利用窄铁K线速度分辨混响映射诊断活动星系核环的运动学$α$
Diagnosing the kinematics of the tori in active galactic nuclei with the velocity-resolved reverberation mapping of the narrow iron K$α$ line
摘要：
活动星系核中尘埃环的性质已经得到了详细的研究，主要集中在几何和组分上，然而，环的运动学仍然不清楚。在6.4 keV的窄铁K $α$线被认为是由X射线从环面反射产生的。因此，它的速度分辨混响映射能够约束环面的运动学。这种努力受到当前CCD探测器光谱分辨率的限制，而下一代X射线卫星上的微量热计应该可以做到。在本文中，我们首先构造的响应函数下的均匀流入，开普勒旋转，和均匀流出的环面。然后根据Athena X射线积分场单元的性能，模拟了窄铁K $α$线的能量依赖光变曲线。最后，计算能量相关的交叉关联函数来揭示运动信号。根据我们的结果，100个观测值，每个5ks曝光是足够的区分上述三个速度场。虽然实际的几何形状和速度场的环面可能比我们假设的更复杂，目前的结果证明了速度分辨混响映射的窄铁K $α$线的可行性。环面动力学与宽线区和宿主星系动力学的结合，对于理解活动星系核的馈送和反馈过程具有指导意义。
英文摘要：
The properties of the dusty tori in active galactic nuclei (AGNs) have been investigated in detail, mainly focusing on the geometry and components; however, the kinematics of the torus is still not clear. The narrow iron K$α$ line at 6.4 keV is thought to be produced by the X-ray reflection from the torus. Thus, the velocity-resolved reverberation mapping of it is able to constrain the kinematics of the torus. Such effort is limited by the spectral resolution of current CCD detectors and should be possible with the microcalorimeter on the next generation X-ray satellite. In this paper, we first construct the response functions of the torus under a uniform inflow, a Keplerian rotation, and a uniform outflow. Then the energy-dependent light curve of the narrow iron K$α$ line is simulated according to the performance of the X-ray Integral Field Unit in Athena. Finally, the energy-dependent cross-correlation function is calculated to reveal the kinematic signal. According to our results, one hundred observations with 5 ks exposure of each are sufficient to distinguish the above three velocity fields. Although the real geometry and velocity field of the torus could be more complex than we assumed, the present result proves the feasibility of the velocity-resolved reverberation mapping of the narrow iron K$α$ line. The combination of the dynamics of the torus with those of the broad line region and the host galaxy is instructive for the understanding of the feeding and feedback process of AGNs.
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