Onoue, MasafusaMasafusaOnoueBañados, EduardoEduardoBañadosMazzucchelli, ChiaraChiaraMazzucchelliVenemans, Bram P.Bram P.VenemansSchindler, Jan-TorgeJan-TorgeSchindlerWalter, FabianFabianWalterHennawi, Joseph F.Joseph F.HennawiAndika, Irham TaufikIrham TaufikAndikaDavies, Frederick B.Frederick B.DaviesDECARLI, ROBERTOROBERTODECARLIFarina, Emanuele P.Emanuele P.FarinaJahnke, KnudKnudJahnkeNagao, TohruTohruNagaoTominaga, NozomuNozomuTominagaWang, FeigeFeigeWang2021-09-012021-09-0120200004-637Xhttp://hdl.handle.net/20.500.12386/31005We present deep (9 hr) Gemini-N/Gemini Near-InfraRed Spectrograph 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 970-2930 Å. There is a clear trend that higher-ionization emission lines show larger blueshifts with C IV $\lambda 1549$ exhibiting ${5510}_{-110}^{+240}$ km s<SUP>-1</SUP> blueshift with respect to the systematic redshift from the far-infrared [C II] $158\,\mu {\rm{m}}$ emission line. Those high-ionization lines have wide profiles with FWHM more than 10,000 km s<SUP>-1</SUP>. A modest blueshift of ${340}_{-80}^{+110}$ km s<SUP>-1</SUP> is also seen in Mg II, the lowest-ionization line identified in the spectrum. The updated Mg II-based black hole mass of ${M}_{\mathrm{BH}}={9.1}_{-1.3}^{+1.4}\times {10}^{8}{M}_{\odot }$ and the Eddington ratio of ${L}_{\mathrm{bol}}/{L}_{\mathrm{Edd}}={1.1}_{-0.2}^{+0.2}$ 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 Si IV/C IV and Al III/C IV 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 Fe II/Mg II 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 Fe II/Mg II measurement changes as a function of spectral modeling. Quasars at even higher redshift or at fainter luminosity range ( ${L}_{\mathrm{bol}}\lesssim {10}^{46}$ erg s<SUP>-1</SUP>) are needed to probe the sites of early metal enrichment and a corresponding change in the Fe II/Mg II ratio.STAMPAenArticle10.3847/1538-4357/aba193https://iopscience.iop.org/article/10.3847/1538-4357/aba1932020ApJ...898..105OFIS/05 - ASTRONOMIA E ASTROFISICAERC sectors::Physical Sciences and Engineering::PE9 Universe sciences: astro-physics/chemistry/biology; solar systems; stellar, galactic and extragalactic astronomy, planetary systems, cosmology, space science, instrumentation