The CGM and IGM at z ~ 5: Metal budget and physical connection

We present further results of a survey for absorption line systems in the spectra of four high redshift quasars (5.79 < zem < 6.13) obtained with the ESO Very Large Telescope X-Shooter. We identify 36 CIV and 7 Si IV systems with a > 5 σ significance. The highest redshift C IV and Si IV absorbers identified in thiswork are at z = 5.80738 ± 0.00017 and z = 5.77495 ± 0.00038, respectively. We compute the comoving mass density of Si IV (ΩSi IV) and find that it evolves from ΩSi IV = 4.3 -2.1+2.1 × 10-9 at 〈 z〉 = 5.05 to ΩSi IV = 1.4-0.4+0.6 × 10-9 at 〈z〉 = 5.66. We also measure ΩC IV = 1.6-0.1+0.4 × 10-8 at 〈z〉 = 4.77 and ΩC IV = 3.4-1.1+1.6 × 10-9 at 〈z〉 = 5.66. We classify our CIV absorber population by the presence of associated low- and/or highionization systems and compute their velocity width (Δv90). We find that all CIV systems with Δ v90 > 200 km s-1 have associated low-ionization systems. We investigate two such systems separated by 550 physical kpc along a line of sight, and find it likely that they are both tracing a multiphase medium where hot and cold gas is mixing at the interface between the circumgalactic medium and intergalactic medium. We further discuss the MgII systems presented in a previous work and we identify 5 Si II, 10 Al II, 12 FeII, 1 CII, 7 MgI, and 1 Ca II associated transitions.We compute the respective comoving mass densities in the redshift range 2-6, as allowed by the wavelength coverage.