A Lower Limit to the Universal Density of Metals at z ∼ 3

Column density distribution functions of C IV with 12.05≤log(N)≤14.35 and Si IV with 11.70≤log(N)≤13.93 have been obtained using 81 C IV absorbers and 35 Si IV absorbers redward of the Lyα forest in the lines of sight to seven quasars with 2.518≤zem≤3.78. These distribution functions have been directly integrated to yield ion densities at z = 3-3.5 of ΩC iv = (2.0 ± 0.5) ×10−8 and ΩSi iv = (7.0±2.6)×10−9 with H0 = 65 km s-1 Mpc-1 and q0=0.02 (1 σ errors). A larger sample of 11 quasar lines of sight was used to measure C II/C IV, Si III/Si IV, and N V/C IV ratios, which suggest that C IV and Si IV are the dominant ionization stages and that corrections to ΩCarbon and ΩSilicon are no more than a factor of 2. Normalizing the α-process elements to silicon and the Fe-coproduction elements to carbon gives a density of heavy elements in these forest clouds of Ωmetals=(3.3±0.8)×10−7 (H0=65,q0=0.02) . The implications for the amount of star formation and for the ionization of the intergalactic medium prior to z=3 are discussed.