A Triple AGN in a Mid-infrared Selected Late-stage Galaxy Merger
A Triple AGN in a Mid-infrared Selected Late-stage Galaxy Merger
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DOI：
10.3847/1538-4357/ab3a9b
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发表时间：
2019-08
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通讯作者：
R. Pfeifle;S. Satyapal;Christina M. Manzano-King;J. Cann;R. O. Sexton;Barry Rothberg;G. Canalizo;C. Ricci;L. Blecha;S. Ellison;M. Gliozzi;N. Secrest;A. Constantin;J. B. Harvey
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作者：
R. Pfeifle;S. Satyapal;Christina M. Manzano-King;J. Cann;R. O. Sexton;Barry Rothberg;G. Canalizo;C. Ricci;L. Blecha;S. Ellison;M. Gliozzi;N. Secrest;A. Constantin;J. B. Harvey
星系与其中心超大质量黑洞通过分级星系合并的共同演化是Λ CDM宇宙学的一个重要预言。当气体和尘埃在合并过程中被输送到SMBH时，SMBH就像活动星系核（AGN）一样发光。在某些情况下，两个星系的合并可能会遇到第三个星系，导致三重合并，如果所有三个SMBH同时吸积，则会表现为三重AGN。使用高空间分辨率X射线、近红外和光学光谱诊断，我们在这里报告了一个令人信服的案例，即在高级合并SDSS J084905.51 + 111447.2（z = 0.077）中存在相互间距<10 kpc的活动星系核三重态。该系统具有三个核X射线源，每个核中的光谱线比与活动星系核一致，一个核中的高激发近红外日冕线，以及两个核中的宽Pa α检测。硬X射线光谱拟合揭示了高柱密度沿着视线，与后期合并托管大量吸收活动星系核的图片相一致。我们的多波长诊断支持一个三重活动星系核的情况下，我们排除了替代的解释，如星星形成活动，冲击驱动的发射，发射少于三个活动星系核。引力束缚的三重SMBH系统的动力学可以显著地减少二进制SMBH螺旋时间尺度，提供了一种可能的手段来克服“最终秒差距问题”。高级合并中的活动星系核三重态是唯一的观测先驱，绑定三重SMBH系统，从而提供了一个一瞥的吸积活动和环境的活动星系核之前的引力约束三相。
The coevolution of galaxies and the supermassive black holes (SMBHs) at their centers via hierarchical galaxy mergers is a key prediction of ΛCDM cosmology. As gas and dust are funneled to the SMBHs during the merger, the SMBHs light up as active galactic nuclei (AGNs). In some cases, a merger of two galaxies can encounter a third galaxy, leading to a triple merger, which would manifest as a triple AGN if all three SMBHs are simultaneously accreting. Using high spatial resolution X-ray, near-IR, and optical spectroscopic diagnostics, we report here a compelling case of an AGN triplet with mutual separations <10 kpc in the advanced merger SDSS J084905.51+111447.2 at z = 0.077. The system exhibits three nuclear X-ray sources, optical spectroscopic line ratios consistent with AGN in each nucleus, a high excitation near-IR coronal line in one nucleus, and broad Paα detections in two nuclei. Hard X-ray spectral fitting reveals a high column density along the line of sight, consistent with the picture of late-stage mergers hosting heavily absorbed AGNs. Our multiwavelength diagnostics support a triple AGN scenario, and we rule out alternative explanations such as star formation activity, shock-driven emission, and emission from fewer than three AGN. The dynamics of gravitationally bound triple SMBH systems can dramatically reduce binary SMBH inspiral timescales, providing a possible means to surmount the “Final Parsec Problem.” AGN triplets in advanced mergers are the only observational forerunner to bound triple SMBH systems and thus offer a glimpse of the accretion activity and environments of the AGNs prior to the gravitationally bound triple phase.