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Research on Evolution of Stellar Systems with Highly Parallelized Special-purpose Computer for Gravitational Many-body Problems

高度并行专用计算机引力多体问题恒星系统演化研究

基本信息

批准号：
02452012
负责人：
SUGIMOTO Daiichiro
金额：
$ 5.12万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-02452012/
关键词：
Special-purpose computer Parallel computer Gravitational Many-body problem Galaxy Stellar system

项目摘要

In 1990 we constructed GRAPE-1A on a wire-wrapped board. It is a prototype of a special-purpose computer for gravitational many-body problems. In close collaboration with Electronic Imaging and Device Research Laboratory of Fuji XEROX Co., Ltd. we then designed a processor chip on one customized LSI which accommodated all the logics of GRAPE-1A. This LSI is 8x8 mm in size and contains 113, 000 transistors. Using this processor chip we constructed a parallelized machine GRAPE-3 in 1991 : We wired 24 processor chips on a VME board, and connected two boards with the host workstation via appropriately designed interface. The machine was tuned in 1991 to reach the peak performance of 14 Gflops, and the sustained speed of 10 Gflops in solving a gravitational 200, 000body problem. It is faster than the any commercially available supercomputer in 1991 so far as the sustained speed is concerned. Using GRAPE-3 we have done a variety of simulations on evolution of stellar systems, and have found … More that collision and resultant merging of galaxies play important roles in evolution of galaxies and their clusters. In what follows we summarize the new findings.1) When two galaxies with central massive black holes collide each other, the black holes suffer from dynamical friction due to the field stars near the apocenter of the orbit. They loose rather their angular momentum than their energy. The eccentricity of the orbit approaches to unity and the black holes may merge quickly. At the same time the field stars aquire energy and become hot. Such picture nicely interprets the relation between the core radius and the total mass of the remnants.2) During the collision of galaxies the gravitational field changes violently. As a result the stars become throughly mixed in the phase space. On the other hand, in the energy space the mixing proceeds quickly only in the initial phases of their collision and much more slowly afterward. Therefore, it is not appropriate to call such process as the "violent" relaxation.3) After such process, the stars in the core (or halo) of each galaxy before the collision tend to stay in the core (or halo) of the merger. Therefore, the color gradient observed in giant elliptical galaxies can not testify against the merger hypothesis of their origin.4) Merging of galaxies proceeds effectively by expelling the angular momentum together with the stars in the halo. Thus, the merging of galaxies may be regarded to be frequent phenomena and may play one of the leading roles in the evolution and history of galaxies and the universe. Less

1990年，我们在一块线包板上构建了GRAPE-1A。它是用于解决引力多体问题的专用计算机的原型。在与富士施乐公司电子成像和器件研究实验室的密切合作下，我们随后在一个定制的大规模集成电路上设计了一个处理器芯片，该芯片容纳了GRAPE-1A的所有逻辑。这种大规模集成电路的尺寸为8x8mm，包含113,000个晶体管。1991年，我们使用这种处理器芯片构建了一台并行机graph -3：我们在一个VME板上连接了24个处理器芯片，并通过适当设计的接口将两块板与主机工作站连接起来。这台机器在1991年进行了调整，达到了14 gps的峰值性能，并在解决引力20万物体问题时保持了10 gps的持续速度。就持续速度而言，它比1991年任何商用超级计算机都要快。利用GRAPE-3，我们对恒星系统的演化进行了各种模拟，并发现星系的碰撞和由此产生的合并在星系及其星团的演化中起着重要作用。下面我们总结一下新的发现。(1)当中心有大质量黑洞的两个星系相互碰撞时，由于轨道中心附近的场星，黑洞受到动力摩擦。它们失去的是角动量而不是能量。轨道的离心率趋于一致，黑洞可能很快合并。与此同时，磁场恒星获得能量并变热。这幅图很好地解释了核心半径与残余物总质量之间的关系。2)在星系碰撞过程中，引力场发生剧烈变化。结果，恒星在相空间中完全混合。另一方面，在能量空间中，混合只在它们碰撞的初始阶段进行得很快，之后要慢得多。因此，称这种过程为“暴力”放松是不恰当的。3)经过这样的过程，碰撞前各星系核心（或光晕）内的恒星倾向于留在合并的核心（或光晕）内。因此，在巨型椭圆星系中观测到的颜色梯度不能证明它们起源的合并假说是错误的。星系的合并是通过与晕中的恒星一起排出角动量而有效进行的。因此，星系合并可以被认为是一种频繁的现象，并可能在星系和宇宙的演化和历史中发挥主导作用之一。少