Black Holes in Dense Star Clusters

大多数恒星形成密集星团，其中最大的星团包含数百万颗恒星。由于星团可以存在数十亿年，它们被认为包含大量致密物体，如黑洞和中子星，它们是很久以前作为死亡大质量恒星的残余物形成的。西北大学的这项研究计划将使用最先进的超级计算机模拟来研究这些致密天体在各种星团环境中的形成和演化。主要的焦点将是产生包含两个黑洞的近距离双星，这些双星最终可以合并并产生潜在的可探测到的引力波爆发。并行计算技术和新算法的发展将具有广泛的相关性，并将引起物理学和天文学以外的科学家的兴趣。天体物理学研究将以学生为导向，大四学生将帮助培养新的团队成员，包括本科生。还计划开展教育和公众宣传活动，利用芝加哥阿德勒天文馆和埃文斯顿西北大学迪尔伯恩天文台的设施。这个项目将解决关于致密星团中致密物体(黑洞和中子星)的形成和动力学演化的一些关键问题。当它们与较轻恒星的背景发生摩擦时，大质量致密天体预计会迅速集中在星系团的致密核心，那里的动力相互作用速率非常高。这些相互作用既可以产生双星，也可以收紧它们的轨道。在某些情况下，通过连续的合并，也许在气体吸积的帮助下，最终可能形成一个中等质量的黑洞。这些过程形成的许多物体都是潜在的多信使来源。该项目将使用蒙特卡洛和N-Body代码相结合的混合方法来优化计算速度、精度和真实感，并克服模拟超大型星团的动态范围问题，在这些星团中，大多数有趣的动力学发生在相对较小、高密度的中心区域。在项目结束时，一个包含一千多个新集群模型的资料库将公开可用。

Most stars form in dense clusters, the largest of which contain many millions of stars. Since star clusters can exist for many billions of years, they are believed to contain large numbers of compact objects, such as black holes and neutron stars that formed a long time ago as the remnants of dead massive stars. This research program at Northwestern University will use state-of-the-art supercomputer simulations to study the formation and evolution of these compact objects in a variety of star cluster environments. The main focus will be on the production of close binaries containing two black holes, which can eventually merge and produce potentially detectable bursts of gravitational waves. The development of parallel computing techniques and new algorithms will have broad relevance and be of interest to scientists outside of physics and astronomy. The astrophysics research will be student-oriented and senior students will help train new team members, including undergraduate students. Education and public outreach activities are also planned that will take advantage of the facilities at the Adler Planetarium in Chicago, and at Dearborn Observatory on the Northwestern University campus in Evanston. This project will address a number of key questions concerning the formation and dynamical evolution of compact objects (black holes and neutron stars) in dense star clusters. As they experience friction against the background of lighter stars, massive compact objects are expected to rapidly concentrate in the dense inner cores of clusters, where the rates of dynamical interactions are very high. These interactions can both produce binaries and tighten their orbits. In some cases, through successive mergers, perhaps helped by accretion of gas, an intermediate mass black hole could eventually be formed. Many of the objects formed by these processes are potential multi-messenger sources. The project will use a hybrid approach of combining Monte Carlo and N-body codes to optimize computing speed, accuracy and realism and overcome the dynamical range problem of simulating very large star clusters in which most of the interesting dynamics happens in a relatively small, high-density central region. A library of more than an thousand new cluster models will be made publicly available at the conclusion of the project.