A population of Optically Quiescent Quasars from WISE and SDSS
A population of Optically Quiescent Quasars from WISE and SDSS
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来自 WISE 和 SDSS 的光学静止类星体群
DOI：
10.1093/mnras/stad3964
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发表时间：
2024
影响因子：
4.8
通讯作者：
Greenwell C
中科院分区：
文献类型：
--
作者：
Greenwell C
在很大一部分人口中，活动星系核(AGN)的生长是在某种形式的遮蔽下发生的。限制这一群体的困难导致了宇宙X射线背景和星系演化模型的高度不确定性。利用SDSS-WISE交叉匹配，我们的目标是红外发光活动星系核(W1−W2 >； 0.8，单色静止帧光度高于λLλ(12μm) ≈ 3 × 1044erg S−1)，但具有被动星系样光谱(光学静止类星体；OQs)。我们发现有47个天体没有显示出明显的活动星系核(λ)5007发射，这是一条典型的强活动星系核光学发射线。作为一个比较样本，我们检查了SDSS选择的2型类星体(QSO2)，根据定义，它显示了一条重要的[Oiii]λ5007线。我们发现，与QSO2相比，OQQ的比例为1：16，这表明OQQ的占空比可能比QSO2的短得多(尽管选择偏差并未完全量化)。我们把观测到的属性与其他星系类型相比较，并检验它们与关于其内在性质的理论的一致性：主要是(A)对周围遮蔽物质的高覆盖系数，阻止了对高电离发射线的探测--‘结茧的活动星系核’；或(B)在窄线区域(NLR)的KPC尺度上没有电离气体，可能是由于‘开启’或‘年轻’的活动星系核。OQQ显然不符合合并驱动的活动星系核和宿主星系演化的标准范式，这意味着我们可能遗漏了活动星系核演化的一部分。
The growth of active galactic nuclei (AGNs) occurs under some form of obscuration in a large fraction of the population. The difficulty in constraining this population leads to high uncertainties in cosmic X-ray background and galaxy evolution models. Using an SDSS–WISEcross-match, we target infrared luminous AGN (W1 −W2 > 0.8, and monochromatic rest-frame luminosity above λLλ(12μm) ≈ 3 × 1044erg s−1), but with passive galaxy-like optical spectra (Optically Quiescent Quasars; OQQs). We find 47 objects that show no significant [Oiii]λ5007 emission, a typically strong AGN optical emission line. As a comparison sample, we examine SDSS-selected Type 2 quasars (QSO2s), which show a significant [Oiii]λ5007 line by definition. We find a 1:16 ratio of OQQs compared to QSO2s, suggesting that the OQQ duty cycle is likely much shorter than that of QSO2s (though selection biases are not fully quantified). We consider observed properties in comparison with other galaxy types, and examine them for consistency with theories on their intrinsic nature: chiefly (a) a high covering factor for surrounding obscuring matter, preventing the detection of high-ionisation emission lines – ‘cocooned AGN’; or (b) ionized gas being absent on the kpc scales of the Narrow Line Region (NLR), perhaps due to a ‘switching on’ or ‘young’ AGN. OQQs do not obviously fit the standard paradigm for merger-driven AGN and host galaxy evolution, implying we may be missing part of the flow of AGN evolution.