Berg, Trystyn A. M.Trystyn A. M.BergFUMAGALLI, MICHELEMICHELEFUMAGALLID'ODORICO, ValentinaValentinaD'ODORICOEllison, Sara L.Sara L.EllisonLópez, SebastiánSebastiánLópezBecker, George D.George D.BeckerChristensen, LiseLiseChristensenCUPANI, GuidoGuidoCUPANIDenney, Kelly D.Kelly D.DenneySANCHEZ RAMIREZ, RUBENRUBENSANCHEZ RAMIREZWorseck, GáborGáborWorseck2022-03-292022-03-2920210035-8711http://hdl.handle.net/20.500.12386/32051We present the measured gas-phase metal column densities in 155 sub-damped Ly α systems (subDLAs) with the aim to investigate the contribution of subDLAs to the chemical evolution of the Universe. The sample was identified within the absorber-blind XQ-100 quasar spectroscopic survey over the redshift range 2.4 ≤ z<SUB>abs</SUB> ≤ 4.3. Using all available column densities of the ionic species investigated (mainly C IV, Si II, Mg II, Si IV, Al II, Fe II, C II, and O I; in order of decreasing detection frequency), we estimate the ionization-corrected gas-phase metallicity of each system using Markov chain Monte Carlo techniques to explore a large grid of CLOUDY ionization models. Without accounting for ionization and dust depletion effects, we find that the H I-weighted gas-phase metallicity evolution of subDLAs is consistent with damped Ly α systems (DLAs). When ionization corrections are included, subDLAs are systematically more metal poor than DLAs (between ≍0.5σ and ≍3σ significance) by up to ≍1.0 dex over the redshift range 3 ≤ z<SUB>abs</SUB> ≤ 4.3. The correlation of gas phase [Si/Fe] with metallicity in subDLAs appears to be consistent with that of DLAs, suggesting that the two classes of absorbers have a similar relative dust depletion pattern. As previously seen for Lyman limit systems, the gas phase [C/O] in subDLAs remains constantly solar for all metallicities indicating that both subDLAs and Lyman limit systems could trace carbon-rich ejecta, potentially in circumgalactic environments.STAMPAenArticle10.1093/mnras/stab1842-s2.0-85111186262http://arxiv.org/abs/2101.07821v1https://academic.oup.com/mnras/article/502/3/4009/6108280?login=true2021MNRAS.502.4009BFIS/05 - ASTRONOMIA E ASTROFISICA