High-Resolution Absorption Spectroscopy of Multi-phase, High-Metallicity Gas Associated with the Luminous Quasar HE 0226-4110

Abstract

We present FUSE and HST/STIS observations of the absorption line system near the emission redshift of the radio-quiet, X-ray bright quasar HE0226-4110 (z = 0.495, V=15.2). The spectra cover the rest-frame wavelength range 610--1150 A, 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. Examination of the O VI 1031, 1037 doublet profiles reveals no evidence for partial coverage or unresolved saturated structure. O III is only detected in a narrow feature which is also traced by H I and C III, 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 N VIII, but the kinematics differ from the O III, implying production in separate gaseous phases. The H I, O II-IV, and C III information in yield an estimate of both the photoionization parameter and metallicity of the O III-bearing gas: [O/H]=+0.12(-0.03/+0.16), log U=-2.29(-0.23/+0.02). 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 (thus, photoionized) component that is only detected in O VI appears 58 km/s redward of the O III-bearing gas with -0.35 < log U < 0.02. Additional structure is detected in the associated absorber in the form of two broad components which only appear in moderate to high ionization species. [highly abridged]