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The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z ∼ 8

Curti, M, D'Eugenio, F, Carniani, S, Maiolino, R, Sandles, L, Witstok, J, Baker, WM, Bennett, JS, Piotrowska, JM, Tacchella, S, Charlot, S, Nakajima, K, Maheson, G, Mannucci, F, Amiri, A, Arribas, S, Belfiore, F, Bonaventura, NR, Bunker, AJ, Chevallard, J , Cresci, G, Curtis-Lake, E, Hayden-Pawson, C, Jones, GC, Kumari, N, Laseter, I, Looser, TJ, Marconi, A, Maseda, MV, Scholtz, J, Smit, R, Übler, H and Wallace, IEB (2022) The chemical enrichment in the early Universe as probed by JWST via direct metallicity measurements at z ∼ 8. Monthly Notices of the Royal Astronomical Society, 518 (1). pp. 425-438. ISSN 0035-8711

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We analyse the chemical properties of three z∼ 8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space Telescope. Exploiting [O III]λ4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12 + log(O/H)≈ 7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass-metallicity plane, the two galaxies at z ∼ 7.6 (log(M∗/M☉) = 8.1, 8.7) have metallicities that are consistent with the extrapolation of the mass-metallicity relation at z∼2-3, while the least massive galaxy at z ∼ 8.5 (log(M∗/M☉) = 7.8) shows instead a significantly lower metallicity. The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z∼ 7.6) being marginally consistent, while the z∼ 8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation, and metal enrichment in place at later epochs.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press (OUP)
SWORD Depositor: A Symplectic
Date Deposited: 16 Mar 2023 15:28
Last Modified: 16 Mar 2023 15:30
DOI or Identification number: 10.1093/mnras/stac2737
URI: https://researchonline.ljmu.ac.uk/id/eprint/19126

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