模拟宇宙空洞中的结构形成

The cosmological model, LCDM, in which dark mater and dark energy are the dominating components, gains lot of supports from the observational data and almost becomes the "standard" model. In this model, the structures form in a hierarchical way: most of objects form in the high density regions by merging of smaller objects. However, in the very low density region of the Universe-voids, the structure forms maybe in a litter different way. With the advent of a mount of new observational data on isolated galaxies in voids, the formation of dark haloes and galaxies in voids are getting more attentions. In this application, we will resimulate several voids in a cosmological simulation, and plan to study the galaxy formation in voids on following issues: we will estimate carefully if the number density of galaxies in voids and check if it agrees with the observed sample. Previous studies claim the number density of galaxies in local groups is far lower than the theoritical prediction, which poses a big challenge for the standard model. Furthermore we will study the satellite sample in Milky Way like dark matter haloes in voids and high density regions to evaluate if the environmental effect could cause the excess of massive satellites in the simulated sample comparing to the observational data, and if it could explain the anisotropy of the satellite's spacial distribution. Furthermore, we will use this well resolved big sample to predict the luminosity function and spacial distribution of isolated galaxies in voids.This could be helpful on designing the next generation galaxy survey of the galaxy in voids.

以冷暗物质暗能量为主要物质构成的宇宙学模型LCDM得到广泛的观测支持而成为"标准"模型。该模型预测宇宙大部分暗晕都集中在宇宙的高密度区以不断并和小的结构这一等级成团机制成长，并得到广泛和深入的研究。随着关于宇宙较低密度区域-空洞（void）中星系的观测数据逐步积累，对于空洞中的结构的形成也得到更多的关注。在本项目中，通过对几个低密度区空洞进行高解析度的再模拟，我们计划在以下方面对空洞中的星系进行研究：空洞中的星系数密度是否和观测吻合，能否缓解观测上星系空洞星系数目远少于模型预测而导致对标准宇宙模型的挑战；通过对空洞中类银河系星系的卫星星系的观测，评估环境因素是否能缓解银河系卫星星系中"大质量卫星丢失问题"以及其空间分布高度各向不同对星系形成模型所提出的质疑。同时，通过这一将具有全世界最高解析度的关于空洞中结构形成的数值模拟，我们希望对将来巡天观测中对空洞星系的分布和光度函数等做出预测。

项目原定计划只限于研究空洞中结构形成。在计划实施的第二年，项目升级修订为VVV项目，项目目标修订为利用多层再模拟技术研究所有质量区间暗晕的结构形成，从LCDM模型里最小的暗晕到宇宙最大质量暗晕（1.e-6---1.e15太阳质量，超过20多个量级。这将是首次对于所有质量区间暗晕的形成历史得以在宇宙背景里正确的得以研究，其研究成果也将对于暗物质间接探测的历史给予正确的预言。基于此新项目的科学目标也大大扩大。新科学目标的科学意义得到极大提升，但这一升级导致项目难度指数增加,从而导致项目滞后于原计划的预期进度。最终经过三年多的工作，修订后的项目目前进展顺利，项目首篇文章预计2018年发表，部分主要结果已经包含在成果报告里。完成了原计划的一套全新的整合了双星演化的星系形成和演化的半解析模型 GABE，相关五篇文章也将马上发表。后续子项目也将接下来的三年内完成。