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Metal-enriched galaxies in the first ∼1 billion years: evidence of a smooth metallicity evolution at z ∼ 5

Abstract : We present seven new abundance measurements of the elements O, C, and Si at z > 4.5, doubling the existing sample of weakly depleted elements in gas-rich galaxies, in order to constrain the first ∼1 billion years of cosmic metal evolution. These measurements are based on quasar spectra of damped Lyman α absorbers (DLAs) and sub-DLAs obtained with the Magellan Inamori Kyocera Echelle (MIKE) and Magellan Echellette (MagE) spectrographs on Magellan-South, and the X-Shooter spectrograph on the Very Large Telescope. We combine these new measurements with those drawn from the literature to estimate the N_{H I}-weighted binned mean metallicity of -1.51 ± 0.18 at z = 4.8. This metallicity value is in excellent agreement with the prediction from lower redshift DLAs, supporting the interpretation that the metallicity evolution is smooth at z ∼ 5, rather than showing a sudden decline at z > 4.7. Furthermore, the metallicity evolution trends for the DLAs and sub-DLAs are similar within our uncertainties. We also find that the [C/O] ratios for z ∼ 5 DLAs are consistent with those of the very metal-poor DLAs. Additionally, using [C/O] and [Si/O] to constrain the nucleosynthesis models, we estimate that the probability distributions of the progenitor star masses for three relatively metal-poor DLAs are centred around 12-17 M. Finally, the z ∼ 5 absorbers show a different metallicity-velocity dispersion relation than lower redshift DLAs, suggesting that they may be tracing a different population of galaxies.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Friday, May 13, 2022 - 10:43:53 AM
Last modification on : Saturday, June 25, 2022 - 3:17:15 AM


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Suraj Poudel, Varsha P. Kulkarni, Frances H. Cashman, Brenda Frye, Céline Péroux, et al.. Metal-enriched galaxies in the first ∼1 billion years: evidence of a smooth metallicity evolution at z ∼ 5. Monthly Notices of the Royal Astronomical Society, 2020, 491, pp.1008-1025. ⟨10.1093/mnras/stz3000⟩. ⟨insu-03667140⟩



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