The Lyα Forest atz∼ 4: Keck HIRES Observations of Q0000−26

This paper describes a study of the Lyman-alpha forest absorption cloudsalong the quasar sightline Q0000-26 (zem=4.1). The spectrum was obtained withthe High Resolution Spectrometer on the 10m Keck telescope. We derive accurateH I column density and Doppler width distributions for the clouds from Voigtprofile fitting. We also analyze simulated Lyman-alpha forest spectra ofmatching characteristics in order to gauge the effects of lineblending/blanketing and noise in the data. The results are compared withsimilar studies at lower redshifts in order to study any possible evolution inthe clouds' properties. We also estimate the mean intensity of the UVbackground at z=4 from an analysis of the proximity effect.Comment: plain TeX containing 23 PS pages, 3 PS tables, and 9 PS figures, ApJ, Dec 1, 1996 issue replacing an earlier version which contains an corrupted table