We present an analysis of the angular momentum content of the circumgalactic medium (CGM) using TNG100, one of the flagship runs of the IllustrisTNG project. We focus on Milky Way-mass halos ($\sim 10^{12} \; M_{\odot}$) at $z=0$ but also analyze other masses and redshifts up to $z=5$. We find that the CGM angular momentum properties are strongly correlated with the stellar angular momentum of the corresponding galaxy: the CGM surrounding high-angular momentum galaxies has a systematically higher angular momentum and is better aligned to the rotational axis of the galaxy itself than the CGM surrounding low-angular momentum galaxies. Both the hot and cold phases of the CGM show this dichotomy, though it is stronger for colder gas. The CGM of high-angular momentum galaxies is characterized by a large wedge of cold gas with rotational velocities at least $\sim1/2$ of the halo's virial velocity, extending out to $\sim 1/2$ of the virial radius, and by biconical polar regions dominated by radial velocities suggestive of galactic fountains; both of these features are absent from the CGM of low-angular momentum galaxies. These conclusions are general to halo masses $\lesssim 10^{12} \; M_{\odot}$ and for $z \lesssim 2$, but they do not apply for more massive halos or at the highest redshift studied. By comparing simulations run with alterations to the fiducial feedback model, we identify the better alignment of the CGM to high-angular momentum galaxies as a feedback-independent effect and the galactic winds as a dominant influence on the CGM's angular momentum.

中文翻译：

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TNG100 模拟中环绕星系介质的角动量

我们使用 IllustrisTNG 项目的旗舰项目之一——TNG100，对环银河介质 (CGM) 的角动量含量进行了分析。我们专注于 $z=0$ 的银河系质量晕（$\sim 10^{12} \; M_{\odot}$），但也分析了其他质量和红移至 $z=5$。我们发现 CGM 角动量特性与相应星系的恒星角动量密切相关：围绕高角动量星系的 CGM 具有系统性更高的角动量，并且比 CGM 更好地与星系本身的旋转轴对齐周围的低角动量星系。CGM 的热相和冷相都显示出这种二分法，尽管它对于较冷的气体更强。高角动量星系的 CGM 的特征是一个大楔形冷气体，其旋转速度至少是晕的维里速度的 $\sim1/2$，延伸到维里半径的 $\sim1/2$，并且由径向速度主导的双锥极区，暗示着银河喷泉；低角动量星系的 CGM 中没有这两个特征。这些结论对于晕质量 $\lesssim 10^{12} \; M_{\odot}$ 和 $z \lesssim 2$，但它们不适用于更大质量的光晕或研究的最高红移。通过将模拟运行与基准反馈模型的改变进行比较，我们将 CGM 与高角动量星系的更好对齐确定为与反馈无关的效应，而银河风则作为对 CGM 角动量的主要影响。