Intrinsic Properties of the 〈z〉 = 2.7 Lyα Forest from Keck Spectra of Quasar HS 1946+7658

We present the highest quality Lyα forest spectra published to date. We have complete 7.9 km s -1 FWHM spectra between the Lyα and Lyβ emission lines of the bright, high-redshift ( V = 15.9, z = 3.05) QSO HS 1946+7658. The mean redshift of observed Lyα forest clouds is ⟨ z ⟩ = 2.7. The spectrum has a signal-to-noise ratio per pixel of 2 km s -1 that varies from 15 at 4190 Å to 100 at 4925 Å. The absorption lines in the spectrum have been fitted with Voigt profiles, and the distribution of Voigt parameters has been analyzed. We show that fitting Voigt profiles to high quality data does not give unique results. We have performed simulations to differentiate between true features of the line distributions and artifacts of line blending and the fitting process. We show that the distribution of H I column densities is a power law of slope -1.5 from N (H I) = 10 14 cm -2 to N (H I) 10 13 cm -2 .