发表机构
Maynooth University; Max-Planck-Institut für Astrophysik; University of Hertfordshire; University of Edinburgh; University College Cork; Georgia Institute of Technology; Universität Heidelberg; University of Cambridge（梅努斯大学; 马克斯·普朗克天体物理学研究所; 赫特福德大学; 爱丁堡大学; 科克大学学院; 佐治亚理工学院; 海德堡大学; 剑桥大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
基于SEEDZ模拟，研究早期宇宙黑洞层级并合，发现强AGN反馈抑制并合增长，NoFB为上限，需在LISA等设施前打破多重简并。
AI 中文摘要
我们利用下一代 SEEDZ 宇宙学放大模拟研究早期宇宙中黑洞（BH）的层级并合过程。我们的模拟套件追踪了两个独立区域（\textsc{Rarepeak} 和 \textsc{Normal1}），并采用三种黑洞反馈方案进行演化：无反馈（NoFB）、弱反馈（WeakFB）和标准热各向同性反馈（FidBH）。我们聚焦于 $z \geq 10$ 时的黑洞并合，探讨并合驱动的黑洞增长以及下一代引力波天文台的可探测性。我们发现，与较弱反馈方案相比，更强的活动星系核（AGN）反馈模型显著抑制了层级黑洞并合。在 NoFB 模拟中，黑洞频繁经历重复并合，其中一些在数百 Myr 内经历超过 50 次并合事件，并仅通过并合就获得超过 $10^8\\,\mathrm{M_{\odot}}$ 的质量。相比之下，FidBH 模拟中的黑洞很少经历超过三次并合。因此，NoFB 代表了超出宇宙中预期情况的黑洞并合驱动增长的上限。FidBH 情形中黑洞并合的抑制并非由星系组装、黑洞占据比例或黑洞种子丰度的差异所致，这些因素在各模拟套件中基本相似。相反，反馈破坏了新形成黑洞种子周围致密气体，抑制了其早期吸积驱动的增长，并阻止它们进入失控的层级并合路径。我们的结果表明，早期宇宙的反馈方案通过并合和吸积两种方式强烈影响层级黑洞增长，从而产生不同的高红移并合种群。结合种子选择和其他黑洞子网格方案，这引入了多重简并，需要在 LISA 和其他下一代引力波设施运行之前加以打破。
英文摘要
We investigate the hierarchical assembly of black holes (BHs) in the early Universe using the next-generation SEEDZ cosmological zoom-in simulations. Our suite follows two independent regions (\textsc{Rarepeak} and \textsc{Normal1}) evolved with three BH feedback prescriptions: no feedback (NoFB), weak feedback (WeakFB), and standard thermal isotropic feedback (FidBH). Focusing on BH mergers at $z \geq 10$, we explore merger-driven BH growth and detectability with next-generation gravitational-wave observatories. We find that stronger AGN feedback models dramatically suppress hierarchical BH assembly compared to weaker feedback implementations. In the NoFB simulations, BHs frequently undergo repeated mergers, with some experiencing more than 50 merger events within a few hundred Myr and gaining over $10^8,\mathrm{M_{\odot}}$ through mergers alone. In contrast, BHs in the FidBH simulations rarely undergo more than three mergers. NoFB therefore represents an upper limit to BH merger-driven growth beyond what is expected in the Universe. The suppression of BH mergers in the FidBH case is not driven by differences in galaxy assembly, BH occupation fractions, or BH seed abundances, which remain broadly similar across the simulation suites. Instead, feedback disrupts the dense gas surrounding newly formed BH seeds, suppressing their early accretion-driven growth and preventing them from entering runaway hierarchical merger pathways. Our results demonstrate that early-Universe feedback prescriptions strongly influence hierarchical BH growth through both mergers and accretion, producing distinct high-redshift merger populations. Coupled with seeding choices and other BH subgrid prescriptions, this introduces multiple degeneracies that will need to be broken in advance of LISA and other next-generation GW facilities.
Comments17 pages, 9 figures, submitted for peer review in the Open Journal of Astrophysics
