标题： 活动星系核扩展区域中大FeK$α$线宽的普遍性和强度 显示英文标题

标题： The Ubiquity and Magnitude of Large FeK$α$ Equivalent Widths in AGN Extended Regions

摘要： Narrow Fe K$\alpha$ fluorescent emission lines arising at $\sim$kpc-scale separations from the nucleus have only been detected in a few AGN. The detections require that the extended line emission be spatially resolved and sufficiently bright. Compared to narrow Fe K$\alpha$ lines arising closer to the nucleus, they have much lower fluxes but show substantially larger equivalent widths, EW$_{\rm Fe K\alpha}$. We show that, in the optically-thin limit, a purely analytical argument naturally predicts large, EW$_{\rm FeK\alpha}\sim$1 keV, values for such lines, regardless of the details of equivalent hydrogen column density, $N_H$, or reprocessor geometry. 蒙特卡洛模拟证实了这一结果，并表明简单的解析等效宽度（EW）$_{\rm FeK\alpha}$公式在更高的$N_H$接近康普顿厚 regimes 时仍然成立。 我们将我们的结果与文献中的$Chandra$观测值进行了比较，并讨论了我们的结果与本地活动星系核（AGN）中报告的大等效宽度（EW）$_{\rm FeK\alpha}$值一致，这些值是在延伸的，直到$\sim$千秒差距尺度的区域中检测到的线。 我们提出，在活动星系核的千秒差距尺度区域中出现大的 EW$_{\rm FeK\alpha}$应该是普遍存在的，因为它们不依赖于中心 X 射线源的绝对亮度，而只是相对于散射连续谱测量的。 我们预测值的量级为$\sim$1 keV 或更大，即使覆盖因子$\ll$为 1，且对于任意小的柱密度也是如此。我们提出，现在用阿塔卡马大型毫米/亚毫米阵列 (ALMA) 常规检测到的大尺度分子物质可能充当扩展的 X 射线散射重新处理器，从而产生$\sim$千秒差距尺度的 Fe K$\alpha$发射。 显示英文摘要

摘要： Narrow Fe K$\alpha$ fluorescent emission lines arising at $\sim$kpc-scale separations from the nucleus have only been detected in a few AGN. The detections require that the extended line emission be spatially resolved and sufficiently bright. Compared to narrow Fe K$\alpha$ lines arising closer to the nucleus, they have much lower fluxes but show substantially larger equivalent widths, EW$_{\rm Fe K\alpha}$. We show that, in the optically-thin limit, a purely analytical argument naturally predicts large, EW$_{\rm FeK\alpha}\sim$1 keV, values for such lines, regardless of the details of equivalent hydrogen column density, $N_H$, or reprocessor geometry. Monte Carlo simulations corroborate this result and show that the simple analytic EW$_{\rm FeK\alpha}$ prescription holds up to higher $N_H$ approaching the Compton-thick regime. We compare to $Chandra$ observations from the literature and discuss that our results are consistent with the large EW$_{\rm FeK\alpha}$ values reported for local AGN, for which the line is detected in extended, up to $\sim$kpc-scale, regions. We argue that large EW$_{\rm FeK\alpha}$ from kpc-scale regions in AGN should be ubiquitous, because they do not depend on the absolute luminosity of the central X-ray source, and are measured only against the scattered continuum. We predict values to be of the order of $\sim$1 keV or larger, even for covering factors $\ll$1, and for arbitrarily small column densities. We propose that the large-scale molecular material that is now routinely being detected with the Atacama Large Millimeter/Submillimeter Array (ALMA) may act as an extended X-ray scattering reprocessor giving rise to $\sim$kpc-scale Fe K$\alpha$ emission.