AI 中文总结
研究本超星系片对银河系和仙女座星系类似物暗物质晕等的影响，通过受限本星系群模拟，发现暗物质晕形状、盘角动量等与本超星系片的关系及受合并影响情况，解释了星系特殊对齐等现象。
AI 中文摘要
大规模环境被认为在塑造星系属性方面起着重要作用。银河系（MW）和仙女座星系（M31）位于本星系群中，嵌入在本超星系片中。为研究该片对MW和M31类似物的暗物质晕形状、自旋和盘方向的影响，我们使用了一套新的受限本星系群模拟，重现了两个主要晕和本超星系片的观测配置。我们确定了它们相对于本超星系片类似物的形状和对齐情况，以及大量合并的吸积和合并的影响。我们发现，我们的MW和M31类似物的暗物质晕形状平均比文献中随机环境中类似质量星系的报告略圆。我们发现片法线与晕的短轴之间存在优先对齐，但与晕的自旋不存在优先对齐。当今的盘角动量（$L_{\rm disk}$）与晕的短轴紧密对齐（在$R_{\rm vir}$处中值为$15^{+15}_{-8}$度），并与晕的自旋对齐。$L_{\rm disk}$的方向通常由过去8 - 10 Gyr内两个最高质量比合并之一设定。虽然最近（$\leq 2$ Gyr）的大量合并可以重新定向外晕的短轴，导致扭曲形状，但$L_{\rm disk}$保留了早期吸积事件的印记。这些结果可以解释MW盘和暗物质晕形状的特殊对齐及其相对于本超星系片的方向。MW外晕的长椭球形形态和方向可以由麦哲伦云（可能还有人马座）从本超星系片内吸积来解释。由于它们的轨道平面几乎垂直于银盘，盘的方向必须更早设定，可能是由GES合并设定。这次合并的估计吸积方向相对于当今的本超星系片高度倾斜，与本超星系片的最大坍缩方向大致一致。
英文摘要
The large-scale environment is thought to play an important role in setting galaxy properties. The Milky Way (MW) and Andromeda (M31) reside in the Local Group, embedded in the Local Sheet (LS). To study the sheet's influence on the dark matter (DM) halo shapes, spins, and disks orientations of MW and M31 analogues, we use a new suite of constrained Local Group simulations that reproduce the observed configuration of the two main halos and the LS. We determine their shapes and alignments relative to the LS analogues, and the effect of infall and coalescence of massive mergers. We find that the DM halo shapes of our MW and M31 analogues are on average slightly rounder than literature reports for similar-mass galaxies in random environments. We find preferential alignment between the sheet normal and the halos' minor axes, but not with the halos' spins. The present-day disk angular momenta ($L_{\rm disk}$) closely align with the halos' minor axes (median $15^{+15}_{-8}$ degrees at $R_{\rm vir}$) and with the halos' spins. The direction of $L_{\rm disk}$ is often set by one of the two highest mass ratio mergers during the last 8-10 Gyr. While recent ($\leq 2$ Gyr) massive mergers can reorient the outer halo's minor axis leading to twisted shapes, $L_{\rm disk}$ retains the imprint of the earlier accretion event. These results can explain the peculiar alignment of the MW's disk and DM halo shape and their orientation relative to the LS. The prolate-like morphology and orientation of the MW's outer halo can be explained by the Magellanic Clouds (and perhaps Sagittarius) accreting from within the LS. As their orbital planes are nearly perpendicular to the Galactic disk, the disk orientation must be set earlier, possibly by the GES merger. This merger's estimated infall direction, highly inclined relative to the present-day LS, is broadly consistent with the LS's direction of maximum collapse.
CommentsSubmitted to A&A. 17 pages, 15 figures
