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

在这一年里，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开发了新的主机接口板，允许用户使用速度更快的主机。对于这块新的主机接口板，我们采用了PCI总线，从个人计算机到超级计算机，现在各种计算机上都可以使用这种总线。今年的主要科学成果包括：(A)确定了CDM晕中心区的结构；(B)研究了合并星系中大质量黑洞双星的演化；(C)系统地考察了相遇对星系团中星系结构的影响。以前对银河系规模暗物质晕形成的模拟通常只使用20,000-30,000个粒子。由于粒子数量很少，10千克秒内的结构受到了真正星系中不存在的二体弛豫效应的强烈影响。我们使用786,432个粒子进行了模拟，并成功地确定了精确到1千秒的结构。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。这一结果和星系与中心黑洞合并的模拟有力地表明，大质量中心天体的动力学效应对于解释观测到的大椭圆形结构是至关重要的。

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.