Lumina 项目：电离气泡与中性岛屿的形态学
The Lumina Project: Morphology of Ionized Bubbles and Neutral Islands
- Massachusetts Institute of Technology（麻省理工学院）
- The University of Texas at Dallas（德克萨斯大学达拉斯分校）
- Philipps Universität Marburg（马尔堡菲利普斯大学）
- Max Planck Institute for Astrophysics（马克斯·普朗克天体物理研究所）
- York University（约克大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究通过分析Lumina模拟中的电离气泡和中性岛屿，揭示了再电离过程中气泡尺寸演化、形状分布及内部性质，并发现晚期残余中性结构呈长球状。
AI中文摘要：
再电离纪元以星系际介质中电离气泡的成核、扩张和渗流为特征。解读来自 JWST 和下一代 21 厘米干涉仪等设施的新兴多波长观测，需要对 HII 区域的 3D 形态以及再电离末期存留的残余中性结构有详细的理论理解。我们分析了大规模 500 Mpc$^3$ 辐射-流体动力学模拟 Lumina 中电离气泡和晚期中性岛屿的几何与物理性质。我们使用 3D 分水岭方法识别离散结构，并测量其体积、形状张量和内部气体性质。体积加权的气泡尺寸分布在整个再电离纪元中显著演化：特征半径从 z>10 时的 Reff~1 cMpc 转变为 z<6 时的 Reff>100 cMpc，而分水岭导出的尺寸在中间红移处超过视线方向平均自由程测量值约 3 倍。大部分气泡群在再电离纪元的大部分时间内主要呈长球状。然而，到 z~6 时，区分扁平结构与拉长结构的三轴性参数 T 的体积加权分布在基准分割中变为双峰，在 T~0.25 附近出现尖锐的扁球峰，这与晚期渗流期间少数非常大的气泡相关。气泡内部的物理性质与由内而外的再电离一致，气泡内气体中值过密度从 z=15 时的 $δ$~1 降至 z=6 时的宇宙平均值。在分辨率尺度附近的最小值之外，内部紫外线辐射能量密度的中值随气泡尺寸增加而增加。z<6 时的残余中性岛屿在体积加权尺寸上峰值位于 Reff~10 cMpc 附近，并保持主要为长球状，这与再电离末期各向异性的残余中性结构一致。
英文摘要：
The Epoch of Reionization is characterized by the nucleation, expansion, and percolation of ionized bubbles in the intergalactic medium. Interpreting emerging multi-wavelength observations from facilities such as JWST and next-generation 21 cm interferometers requires a detailed theoretical understanding of the 3D morphology of these HII regions and of the residual neutral structures that survive near the end of reionization. We analyze the geometry and physical properties of ionized bubbles and late-time neutral islands in the large-volume 500 Mpc$^3$ radiation-hydrodynamics simulation Lumina. We identify discrete structures with a 3D watershed method and measure their volumes, shape tensors, and internal gas properties. The volume-weighted bubble size distributions evolve substantially across the EoR: characteristic radii shift from Reff~1 cMpc at z>10 to Reff>100 cMpc by z< 6, while watershed-derived sizes exceed line-of-sight mean-free-path measurements by roughly a factor of 3 at intermediate redshifts. The bulk bubble population is predominantly prolate through most of the EoR. By z~6, however, the volume-weighted distribution of the triaxiality parameter T, which distinguishes flattened from elongated structures, becomes bimodal in the fiducial segmentation, with a sharp oblate peak near T~0.25 associated with a small number of very large bubbles during late percolation. The properties of bubble interiors are consistent with inside-out reionization, with median gas overdensities within bubbles decreasing from $δ$~1 at z=15 toward the cosmic mean by z=6. Beyond a minimum near the resolution scale, the median internal UV radiation energy density increases with bubble size. The residual neutral islands at z< 6 peak in volume-weighted size near Reff~10 cMpc and remain predominantly prolate, consistent with anisotropic residual neutral structure near the end of reionization.
