We have vastly increased the CIV statistics at intermediate redshift by surveying the thousands of quasars in the Sloan Digital Sky Survey (SDSS) Data-Release 7. We visually verified over 16000 CIV systems with 1.46<z<4.55 - a sample size that renders Poisson error negligible. Detailed Monte Carlo simulations show that we are approximately 50% complete down to rest equivalent widths W_r_{approx}0.6{AA}. We analyzed the sample as a whole and in 10 small redshift bins with approximately 1500 doublets each. The equivalent width frequency distributions f(W_r_) were well modeled by an exponential, with little evolution in shape. In contrast with previous studies that modeled the frequency distribution as a single power law, the fitted exponential gives a finite mass density for the CIV ions. The comoving line density dN_CIV_/dX evolved smoothly with redshift, increasing by a factor of 2.37+/-0.09 from z=4.55-1.96, then plateauing at dN_CIV_/dX~0.34 for z=1.96-1.46. Comparing our SDSS sample with z5 (infrared) surveys, we see an approximately 10-fold increase in dN_CIV_/dX over z{approx}6->0, for W_r_>=0.6{AA}. This suggests a monotonic and significant increase in the enrichment of gas outside galaxies over the 12Gyr lifetime of the universe.

Cone search capability for table J/ApJ/763/37/table2 (Sightline summary)