发表机构
INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna; INAF - Osservatorio Astronomico di Roma; University of Bristol; INAF — Osservatorio Astrofisico di Arcetri; Università di Pisa; INAF – Osservatorio Astronomico di Trieste; IFPU - Institute for Fundamental Physics of the Universe（意大利国家天体物理研究所-博洛尼亚天体物理与空间科学天文台; 意大利国家天体物理研究所-罗马天文台; 布里斯托大学; 意大利国家天体物理研究所-阿尔切特里天体物理天文台; 比萨大学; 意大利国家天体物理研究所-的里雅斯特天文台; 基础物理宇宙研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究利用28个明亮高红移类星体样本，发现其X射线谱普遍陡峭，与黑洞增长效率无显著相关，且可能降低未来巡天对早期AGN的探测能力。
AI 中文摘要
在再电离纪元（EoR，$z\gtrsim6$）的明亮类星体（QSO）中，寄居着在宇宙最初十亿年内聚集形成的十亿太阳质量黑洞。它们的X射线辐射探测了最内层的吸积区域，并约束了早期超大质量黑洞（SMBH）增长过程中冕的物理状态。此前基于HYPERluminous类星体在再电离纪元（HYPERION）样本（包含由增长最快的SMBH驱动的$z \gtrsim 6$ QSO）的结果表明，X射线谱斜率与长期增长效率之间存在联系。我们利用一个主要扩展到最低增长效率的样本，检验了明亮的z>6 QSO的陡峭X射线谱是早期SMBH增长的普遍特性，还是增长效率最高的SMBH所特有的性质。我们分析了最大且对X射线最敏感的样本，包含28个位于$z \simeq 5.85-7.56$的明亮QSO（其中26个用于相关性分析），结合了HYPERION目标、明亮的非HYPERION源，以及在我们XMM-Newton大型计划中新观测到的由中等吸积SMBH驱动的QSO。我们统一地重新推导了整个样本的黑洞质量和增长指标，并结合了最新的基于JWST的光谱测量，以确保对所有目标进行最一致和高质量的表征。我们发现冕的谱参数与黑洞增长指标之间没有统计学显著的相关性：明亮的$z \gtrsim 6$ QSO系统地表现出陡峭的X射线连续谱，具有高光子指数和/或低高能截断，这与冷冕一致，可能与大吸积率有关。最后，如果陡峭的X射线斜率在早期活动星系核（AGN）中普遍存在，那么在固定内禀光度下，它们可能显著降低未来EoR巡天中的计数率，影响陡谱X射线源的探测能力，从而影响早期AGN种群的普查。
英文摘要
Luminous quasars (QSOs) at the Epoch of Reionization (EoR, $z\gtrsim6$) host billion-solar-mass black holes assembled within the first Gyr of cosmic time. Their X-ray emission probes the innermost accreting regions and constrains the physical state of the corona during early supermassive black hole (SMBH) growth. Previous results from the HYPerluminous quasars at the Epoch of ReionizatION (HYPERION) sample of $z \gtrsim 6$ QSOs, powered by the most rapidly accreted SMBHs, suggested a link between X-ray spectral slope and long-term growth efficiency. We test whether the steep X-ray spectra of luminous z>6 QSOs are a general property of early SMBH growth or a peculiarity of the most efficiently grown SMBHs, using a sample extended mainly to the lowest growth efficiencies. We analysed the largest and most X-ray sensitive sample of 28 luminous QSOs at $z \simeq 5.85-7.56$ (26 used in the correlation analysis), combining HYPERION targets, luminous non-HYPERION sources, and QSOs powered by moderately accreting SMBHs newly observed in our XMM-Newton Large Programme. We re-derived black hole masses and growth indicators for the entire sample homogeneously, incorporating the latest JWST-based spectroscopic measurements to ensure the most consistent and high-quality characterization across all targets. We found no statistically significant correlation between coronal spectral parameters and BH growth indicators: luminous $z \gtrsim 6$ QSOs systematically show steep X-ray continua, with high photon indices and/or low high-energy cutoffs, consistent with cold coronae, possibly linked to rapid accretion. Finally, if steep X-ray slopes are common among early AGN, they may significantly reduce count rates, at fixed intrinsic luminosity, in future surveys of the EoR, affecting the detectability of steep-spectrum X-ray sources and thus the census of the early AGN population.
CommentsRevised version submitted to A&A
