使用新原子数据集改进了AGN的Fe II发射线模型
Improved Fe II emission line models for AGN using new atomic datasets
摘要：
几十年来，了解活动星系核（AGN）的Fe II发射一直是一个巨大的挑战。了解活动星系核光谱的回报将是巨大的，涉及类星体分类方案，如“特征向量1”和追踪宇宙的化学演化。最近，三个大的Fe II原子数据集与辐射和电子碰撞率已成为可用。我们已经将这些纳入光谱合成代码Cloudy，并使用新一代AGN光谱能量分布（SED）检查预测，这表明UV发射可能会因所使用的数据集而异。Smyth等人的数据集更好地再现了在紫外和光学区域观测到的I ZW 1 Seyfert星系的Fe II模板，我们采用了这些数据。我们认为热和微湍流云，并表明，微观湍流的$\approx$ 100公里/秒再现观察到的形状和强度的所谓的Fe II“紫外线凸点”。比较我们的预测与所观察到的Fe II模板，我们得出一个典型的云密度的$10^{11}$厘米$^{-3}$和光子通量的$10^{20}$厘米$^{-2}$的$^{-1}$，并表明，这些很大程度上再现了所观察到的Fe II的紫外和光学发射。我们用最佳拟合模型计算了$I$（Fe II）/ $I$（Mg II）的发射线强度比，得到log（$I$（Fe II）/ $I$（Mg II））$\sim$ 0. 7，表明许多活动星系核具有近似太阳的Fe/Mg丰度比。最后，我们改变爱丁顿比和SED形状作为理解特征向量1相关性的一个步骤。
英文摘要：
Understanding the Fe II emission from Active Galactic Nuclei (AGN) has been a grand challenge for many decades. The rewards from understanding the AGN spectra would be immense, involving both quasar classification schemes such as "Eigenvector 1" and tracing the chemical evolution of the cosmos. Recently, three large Fe II atomic datasets with radiative and electron collisional rates have become available. We have incorporated these into the spectral synthesis code Cloudy and examine predictions using a new generation of AGN Spectral Energy Distribution (SED), which indicates that the UV emission can be quite different depending on the dataset utilized. The Smyth et al dataset better reproduces the observed Fe II template of the I ZW 1 Seyfert galaxy in the UV and optical regions, and we adopt these data. We consider both thermal and microturbulent clouds and show that a microturbulence of $\approx$ 100 km/s reproduces the observed shape and strength of the so-called Fe II "UV bump". Comparing our predictions with the observed Fe II template, we derive a typical cloud density of $10^{11}$ cm$^{-3}$ and photon flux of $10^{20}$ cm$^{-2}$ s$^{-1}$, and show that these largely reproduce the observed Fe II emission in the UV and optical. We calculate the $I$(Fe II)/$I$(Mg II) emission-line intensity ratio using our best-fitting model and obtain log($I$(Fe II)/$I$(Mg II)) $\sim$ 0.7, suggesting many AGNs have a roughly solar Fe/Mg abundance ratio. Finally, we vary the Eddington ratio and SED shape as a step in understanding the Eigenvector 1 correlation.
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