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We have compiled the emission-line fluxes of O I 8446, O I 11287, and thenear-IR Ca II triplet (8579) observed in 11 quasars. These lines are consideredto emerge from the same gas as do the Fe II lines in the low-ionized portion ofthe broad emission line region (BELR). The compiled quasars are distributedover wide ranges of redshift (0.06 < z < 1.08) and of luminosity (-29.8 < M_B <-22.1), thus representing a useful sample to investigate the line-emitting gasproperties in various quasar environments. The measured line strengths andvelocities, as functions of the quasar properties, are analyzed usingphotoionization model calculations. We found that the flux ratio between Ca IIand O I 8446 is hardly dependent on the redshift or luminosity, indicatingsimilar gas density in the emission region from quasar to quasar. On the otherhand, a scatter of the O I 11287/8446 ratios appears to imply the diversity ofthe ionization parameter. These facts invoke a picture of the line-emittinggases in quasars that have similar densities and are located at regions exposedto various ionizing radiation fluxes. The observed O I line widths are found tobe remarkably similar over more than 3 orders of magnitude in luminosity, whichindicates a kinematically determined location of the emission region and is inclear contrast to the well-studied case of H I lines. We also argue about thedust presence in the emission region since the region is suggested to belocated near the dust sublimation point at the outer edge of the BELR.

Low-Ionization Emission Regions in Quasars: Gas Properties Probed with Broad O I and Ca II Lines