Sub-damped Lyman α systems in the XQ-100 survey – II. Chemical evolution at 2.4 ≤ z ≤ 4.3. Issue 3 (22nd January 2021)

• Record Type: Journal Article
• Authors: Berg, Trystyn A M; Fumagalli, Michele; D'Odorico, Valentina; Ellison, Sara L; López, Sebastián; Becker, George D; Christensen, Lise; Cupani, Guido; Denney, Kelly D; Sánchez-Ramírez, Rubén; Worseck, Gábor
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 502:Issue 3(2021)
• Page Start: 4009
• Page End: 4025
• Publication Date: 2021-01-22
• Subjects: galaxies: high-redshift -- galaxies: ISM -- quasars: absorption lines; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab184
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We 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 abs ≤ 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 abs ≤ 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.