The broad O vi absorber at z = 3 . 02 toward CTQ 325

We report on the multiphase absorption-line system detected at a redshift z abs =3.021 in the spectrum of the quasi-stellar object CTQ 325 (zem = 3.212). The system is displaced by ≃ 14, 000 km s −1 to the blue of the systemic velocity defined by the center of the symmetric O i quasar emission line. It consists of shallow and broad (∼ 700 km s −1 FWHM) absorption lines of H i λ1215, C iv λλ1548, 1550, and O vi λλ1032, 1038, produced by collisionally ionized gas and of narrow absorption lines (FWHM < 20 km s −1) of Ly α,β,...,6 , Si iii λ1206, and C iii λ977 produced by photoionized gas. Possible origins of this system are discussed.