宇宙古生物学：仅重力模拟中的化石群统计
Cosmo-Paleontology: Statistics of Fossil Groups in a Gravity-Only Simulation
摘要：
我们提出了一个详细的研究化石组候选人确定的“最后的旅程”，一个重力宇宙学模拟覆盖的$(3.4\, h^{-1}\mathrm{Gpc})^3$体积与粒子质量分辨率为$m_p \approx 2.7 \times 10^9\, h^{-1}\mathrm{M}_\odot$。该模拟使我们能够同时捕获大量群体规模的光环并解析其内部结构。从历史上看，化石群的特征是X射线亮度高，最亮和第二亮的星系之间有很大的光度差距。为了确定候选晕宿主化石群，我们使用晕合并树信息引入两个参数：发光合并质量阈值（$M_\mathrm{LM}$）和最后一个发光合并红移截止值（$z_\mathrm{LLM}$）。最后的参数选择是由观测数据提供的，并允许我们从模拟中识别一个合理的化石组样本。候选晕的特点是减少子结构，因此不太可能主办明亮的星系以外的最明亮的中央星系。我们对这个样本进行了详细的研究，包括晕属性和聚类分析。我们发现，我们简单的假设导致化石组候选人形成早期，具有更高的浓度，并且与相同质量范围内的其他晕相比更轻松。
英文摘要：
We present a detailed study of fossil group candidates identified in "Last Journey", a gravity-only cosmological simulation covering a $(3.4\, h^{-1}\mathrm{Gpc})^3$ volume with a particle mass resolution of $m_p \approx 2.7 \times 10^9\, h^{-1}\mathrm{M}_\odot$. The simulation allows us to simultaneously capture a large number of group-scale halos and to resolve their internal structure. Historically, fossil groups have been characterized by high X-ray brightness and a large luminosity gap between the brightest and second brightest galaxy in the group. In order to identify candidate halos that host fossil groups, we use halo merger tree information to introduce two parameters: a luminous merger mass threshold ($M_\mathrm{LM}$) and a last luminous merger redshift cut-off ($z_\mathrm{LLM}$). The final parameter choices are informed by observational data and allow us to identify a plausible fossil group sample from the simulation. The candidate halos are characterized by reduced substructure and are therefore less likely to host bright galaxies beyond the brightest central galaxy. We carry out detailed studies of this sample, including analysis of halo properties and clustering. We find that our simple assumptions lead to fossil group candidates that form early, have higher concentrations, and are more relaxed compared to other halos in the same mass range.
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