The Type 1 and Type 2 AGN dichotomy according to their ZTF optical variability
The Type 1 and Type 2 AGN dichotomy according to their ZTF optical variability
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根据 ZTF 光学可变性的 1 型和 2 型 AGN 二分法
DOI：
10.1093/mnras/stac3174
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发表时间：
2022
影响因子：
4.8
通讯作者：
Sánchez-Sáez, P.
中科院分区：
文献类型：
--
作者：
López-Navas, E.;Arévalo, P.;Bernal, S.;Graham, Matthew J.;Hernández-García, L.;Lira, P.;Sánchez-Sáez, P.
光谱分类的 2 型活动星系核 (AGN) 中稀缺的光学变异性研究导致发现了与最简单的统一模型 (UM) 不兼容的异常物体。本文重点探讨不同的可变性特征，这些特征可以区分模糊的 2 型活动星系核和可变的、不模糊的 1 型活动星系核。我们系统地分析了兹威基瞬变设施、斯隆数字巡天数据第 16 版中约 15 000 个 AGN 的 2.5 年长光变曲线，由于缺乏强宽发射线 (BEL)，这些 AGN 通常被认为是 2 型。与 UM 的预期一致，不同群体的变异特征分布不同，光谱分类的弱 1 型显示出比 2 型大一个数量级的方差。我们发现，对于 τg> 16 d 和长期结构函数 SF∞,g> 0.07 mag 的物体，阻尼随机游走模型给出的参数会导致更宽的 H α 等效宽度。通过限制可变性特征，我们发现约 11% 的 2 型光源显示出光学变化的证据。对变化最大的源（约 1% 的 2 型样本）进行详细的光谱分析，发现了错误分类的 1 型源，其 BEL 较弱，并且候选状态不断变化。这项工作是迄今为止对 2 型 AGN 光学变异性进行的最大的系统研究之一，为未来的大型光度测量做好准备。
The scarce optical variability studies in spectrally classified Type 2 active galactic nuclei (AGNs) have led to the discovery of anomalous objects that are incompatible with the simplest unified models (UMs). This paper focuses on the exploration of different variability features that allow to distinguish between obscured, Type 2 AGNs and the variable, unobscured Type 1s. We analyse systematically the Zwicky Transient Facility, 2.5-yr-long light curves of ∼15 000 AGNs from the Sloan Digital Sky Survey Data Release 16, which are generally considered Type 2s due to the absence of strong broad emission lines (BELs). Consistent with the expectations from the UM, the variability features are distributed differently for distinct populations, with spectrally classified weak Type 1s showing one order of magnitude larger variances than the Type 2s. We find that the parameters given by the damped random walk model lead to broader H α equivalent width for objects with τg> 16 d and long-term structure function SF∞,g> 0.07 mag. By limiting the variability features, we find that ∼11 per cent of Type 2 sources show evidence for optical variations. A detailed spectral analysis of the most variable sources (∼1 per cent of the Type 2 sample) leads to the discovery of misclassified Type 1s with weak BELs and changing-state candidates. This work presents one of the largest systematic investigations of Type 2 AGN optical variability to date, in preparation for future large photometric surveys.