Absorption systems in the spectra of 66 z ≳ 4 quasars

We present high signal-to-noise, similar to5 Angstrom resolution (FWHM) spectra of 66 z greater than or similar to 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-HI greater than or equal to 1.6 x 10(17) atoms cm(-2)) and damped Ly alpha systems (column densities N-IH greater than or equal to 2 x 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 Ly alpha 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.