We perform a comparison, object by object and statistically, between the Munich semi-analytical model, L-GALAXIES, and the IllustrisTNG hydrodynamical simulations. By running L-GALAXIES on the IllustrisTNG dark matter-only merger trees, we identify the same galaxies in the two models. This allows us to compare the stellar mass, star formation rate, and gas content of galaxies, as well as the baryonic content of subhaloes and haloes in the two models. We find that both the stellar mass functions and the stellar masses of individual galaxies agree to better than ${\sim} 0.2\,$dex. On the other hand, specific star formation rates and gas contents can differ more substantially. At z = 0, the transition between low-mass star-forming galaxies and high-mass quenched galaxies occurs at a stellar mass scale ${\sim} 0.5\,$dex lower in IllustrisTNG than that in L-GALAXIES. IllustrisTNG also produces substantially more quenched galaxies at higher redshifts. Both models predict a halo baryon fraction close to the cosmic value for clusters, but IllustrisTNG predicts lower baryon fractions in group environments. These differences are primarily due to differences in modelling feedback from stars and supermassive black holes. The gas content and star formation rates of galaxies in and around clusters and groups differ substantially, with IllustrisTNG satellites less star forming and less gas rich. We show that environmental processes such as ram-pressure stripping are stronger and operate to larger distances and for a broader host mass range in IllustrisTNG. We suggest that the treatment of galaxy evolution in the semi-analytic model needs to be improved by prescriptions that capture local environmental effects more accurately.

中文翻译：

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比较 L-GALAXIES 半解析模型和 IllustrisTNG 模拟中的星系形成

我们在慕尼黑半解析模型、L-GALAXIES 和 IllustrisTNG 流体动力学模拟之间进行逐个对象和统计的比较。通过在 IllustrisTNG 仅暗物质合并树上运行 L-GALAXIES，我们在两个模型中识别出相同的星系。这使我们能够比较两个模型中的恒星质量、恒星形成率和星系的气体含量，以及亚晕和晕的重子含量。我们发现恒星质量函数和单个星系的恒星质量都同意优于${\sim} 0.2\,$dex。另一方面，特定的恒星形成率和气体含量可能会有更大的差异。在 z = 0 时，低质量恒星形成星系和高质量猝灭星系之间的过渡发生在恒星质量尺度 ${\sim} 0.5\，IllustrisTNG 中的 $dex 低于 L-GALAXIES。IllustrisTNG 还会在更高的红移处产生更多的淬灭星系。两种模型都预测了接近星团宇宙值的晕重子分数，但 IllustrisTNG 预测群体环境中的重子分数较低。这些差异主要是由于来自恒星和超大质量黑洞的建模反馈不同。星系团和星系团内部和周围的星系的气体含量和恒星形成率差异很大，IllustrisTNG 卫星的恒星形成较少且气体较少。我们表明，在 IllustrisTNG 中，冲压压力剥离等环境过程更强大，可以运行到更远的距离和更广泛的宿主质量范围。