We present deep (9 hours) Gemini-N/GNIRS near-infrared spectroscopic observations of ULAS J1342+0928, a luminous quasar at z=7.54. Various broad emission lines were detected, as well as the underlying continuum and iron forests over the rest-frame wavelength 970-2930A. There is a clear trend that higher-ionization emission lines show larger blueshifts with CIV1549 exhibiting 5510^{+240}_{-110} km s-1 blueshift with respect to the systematic redshift from the far-infrared [CII] 158um emission line. Those high ionization lines have wide profiles with FWHM more than 10000 km s-1. A modest blueshift of 340^{+110}_{-80} km s-1 is also seen in MgII, the lowest ionization line identified in the spectrum. The updated MgII-based black hole mass of M_BH=9.1_{-1.3}^{+1.4} x 10^8 M_sun and the Eddington ratio of L_bol/L_Edd=1.1_{-0.2}^{+0.2} confirm that ULAS J1342+0928 is powered by a massive and actively accreting black hole. There is no significant difference in the emission line ratios such as SiIV/CIV and AlIII/CIV when compared to lower-redshift quasars in a similar luminosity range, which suggests early metal pollution of the broad-line-region clouds. This trend also holds for the FeII/MgII line ratio, known as a cosmic clock that traces the iron enrichment in the early universe. Different iron templates and continuum fitting ranges were used to explore how the FeII/MgII measurement changes as a function of spectral modeling. Quasars at even higher redshift or at fainter luminosity range (L_bol<10^46 erg s-1) are needed to probe the sites of early metal enrichment and a corresponding change in the FeII/MgII ratio.

中文翻译：

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直到 z = 7.54 的宽线区金属度没有红移演化：ULAS J1342+0928 的深近红外光谱

我们展示了 ULAS J1342+0928（z=7.54 处的发光类星体）的深（9 小时）Gemini-N/GNIRS 近红外光谱观测。在静止帧波长 970-2930A 上检测到各种宽发射线，以及下面的连续谱和铁森林。有一个明显的趋势，即更高电离的发射线显示出更大的蓝移，CIV1549 表现出 5510^{+240}_{-110} km s-1 蓝移，相对于来自远红外 [CII] 158um 发射线的系统红移. 那些高电离线的轮廓很宽，FWHM 超过 10000 km s-1。在 MgII 中也看到了 340^{+110}_{-80} km s-1 的适度蓝移，MgII 是光谱中确定的最低电离线。更新后的基于 MgII 的黑洞质量 M_BH=9.1_{-1.3}^{+1.4} x 10^8 M_sun 和爱丁顿比率 L_bol/L_Edd=1.1_{-0.2}^{+0。2} 确认 ULAS J1342+0928 由一个巨大且活跃吸积的黑洞提供动力。与类似光度范围内的低红移类星体相比，SiIV/CIV 和 AlIII/CIV 等发射线比率没有显着差异，这表明宽线区云的早期金属污染。这种趋势也适用于 FeII/MgII 线比，被称为宇宙钟，可追踪早期宇宙中的铁含量。使用不同的铁模板和连续谱拟合范围来探索 FeII/MgII 测量值如何随光谱建模而变化。需要具有更高红移或更微弱光度范围 (L_bol<10^46 erg s-1) 的类星体来探测早期金属富集的位置以及 FeII/MgII 比率的相应变化。