发表机构
Center for Computational Astrophysics, Flatiron Institute; Department of Astrophysical Sciences, Princeton University（计算天体物理学中心，平顿研究所; 普林斯顿大学天体物理科学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过三维多频辐射磁流体动力学模拟发现AGN吸积盘结构可决定其变异性，厚盘的光变特征契合近期观测，无需宽线区即可解释吸积盘大小问题，还可利用紫外-光学光变曲线预测盘厚度。
AI 中文摘要
变异性是探测活动星系核（AGN）吸积盘的关键手段，但吸积盘的结构与内部物理对变异性的影响尚未被充分理解。我们对AGN吸积盘的1300-5940埃发射区开展了三维多频辐射磁流体动力学模拟，该湍流盘模拟偶然出现了盘面上方与下方不同的盘厚度。从盘薄顶部发射的光变曲线与传统变异性模型大致一致，其中日冕发射的X射线是紫外-光学光变曲线变异性的主要驱动因素；相反，从盘厚底部发射的紫外-光学光变曲线与X射线光变曲线无强相关性，且盘连续谱反响映射滞后量比光行时间长3-5倍。这些特征与传统变异性模型不符，但与诸多近期观测结果吻合。我们的模拟使我们能通过AGN吸积盘的新模型解释这些近期观测：较厚的盘会导致更强的X射线吸收、更大盘半径处更少的X射线再处理，以及AGN吸积盘波动驱动的本征变异性信号更强。在模拟中，我们可测量这些波动的流入时标，表现为不同盘半径发射的光变曲线间的长滞后。理解盘结构如何影响AGN变异性与反响映射，可让我们利用紫外-光学AGN光变曲线预测AGN吸积盘的厚度。
英文摘要
Variability is a crucial probe of active galactic nuclei (AGN) disks, but the impact of the structure and internal physics of the disk on this variability is poorly understood. We perform 3D multi-frequency radiation magnetohydrodynamic simulations of the $1300-5940~\rmÅ$ emitting region of an AGN disk. This turbulent disk simulation happens to stochastically have different disk thickness above and below the midplane. Light curves emitted from the thin top of the disk are broadly consistent with traditional variability models, where the X-ray irradiation emitted from the corona is the main driver of variability in UV-optical light curves. Conversely, the UV-optical light curves emitted from the thicker bottom of the disk are not strongly correlated with the X-ray light curve and have disk continuum reverberation mapping lags that are $3-5\times$ longer than the light travel time. While these features are inconsistent with traditional variability models, they are in good agreement with numerous recent observations. Our simulations allow us to interpret these recent observations with a new model for AGN disks, where the thicker disk leads to greater X-ray absorption, less X-ray reprocessing at larger disk radii, and a stronger signal from intrinsic variability driven by fluctuations in the AGN disk. In our simulations, we can measure the inflow timescale of these fluctuations as a long lag between light curves emitted from different disk radii. Understanding how disk structure impacts AGN variability and reverberation mapping can allow us to predict the thickness of AGN disks using UV-optical AGN light curves.
Commentssubmitted to ApJ
