[论文解读] Kicking massive black holes off clusters: Intermediate-mass ratio inspirals

Symeon Konstantinidis, Pau Amaro‐Seoane+1 more|arXiv (Cornell University)|Aug 25, 2011

Adaptive optics and wavefront sensing被引用 1

一句话总结

本研究利用包含相对论效应的N体模拟，模拟球状星团中中等质量黑洞（IMBHs）的演化，表明IMBH-恒星级黑洞双星可经历中等质量比旋进（IMRIs），产生LISA类观测站可探测的引力波辐射；在一种情况下，IMBH反冲速度超过星团逃逸速度，为IMBH的存在提供了直接证据，并可作为广义相对论的检验。

ABSTRACT

Contrary to supermassive and stellar-mass black holes (SBHs), the existence of intermediate-mass black holes (IMBHs) with masses ranging between 10^{2-5} Msun has not yet been confirmed. The main problem in the detection is that the innermost stellar kinematics of globular clusters (GCs) or small galaxies, the possible natural loci to IMBHs, are very difficult to resolve. However, if IMBHs reside in the centre of GCs, a possibility is that they interact dynamically with their environment. A binary formed with the IMBH and a compact object of the GC would naturally lead to a prominent source of gravitational radiation, detectable with future observatories. We use N-body simulations to study the evolution of GCs containing an IMBH and calculate the gravitational radiation emitted from dynamically formed IMBH-SBH binaries and the possibility that the IMBH escapes the GC after an IMBH-SBH merger. We run for the first time direct-summation integrations of GCs with an IMBH including the dynamical evolution of the IMBH with the stellar system and relativistic effects, such as energy loss in gravitational waves (GWs) and periapsis shift, and gravitational recoil. We find in one of our models an intermediate mass-ratio inspiral (IMRI), which leads to a merger with a recoiling velocity higher than the escape velocity of the GC. The GWs emitted fall in the range of frequencies that a LISA-like observatory could detect, like the European eLISA or in mission options considered in the recent preliminary mission study conducted in China. The merger has an impact on the global dynamics of the cluster, as an important heating source is removed when the merged system leaves the GC. The detection of one IMRI would constitute a test of GR, as well as an irrefutable proof of the existence of IMBHs.

研究动机与目标

• 利用高保真模拟研究中等质量黑洞（IMBHs）在球状星团（GCs）中的动力学演化。
• 评估在球状星团中通过动力学形成IMBH-恒星级黑洞双星所辐射的引力波（GW）特性。
• 探讨合并后由于引力反冲导致IMBH从星团中被弹射的可能性。
• 确定此类事件是否可被未来如eLISA或中国任务概念类的空间引力波观测站探测到。

提出的方法

• 对包含IMBH的球状星团进行直接求和N体模拟，完整模拟IMBH在恒星系统内的动力学演化。
• 引入相对论效应，如引力波能量损失、近日点进动以及不对称引力波辐射引起的反冲。
• 通过星团环境中的动力学相互作用，模拟IMBH-恒星级黑洞双星的形成与演化。
• 追踪双星系统的轨道演化与并合过程，包括并合后的反冲速度与星团逃逸情况。
• 计算引力波信号特征及其在LISA类观测站相关频段内的可探测性。

实验结果

研究问题

• RQ1 在含有IMBH的球状星团中，能否形成中等质量比旋进（IMRIs）？
• RQ2 此类IMRI事件期间辐射的引力波的振幅与频率谱为何？
• RQ3 合并引起的反冲速度是否足以将IMBH从星团中弹射出去？
• RQ4 此类引力波信号是否可被eLISA等未来空间引力波观测站探测到？
• RQ5 此类事件的探测能否为中等质量黑洞的存在提供无可辩驳的证据？

主要发现

• 一个模拟模型成功产生了清晰的中等质量比旋进（IMRI），导致IMBH与一颗恒星级黑洞并合。
• 并合事件导致引力反冲速度超过球状星团的逃逸速度，使IMBH被成功弹射。
• IMRI过程中辐射的引力波信号落入LISA类观测站（如eLISA和中国任务概念）的可探测频段。
• 并合系统的弹射显著改变了星团的动力学结构，因其移除了内部加热的主要来源。
• 此类事件的探测将为中等质量黑洞的存在提供决定性证据。
• 该观测还将作为强场区域广义相对论的严格检验。