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
Journal:
Monthly Notices of the Royal Astronomical Society
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<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.
URL:
https://ui.adsabs.harvard.edu/#abs/2021MNRAS.502.4009B/abstract
Keywords:
galaxies: high-redshift;galaxies: ISM;quasars: absorption lines;Astrophysics - Astrophysics of Galaxies