2006MNRAS.371..769G

We report the discovery of a new high-redshift quasar at z = 5.96, observed with the long-slit Faint Object Camera and Spectrograph on board the Subaru Telescope. The spectrum shows strong and broad Lyα + Nv emission lines with a sharp discontinuity to the blue side. A Lyβ + Ovi emission line is also detected, providing a consistent redshift measurement with the Lyα + Nv emission. The quasi-stellar object (QSO) has an absolute magnitude of M_AB,1450= -26.9 (H₀= 50 km/s/Mpc, q₀= 0.5). The spectrum shows significant flux in the region 8000-8300 Å and thus does not show a complete Gunn-Peterson trough in the redshift range 5.58-5.82, along the line of sight to this z = 5.96 QSO. Therefore, the Universe was already highly ionized at z = 5.82.