ABSORPTION-SPECTRA OF Q-0000-263 AND 1442+101

We present a new analysis of the Ly alpha forest for the high-redshift QSOs 1442 + 101 (z = 3.544) and 0000 - 263 (z = 4.11 1). We have performed detailed profile fitting to spectra of moderate resolution and high signal-to-noise ratio. The results are compared to a more conventionally derived line list. As a result, we provide a high-redshift extension to the previously reported Ly a forest samples of Bajtlik, Duncan & Ostriker, Lu, Wolfe & Turnshek and Rauch et al. If the evolution of the number of lines per unit redshift has the functional form (1 + z) gamma then we find a best-fitting value of gamma = 2.5 9 +/- 0.49 for an equivalent width completeness limit of W(thr) = 0.21 angstrom. If the equivalent widths are distributed as exp(- W/W*), we determine a characteristic equivalent width W* = 0.084 +/-0.008 for the new data. Relating this to a column density distribution of the form p(N(H1) is-proportional-to N(H1)-beta we find that beta almost-equal-to 1.9. The new data combined with the Rauch et al. sample give W* = 0. 1 79 +/- 0.0 1 0, which corresponds to beta almost-equal-to 1.7. Our values for W* and beta imply that the new data are not consistent with the typical intermediate-resolution sample. The larger values that we have determined for beta are, however, consistent with high-resolution spectra.