2001/10/31 by Antoinette Songaila · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/324761
published as Astrophys.J.561:L153-L156,2001 · This posting (v3) adds a factor of (1/c) in equation (1), and also the definition of Delta X, both omitted from v2. This is a typographical error and there is no impact on the published values of Omega_ion in the text and figures. v2: Revised to correct an error in equation (1) in the published version. This was a typographical error only and all values of Omega_ion in the text and figures of the published version were correctly computed with H_0 = 65 km/s/Mpc and Omega_m = 1. (5 pages including 4 figures.)
It appears that the Lyman alpha forest is becoming thick at a redshift of about 5.5, cutting off the higher redshift intergalactic medium from view in neutral hydrogen. However, the effects of star formation at higher redshift are still readable in the intergalactic metal lines. In this paper I use observations of 32 quasars with emission redshifts in the range 2.31 to 5.86 to study the evolution of the intergalactic metal density from z = 1.5 to z = 5.5. The C IV column density distribution function is consistent with being invariant throughout this redshift range. From direct integration, I determine OmegaCIV to be in the range (2.5 - 7) × 10-8 and OmegaSiIV in the range (0.9 - 3) × 10-8 between z = 1.5 and z = 5. The metallicity at z = 5 exceeds 3.5 × 10-4, which in turn implies that this fraction of the universal massive star formation took place beyond this redshift. This is sufficient to have ionized the intergalactic medium.