2025/03/22 by Yu, Xiaodi, Qu, Zhijie, Cai, Zheng +3 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2503.17732
As part of the HIERACHY program, we collect the high-SN and high-spectral resolution optical spectra of 25 quasars at z≈4-5 to constrain the C IV evolution at z≈ 3-5. In this paper, we report a catalog of 626 (1263) C IV absorption systems (components) at z≈3-5 with a 50% completeness column density of log(N\rm CIV/\rm cm-2) ≈ 12.3. The HIERACHY/MIKE C IV sample is one of the best C IV absorber samples optimized to study the IGM during the He II reionization epoch. Using 557 (1090) intervening absorption systems (components), we found the column density distribution function of C IV absorption systems with log(N\rm CIV/\rm cm-2)\gtrsim 12.3 has a broken power-law shape, with the turn-over column density log(N\rm crit/\rm cm-2) = 13.35+0.20-0.19, which is close to or smaller than the detection limit of most literature samples. We also found that both comoving path length number density dn/dX and cosmic abundance Ω for C IV absorption systems with log(N\rm CIV/\rm cm-2)> 13.2 show an increase (at the 2.2σ and 1.4σ levels, respectively) from redshift z≈5 to 3, while absorption systems with log(N\rm CIV/\rm cm-2)= 12.3-13.2 exhibit a constant dn/dX and Ω\rm CIV.