WoU-MMA: The Evolution, Destruction, and Gravitational-wave Sources of Dense Star Clusters in Cosmological Simulations

两个重黑洞的合并是通过探测引力波（GW）或时空涟漪观察到的第一个事件。双星黑洞是如何形成的是天体物理学中的一个重要问题。一种有希望的情况是，它们是通过密集恒星团（DSC）中恒星的动力学相互作用形成的，其中恒星比星系的其他部分更接近，并且可以通过相互引力经常相互作用。卡内基梅隆大学的一个研究小组将创建第一个自洽的、逐星星的密集星星集群模型，这些模型的初始条件来自宇宙学模拟，或者是对大型恒星群如何从巨大的气体云中形成的模拟。然后，科学家们将使用这些模型来创建一个由星星团和孤立形成的双星组成的BBH合并种群，使用相同的初始条件和恒星物理学。然后，该团队将对未来的GW探测器（如Advanced LIGO和Virgo）进行详细的预测，并建立我们对宇宙学和星系组装的理解与引力波天文学新领域之间的联系。该项目还将用于向更大的社区介绍GW天文学。在研究过程中，首席科学家将与至少两名本科生合作，他们将得到卡内基梅隆大学暑期项目的支持。首席研究员（PI）还将继续访问专门为STEM中代表性不足的学生举办的会议，以展示工作并招募学生。研究人员将检查作为真实环境反馈（FIRE）项目的一部分创建的几个星系模型，该项目最近开发了足够的分辨率来解决巨大分子云的形成和崩溃，这些分子云是DSC的祖先。这些初始条件将使用直接N体和蒙特卡罗方法集成到当今的星星团建模，其中包括所有必要的物理学（恒星演化、引力波等）预测这些DSC的现今外观以及它们在演化过程中产生的二元黑洞（BBH）合并。PI之前已经证明，在DSC中形成的BBH具有独特的特征，这将使它们与其他形成通道区分开来。这些特征，如质量和轨道偏心率，敏感地依赖于初始质量，金属丰度和核心浓度的DSC。通过使用相同的恒星物理学和现实的宇宙学初始条件，这项工作将显示不同的星系性质，如星系类型和恒星形成历史如何影响局部宇宙的引力波景观。该组织计划将他们的数据公开并易于访问，这将在许多领域具有广泛的实用性。 该项目推进了NSF宇宙大创意窗口的目标。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The merger of two heavy black holes was the first event observed through the detection of gravitational waves (GWs), or ripples in spacetime. How these binary black holes (BBHs) form is an important question in astrophysics. One promising scenario is that they form through dynamical interactions of stars in dense stellar clusters (DSCs), in which stars are closer together than in other parts of a galaxy and can frequently interact through their mutual gravity. A research team at Carnegie Mellon University will create the first self-consistent, star-by-star models of dense star clusters with realistic initial conditions taken from cosmological simulations, or simulations of how large groups of stars form from giant clouds of gas. The scientists will then use these models to create a population of the BBH mergers arising in star clusters and also from binaries formed in isolation, using identical initial conditions and stellar physics. The team will then make detailed predictions for future observations from GW detectors such as Advanced LIGO and Virgo, and establish the connection between our understanding of cosmology and galaxy assembly and the new field of gravitational-wave astronomy. This project will also be used to introduce GW astronomy to a larger community. During the course of the research, the lead scientists will work with at least two undergraduate students, who will be supported by summer programs at Carnegie Mellon. The principal investigator (PI) will also continue to visit conferences dedicated to under-represented students in STEM, both to present the work and recruit students. The researchers will examine several galaxy models created as part of the Feedback in Realistic Environments (FIRE) project, which has recently developed sufficient resolution to resolve the formation and collapse of giant molecular clouds, the progenitors of DSCs. These initial conditions will be integrated forward to the present day using direct N-body and Monte Carlo methods for modeling star clusters, which include all the necessary physics (stellar evolution, gravitational waves, etc.) to predict the present-day appearance of these DSCs and the binary black hole (BBH) mergers that they produce during their evolution. The PI has demonstrated before that there are unique features of BBHs formed in DSCs which will allow them to be distinguished from other formation channels. These features, such as the masses and the orbital eccentricities, depend sensitively on the initial masses, metallicities, and core concentrations of the DSCs. By using the same stellar physics and realistic cosmological initial conditions, this work will show how different galaxy properties, such as the galaxy type and star-formation history influence the gravitational-wave landscape of the local universe. The group plans to make their data public and easily accessible, which will have broad utility in many fields. This project advances the goals of the NSF Windows on the Universe Big Idea.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.