The CGM and IGM at z5: metal budget and physical connection
Abstract
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 SiIV systems with a 5σ significance. The highest redshift CIV and SiIV absorbers identified in this work are at z = 5.80738 0.00017 and z = 5.77495 0.00038, respectively. We compute the comoving mass density of SiIV (SiIV) and find that it evolves from SiIV = 4.3+2.1-2.1 ×10-9 at <z> = 5.05 to SiIV = 1.4+0.6-0.4 ×10-9 at <z> = 5.66. We also measure CIV = 1.6+0.4-0.1 ×10-8 at <z> = 4.77 and CIV = 3.4+1.6-1.1 ×10-9 at <z> = 5.66. We classify our CIV absorber population by the presence of associated low and/or high ionisation systems and compute their velocity width (90). We find that all CIV systems with 90 > 200 kms-1 have associated low ionisation 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 multi-phase medium where hot and cold gas is mixing at the interface between the CGM and IGM. We further discuss the MgII systems presented in a previous work and we identify 5 SiII, 10 AlII, 12 FeII, 1 CII, 7 MgI and 1 CaII associated transitions. We compute the respective comoving mass densities in the redshift range 2 to 6, as allowed by the wavelength coverage.
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