On I Line Emission in the Quasar PG 1116+215

Abstract

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 I lines (λ1304, λ8446, and λ11287) in a quasar for the first time. The photon flux ratios of the O I 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 I line flux ratios between the quasar and the other Seyferts, suggesting that the gas density in the O I and Fe II 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 I λ11287 is significantly narrower than that of Lyα, which is consistent with O I and Fe II emission occurring in the partly ionized regions at the outermost portion of the broad-line region where velocities are small.