Coronal-Line Forest Active Galactic Nuclei (CLiF AGN) are characterized by strong high-ionization lines, which contrast to what is found in most AGNs. Here, we carry out a multiwavelength analysis aimed at understanding the physical processes in the Narrow Line Region (NLR) of these objects and unveiling if they are indeed a special class of AGN. By comparing coronal emission-line ratios we conclude that there are no differences between CLiF and non-CLiF AGNs. We derive physical conditions of the narrow line region (NLR) gas and found electron densities in the range $3.6\times$10$^{2}$ - $1.7\times$10$^{4}$ cm$^{-3}$ and temperatures of $3.7\times$10$^{3}$ - $6.3\times$10$^{4}$ K, suggesting that the ionization mechanism is associated primarily with photoionization by the AGN. We suggest a NLR dominated by matter-bounded clouds to explain the high-ionization line spectrum observed. The mass of the central black hole, derived from the stellar velocity dispersion show that most of the objects have values in the interval 10$^{7-8}$~M$\odot$. Our results imply that CLiF AGN is not a separate category of AGNs. In all optical/near-infrared emission-line properties analyzed, they represent an extension to the low/high ends of the distribution within the AGN class.

中文翻译：

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日冕森林活动星系核——I. 发射线区域的物理特性

日冕线森林活动星系核 (CLiF AGN) 的特点是强烈的高电离线，这与大多数 AGN 中发现的线形成鲜明对比。在这里，我们进行了多波长分析，旨在了解这些物体在窄线区域 (NLR) 中的物理过程，并揭示它们是否确实是一类特殊的 AGN。通过比较日冕发射线比率，我们得出结论，CLiF 和非 CLiF AGN 之间没有差异。我们推导出窄线区 (NLR) 气体的物理条件，发现电子密度在 $3.6\times$10$^{2}$ - $1.7\times$10$^{4}$ cm$^{-3}$ 和$3.7\times$10$^{3}$ - $6.3\times$10$^{4}$ K，表明电离机制主要与 AGN 的光电离有关。我们建议以物质有界云为主的 NLR 来解释观察到的高电离线谱。来自恒星速度色散的中心黑洞质量表明，大多数物体的值在 10$^{7-8}$~M$\odot$ 区间内。我们的结果意味着 CLiF AGN 不是一个单独的 AGN 类别。在分析的所有光学/近红外发射线特性中，它们代表了 AGN 类内分布的低端/高端的扩展。