Absorption Systems in the Spectra of 66 z ≳ 4 Quasars

We present high signal-to-noise, ~5 Å resolution (FWHM) spectra of 66 z ≳ 4 bright quasars obtained with the 4 m Cerro Tololo Inter-American Observatory and 4.2 m William Hershel telescopes. The primary goal of these observations was to undertake a new survey for intervening absorption systems detected in the spectra of background quasars. We look for both Lyman-limit systems (column densities N_(H I) ≥ 1.6 × 10^(17) atoms cm^(-2)) and damped Lyα systems (column densities N_(H I) ≥ 2 × 10^(20) atoms cm^(-2)). This work resulted in the discovery of 49 Lyman-limit systems, 15 of which are within 3000 km s^(-1) of the quasar emission and thus might be associated with the quasar itself, 26 new damped Lyα absorption candidates, 15 of which have z > 3.5, and numerous metal absorption systems. In addition, 10 of the quasars presented here exhibit intrinsic broad absorption lines