标题： 宇宙空洞的星系偏差轮廓 显示英文标题

标题： The galaxy bias profile of cosmic voids

摘要： 宇宙空洞是宇宙大尺度结构中的低密度区域，其物理尺度范围很广——从几兆秒差距（Mpc）到最大的可观测结构。 它们独特的性质使其成为有价值的宇宙学探针，并为星系形成研究提供了独特的实验室。 在此背景下，需要研究的一个关键方面是空洞内的星系偏差，$b$，即这些低密度区域中的星系如何追踪潜在的暗物质密度场。 我们想要测量大尺度星系偏差与到空洞中心距离的依赖关系，并评估这种偏差分布是否随空洞特性及识别方法而变化。 我们应用了一种基于球形高密度的空洞识别方案，对来自IllustrisTNG磁流体动力学模拟的星系数据进行分析。 在聚类测量方面，我们使用了一种逐对象的大尺度星系偏差估计方法，这种方法相比基于相关函数或功率谱比值的标准方法具有显著优势。 我们发现，当以空洞半径归一化时，空洞内星系的平均大尺度偏差随着空洞中心距离的增加而增加。 对于空洞内的整个星系群体，平均偏差随着周围环境的密度增加而增加，因此随着空洞尺寸的增大而减少。 由于这种环境依赖性，S型空洞——嵌入大尺度高密度区域中的空洞——在所有距离处的平均星系偏差明显更高（$\langle b\rangle_{\rm in} > 0$），相比于被低密度区域包围的R型空洞（$\langle b\rangle_{\rm in} < 0$）。 S型空洞的偏差分布也略微更陡。 由于这两种类型的空洞都拥有质量相似的晕族，观测到的偏差差异可以解释为次级偏差效应。 显示英文摘要

摘要： Cosmic voids are underdense regions within the large-scale structure of the Universe, spanning a wide range of physical scales - from a few megaparsecs (Mpc) to the largest observable structures. Their distinctive properties make them valuable cosmological probes and unique laboratories for galaxy formation studies. A key aspect to investigate in this context is the galaxy bias, $b$, within voids - that is, how galaxies in these underdense regions trace the underlying dark-matter density field. We want to measure the dependence of the large-scale galaxy bias on the distance to the void center, and to evaluate whether this bias profile varies with the void properties and identification procedure. We apply a void identification scheme based on spherical overdensities to galaxy data from the IllustrisTNG magnetohydrodynamical simulation. For the clustering measurement, we use an object-by-object estimate of large-scale galaxy bias, which offers significant advantages over the standard method based on ratios of correlation functions or power spectra. We find that the average large-scale bias of galaxies inside voids tends to increase with void-centric distance when normalized by the void radius. For the entire galaxy population within voids, the average bias rises with the density of the surrounding environment and, consequently, decreases with increasing void size. Due to this environmental dependence, the average galaxy bias inside S-type voids - embedded in large-scale overdense regions - is significantly higher ($\langle b\rangle_{\rm in} > 0$) at all distances compared to R-type voids, which are surrounded by underdense regions ($\langle b\rangle_{\rm in} < 0$). The bias profile for S-type voids is also slightly steeper. Since both types of voids host halo populations of similar mass, the measured difference in bias can be interpreted as a secondary bias effect.