The broad O VI absorber at z = 3.02 toward CTQ 325

We report on the multiphase absorption-line system detected at a redshift $z_{\rm abs}=3.021$ in the spectrum of the quasi-stellar object CTQ 325 ($z_{\rm em}= 3.212$). The system is displaced by $\simeq$$14\,000$ km s -1 to the blue of the systemic velocity defined by the center of the symmetric $\ion{O}{i}$ quasar emission line. It consists of shallow and broad (~700 km s -1 FWHM ) absorption lines of $\ion{H}{i}$ $\lambda1215$, $\ion{C}{iv}$ $\lambda\lambda1548, 1550$, and $\ion{O}{vi}$ $\lambda\lambda1032, 1038$, produced by collisionally ionized gas and of narrow absorption lines (${\it FWHM} -1 ) of Ly$_{\alpha, \beta, \ldots, 6}$, $\ion{Si}{iii}$ $\lambda1206$, and $\ion{C}{iii}$ $\lambda977$ produced by photoionized gas. Possible origins of this system are discussed.