发表机构
The University of Texas at Austin; University of California Santa Barbara; University of Colorado, Boulder; NASA-Goddard Space Flight Center（德克萨斯大学奥斯汀分校; 加州大学圣塔芭芭拉分校; 科罗拉多大学博尔德分校; 美国宇航局戈达德太空飞行中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用JWST光谱数据，在COSMOS-Web最亮亚毫米波星系AzTEC-1中发现z=4.3的候选超大质量黑洞双星，若证实将成为研究低频引力波的优质实验室。
AI 中文摘要
我们展示了COSMOS河外场中红移z=4.34的大质量亚毫米波亮星系AzTEC-1的JWST/NIRSpec PRISM和G395M光栅光谱数据。PRISM光谱显示出强Hα线、显著的巴耳末断裂，且未检测到Hβ线，这表明该星系拥有年龄为1亿至4亿年的恒星族，且尘埃消光程度较高。BPT线比率指示存在活动星系核（AGN）。通过分解窄线和宽线成分，我们恢复出宽的蓝移Hα线，其相对于系统窄线速度的速度偏移为1245 km/s，半高全宽（FWHM）约为2500 km/s。AzTEC-1的平滑形态和恒星年龄暗示过去曾发生过并合诱导的星暴阶段，该阶段可能引入了第二个超大质量黑洞，从而产生了超大质量黑洞双星系统的可能性。在该场景中，我们假设质量较低的黑洞拥有宽线区，围绕着一个处于宁静状态的主黑洞运行。在2D光谱、NIRCam成像、尘埃连续谱的高分辨率ALMA观测，以及CO、[C II]₁₅₇ μm和[N II]₂₀₅ μm运动学数据中，均未发现扩展外流的证据。AzTEC-1的高中心气体质量面密度和动力学不稳定的气体盘表明，候选超大质量黑洞双星轨道外的大质量气体云可能通过动力学力矩作用，使内落过程从约10 Myr延迟至约100 Myr，这一过程已在AzTEC-1这类大质量星系的核区理论上被证实存在。若该超大质量黑洞双星得到证实，AzTEC-1将成为研究驱动低频引力波探测的天体物理过程的绝佳实验室。
英文摘要
We present JWST/NIRSpec PRISM and G395M grating spectroscopy for AzTEC-1, a massive sub-mm bright galaxy at $z=4.34$ in the COSMOS extragalactic field. The PRISM spectrum reveals strong H$α$, a significant Balmer break, and no H$β$ detection, indicating a $100-400$ Myr-old stellar population and high dust attenuation. BPT line ratios indicate the presence of an Active Galactic Nucleus (AGN). Decomposing narrow and broad line components, we recover broad, blueshifted H$α$ with a velocity offset of $1245{\,\rm km\,s^{-1}}$ from the systemic narrow line velocity and with FWHM$\,\sim2500\,{\rm km\,s^{-1}}$. AzTEC-1's smooth morphology and stellar age is suggestive of a past merger-induced starburst period that would have brought in a second supermassive black hole, raising the possibility for a binary supermassive black hole system. In this scenario, we assume that the lower mass black hole hosts a broad line region orbiting a quiescent primary. Evidence for an extended outflow is not found in the 2D spectrum, NIRCam imaging, resolved ALMA observations of dust continuum, or CO, [C II]$_{157\,μ\rm m}$ and [N II]$_{\rm 205\,μm}$ kinematics. AzTEC-1's high central gas mass surface density and dynamically unstable gas disk indicates that massive gas clouds external to the candidate binary SMBH's orbit might have played a role in stalling infall from $\sim10$ Myr to $\sim100$ Myr through dynamical torques, which has been theorized to occur in the nuclei of massive galaxies like AzTEC-1. If the supermassive black hole binary is confirmed, AzTEC-1 would be an excellent laboratory into the astrophysics driving low-frequency gravitational wave detections.
Comments17 pages, 12 figures, accepted to ApJL
