feedback is dominated by stars and black holes in low-mass and high-mass galaxies, respectively.▪Adjusting or disabling the processes implemented in simulations can elucidate their impact on observables, but outcomes can be degenerate.▪Similar galaxy populations can emerge in simulations with dissimilar feedback implementations. However, these models generally predict markedly different gas flow rates into, and out of, galaxies and their halos. CGM observations are thus a promising means of breaking this degeneracy and guiding the development of new feedback models.

中文翻译：

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星系群的流体动力学模拟：持久的成功和突出的挑战


我们回顾了在 ΛCDM 宇宙学的水动力学模拟中对星系群进行建模的进展。最先进的模拟现在广泛地再现了观察到的星系空间聚集;关键特征的分布，例如质量、大小和 SFR;以及将不同属性连接到质量的缩放关系。这些改进使人们对从模拟中获得的见解充满信心。然而，许多重要的结果，特别是银河系周围气体的性质，对用于近似未解析物理学的宏观效应（例如反馈过程）的子网格模型的细节很敏感。我们将领先仿真套件的结果与观察结果进行比较，并相互比较，以确定它们所取得的持久成功以及需要使用下一代模型应对的突出挑战。我们的主要结论包括：▪通过校准子网格反馈模型的不良约束参数，可以再现逼真的星系。在低质量和高质量星系中，恒星和黑洞分别以反馈为主。▪调整或禁用模拟中实现的过程可以阐明它们对可观测物的影响，但结果可能是退化的。▪类似的星系种群可能会出现在具有不同反馈实现的模拟中。然而，这些模型通常预测进出星系及其光晕的气体流速明显不同。因此，CGM 观测是打破这种退化并指导新反馈模型开发的有前途的方法。