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arXiv 2402.05992astro-ph.GAastro-ph.HE
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[O IV]和[Ne V]弱活动星系核隐藏在晚期并合星系中的康普顿厚物质中

[O IV] and [Ne V]-weak AGNs Hidden by Compton-thick Material in Late Mergers

Satoshi Yamada, Yoshihiro Ueda, Taiki Kawamuro, Claudio Ricci, Yoshiki Toba, Masatoshi Imanishi, Takamitsu Miyaji, Atsushi Tanimoto, Kohei Ichikawa, Martin Herr… 展开作者

Satoshi Yamada, Yoshihiro Ueda, Taiki Kawamuro, Claudio Ricci, Yoshiki Toba, Masatoshi Imanishi, Takamitsu Miyaji, Atsushi Tanimoto, Kohei Ichikawa, Martin Herrera-Endoqui, Shoji Ogawa, Ryosuke Uematsu, Keiichi Wada

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13 pages, 10 figures, and 1 table, accepted for publication in ApJ
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AI总结：

本研究利用[O IV]和[Ne V]弱线指标，在超/亮红外星系中识别出埋藏AGN候选体，发现其康普顿厚物质覆盖分数高，且晚期并合中比例增加，表明辐射压力和并合供给共同调控其环核物质。

摘要：

我们研究了超/亮红外星系（U/LIRGs）中几乎完全被环核物质覆盖的\"埋藏\"活动星系核（AGNs），这些星系表现出来自窄线区的弱电离线。利用[O IV] 25.89微米或[Ne V] 14.32微米谱线与12微米AGN光度之比作为指示器，我们在本地U/LIRGs的30个AGNs中发现了17个埋藏AGN候选体，它们具有[O IV]弱（$L_{\rm [O\\,IV]}$/$L_{\rm 12,AGN} \leq -$3.0）或[Ne V]弱（$L_{\rm [Ne\\,V]}$/$L_{\rm 12,AGN} \leq -$3.4）的特征。对于[O IV]弱的AGNs，我们使用X射线团块环状模型估计其康普顿厚（CT；$N_{\rm H} \geq 10^{24}$ cm$^{-2}$）物质的覆盖分数，平均为$f^{\rm (spec)}_{\rm CT} = 0.55\pm0.19$。该值与U/LIRGs中[O IV]弱AGNs中CT AGNs的比例（$f^{\rm (stat)}_{\rm CT} = 53\pm12$%）一致，且远大于Swift/BAT AGNs中的比例（$23\pm6$%）。[O IV]弱AGNs的比例从早期并合的$27^{+13}_{-10}$%增加到晚期并合的$66^{+10}_{-12}$%。使用[Ne V]谱线也得到了类似的结果。晚期并合中的[O IV]或[Ne V]弱AGNs表现出比Swift/BAT AGNs更大的$N_{\rm H}$和爱丁顿比率（$λ_{\rm Edd}$），最大$N_{\rm H}$在${\log}λ_{\rm Edd} \sim -$1处约为$\gtrsim$10$^{25}$ cm$^{-2}$，接近CT物质的有效爱丁顿极限。这些结果表明：（1）埋藏AGNs中的环核物质受到高$λ_{\rm Edd}$ AGNs对CT遮蔽物的辐射压力调控；（2）它们在U/LIRGs中具有大$f^{\rm (spec)}_{\rm CT}$（$\sim 0.5 \pm 0.1$）的致密物质可能是埋藏AGNs独特结构的成因，其物质数量可能通过并合诱导的宿主星系供给得以维持。

英文摘要：

We study "buried" active galactic nuclei (AGNs) almost fully covered by circumnuclear material in ultra-/luminous infrared galaxies (U/LIRGs), which show weak ionized lines from narrow line regions. Employing an indicator of [O IV] 25.89-um or [Ne V] 14.32-um line to 12-um AGN luminosity ratio, we find 17 buried AGN candidates that are [O IV]-weak ($L_{\rm [O\,IV]}$/$L_{\rm 12,AGN} \leq -$3.0) or [Ne V]-weak ($L_{\rm [Ne\,V]}$/$L_{\rm 12,AGN} \leq -$3.4) among 30 AGNs in local U/LIRGs. For the [O IV]-weak AGNs, we estimate their covering fractions of Compton-thick (CT; $N_{\rm H} \geq 10^{24}$ cm$^{-2}$) material with an X-ray clumpy torus model to be $f^{\rm (spec)}_{\rm CT} = 0.55\pm0.19$ on average. This value is consistent with the fraction of CT AGNs ($f^{\rm (stat)}_{\rm CT} = 53\pm12$%) among the [O IV]-weak AGNs in U/LIRGs and much larger than that in Swift/BAT AGNs ($23\pm6$%). The fraction of [O IV]-weak AGNs increases from $27^{+13}_{-10}$% (early) to $66^{+10}_{-12}$% (late mergers). Similar results are obtained with the [Ne V] line. The [O IV] or [Ne V]-weak AGNs in late mergers show larger $N_{\rm H}$ and Eddington ratios ($λ_{\rm Edd}$) than those of the Swift/BAT AGNs, and the largest $N_{\rm H}$ is $\gtrsim$10$^{25}$ cm$^{-2}$ at ${\log}λ_{\rm Edd} \sim -$1, close to the effective Eddington limit for CT material. These suggest that (1) the circumnuclear material in buried AGNs is regulated by the radiation force from high-$λ_{\rm Edd}$ AGNs on the CT obscurers, and (2) their dense material with large $f^{\rm (spec)}_{\rm CT}$ ($\sim 0.5 \pm 0.1$) in U/LIRGs is a likely cause of a unique structure of buried AGNs, whose amount of material may be maintained through merger-induced supply from their host galaxies.

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