Black hole mergers in active galactic nuclei

这项研究属于RC的粒子天体物理引力波研究领域。LIGO、Virgo和KAGRA最近对引力波的探测打开了一扇了解宇宙的新窗口，为进入传统电磁观测站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，恒星质量的黑洞在宇宙中频繁合并，但这些合并的天体物理起源和宿主环境尚不清楚。该项目的目标是研究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态圆盘的数值模型，并研究了该区域内的一群恒星质量黑洞是如何在圆盘内相互作用的。我们研究了黑洞在近距离相遇时形成双星的可能性，以及这种双星与其他恒星和黑洞的动力学相互作用。流体力学和引力波效应的相互作用可能会导致黑洞在这些环境中有效地合并。我们确定了预期的合并速率和来自这些系统的引力波的特征，并将这些理论模型的预测与观测到的LIGO、Virgo和KAGRA源群体进行了比较。我们还将探索对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。活动星系核中的黑洞合并会产生引力波事件和可能的电磁对应物。如果是这样的话，这些来源使它们有可能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的行星体的演化有关。为该项目开发的数值方法和理论框架也可应用于行星形成问题。

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.