AI 中文总结
该研究通过GIZMO流体动力学模拟发现，AGN反馈会抑制大质量黑洞双星的自旋对齐，使其停滞并影响吸积，这对LISA引力波观测的解释具有重要意义。
AI 中文摘要
大质量黑洞（MBH）双星与环绕双星盘（CBD）的相互作用会影响并合双星的自旋取向，这是未来LISA任务的关键可观测物理量。尽管已知气体吸积会通过巴丁-彼得森（Bardeen-Petterson）效应使黑洞自旋与轨道角动量对齐，但活动星系核（AGN）反馈对这一过程的影响在很大程度上仍未被探索。我们使用GIZMO代码开展流体动力学模拟，该代码带有可自洽演化黑洞质量、自旋及各向异性AGN反馈的亚网格模型，模拟对象为嵌入环绕双星盘的等质量大质量黑洞双星。我们探究了不同黑洞自旋的大小与取向，以确定对盘结构和双星演化产生最强反馈效应的构型。AGN风会显著改变环绕双星盘与迷你盘的结构，扩大中心空腔，且在所有含反馈的模拟中，经过20至25个双星轨道后会摧毁迷你盘。反馈驱动的空腔挖掘会抑制驱动轨道演化的引力矩，导致双星停滞。AGN反馈会极大影响大质量黑洞吸积，使爱丁顿比值降低1至2个数量级，最终完全抑制吸积。这强烈抑制了巴丁-彼得森自旋对齐，使其延迟至远超过无反馈情形的时间尺度。将一个模拟扩展至70个双星轨道后，发现了反馈调控的活跃与静默交替的工作周期，双星大部分时间处于低密度的静默状态，进一步抑制了自旋对齐。这些结果表明，AGN反馈是大质量黑洞双星并合前保留自旋不对齐的一个重要且此前被忽视的渠道，对解释LISA引力波观测具有直接意义。
英文摘要
The interaction between massive black hole (MBH) binaries and circumbinary discs (CBDs) affects the spin orientations of merging binaries - a key observable for the future LISA mission. While gas accretion is known to align BH spins with the orbital angular momentum via the Bardeen-Petterson effect, the impact of AGN feedback on this process has remained largely unexplored. We present hydrodynamical simulations of an equal-mass MBH binary embedded in a CBD, using the GIZMO code with a subgrid model that self-consistently evolves BH mass, spin, and anisotropic AGN feedback. We explore different BH spin magnitudes and orientations to identify the configurations producing the strongest feedback effect on the disc structure and binary evolution. AGN winds substantially modify the CBD and minidisc structure, enlarging the central cavity and, after 20-25 binary orbits, destroying the minidiscs in all feedback simulations. Feedback-driven cavity excavation suppresses the gravitational torques driving orbital evolution, causing the binary to stall. AGN feedback dramatically affects MBH accretion, reducing the Eddington ratio by one to two orders of magnitude before ultimately suppressing it entirely. This strongly inhibits Bardeen-Petterson spin alignment, delaying it well beyond the feedback-free timescale. Extending one simulation to 70 binary orbits reveals a feedback-regulated duty cycle of alternating active and quiescent phases, with the binary spending most of its time in low-density, quiescent conditions that further suppress alignment. These results indicate that AGN feedback is an important, previously overlooked channel for preserving spin misalignment in MBH binaries prior to coalescence, with direct implications for interpreting LISA gravitational-wave observations.
