标题： 晕系中重子的角动量标度关系的微小影响 显示英文标题

标题： Negligible Effects of Baryons on the Angular Momentum Scaling Relations of Galactic Dark Matter Halos

摘要： 在没有重子物质的宇宙学模拟中，星系暗物质晕的比角动量$j_{\rm h}$与质量$M_{\rm h}$之间的关系具有已确立的形式$j_{\rm h} \propto M_{\rm h}^{2/3}$。 这通常被用作理解星系恒星部分的比角动量$j_{\ast}$与质量$M_{\ast}$之间类似关系的起点，这些关系常常通过保留分数$f_j = j_{\ast} / j_{\rm h}$和$f_M = M_{\ast} / M_{\rm h}$相对于相应的晕属性进行重新表达。 一个重要的注意事项是，所采用的$j_{\rm h} \propto M_{\rm h}^{2/3}$关系在原则上可能会因重子物质对暗物质（DM）的引力反作用而被修改。我们通过比较包含重子物质（全物理运行）的IllustrisTNG100和TNG50模拟中的$j_{\rm h}$-$M_{\rm h}$关系及其不包含重子物质的对应关系（DM-only运行）来测试这种可能性。在所有情况下，我们发现形式为$j_{\rm h} \propto M_{\rm h}^{\alpha}$的标度关系，在此处研究的质量和红移范围内，$\alpha \approx 2/3$为$M_{\rm h} \geq 10^{10} \, M_{\odot}$和$0 \leq z \leq 2$。 $\alpha$的值在相同红移下的全物理和 DM 仅运行中几乎完全相同。 重子对$j_{\rm h}$-$M_{\rm h}$关系的唯一可检测影响是归一化略有提高，在$z=0$处提高了 12%-15%，在$z=2$处提高了 5%。 这意味着基于 DM 仅模拟的$f_j$的现有估计值应相应地向下调整。 最后，我们简要讨论了这项工作对星系形成研究的一些影响。 显示英文摘要

摘要： In cosmological simulations without baryons, the relation between the specific angular momentum $j_{\rm h}$ and mass $M_{\rm h}$ of galactic dark matter halos has the well-established form $j_{\rm h} \propto M_{\rm h}^{2/3}$. This is invariably adopted as the starting point in efforts to understand the analogous relation between the specific angular momentum $j_{\ast}$ and mass $M_{\ast}$ of the stellar parts of galaxies, which are often re-expressed relative to the corresponding halo properties through the retention fractions $f_j = j_{\ast} / j_{\rm h}$ and $f_M = M_{\ast} / M_{\rm h}$. An important caveat here is that the adopted $j_{\rm h} \propto M_{\rm h}^{2/3}$ relation could, in principle, be modified by the gravitational back-reaction of baryons on dark matter (DM). We have tested for this possibility by comparing the $j_{\rm h}$-$M_{\rm h}$ relations in the IllustrisTNG100 and TNG50 simulations that include baryons (full-physics runs) with their counterparts that do not (DM-only runs). In all cases, we find scaling relations of the form $j_{\rm h} \propto M_{\rm h}^{\alpha}$, with $\alpha \approx 2/3$ over the ranges of mass and redshift studied here: $M_{\rm h} \geq 10^{10} \, M_{\odot}$ and $0 \leq z \leq 2$. The values of $\alpha$ are virtually identical in the full-physics and DM-only runs at the same redshift. The only detectable effect of baryons on the $j_{\rm h}$-$M_{\rm h}$ relation is a slightly higher normalization, by 12%-15% at $z=0$ and by 5% at $z=2$. This implies that existing estimates of $f_j$ based on DM-only simulations should be adjusted downward by similar amounts. Finally, we discuss briefly some implications of this work for studies of galaxy formation.