Discovery of strong CIV absorption in the highest redshift quasar⋆

We report the near-IR detection of a prominent CIV absorption in the rest-frame UV spectrum of the most distant known QSO, SDSS J104433.04−012502.2, at z = 5.80. This QSO was recently observed with XMM-Newton and it was found to be notably X-ray weak. The equivalent width of the CIV absorption feature (∼10Å) strongly supports the idea that the X-ray faintness of this QSO is due to heavy absorption by gas with a column density NH > 10 cm. The shape of the CIV feature suggests that this is a Broad Absorption Line QSO. Although absorbed by a huge column of gas, the observed continuum in the 0.9–2.4μm range (∼1300–3500 Å rest frame) exactly matches the template of unabsorbed QSOs without invoking any reddening (EB−V < 0.08 mag), indicating that dust in the absorbing gas is either absent or composed of large grains.