X-RAY INSIGHTS INTO THE NATURE OF PHL 1811 ANALOGS AND WEAK EMISSION-LINE QUASARS: UNIFICATION WITH A GEOMETRICALLY THICK ACCRETION DISK?
X-RAY INSIGHTS INTO THE NATURE OF PHL 1811 ANALOGS AND WEAK EMISSION-LINE QUASARS: UNIFICATION WITH A GEOMETRICALLY THICK ACCRETION DISK?
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DOI：
10.1088/0004-637x/805/2/122
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发表时间：
2015-03
期刊：
影响因子：
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通讯作者：
B. Luo;W. Brandt;P. Hall;Jianfeng Wu;S. Anderson;G. Garmire;R. Gibson;R. Plotkin;G. Richards-G.-Ric
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作者：
B. Luo;W. Brandt;P. Hall;Jianfeng Wu;S. Anderson;G. Garmire;R. Gibson;R. Plotkin;G. Richards-G.-Ric
我们对 33 个弱发射线类星体 (WLQ) 和 18 个类星体进行了 X 射线和多波长研究，这些类星体是极端 WLQ（PHL 1811）的类似物，z ≈ 0.5 ?> –2.9。对 32 个天体进行了新的钱德拉 1.5-9.5 ks 探索性观测，而其他天体则有档案 X 射线观测。与典型类星体相比，这些发光 1 型类星体的很大一部分 X 射线明显较弱，包括 16 个 (48%) 的 WLQ 和 17 个 (94%) 的 PHL 1811 类似物，平均 X 射线弱因子分别为 17 和 39。我们测量了一堆 X 射线弱子样本的相对硬 ( Γ = 1.16 − 0.32 + 0.37 ?> ) 有效幂律光子指数，表明 X 射线吸收，并且对 PHL 1811 类似物 J1521+5202 的光谱分析也表明显着的本征 X 射线吸收。我们比较了 X 射线弱和 X 射线正常群的复合斯隆数字巡天光谱，并找到了几种 X 射线弱的光学-紫外示踪剂，例如 Fe ii 静止框架等效宽度 (REW) 和相对颜色。我们描述了我们之前提出的“保护气体”场景下的定向效应如何可能统一 X 射线弱群体和 X 射线正常群体。我们建议，保护气体自然可以被理解为几何厚度的内部吸积盘，它将宽线区域与电离连续体屏蔽开。如果 WLQ 和 PHL 1811 类似物具有非常高的爱丁顿比率，则内盘可能会显着膨胀（例如，薄盘）。几何厚圆盘对宽发射线区域的屏蔽可能在更普遍地设置类星体 C iv REW 和蓝移的宽分布方面发挥重要作用。
We present an X-ray and multiwavelength study of 33 weak emission-line quasars (WLQs) and 18 quasars that are analogs of the extreme WLQ, PHL 1811, at z ≈ 0.5 ?> –2.9. New Chandra 1.5–9.5 ks exploratory observations were obtained for 32 objects while the others have archival X-ray observations. Significant fractions of these luminous type 1 quasars are distinctly X-ray weak compared to typical quasars, including 16 (48%) of the WLQs and 17 (94%) of the PHL 1811 analogs with average X-ray weakness factors of 17 and 39, respectively. We measure a relatively hard ( Γ = 1.16 − 0.32 + 0.37 ?> ) effective power-law photon index for a stack of the X-ray weak subsample, suggesting X-ray absorption, and spectral analysis of one PHL 1811 analog, J1521+5202, also indicates significant intrinsic X-ray absorption. We compare composite Sloan Digital Sky Survey spectra for the X-ray weak and X-ray normal populations and find several optical–UV tracers of X-ray weakness, e.g., Fe ii rest-frame equivalent width (REW) and relative color. We describe how orientation effects under our previously proposed “shielding-gas” scenario can likely unify the X-ray weak and X-ray normal populations. We suggest that the shielding gas may naturally be understood as a geometrically thick inner accretion disk that shields the broad line region from the ionizing continuum. If WLQs and PHL 1811 analogs have very high Eddington ratios, the inner disk could be significantly puffed up (e.g., a slim disk). Shielding of the broad emission-line region by a geometrically thick disk may have a significant role in setting the broad distributions of C iv REW and blueshift for quasars more generally.