The Study of the evolution of star clusters, galaxies, clusters of galaxies by ultra-fast Special-purpose Computer for many-body problem

在这一年，我们继续使用GRAPE-4模拟球状星团，星系和星系团的演化。此外，我们还为GRAPE-4开发了一个新的主机接口板，允许使用更快的主机。对于这个新的主机接口板，我们采用了PCI总线，它现在可用于从个人计算机到超级计算机的各种计算机。我们购买了具有该PCI接口的高性能工作站作为新的主机，快速且大型的磁带系统来保存数据，并增强了主机的内存容量。今年的主要科学成果包括：（a）CDM晕中心区域结构的确定，（B）合并星系中大质量黑洞双星演化的研究，（c）星系团中星系碰撞对星系结构影响的系统研究。以前在银河系尺度上对暗物质晕形成的模拟通常只使用了20，000 - 30，000个粒子。由于粒子数量很少，10千秒差距内的结构受到两体弛豫效应的强烈影响，这在真实的星系中是不存在的。我们使用786，432个粒子进行了模拟，并成功地确定了1千秒差距的结构。结果是，内部区域几乎是等温的，温度向内略有下降，这与观测到的大椭圆星系的结构不一致。这一结果以及星系与中心黑洞合并的模拟强烈表明，大质量中心天体的动力学效应对于解释观测到的大椭圆星系结构至关重要。

In this year, we continued the simulation of the evolution of globular clusters, galaxies and clusters of galaxies using GRAPE-4. In addition, we developed a new host interface board for GRAPE-4, which allows use to use faster host computers. For this new host interface board we adopted the PCI bus, which is now available on wide variety of computers from personal computers to supercomputers. We bought high-performance workstations with this PCI interface as new host computers, fast and large tape systems to save the data, and enhanced the memory capacity of host computersMain scientific results of this year include (a) The determination of the structure of the central region of the CDM halo, (b) The study of the evolution of the massive black hole binaries in merging galaxies, and (c) the systematic survey of the effect of encounters to the structure of galaxies in the clusters.Here we briefly summarize (a). Previous simulations of the formation of the dark matter halo in galactic scale typically employed only 20,000-30,000 particles. Because of this small number of particles, the structure within 10 kilo parsec was strongly affected by the two-body relaxation effect, which is not present in real galaxies. We performed the simulation using 786,432 particles, and successfully determined the structure down to 1 kilo parsec. The result is that the inner region is almost isothermal with temperature slightly decreasing inward, which is inconsistent with the observed structure of large elliptical galaxies. This result and the simulation of galaxy merger with central black holes strongly suggest the dynamical effect of massive central objects is crucial to explain the observed structure of large ellipticals.