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Study on the formation and evolution of galaxies by Large-scale numerical simulations on special-purpose computers.

通过专用计算机大规模数值模拟研究星系的形成和演化。

基本信息

批准号：
13440058
负责人：
MAKINO Junichiro
金额：
$ 10.88万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440058/
关键词：
large scale stuctuve galaxy formation dark matter halo cosmology N-body simulation dwarf galaxy cold dark matter 宇宙の大規模構造ダークハロー並列計算機専用計算機ツリー法衛星銀河銀河団

项目摘要

1. We have developed a high-efficiency parallel implementation of the Barnes-Hut tree algorithm on parallel GRAPE system. Using this calculation code, it is now feasible to perform simulations of cosmological structure formation in the spatial scale smaller than clusters of galaxies using 〜 10^8 particles. Only one such simulation has been previously reported.2. By cosmological simulations with more than 30 million particles, we have determined the slope of the central cusp of the dark-matter halo in CDM cosmology with unprecedented accuracy and reliability. The slope is around -1.4. We have not observed any tendency of the slope to approach to ―1. This slope does not depend on the cosmological models.3. We have found the reason of the discrepancy between N-body simulations and semi-analytic calculations of the orbital evolution of satellite galaxies. The evolution of the satellite galaxies in recent high-accuracy N-body simulations turned out to be significantly slower than the result of approximate calculations using Chandrasekhar's dynamical friction formula. We found that the discrepancy is not due to the dynamical friction formula itself, but due to the common exercise of taking the size of the parent galaxy as the upper limit for the Coulomb logarithm. By taking the theoretical preferred value, namely the distance of the satellite from the center of the parent galaxy, we resolved the discrepancy. In the case of the satellite from internal degree of freedom, we found that the evolution is faster than that for analytic dynamical friction formula.

1. 我们在并行GRAPE系统上开发了Barnes-Hut树算法的高效并行实现。使用此计算代码，现在可以使用〜10^8粒子在小于星系团的空间尺度上模拟宇宙结构的形成。以前只报道过一种这样的模拟。2．通过超过 3000 万个粒子的宇宙学模拟，我们以前所未有的准确性和可靠性确定了 CDM 宇宙学中暗物质晕中心尖点的斜率。坡度约为-1.4。我们没有观察到斜率有任何接近“1”的趋势。该斜率不依赖于宇宙学模型。3．我们找到了卫星星系轨道演化的N体模拟与半解析计算之间存在差异的原因。最近高精度 N 体模拟中卫星星系的演化结果明显慢于使用钱德拉塞卡动态摩擦公式近似计算的结果。我们发现这种差异并不是由于动摩擦公式本身造成的，而是由于通常将母星系的大小作为库仑对数的上限造成的。通过取理论首选值，即卫星距母星系中心的距离，我们解决了这一差异。对于卫星内部自由度的情况，我们发现其演化速度比解析动摩擦公式的演化速度要快。