Approaching Reionization: The Evolution of the Lyman Alpha Forest from Redshifts Four to Six

摘要: We analyze the Ly alpha forest properties of a sample 15 high redshift quasars lying between z = 4.42 and 5.75, using signal-to-noise spectra obtained with ESI on Keck II 10 m telescope. The distribution transmissions in region this range is shown to be consistent that found lambda cold dark matter simulations smoothly evolving ionization rate as function redshift. extrapolation ionizing flux 6.05 lies factor two higher than 2 sigma upper limit placed by Cen & McDonald (2001) at redshift, based Becker et al. 6.28 quasar SDSS 1030+0524. However, data are also models which there substantial variation parameter about mean value, case, gaps such those seen become much more likely. conclude further needed before we can sure have epoch reionization. summarize damped systems these lines sight measure their metallicities kinematic properties. argue DLA metallicity has dropped substantially 5 compared its value < 4.