发表机构
Durham University; Stockholm University; University of Cambridge（杜伦大学; 斯德哥尔摩大学; 剑桥大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用Auriga宇宙学模拟套件，发现银河系恒星晕的缓慢旋转源于卫星各向异性吸积，类GES子结构、盘翻转均会导致旋转变慢，且恒星与暗物质晕旋转存在相关性，提出银河系经历过盘翻转且暗物质晕旋转缓慢。
AI 中文摘要
银河系（MW）的恒星晕呈现出微弱的顺行旋转信号（$v_{\rm \nphi} \nlesssim 25$ km·s⁻¹），但其起源仍未得到解释。为探究该问题，我们使用银河系质量晕的Auriga宇宙学模拟套件，在红移范围$z_{\rm red}=0-2.5$内研究恒星晕的旋转。发现旋转信号在该红移范围内持续存在。我们表明，恒星晕的卫星前身体的并合方向呈非均匀分布，虽存在显著离散，但倾向于与宿主盘对齐。因此，我们将净旋转归因于卫星的各向异性吸积。拥有类Gaia-Enceladus-Sausage（GES）子结构的晕始终呈现较慢的旋转速度，这可能是由于此类系统中主导前身体的正面、更径向轨迹所致。恒星盘重新定向≥90°的晕也呈现较慢旋转，这可能是因为晕的动力学时标更长，使其无法快速适应盘的重新定向。我们还报告了恒星晕与暗物质晕旋转之间的相关性，表明各向异性吸积可能是驱动二者共同起源的因素。因此，我们认为银河系经历了一次盘翻转，且拥有一个缓慢旋转的暗物质晕。
英文摘要
The stellar halo of the Milky Way (MW) exhibits a weak net prograde rotational signal ($v_ϕ \lesssim 25$ km~s$^{-1}$), yet its origin remains unexplained. To investigate this, we use the Auriga cosmological simulation suite of MW-mass haloes to probe the rotation of stellar haloes over the redshift range $z_{\mathrm{red}}=0-2.5$. The rotational signal is found to persist over this redshift range. We show that satellite progenitors of the stellar halo exhibit a non-uniform distribution of infall directions, with a tendency to align with the host disc, albeit with significant scatter. Thus, we attribute the net rotation to the anisotropic accretion of satellites. Haloes that host \textit{Gaia}-Enceladus-Sausage (GES)-like substructures exhibit consistently slower rotational velocity, likely due to the head-on, more radial trajectory of the dominant progenitor in such systems. Haloes whose stellar discs have reorientated by $\geq 90^{\circ}$ also exhibit slower rotation, likely because the longer dynamical timescales of haloes prevent them from quickly adjusting to disc reorientations. We also report a correlation between the rotation of stellar and dark matter haloes, suggesting a possible common origin driven by anisotropic accretion. We therefore suggest that the MW experienced a disc flip and has a slowly rotating dark matter halo.
Comments12 pages, 11 figures, accepted to MNRAS
