活动星系核的eROSITA X射线光度函数
The eROSITA X-ray luminosity function of active galactic nuclei
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中文总结 AI 辅助
本研究利用eROSITA DR2 AGN星表，测量红移至$z\backsimeq6$的AGN软XLF，提出红移依赖的平滑断裂幂律参数化方法，揭示AGN空间密度演化及紫外漏检规律，为后续巡天策略提供参考。
中文摘要 AI 辅助
活动星系核（AGN）的X射线光度函数（XLF）是研究宇宙中超大质量黑洞（SMBH）随时间增长的观测探针。Spectrum Roentgen Gamma（SRG）/eROSITA凭借其大巡天覆盖范围，在光度-红移平面上实现了与 pencil-beam 巡天互补的深度-面积平衡，提供了探测稀有亮AGN所需的体积，解决了此前因样本量小导致的统计限制。我们利用覆盖约8个数量级光度、红移至$z\backsimeq6$的eROSITA样本测量软XLF，这使我们能以更高精度研究光度依赖的演化，并推断SMBH吸积历史及光学/紫外漏检的AGN群体。我们引入一种新的红移依赖平滑断裂幂律参数化方法，其中所有XLF模型参数均可随红移连续演化。我们发现低红移处中等及极亮AGN的空间密度更低，而最高红移处的丰度比此前测量结果更高。将其与转换为静止系2-10 keV的光学/紫外类星体LF对比可知，紫外漏检比例随光度增加而降低，且在最亮的光度区间内随红移升高而增加。对XLF积分得到的黑洞吸积率密度在$z\backsimeq1.5$处达到峰值，对应的累积黑洞质量密度显示，相对于通过标度关系推导的局域黑洞质量估计值，软X射线选样本漏检的遮挡增长约占$80^{+11}_{-23}\%$。本研究发布了eROSITA DR2 AGN星表，包含对应天体及其红移信息。我们还讨论了这些结果如何为未来旨在改进AGN人口统计约束的光谱、测光及X射线巡天策略提供参考。
英文摘要
The X-ray luminosity function (XLF) of active galactic nuclei (AGN) provides an observational probe of the growth of supermassive black holes (SMBHs) across cosmic time. With its large survey grasp, Spectrum Roentgen Gamma (SRG)/eROSITA samples the luminosity--redshift plane with a depth--area balance complementary to pencil-beam surveys, providing the volume needed to detect rare luminous AGN, previously limited by small-number statistics. We measure the soft XLF, leveraging an eROSITA sample spanning approximately eight orders of magnitude in luminosity out to $z\simeq6$. This enables us to study luminosity-dependent evolution with improved constraints, and to infer both the SMBH accretion history and optical/UV missed AGN population. We introduce a new redshift-dependent smoothly broken power-law parameterisation in which all XLF model parameters are allowed to evolve continuously with redshift. We find lower space densities for moderately and very luminous AGN at low redshift, while the abundance is higher than previously found at the highest redshifts. Comparisons to optical/UV quasar LFs converted to rest-frame $2\!-\!10\,\mathrm{keV}$ show that the UV-missed fraction decreases with luminosity, and, in the most luminous bin, increases with redshift. Integrating the XLF yields a black-hole accretion-rate density peaking at $z \simeq 1.5$, with the corresponding cumulative black-hole mass density indicating $\sim80^{+11}_{-23}\%$ obscured growth relative to locally-inferred BH mass estimates derived from scaling relations and missed by the soft X-ray selection of our sample. With this work, we release the eROSITA DR2 AGN catalogue, including counterparts and their redshift information. We then discuss how these results can inform future spectroscopic, photometric, and X-ray survey strategies aimed at improving AGN demographic constraints.
