Sub-damped Lyman α systems in the XQ-100 survey – II. Chemical evolution at 2.4 ≤ z ≤ 4.3

Berg, Trystyn AM; 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

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 ≤ zabs ≤ 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 ≤ zabs ≤ 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.

Citation

Berg, T. A., Fumagalli, M., D’Odorico, V., Ellison, S. L., López, S., Becker, G. D., …Worseck, G. (2021). Sub-damped Lyman α systems in the XQ-100 survey – II. Chemical evolution at 2.4 ≤ z ≤ 4.3. Monthly Notices of the Royal Astronomical Society, 502(3), 4009-4025. https://doi.org/10.1093/mnras/stab184

• Journal Article Type: Article
• Acceptance Date: Jan 18, 2021
• Online Publication Date: Jan 22, 2021
• Publication Date: 2021-04
• Deposit Date: Sep 21, 2021
• Publicly Available Date: Sep 21, 2021
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 502
• Issue: 3
• Pages: 4009-4025
• DOI: https://doi.org/10.1093/mnras/stab184
• Public URL: https://durham-repository.worktribe.com/output/1235750