Fe Ⅱ/Mg Ⅱ EMISSION-LINE RATIOS OF QSOs WITHIN 0 < z < 5.3

摘要

Near-infrared spectra of 13 QSOs located between 4.4 < z < 5.3 were obtained by the OH-airglow suppression spectrograph mounted on the Subaru telescope. The Fe Ⅱ/Mg Ⅱ emission-line ratios of the QSOs at various redshifts were examined by applying the same fitting algorithm to the present data together with published or archived spectra. We found a trend of a decreasing Fe Ⅱ/Mg Ⅱ ratio from z ～ 5 to 1,5, almost independent of their luminosities. We also confirmed the Baldwin effect on the Mg Ⅱ emission line.