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arXiv · 2511.00705

The JWST EXCELS Survey: gas-phase metallicity evolution at 2 < z < 8

T. M. Stanton·F. Cullen·A. C. Carnall·D. Scholte·K. Z. Arellano-Córdova·A. E. Shapley·D. J. McLeod·C. T. Donnan·R. Begley·R. Davé·J. S. Dunlop·R. J. McLure·K. Rowlands·C. Bondestam·M. L. Hamadouche·H. -H. Leung·S. D. Stevenson·E. Taylor
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Abstract

We present an analysis of the gas-phase mass-metallicity relationship (MZR) and fundamental metallicity relationship (FMR) for $65$ star-forming galaxies at $2 < z < 8$ from the JWST/EXCELS survey. We calculate gas-phase metallicities (12 + log(O/H)) using strong-line calibrations explicitly tested against the EXCELS sample, and report direct-method metallicities for $19$ galaxies. Our sample spans $8.1<\log(\rm M_\star/M_\odot)<10.3$ and $0<\log(\rm SFR/M_\odot \, yr^{-1})<2$, consistent with main-sequence star-forming galaxies at the same redshifts. We find a clear MZR at both $2 3$ studies. We discuss potential drivers of this offset, noting that high-redshift samples have significantly different physical properties compared to local samples used to define the $z=0$ FMR. Our results confirm that low-mass, high specific star-formation rate galaxies common at high redshift are inconsistent with the equilibrium conditions underlying the local FMR, and highlight the rapid chemical enrichment at early cosmic epochs.

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T. M. Stanton, F. Cullen, A. C. Carnall, D. Scholte, K. Z. Arellano-Córdova, A. E. Shapley, D. J. McLeod, C. T. Donnan, R. Begley, R. Davé, J. S. Dunlop, R. J. McLure, K. Rowlands, C. Bondestam, M. L. Hamadouche, H. -H. Leung, S. D. Stevenson, E. Taylor. 2025-11-01. The JWST EXCELS Survey: gas-phase metallicity evolution at 2 < z < 8. https://doi.org/10.1093/mnras%2Fstag449

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