The Cosmic Evolution of C IV Absorbers at 1.4 < z < 4.5: Insights from 100,000 Systems in DESI Quasars

We present the largest catalog to date of triply ionized carbon (C iv) 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 C iv systems in the redshift range 1.4 &lt; z &lt; 4.5 from 300,637 quasar spectra. Completeness is estimated via Monte Carlo simulations, and the catalog is 50% complete at EWC IV ≥ 0.4 Å. 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 ≈ 4.5 to z ≈ 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 C iv, ΩC IV, which increases by a factor of ∼3.8 from (0.82 ± 0.05) × 10−8 at z ≈ 4.5 to (3.16 ± 0.2) × 10−8 at z ≈ 1.4. From ΩC IV, we estimate a lower limit on intergalactic medium metallicity log ( Z IGM / Z ⊙ ) ≳ − 3.25 at z ∼ 2.3, with a smooth decline at higher redshifts. These trends trace the cosmic star formation history and He ii photoheating rate, suggesting a link between C iv enrichment, star formation, and UV background over ∼3 Gyr. The catalog also provides a critical resource for future studies connecting circumgalactic metals to galaxy evolution, especially near cosmic noon.