📝 SummarXiv

Abstract

We present the largest catalog to date of triply ionized carbon (CIV) absorbers detected in quasar spectra from the Dark Energy Spectroscopic Instrument. Using an automated matched-kernel convolution method with adaptive signal-to-noise thresholds, we identify $101,487$ CIV systems in the redshift range $1.4 < z < 4.5$ from $300,637$ quasar spectra. Completeness is estimated via Monte Carlo simulations and catalog is $50\%$ complete at $\mathrm{EW}_{\mathrm{CIV}} \geq 0.4$ Angstroms. The differential equivalent width frequency distribution declines exponentially and shows weak redshift evolution. The absorber incidence per unit comoving path increases by a factor of $2-5$ from $z \approx 4.5$ to $z \approx 1.4$, with stronger redshift evolution for strong systems. Using column densities derived from the apparent optical depth method, we constrain the cosmic mass density of CIV, $\Omega_{\mathrm{CIV}}$, which increases by a factor of $\sim 3.8$ from $(0.82 \pm 0.05) \times 10^{-8}$ at $z \approx 4.5$ to $(3.16 \pm 0.2) \times 10^{-8}$ at $z \approx 1.4$. From $\Omega_{\rm CIV}$, we estimate a lower limit on intergalactic medium metallicity $\log(Z_{\rm IGM}/Z_{\odot}) \gtrsim -3.25$ at $z \sim 2.3$, with a smooth decline at higher redshifts. These trends trace the cosmic star formation history and HeII photoheating rate, suggesting a link between CIV enrichment, star formation, and UV background over $\sim 3$ Gyr. The catalog also provides a critical resource for future studies connecting circumgalactic metals to galaxy evolution, especially near cosmic noon.