论文标题
暗物质光环的半径依赖性旋转过渡
Radius-Dependent Spin Transition of Dark Matter Halos
论文作者
论文摘要
报道了对半径依赖性旋转过渡的数值检测。分析来自Illustristng模拟的数据，我们测量了病毒边界内几个内部半径的光环自旋矢量，并在潮汐和速度剪切场的主要框架中研究了它们的方向，称为Tweb和Vweb。高质量截面中的光环自旋矢量显示出从tweb中间到主要主轴的过渡，因为它们在更内部的半径上进行了测量，该半径均适用于暗物质和重型分量。过渡发生的半径阈值取决于$ r_ {f} $的平滑刻度，变大，随着$ r_ {f} $减小。对于VWEB的情况，仅当$ r_ {f} \ ge 1 \，h^{ - 1} $ mpc时，仅当半径依赖性旋转过渡的发生。重复相同的分析，但使用涡旋向量，我们揭示了与自旋的关键差异。无论$ r_ {f} $，涡旋矢量总是垂直于tweb（vweb）主要主轴，这表明晕圈内旋转并未受到涡流产生的强烈影响。还表明，在涡流矢量具有较高幅度的区域中，光环旋转以及tweb（VWEB）主轴具有更大的方向相干性。讨论了我们结果的物理解释和含义。
A numerical detection of the radius-dependent spin transition of dark matter halos is reported. Analyzing the data from the IllustrisTNG simulations, we measure the halo spin vectors at several inner radii within the virial boundaries and investigate their orientations in the principal frames of the tidal and velocity shear fields, called the Tweb and Vweb, respectively. The halo spin vectors in the high-mass section exhibit a transition from the Tweb intermediate to major principal axes as they are measured at more inner radii, which holds for both of the dark matter and baryonic components. The radius threshold at which the transition occurs depends on the smoothing scale, $R_{f}$, becoming larger as $R_{f}$ decreases. For the case of the Vweb, the occurrence of the radius-dependent spin transition is witnessed only when $R_{f}\ge 1\, h^{-1}$Mpc. Repeating the same analysis but with the vorticity vectors, we reveal a critical difference from the spins. The vorticity vectors are always perpendicular to the Tweb (Vweb) major principal axes, regardless of $R_{f}$, which indicates that the halo inner spins are not strongly affected by the generation of vorticity. It is also shown that the halo spins, as well as the Tweb (Vweb) principal axes, have more directional coherence over a wide range of radial distances in the regions where the vorticity vectors have higher magnitudes. The physical interpretations and implications of our results are discussed.
