通过宇宙网追踪星系 bias：纤维的作用
Tracing Galaxy Bias Through the Cosmic Web: The Role of Filaments
AI总结：
本研究利用 DisPerSE 算法分析 IllustrisTNG 模拟数据，发现星系 bias 与纤维长度、节点距离等相关，节点外围星系 bias 最高，且短纤维 bias 分布均匀、长纤维 bias 向节点递增。
AI中文摘要：
星系的大尺度成团性不仅取决于其自身属性，还取决于其在宇宙网中的位置，宇宙网定义了星系形成和演化的各向异性环境。纤维是桥梁，星系和暗物质通过它从低密度区域流向最高密度的节点。本研究旨在通过宇宙网绘制星系 bias（量化这些示踪剂如何跟随潜在暗物质密度场），特别关注纤维。我们研究其对纤维属性（如长度和密度）的依赖性，并表征大尺度 bias 沿纤维脊的空间变化。我们应用 DisPerSE 算法在 IllustrisTNG 模拟的 TNG300 体积中识别宇宙网。为测量大尺度星系 bias，我们采用了逐个天体的估计器，它比标准估计器更具优势。我们发现，节点外围的星系表现出最高的大尺度 bias 值，达到仅基于晕质量的理论模型预期值的约 4 倍。纤维和纤维外围的低质量红星系也表现出增强的 bias，在排除靠近节点的星系后，这种增强大幅降低。这些结果共同表明，靠近大质量节点在塑造环境次级 bias 中起核心作用。此外，星系 bias 随纤维长度增加而降低，短纤维的平均 bias 为 1.4，较长结构的平均 bias 为 -0.5。该关系在固定晕质量和星系颜色时仍然存在，且并非主要由纤维的平均局部星系密度驱动。最后，短纤维表现出近似均匀的纵向 bias 分布，而长纤维的归一化 bias 从鞍点附近的约 0.85 增加到节点附近的约 1.06。
英文摘要：
The large-scale clustering of galaxies depends not only on their internal properties but also on their location within the cosmic web, which defines the anisotropic environments where galaxies form and evolve. Filaments serve as bridges through which galaxies and dark matter flow from low-density regions toward the highest-density nodes. In this work, we aim to map galaxy bias, which quantifies how these tracers follow the underlying dark matter density field, through the cosmic web, with a special emphasis on filaments. We look for dependencies on filament properties, such as length and density, and characterize the spatial variations of the large-scale bias along the filamentary spine. We applied the DisPerSE algorithm to identify the cosmic web in the TNG300 volume of the IllustrisTNG simulation. To measure large-scale galaxy bias, we utilized an object-by-object estimator, which provides advantages over standard estimators. We find that galaxies in node outskirts exhibit the highest large-scale bias values, reaching up to $\sim4$ times the values expected from theoretical models based on halo mass alone. Low-mass red galaxies in filaments and filament outskirts also display enhanced bias, which is strongly reduced after excluding galaxies close to nodes. Together, these results suggest that proximity to massive nodes plays a central role in shaping environmental secondary bias. Furthermore, galaxy bias decreases with filament length, from mean values of $1.4$ for short filaments to $-0.5$ for longer structures. This relation persists at fixed halo mass and galaxy color, and is not primarily driven by the average local galaxy density of the filament. Finally, short filaments exhibit an approximately uniform longitudinal bias profile, whereas long filaments show an increase in normalized bias from $\sim0.85$ near the saddle point to $\sim1.06$ close to the node.
