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We investigate the abundance and distribution of metals in the high-redshiftintergalactic medium and circum-galactic medium through the analysis of asample of almost 600 SiIV absorption lines detected in high and intermediateresolution spectra of 147 quasars. The evolution of the number density of SiIVlines, the column density distribution function and the cosmic mass density arestudied in the redshift interval 1.7 <= z <= 6.2 and for log N(SiIV) >= 12.5.All quantities show a rapid increase between z~6 and z< 5 and then an almostconstant behaviour to z~2 in very good agreement with what is already observedfor CIV absorption lines. The present results are challenging for numericalsimulations: when simulations reproduce our SiIV results, they tend tounderpredict the properties of CIV, and when the properties of CIV arereproduced, the number of strong SiIV lines (log N(SiIV) > 14) isoverpredicted.

The evolution of the Si IV content in the Universe from the epoch of reionization to cosmic noon