WISSH类星体项目。XII. 宇宙正午最亮类星体的X射线视图
The WISSH quasar project. XII. X-ray view of the most luminous quasi-stellar objects at Cosmic Noon
AI总结：
本研究通过分析WISSH超亮类星体样本的X射线谱，发现其X射线光度离散大且与爱丁顿比率无关，并确认了与CIV外流的相关性，提示在高光度下使用其他波段作为X射线替代指标需谨慎。
摘要：
为了提高我们对宇宙正午时期明亮类星体核发射的认识，我们研究了WISE/SDSS选出的超亮（WISSH）类星体样本的X射线发射：85个宽发射线活动星系核，其$L_{bol}>几\times 10^{47}\\,erg\\,s^{-1}$，红移$z\sim 2-4$。我们的目标是描述它们的X射线谱特征，并探索X射线光度与其他波段之间的关系，将强功率类星体与一般活动星系核群体进行比较。我们对约一半的样本进行了谱分析；16个源通过硬度比进行分析；对于其他源，我们估计了其内禀光度$L_{2-10\\,keV}$。只有8个源未被探测到。我们报告了$L_{2-10\\,keV}$的大离散度，尽管$L_{bol}$、$L_{2500\\,\AA}$和$\lambda L_{6\\,\mu m}$的分布较窄（约三分之一的源被分类为X射线弱）。这表明超亮活动星系核与较低功率活动星系核在X射线日冕和吸积流物理上存在差异。X射线光子指数分布与较低红移、较低$L_{bol}$的活动星系核一致，并且不依赖于爱丁顿比率（$\lambda_{Edd}$）或X射线弱性。大多数具有内禀吸收估计的WISSH类星体显示出很少或没有遮蔽（$N_H \le 5\times 10^{22}\\,cm^{-2}$）。在被遮蔽的源中，我们在$Log(N_H)-Log(\lambda_{Edd})$平面的“禁戒区域”内发现了没有宽吸收线的蓝色类星体，该区域通常由尘埃红化的类星体占据，并与强烈的反馈相关。我们确认了$L_{2-10\\,keV}$与CIV线蓝移（核电离外流的示踪物）之间的相关性。多波段数据和完整的X射线覆盖使得在最高光度状态下研究盘-日冕相互作用成为可能。热改正和X射线到光学指数的宽分布表明，在将$L_{bol}$、$L_{2500\\,\AA}$或$L_{6\\,\mu m}$用作单个明亮类星体的直接X射线替代指标时需谨慎。
英文摘要：
To improve our knowledge of nuclear emission in luminous QSOs at Cosmic Noon, we studied the X-ray emission of the WISE/SDSS-selected hyper-luminous (WISSH) QSO sample: 85 broad-line AGN with $L_{bol}>few\times 10^{47}\,erg\,s^{-1}$ at $z\sim 2-4$. Our aim is to characterise their X-ray spectra and explore relations between X-ray luminosity and other bands, comparing powerful QSOs with the general AGN population. We performed spectral analysis for about half of the sample; 16 sources were analysed via their hardness ratio; for the others we estimated their intrinsic luminosity $L_{2-10\,keV}$. Only 8 sources are undetected. We report a large dispersion in $L_{2-10\,keV}$ despite the narrow distribution of $L_{bol}$, $L_{2500\,Å}$ and $λL_{6\,μm}$ (about one-third of the sources classified as X-ray weak). This suggests differences in X-ray corona and accretion flow physics between hyper-luminous and less powerful AGN. X-ray photon index distribution is consistent with that of lower-$z$, lower-$L_{bol}$ AGN, and does not depend on the Eddington ratio ($λ_{Edd}$) or X-ray weakness. Most WISSH QSOs with intrinsic absorption estimates show little to no obscuration ($N_H \le 5\times 10^{22}\,cm^{-2}$). Among the obscured sources we find blue QSOs without broad absorption lines within the "forbidden region" of the $Log(N_H)-Log(λ_{Edd})$ plane, typically occupied by dust-reddened QSOs and associated with intense feedback. We confirm a correlation between $L_{2-10\,keV}$ and CIV line blueshift, a tracer of nuclear ionized outflows. Multi-wavelength data and complete X-ray coverage enabled the investigation of the disk-corona interplay at the highest luminosity regimes. The broad distribution of bolometric correction and X-ray - to - optical index suggest caution when using $L_{bol}$, $L_{2500\,Å}$ or $L_{6\,μm}$ as direct X-ray proxy for individual luminous QSOs.
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