Black hole mergers in active galactic nuclei

这项研究属于RC粒子天体物理学引力波研究领域。最近，LIGO、VIRGO和KAGRA对引力波的探测为研究宇宙打开了一扇新的窗口，为传统电磁天文台完全隐藏的空间和时间区域提供了前所未有的观测机会。引力波探测表明，恒星质量黑洞在宇宙中经常合并，但这些合并的天体物理起源和宿主环境尚不清楚。该项目的目标是检验一种可能解释引力波观测的新可能性。我们研究了观测到的恒星质量黑洞合并起源于超大质量黑洞附近的活动星系核的可能性。我们建立了围绕超大质量黑洞的气体盘的数值模型，并研究了该区域的恒星质量黑洞群如何在盘内相互作用。我们研究了黑洞在近距离接触中形成双星的可能性，以及这种双星与其他恒星和黑洞的动态相互作用。流体动力学和引力波效应的相互作用可能导致这些环境中黑洞的有效合并。我们确定了这些系统的预期合并率和引力波的特征，并将这些理论模型的预测与LIGO、VIRGO和KAGRA观测到的源群进行了比较。我们还将探讨对LISA太空任务的预期影响。这项研究的潜在影响不仅限于引力波科学，而且可能在宇宙学和行星形成方面有应用。活跃星系核中的黑洞合并产生引力波事件，可能伴随电磁对应物。如果是这样的话，这些来源就有可能将它们作为标准蜡烛来探索宇宙的宇宙学模型。此外，气体环境中点质量的动力学也可能与理解原行星盘中星子的演化有关。为这个项目开发的数值方法和理论框架也可以应用于行星形成的背景。

This research falls within the RC's Particle Astrophysics Gravitational Waves research area. The recent detections of gravitational waves by LIGO, VIRGO, and KAGRA opened a new window on the Universe, giving unprecedented observational opportunities into regions of space and time which are completely hidden to traditional electromagnetic observatories. The gravitational wave detections have shown that stellar mass black holes merge frequently in the Universe, but the astrophysical origin and host environments of these mergers is not well understood. The objective of the project is to examine a novel possibility that may explain the gravitational wave observations. We examine the possibility that the observed stellar mass black hole mergers originate in active galactic nuclei in the vicinity of a supermassive black hole. We build numerical models of the gaseous disk surrounding a supermassive black hole and investigate how a population of stellar mass black holes in this region interact within the disk. We investigate the possibility that black holes form binaries during close encounters, and dynamical interaction of such binaries with other stars and black holes. The interplay of hydrodynamical and gravitational wave effects may lead to an efficient merger of black holes in these environments. We determine the expected rate of mergers and the characteristics of the gravitational waves from these systems, and compare the predictions of these theoretical models with the observed source population of LIGO, VIRGO, and KAGRA. We will also explore the expected implications for the LISA space mission.The potential impact of this research is not limited to gravitational wave science but it may have applications in cosmology and planet formation. Black hole mergers in active galactic nuclei generate gravitational wave events with possible electromagnetic counterparts. If so, these sources make it possible to use them as standard candles to probe the cosmological model of the Universe. Furthermore, the dynamics of point masses in gaseous environments may also be relevant to understand the evolution of planetesimals in protoplanetary disks. The numerical methodology and theoretical framework developed for this project may be applied in the context of planet formation as well.