论文标题
比较恒星簇中的分层黑洞合并和活跃的银河核
Comparing hierarchical black hole mergers in star clusters and active galactic nuclei
论文作者
论文摘要
星形簇（SC）和主动银河核（AGN）是出现分层黑洞（BH）合并的有前途的位点。我们使用简单的模型比较两个动态形成通道中的层次BH合并。我们发现，AGN中层次合并的主要质量分布高于SCS，$ \ sim $$ 50 \，m _ {\ odot} $和$ \ sim $$ 13 \，m _ {\ odot} $的峰值。有效的自旋（$χ_ {\ rm eff} $）在SCS中的层次合并分布在零左右，如预期的，$ \ sim $$ 50 \％的合并具有$ | c _ |χ_ {\ rm eff} |> 0.2 $。 $χ_ {\ rm eff} $在AGNS中的分布狭窄，并且更喜欢正值，而$χ_ {\ rm eff} \ ge0.3 $的峰值由于AGN磁盘的帮助。 AGN的BH层次结构增长效率至少$ \ sim $ 30 \％的合并为层次结构，远高于SCS的效率。此外，SC和AGN中层次合并的质量比和有效进动参数存在明显差异。我们认为，只要AGN获得一半的层次合并率，Ligo-Virgo检测到的大多数层次合并候选者可能起源于AGN渠道。
Star clusters (SCs) and active galactic nuclei (AGNs) are promising sites for the occurrence of hierarchical black hole (BH) mergers. We use simple models to compare hierarchical BH mergers in two of the dynamical formation channels. We find that the primary mass distribution of hierarchical mergers in AGNs is higher than that in SCs, with the peaks of $\sim$$50\,M_{\odot}$ and $\sim$$13\,M_{\odot}$, respectively. The effective spin ($χ_{\rm eff}$) distribution of hierarchical mergers in SCs is symmetrical around zero as expected and $\sim$$50\%$ of the mergers have $|χ_{\rm eff}|>0.2$. The distribution of $χ_{\rm eff}$ in AGNs is narrow and prefers positive values with the peak of $χ_{\rm eff}\ge0.3$ due to the assistance of AGN disks. BH hierarchical growth efficiency in AGNs, with at least $\sim$$30\%$ of mergers being hierarchies, is much higher than the efficiency in SCs. Furthermore, there are obvious differences in the mass ratios and effective precession parameters of hierarchical mergers in SCs and AGNs. We argue that the majority of the hierarchical merger candidates detected by LIGO-Virgo may originate from the AGN channel as long as AGNs get half of the hierarchical merger rate.
