AI 中文总结
研究低质量和中等质量星系中超大质量黑洞合并时间尺度，利用KETJU代码进行模拟，通过改变超新星外流速度改变恒星反馈强度，发现其对合并延迟影响大，还表明可通过外推核恒星属性恢复合并时间尺度，为黑洞合并建模提供途径。
AI 中文摘要
低质量和中等质量星系中合并的超大质量黑洞是未来如LISA等毫赫兹引力波天文台的重要源。预测星系合并与超大质量黑洞合并之间的延迟对模拟可观测的超大质量黑洞合并群体至关重要。利用KETJU代码，进行了16次等质量星系合并模拟，研究恒星质量低于\(M_{\star}\lesssim10^{10}\,{\rm M}_{\odot}\)的星系中超大质量黑洞双星演化。通过改变超新星外流速度约4倍来系统改变恒星反馈强度，同时产生与观测缩放关系一致的星系。发现硬化后超大质量黑洞合并时间尺度跨越约30 - 500 Myr，更强的恒星反馈通过影响合并残余物的中心恒星密度产生更长的合并延迟。合并时间尺度变化超过一个数量级，表明仅恒星反馈的不确定性就能转化为超大质量黑洞合并延迟的巨大不确定性。在硬化开始时，双星演化与基于二元影响球附近局部恒星密度和速度弥散的恒星动力学硬化模型一致。以KETJU为基准表明，当从高达约100 \(R_{\rm infl}\)的尺度外推这些核恒星属性时，可以以有用的精度恢复合并时间尺度。这些结果为宇宙学模拟中的超大质量黑洞合并建模提供了一条有前景的途径。
英文摘要
Merging supermassive black holes (SMBHs) in low- and intermediate-mass galaxies are important sources for future millihertz gravitational-wave observatories such as LISA. Predicting the delay between galaxy coalescence and SMBH merger is therefore critical for modelling the observable SMBH merger population. Using the KETJU code, we perform 16 equal-mass galaxy merger simulations as part of the Resolving supermAssive Black hole Binaries In galacTic hydrodynamical Simulations (RABBITS) series to investigate SMBH binary evolution in galaxies with stellar masses below $M_{\star}\lesssim10^{10}\,{\rm M}_{\odot}$. We systematically vary the strength of stellar feedback by altering the supernova outflow velocity by a factor of $\sim4$, while still producing galaxies consistent with observed scaling relations. We find post-hardening SMBH merger time-scales spanning $\sim30$-$500\,{\rm Myr}$, with stronger stellar feedback producing systematically longer merger delays through its impact on the central stellar density of the merger remnants. Across our suite, merging time-scales vary by more than an order of magnitude, demonstrating that uncertainties in stellar feedback alone can translate into large uncertainties in SMBH merger delays. At the onset of hardening, the binary evolution remains consistent with stellar-dynamical hardening models based on the local stellar density and velocity dispersion near the binary sphere of influence. Using KETJU as a benchmark, we show that merging time-scales can be recovered with useful accuracy when these nuclear stellar properties are extrapolated from scales up to $\sim 100\,R_{\rm infl}$. These results provide a promising route for modelling SMBH mergers in cosmological simulations.
CommentsSubmitted to MNRAS. 25 pages, 14 figures
