Black hole, neutron star, and white dwarf merger rates in AGN discs
Black hole, neutron star, and white dwarf merger rates in AGN discs
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DOI：
10.1093/mnras/staa2681
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发表时间：
2020-01
影响因子：
4.8
通讯作者：
B. McKernan;K. Ford;R. O’Shaughnessy
中科院分区：
文献类型：
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作者：
B. McKernan;K. Ford;R. O’Shaughnessy
Advanced LIGO & Advanced Virgo 正在探测大量双星起源黑洞 (BH) 合并。加速黑洞合并的一个有希望的通道在于超大质量黑洞周围的活跃星系核（AGN）气体盘。在这里，我们通过蒙特卡罗模拟研究了 AGN 盘模型中致密天体合并的相对数量，包括 BH、中子星 (NS) 和白矮星。我们发现大容量磁盘中所有合并类型的数量增长 $\propto t^{1/3}$，这是由更大规模的合并组件的 Hill 球体驱动的。 AGN 盘中 NS-BH 合并的中值质量比为 $\tilde{q}=0.07\pm 0.06(0.14\pm 0.07)$，质量函数 (MF) $M^{-1(-2)}$。如果观察到的 BH-BH 合并率 (${\cal}{R}_{BH-BH}$) 的一小部分 $f_{AGN}$ 来自 AGN，则我们预计来自 AGN 通道的 NS-BH (NS-NS) 合并率为 ${\cal}{R}_{BH-NS} \sim f_{AGN}[10,300]\rm{Gpc}^{-3} \rm{yr}^{-1}$,(${\cal}{R}_{NS-NS}\leq f_{AGN}400\rm{Gpc}^{-3}\rm{yr}^{-1}$)。考虑到 NS-NS/BH-BH LIGO 搜索量的比率，根据 O3 的初步结果，我们可以排除 AGN 通道对观测到的 NS-NS 合并的主要贡献。该通道中较低质量间隙事件的数量是核 MF 和质量分离效率的重要函数。来自 LIGO 的紧凑天体合并比率可以限制 MF、质量分离和 AGN 盘中嵌入的种群模型。 $z<1$ 处 AGN 盘中 NS-BH 合并的 EM 对应项的预期数量为 $\sim [30,900]{\rm{yr}}^{-1}(f_{AGN}/0.1)$。由于大型 AGN 调查中的嵌入事件而导致的 EM 搜索将补充 LIGO 对 AGN 模型以及必须生活在其中的嵌入人群的限制。
Advanced LIGO \& Advanced Virgo are detecting a large number of binary stellar origin black hole (BH) mergers. A promising channel for accelerated BH merger lies in active galactic nucleus (AGN) disks of gas around super-masssive black holes. Here we investigate the relative number of compact object mergers in AGN disk models, including BH, neutron stars (NS) and white dwarfs, via Monte Carlo simulations. We find the number of all merger types in the bulk disk grows $\propto t^{1/3}$ which is driven by the Hill sphere of the more massive merger component. Median mass ratios of NS-BH mergers in AGN disks are $\tilde{q}=0.07\pm 0.06(0.14\pm 0.07)$ for mass functions (MF) $M^{-1(-2)}$. If a fraction $f_{AGN}$ of the observed rate of BH-BH mergers (${\cal}{R}_{BH-BH}$) come from AGN, we expect a rate of NS-BH (NS-NS) mergers from the AGN channel of ${\cal}{R}_{BH-NS} \sim f_{AGN}[10,300]\rm{Gpc}^{-3} \rm{yr}^{-1}$,(${\cal}{R}_{NS-NS} \leq f_{AGN}400\rm{Gpc}^{-3} \rm{yr}^{-1}$). Allowing for the ratio of NS-NS/BH-BH LIGO search volumes, from preliminary O3 results we can rule out the AGN channel as a dominant contribution to observed NS-NS mergers. The number of lower mass gap events in this channel is a strong function of the nuclear MF and mass segregation efficiency. Compact object merger ratios derived from LIGO can restrict models of MF, mass segregation and populations embedded in AGN disks. The expected number of EM counterparts to NS-BH mergers in AGN disks at $z<1$ is $\sim [30,900]{\rm{yr}}^{-1}(f_{AGN}/0.1)$. EM searches for flaring due to embedded events in large AGN surveys will complement LIGO constraints on AGN models and the embedded populations that must live in them.