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arXiv 2301.02675astro-ph.GAastro-ph.COastro-ph.HE
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利用 z=2 类星体中 CIV 和 HeII 发射线族群特征检验 AGN 外流与吸积模型

Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars

Matthew J. Temple, James H. Matthews, Paul C. Hewett, Amy L. Rankine, Gordon T. Richards, Manda Banerji, Gary J. Ferland, Christian Knigge, Matthew Stepney

备注：
Resubmitted to MNRAS. Minor edits to text; figures updated; licence updated
发表信息：
MNRAS 523, 646 (2023)
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AI总结：

该研究基于 SDSS DR7 的 19 万条 z=2 类星体光谱，分析 CIV 蓝移与 HeII EW 随黑洞质量和爱丁顿比率的变化，并结合 X 射线数据支持低自旋、辐射线驱动外流的吸积模型。

摘要：

利用斯隆数字巡天（Sloan Digital Sky Survey）第十七次数据发布中的 190,000 条光谱，我们研究了 z=2 类星体的紫外发射线性质。具体而言，我们量化了 CIV 1549Å 的线型以及 HeII 1640Å 的等值宽度（EW）如何依赖于由 MgII 2800Å 推断出的黑洞质量和爱丁顿比率。在 L/L_Edd>0.2 以上，CIV 蓝移和 HeII EW 均表现出强烈的质量依赖性。较大的 CIV 蓝移仅在同时具有高质量和高吸积率的区域中被观测到。通过纳入一个含 5,000 个天体的子样本的 X 射线测量结果，我们在 AGN 吸积和外流机制的背景下解释这些观测。HeII 和 2 keV 强度的观测趋势大体上与低自旋黑洞的 AGN 光谱能量分布（SED）理论 QSOSED 模型相符；在该模型中，电离 SED 取决于吸积盘温度和软超量的强度。高自旋模型与观测不符，表明 z=2 的 SDSS 类星体总体上可能具有较低的自旋。我们在 L/L_Edd<0.2 处发现行为发生显著转变：紫外发射性质表现出弱得多的趋势，并且不再与 QSOSED 预测一致，暗示宽线区结构发生变化。总体而言，观测到的发射线趋势通常与辐射线驱动的预测相符，即类星体外流受 SED 控制，而 SED 本身源于吸积流，因此同时取决于超大质量黑洞（SMBH）质量和吸积率。

英文摘要：

Using 190,000 spectra from the seventeenth data release of the Sloan Digital Sky Survey, we investigate the ultraviolet emission line properties in z=2 quasars. Specifically, we quantify how the shape of CIV 1549A and the equivalent width (EW) of HeII 1640A depend on the black hole mass and Eddington ratio inferred from MgII 2800A. Above L/L_Edd>0.2, there is a strong mass dependence in both CIV blueshift and HeII EW. Large CIV blueshifts are observed only in regions with both high mass and high accretion rate. Including X-ray measurements for a subsample of 5,000 objects, we interpret our observations in the context of AGN accretion and outflow mechanisms. The observed trends in HeII and 2 keV strength are broadly consistent with theoretical QSOSED models of AGN spectral energy distributions (SEDs) for low spin black holes, where the ionizing SED depends on the accretion disc temperature and the strength of the soft excess. High spin models are not consistent with observations, suggesting SDSS quasars at z=2 may in general have low spins. We find a dramatic switch in behaviour at L/L_Edd<0.2: the ultraviolet emission properties show much weaker trends, and no longer agree with QSOSED predictions, hinting at changes in the structure of the broad line region. Overall the observed emission line trends are generally consistent with predictions for radiation line driving where quasar outflows are governed by the SED, which itself results from the accretion flow and hence depends on both the SMBH mass and accretion rate.

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