绘制紫外波段的类星体主序：与紫外 Fe III 发射的联系
Mapping the Quasar Main Sequence in the UV range: A Connection with the UV Fe III Emission
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中文总结 AI 辅助
本研究利用紫外 1900 混合发射及 Fe III/Fe II 发射构建类星体主序的紫外对应平面，验证其可区分不同族群并识别高吸积 xA 源，为高红移研究提供新途径。
中文摘要 AI 辅助
类星体主序（MS）为 I 型活动星系核提供了一种一致性的统一方案。该框架基于光学发射 Hβ 与 Fe II (λ4570) 之间的相对流量以及 FWHM(Hβ) 构建，将类星体分为两个族群（B、A）及亚族群 xA，后者通常由高吸积源组成。我们探索了使用紫外 1900 混合发射（Al III λ1860、Si III] λ1892、C III] λ1909）以及 1700 至 2200 埃之间的 Fe III 和 Fe II 跃迁作为该主序的示踪物。我们对由哈勃太空望远镜（HST）观测到的 69 个低红移（z≲0.8）类星体样本拟合了这些发射，这些天体具有可用的光学测量数据，从而能够与光学类星体主序进行直接比较。我们发现了一个由 FWHM(Al III) 和 Fe III 与 Fe II 组合发射的等值宽度定义的紫外平面。由这些参数定义的平面在光学波段反映了类星体主序，并显示出不同族群之间的明显区分。该平面还能以高完备性但存在不可忽略的误报率来识别 xA 源。我们的结果表明，1900 混合发射附近的紫外铁发射可用于追踪类星体主序趋势，为在高红移下研究这一方案提供了替代途径。
英文摘要
The quasar main sequence (MS) provides a consistent unification scheme for type I AGNs. This framework, constructed from the relative flux between the optical emissions $\mathrm{H}β$ and $\mathrm{Fe\,II\,(\lambda4570)}$, and the $\mathrm{FWHM(Hβ)}$, organizes quasars into two populations (B, A) and the subpopulation xA, which typically consists of highly accreting sources. We explored the use of the UV 1900 blend emissions ($\mathrm{Al\,III}\,\mathrmλ1860$, $\mathrm{Si\,III]}\,\mathrmλ1892$, $\mathrm{C\,III]}\,\mathrmλ1909$) and the $\mathrm{Fe\,III}$ and $\mathrm{Fe\,II}$ transitions between 1700 and 2200 Angstrom as tracers of this main sequence. We fitted these emissions for a sample of 69 low-$z$ ($z\lesssim0.8$) quasars observed with the Hubble Space Telescope (HST) that had available optical measurements, enabling a direct comparison with the optical quasar main sequence. We found a UV plane defined by $\mathrm{FWHM}(\mathrm{Al\,III})$ and the equivalent width of the combined emissions of $\mathrm{Fe\,III}$ and $\mathrm{Fe\,II}$. The plane defined by these parameters mirrors the quasar main sequence in the optical regime and shows a clear distinction between the different populations. The plane also enables the identification of xA sources with high completeness but a non-negligible rate of false positives. Our results suggest that the UV iron emission around the 1900 blend could be used to trace the quasar main sequence trend, offering an alternative way to study this scheme at high redshift.
