Abstract
We present spectra of six luminous quasars at z ∼ 2, covering rest wavelengths 1600-3200 A. The fluxes of the UV Fe II emission lines and Mg II λ2798 doublet, the line widths of Mg II and the 3000 A luminosity were obtained from the spectra. These quantities were compared with those of low-redshift quasars at z = 0.06-0.55 studied by Tsuzuki et al. In a plot of the Fe II(UV)/Mg II flux ratio as a function of the central black hole mass, Fe II(UV)/Mg II in our z ∼ 2 quasars is systematically greater than in the low-redshift quasars. We confirmed that luminosity is not responsible for this excess. It is unclear whether this excess is caused by rich Fe abundance at z ∼ 2 over low-redshift or by non-abundance effects such as high gas density, strong radiation field and high microturbulent velocity.
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