Properties of Interstellar Medium In Infrared-Bright QSOs Probed by [O I] 63 μm and [C II] 158 μm Emission Lines

We present a study of the interstellar medium (ISM) in the host galaxies of nine QSOs at 0.1 1 IR-bright QSOs. One target, W0752+19, shows an additional broad velocity component (~720 km s^(−1)) and exceptionally strong [O I] 63 μm emission with L_([O I]63μm)/L_(FIR) of 10^(−2), an order of magnitude higher than the average value found among local (U)LIRGs. Combining with the analyses of the Sloan Digital Sky Survey optical spectra, we conclude that the [O I] 63 μm emission in these QSOs is unlikely excited by shocks. We infer that the broad [O I] 63 μm emission in W0752+19 could arise from the warm and dense ISM in the narrow-line region of the central active galactic nucleus. Another possible explanation is the existence of a dense gas outflow with n_H ~ 10^4 cm^(−3), where the corresponding broad [C II] emission is suppressed. Based on the far-IR [O I] and [C II] line ratios, we estimate constraints on the ISM density and UV radiation field intensity of n_H ≾ 10^(3.3) cm^(−3) and 10^3 10^4