AI 中文总结
研究超大质量黑洞双星在星系合并中的扰动驱动动力学，通过高分辨率模拟对比无扰动及不同质量扰动体情况，发现大质量扰动体使轨道偏心率散射增加，因质量比关系，此现象不太可能影响与引力波背景相关的黑洞双星合并。
AI 中文摘要
大质量黑洞双星（MBHBs）在双星形成时的轨道偏心率塑造了脉冲星计时阵列（PTAs）可探测的随机引力波背景（GWB）。先前的N体模拟显示该量存在较大的运行间散射，主要由泊松噪声主导，引发了物理子结构是否增加真正天体物理随机性的问题。我们用IllustrisTNG100 - 1的一次主要合并的高分辨率重新模拟进行测试，使用Griffin N体代码演化。将无扰动控制与两个匹配组进行比较，其中主星系核质量的\(f_{\mathrm{target}} = 0.1\)被重新分配为质量相等的\(10^7 M_\odot\)（\(\mu_{\mathrm{p}}\approx3.2\times10^{-3}\)）和\(10^8 M_\odot\)（\(\mu_{\mathrm{p}}\approx3.2\times10^{-2}\)）的扰动体，每个场景有四个实现。控制组给出\(\sigma_e\approx0.11\)，与该分辨率下的泊松噪声底限一致。\(10^7 M_\odot\)的情况给出\(\sigma_e\approx0.115\)，与控制组无差异，而\(10^8 M_\odot\)的情况给出\(\sigma_e\approx0.26\)，比底限高\(2.4\)倍，尽管仅有四个实现，在统计上不显著。这种额外的散射与轨道能量和角动量中更大的事件对齐残差以及更强的扭矩尖峰一致，与近脉冲扰动体 - MBHB相遇相符。在双星 - 单星散射理论中，转变由扰动体 - MBHB质量比\(\mu_{\mathrm{p}}\)设定：\(10^7 M_\odot\)的情况仍为扩散型，而\(10^8 M_\odot\)的情况接近近脉冲 regime。由于大质量椭圆星系中预期的扰动体群体大多低于此 regime，扰动体驱动的偏心率随机化不太可能影响与GWB相关的MBHB合并。
英文摘要
The orbital eccentricity of massive black hole binaries (MBHBs) at binary formation shapes the stochastic gravitational-wave background (GWB) detectable by pulsar timing arrays (PTAs). Previous $N$-body simulations show large run-to-run scatter in this quantity, dominated by Poisson noise, raising the question of whether physical substructure adds genuine astrophysical stochasticity. We test this with high-resolution re-simulations of a major merger from IllustrisTNG100-1, evolved with the Griffin $N$-body code. A no-perturber control is compared with two matched suites in which $f_{\mathrm{target}}=0.1$ of the primary bulge mass is redistributed into equal-mass perturbers of $10^7,M_\odot$ ($μ_{\mathrm{p}}\approx3.2\times10^{-3}$) and $10^8,M_\odot$ ($μ_{\mathrm{p}}\approx3.2\times10^{-2}$), with four realisations per scenario. The control gives $σ_e\approx0.11$, consistent with the Poisson noise floor at this resolution. The $10^7,M_\odot$ case gives $σ_e\approx0.115$, indistinguishable from the control, whereas the $10^8,M_\odot$ case gives $σ_e\approx0.26$, a factor of $2.4$ above the floor, although statistically marginal given only four realisations. This excess scatter coincides with larger event-aligned residuals in orbital energy and angular momentum and stronger torque spikes, consistent with near-impulsive perturber--MBHB encounters. In binary--single scattering theory, the transition is set by the perturber--MBHB mass ratio $μ_{\mathrm{p}}$: the $10^7,M_\odot$ case remains diffusive, whereas the $10^8,M_\odot$ case approaches the near-impulsive regime. Because the expected perturber population in massive ellipticals lies mostly below this regime, perturber-driven eccentricity randomisation is unlikely to affect GWB-relevant MBHB mergers.
CommentsAccepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS) on 13 July 2026
