Fe II/Mg II Emission-Line Ratios of QSOs within 0 < z < 5.3
Doi, Mamoru; Yoshii, Yuzuru; Motohara, Kentaro; Iwamuro, Fumihide; Maihara, Toshinori; Kimura, Masahiko
Japan, United States
Abstract
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.