2005PASJ...57..563M

By observing the near-infrared spectrum of the quasar PG 1116+215 at z = 0.176 and combining with the HST/FOS spectrum, we obtained the relative strengths of three permitted O <FONT SIZE="-2">I</FONT> lines (l1304, l8446, and l11287) in a quasar for the first time. The photon flux ratios of the O <FONT SIZE="-2">I</FONT> lines of the quasar were compared with those previously measured in a Seyfert 1 and six narrow-line Seyfert 1s. No significant differences were found in the O <FONT SIZE="-2">I</FONT> line flux ratios between the quasar and the other Seyferts, suggesting that the gas density in the O <FONT SIZE="-2">I</FONT> and Fe <FONT SIZE="-2">II</FONT> line-emitting regions in the quasar is of the same order as those in low-luminosity AGNs. It was also found that the line width of O <FONT SIZE="-2">I</FONT> l11287 is significantly narrower than that of Lya, which is consistent with O <FONT SIZE="-2">I</FONT> and Fe <FONT SIZE="-2">II</FONT> emission occurring in the partly ionized regions at the outermost portion of the broad-line region where velocities are small.