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arXiv 2006.08617astro-ph.GAastro-ph.HE
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类星体中Fe的III发射:稠密湍流介质的证据

Fe III emission in quasars: evidence for a dense turbulent medium

Matthew J. Temple, Gary J. Ferland, Amy L. Rankine, Paul C. Hewett, N. R. Badnell, C. P. Ballance, G. Del Zanna, R. P. Dufresne

摘要:

最近的改进,原子能级数据允许,第一次,准确的预测作出的Fe III线的发光光谱,$L_\text{bol}=10^{46}-10^{48}$ erg/s,活动星系核的发射强度。Fe III发射气体必须主要是光致电离的,与线混响的观测结果一致。我们使用云模型探索了广泛的参数空间,以及26,500个来自斯隆数字巡天的静止帧紫外光谱,以限制线发射气体的物理条件。所观察到的Fe III发射最好由致密的($n_H=10^{14}$ cm $^{-3}$)气体来解释,该气体是微湍流的,导致较小的线光学深度和荧光激发。这种高密度气体似乎存在于大多数发光类星体的中心区域。利用我们所支持的模型,我们提出了理论预测的Fe III UV 34 $λλ$ 1895,1914,1926多重峰的相对强度。这个多重态与Si III] $λ$ 1892和C III] $λ$ 1909发射线混合,当使用这些线来推断类星体中宽线区域的物理信息时,精确减去UV 34是必不可少的。

英文摘要:

Recent improvements to atomic energy-level data allow, for the first time, accurate predictions to be made for the Fe III line emission strengths in the spectra of luminous, $L_\text{bol}=10^{46}-10^{48}$ erg/s, Active Galactic Nuclei. The Fe III emitting gas must be primarily photoionized, consistent with observations of line reverberation. We use CLOUDY models exploring a wide range of parameter space, together with 26,500 rest-frame ultraviolet spectra from the Sloan Digital Sky Survey, to constrain the physical conditions of the line emitting gas. The observed Fe III emission is best accounted for by dense ($n_H=10^{14}$ cm$^{-3}$) gas which is microturbulent, leading to smaller line optical depths and fluorescent excitation. Such high density gas appears to be present in the central regions of the majority of luminous quasars. Using our favoured model, we present theoretical predictions for the relative strengths of the Fe III UV34 $λλ$1895,1914,1926 multiplet. This multiplet is blended with the Si III] $λ$1892 and C III] $λ$1909 emission lines and an accurate subtraction of UV34 is essential when using these lines to infer information about the physics of the broad line region in quasars.

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