Probing the He ii Reionization ERA via Absorbing C iv Historical Yield (HIERACHY). III. The C iv Absorber Catalog and Initial Results on Cosmic Abundance Evolution at z ≈ 3–5

Abstract

As part of the HIERACHY program, we collect the high signal-to-noise ratio 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 _C _iv /cm ^−2 ) ≈ 12.3. The HIERACHY/MIKE C iv sample is one of the best C iv absorber samples optimized to study the intergalactic medium 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 _C _iv /cm ^−2 ) ≳ 12.3 has a broken power-law shape, with the turnover column density log $({N}_{\mathrm{crit}}/{\mathrm{cm}}^{-2})=13.3{5}_{-0.19}^{+0.20}$ , 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 _C _iv /cm ^−2 ) > 13.2 show an increase (at the 2.2 σ and 1.4 σ levels, respectively) from redshift z ≈ 5–3, while absorption systems with log( N _C _iv /cm ^−2 ) = 12.3–13.2 exhibit a constant dn / dX and Ω _C _iv .

Keywords

• Intergalactic medium
• Quasar absorption line spectroscopy
• Reionization
• Circumgalactic medium