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arXiv 2302.08338astro-ph.GA
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活动星系核中超大质量黑洞密近双星的微分干涉特征:II。合并的宽线区域

Differential Interferometric Signatures of Close Binaries of Supermassive Black Holes in Active Galactic Nuclei: II. Merged Broad Line Regions

Yu-Yang Songsheng, Jian-Min Wang

摘要:

不同阶段的超大质量黑洞对是在星系形成和演化的等级框架下星系合并的自然结果。然而,在观测中具有亚秒差距的SMBH的近距离双星(CB-SMBH)的识别仍然是难以捉摸的。最近,通过光谱天体测量(SA),超大望远镜干涉仪上的重力/重力+实现了前所未有的空间分辨率,为解决CB-SMBH提供了新的机会。具有两个独立宽线区(BLR)的CB-SMBH的微分相位曲线被发现具有与单个BLR \citep{songsheng2019}不同的特征结构。一旦CB-SMBH演化到BLR合并形成环双星BLR的阶段,它将有望在不久的将来被脉冲星定时阵列(PTA)作为纳赫兹引力波源解决。在这项工作中,我们使用一个参数化模型的circumbinary BLR计算线轮廓和微分相位曲线SA观测。我们发现,这两个配置文件和相位曲线表现出不对称性所造成的多普勒增强效应的吸积盘周围的个别黑洞,这取决于轨道参数的二进制和几何形状的BLR。我们还使用该模型生成模拟SA数据,然后通过拟合模拟数据来恢复轨道参数。参数间的退化对参数的不确定性有很大影响,但可以通过多历元SA观测和混响映射的联合分析来缓解。

英文摘要:

Pairs of supermassive black holes (SMBHs) at different stages are natural results of galaxy mergers in the hierarchical framework of galaxy formation and evolution. However, identifications of close binaries of SMBHs (CB-SMBHs) with sub-parsec separations in observations are still elusive. Recently, unprecedented spatial resolutions achieved by GRAVITY/GRAVITY+ onboard The Very Large Telescope Interferometer through spectroastrometry (SA) provide new opportunities to resolve CB-SMBHs. Differential phase curves of CB-SMBHs with two independent broad-line regions (BLRs) are found to have distinguished characteristic structures from a single BLR \citep{songsheng2019}. Once the CB-SMBH evolves to the stage where BLRs merge to form a circumbinary BLR, it will hopefully be resolved by the pulsar timing array (PTA) in the near future as sources of nano-hertz gravitational waves. In this work, we use a parameterized model for circumbinary BLRs to calculate line profiles and differential phase curves for SA observations. We show that both profiles and phase curves exhibit asymmetries caused by the Doppler boosting effect of accretion disks around individual black holes, depending on the orbital parameters of the binary and geometries of the BLR. We also generate mock SA data using the model and then recover orbital parameters by fitting the mock data. Degeneracies between parameters contribute greatly to uncertainties of parameters but can be eased through joint analysis of multiple-epoch SA observations and reverberation mappings.

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