High‐Resolution Absorption Spectroscopy of Multiphase, High‐Metallicity Gas Associated with the Luminous Quasar HE 0226−4110

We present FUSE and HST/STIS observations of the absorption line system nearthe 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 adjacentstages of oxygen (O III-VI), which reveal a striking change in gas kinematicswith ionization. Examination of the O VI 1031, 1037 doublet profiles reveals noevidence for partial coverage or unresolved saturated structure. O III is onlydetected in a narrow feature which is also traced by H I and C III, suggestingthat they arise in the same gas. Absorption at the same velocity is alsopresent in other species N IV, O IV-VI, S IV, and possibly N VIII, but thekinematics differ from the O III, implying production in separate gaseousphases. The H I, O II-IV, and C III information in yield an estimate of boththe 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 possiblelocations for the gas in this associated absorption-line system: the narrowemission line region of the quasar, and the halo of the quasar host galaxy. Anadditional narrow (thus, photoionized) component that is only detected in O VIappears 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 twobroad components which only appear in moderate to high ionization species.[highly abridged]Comment: 25 pages, including 14 figures; uses emulateapj.cls document class; accepted for publication in The Astrophysical Journa