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 ( ~ 10 Å) strongly supports the idea that the X-ray faintness of this QSO is due to heavy absorption by gas with a column density N_H > 10²⁴ cm^-2. 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 0.9-2.4 mu m range ( ~ 1300-3500 Å\ rest frame) exactly matches the template of unabsorbed QSOs without invoking any reddening (E_B-V<0.08 mag), indicating that dust in the absorbing gas is either absent or composed of large grains. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the CNAA (Consorzio Nazionale per l'Astronomia e l'Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.