Evolution of CIV Absorbers I. The Cosmic Incidence

Abstract

We present a large high-resolution study of the distribution and evolution of C iv absorbers, including the weakest population with equivalent widths W r < 0.3 Å. By searching 369 high-resolution, high signal-to-noise spectra of quasars at 1.1 ≤ z em ≤ 5.3 from Keck/HIRES and VLT/UVES, we find 1318 C iv absorbers with W r ≥ 0.05 Å (our ∼ 50% completeness limit) at redshifts 1.0 ≤ z ≤ 4.75. A Schechter function describes the observed equivalent width distribution with a transition from powerlaw to exponential decline at W r 0.5 Å. The power-law slope α rises and normalization n falls by ∼ 20% from 1.0 ≤ z < 2.5 to 2.5 ≤ z ≤ 4.75. We find that the co-moving redshift path density, dN/dX, of W r ≥ 0.05 Å absorbers rises by ∼ 1.8 times from z = 4.75 to z = 1, while the increase in the W r ≥ 0.6 Å dN/dX is ∼ 4.5 times as much. We quantify the observed evolution by a model in which dN/dX decreases linearly with increasing redshift. The model suggests that populations with larger W r thresholds evolve faster with redshift and appear later in the universe. The cosmological Technicolor Dawn simulations at 3 ≤ z ≤ 5 over-produce the observed abundance of absorbers with W r ≤ 0.3 Å, while yielding good agreement at higher W r . Our empirical linear model successfully describes C iv evolution in the simulations and the observed evolution of W r ≥ 0.6 Å C iv for the past ∼12 Gyr. Combining our measurements with the literature gives us a picture of C iv-absorbing structures becoming more numerous and/or larger in physical size over the last ≈13 Gyr of cosmic time (z ∼ 6 to z ∼ 0).

The CGM at Cosmic Noon with KCWI: Outflows from a Star-forming Galaxy at z = 2.071

“…The latter quasar sample includes many quasars that are listed in KODIAQ DR2 (O'Meara et al 2017). The absorbers were drawn from the Mathes et al (2017) and Hasan et al (2020) sample, where Mg ii and Civ absorption were systematically and automatically searched using a matched-filter analysis similar to Zhu & Ménard (2013) and then later visually confirmed.…”

Probing the He II re-Ionization ERa via Absorbing C IV Historical Yield (HIERACHY) I: A Strong Outflow from a z~4.7 Quasar

“…Except for component "c" of the 0th absorption system (partial covering, broad and close to quasar), as listed in Table 3 and shown in Fig. 3, we can not rule out the possibility that these absorption features are from the intervening inter-galactic absorbers (e.g., Hasan et al 2020). The derived velocity for component "c" of the 0th absorption system is small and has a large error (i.e., −124.5 ± 264 km s −1 ), therefore it may be produced by any kinds of gas closed to quasar (e.g., outflow gas, infalling gas and gas within host galaxies).…”