Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem
Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem
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DOI：
10.1093/mnras/stx2524
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发表时间：
2017-09
影响因子：
4.8
通讯作者：
Taeho Ryu;R. Perna;Z. Haiman;J. Ostriker;N. Stone
中科院分区：
文献类型：
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作者：
Taeho Ryu;R. Perna;Z. Haiman;J. Ostriker;N. Stone
利用少体模拟方法，研究了星系($M_{\star}=10^{10}-10^{12}{\rM}_{\odot}$在$z=0$)中的超大质量黑洞(SMBH)在$0<；z<；4的演化.根据千禧年模拟中的星系合并树，我们用两种极端的双星衰变场景对黑洞合并进行建模，以用于“硬双星”阶段：满的或空的损失锥。这两个模型应该支持真实的演化，并允许我们分别探讨动力摩擦和多体BH相互作用在BH合并中的作用。利用计算的合并率，我们推断出随机引力波背景(GWB)。我们的动力学方法是首次尝试研究不同质量比($10^{-4}<；q_{\star}<；1$)合并的宿主星系中多个SMBH的动力学演化。我们的主要结果表明，SMBH二进制文件能够在这两种情况下合并。在空损锥的情况下，我们发现BHS通过多体相互作用合并，避免了“最后的帕秒”问题，并以相当大的轨道偏心率进入PTA带。我们的全损失锥处理，虽然更近似，表明当GWS成为主导时，偏心率变得更高，导致快速合并(双寿命$\rm~Gyr}$)。尽管在空损失锥情况下合并率较低，但由于其较高的质量比和较低的红移，全/空损失锥模型中的GWB具有可比性(分别为0.70美元/10^-15美元和0.53美元/10^-15美元，频率为1美元/年)。最后，我们计算了高偏心率对GWB谱的影响。
Using few-body simulations, we investigate the evolution of supermassive black holes (SMBHs) in galaxies ($M_{\star}=10^{10}-10^{12}{\rm M}_{\odot}$ at $z=0$) at $0<z<4$. Following galaxy merger trees from the Millennium simulation, we model BH mergers with two extreme binary decay scenarios for the `hard binary' stage: a full or an empty loss cone. These two models should bracket the true evolution, and allow us to separately explore the role of dynamical friction and that of multi-body BH interactions on BH mergers. Using the computed merger rates, we infer the stochastic gravitational wave background (GWB). Our dynamical approach is a first attempt to study the dynamical evolution of multiple SMBHs in the host galaxies undergoing mergers with various mass ratios ($10^{-4} < q_{\star} < 1$). Our main result demonstrates that SMBH binaries are able to merge in both scenarios. In the empty loss cone case, we find that BHs merge via multi-body interactions, avoiding the `final parsec' problem, and entering the PTA band with substantial orbital eccentricity. Our full loss cone treatment, albeit more approximate, suggests that the eccentricity becomes even higher when GWs become dominant, leading to rapid coalescences (binary lifetime $\lesssim1 {\rm ~Gyr}$). Despite the lower merger rates in the empty loss cone case, due to their higher mass ratios and lower redshifts, the GWB in the full/empty loss cone models are comparable ($0.70\times10^{-15}$ and $0.53\times10^{-15}$ at a frequency of $1~{\rm yr}^{-1}$, respectively). Finally, we compute the effects of high eccentricities on the GWB spectrum.