2006ApJ...645..868G

We present FUSE and HST STIS observations of the absorption-line system near the emission redshift of the radio-quiet, X-ray-bright quasar HE 0226-4110 (z=0.495, V=15.2). The spectra cover the rest-frame wavelength range 610-1150 Å, and we detect a wide range of ionization species, including four adjacent stages of oxygen: O III-VI, which reveal a striking change in gas kinematics with ionization. Examinaton of the O VI λλ1031, 1037 doublet profiles reveals no evidence for partial coverage or unresolved saturated structure. O III is only detected in a narrow feature that is also traced by the H I and C III lines, suggesting that they arise in the same gas. Absorption at the same velocity is also present in other species (N IV, O IV-VI, S IV, and possibly Ne VIII), but the kinematics differ from the O III, implying production in separate gaseous phases. The combination of H I, O III, and C III information yields an estimate of both the photoionization parameter and the metallicity of the O III-bearing gas: [O/H]=+0.12^+0.16_–0.03, logU=-2.29^+0.02_–0.23. We discuss two possible locations for the gas in this associated absorption-line system: the narrow emission line region of the quasar, and the halo of the quasar host galaxy. An additional narrow (and thus photoionized) component that is only detected in O VI appears 58 km/s redward of the O III-bearing gas with -0.35≲logU≲0.02. Additional structure is detected in the associated absorber in the form of two broad components that only appear in moderate- to high-ionization species.