JADES: the mass-metallicity relation at $z=1-10$. New calibrations, extremely metal-poor galaxies, and chemical diversity

Yuki Isobe, Mirko Curti, Roberto Maiolino, Qiao Duan, William McClymont, Dávid Puskás, Francesco D'Eugenio, Pierluigi Rinaldi, James A. A. Trussler, Jan Scholtz, Tobias J. Looser, Erica Nelson, Xihan Ji, Danial Langeroodi, Sandro Tacchella, Gareth C. Jones, Ignas Juodžbalis, Robert G. Pascalau, Tiger Yu-Yang Hsiao, Hannah Übler, William M. Baker, Andrew J. Bunker, Stefano Carniani, Stéphane Charlot, Emma Curtis-Lake, Sophia Geris, Maria Koller, Jianwei Lyu, Brant Robertson, Christina C. Williams, Zihao Wu

First listed 2026-06-11 | Last updated 2026-06-09

Abstract

We present gas-phase metallicities of star-forming galaxies at $z=1$-10 with deep JWST/NIRSpec spectra from the JADES full data release, Dark Horse, and OASIS programmes. We stack $\sim$1500 medium-resolution spectra, yielding detections of the [OIII]$λ$4363 auroral line down to $12+\log(\mathrm{O/H})=7.0$ to derive stack-based strong-line calibrations over the metallicity range $12+\log(\mathrm{O/H})=7.0$-8.7. At a fixed metallicity, our stacks exhibit [OIII]$λ$5007/H$β$ and [OIII]$λ$5007/[OII]$λλ$3726,3729 values generally lower than calibrations based on high-$z$ individual auroral-line emitters, suggesting an observational bias towards higher excitation introduced when requiring auroral line detections in individual spectra. Based on our new calibrations, we obtain canonical mass-metallicity relations (MZRs) at z$=$1-10, identifying a decrease in metallicities from $z\sim0$ to z$\sim$4-10, without significant change in slope. Moreover, we identify 50 promising candidates of extremely metal-poor galaxies (EMPGs) with $12+\log(\mathrm{O/H})=6.7$-7.3 (1-4\% solar metallicity) at $z=1.2$-9.1. The MZRs of EMPGs are characterised by a large scatter, with those having lower metallicities generally exhibiting lower sSFRs, opposite of what expected from the local Fundamental Metallicity Relation. These results support a stochastic star-formation history involving gas consumption/ejection and metal-poor inflow, strongly affecting metallicities of low-mass galaxies. Furthermore, we identify two Little Red Dots in our EMPG candidates, both exhibiting broad H$α$ and prominent Ly$α$, offering insights into the early black-hole growth in extremely metal-poor environments.

Short digest

This paper builds new high-redshift metallicity calibrations by stacking about 1500 JWST/NIRSpec medium-resolution spectra from JADES, Dark Horse, and OASIS, detecting the [OIII] λ4363 auroral line down to 12+log(O/H)=7.0 and extending stack-based strong-line calibrations across 12+log(O/H)=7.0-8.7. A key result is that, at fixed metallicity, the stacks show lower [OIII] λ5007/Hβ and [OIII] λ5007/[OII] λλ3726,3729 than calibrations based on individual auroral-line emitters, implying that auroral-selected samples are biased toward unusually high-excitation systems. With these recalibrations the authors recover canonical mass-metallicity relations from z=1 to 10, with metallicity dropping from z∼0 to z∼4-10 but little change in slope, and they identify 50 promising EMPG candidates at 12+log(O/H)=6.7-7.3 across z=1.2-9.1. Those EMPGs show large metallicity scatter and an inverted sSFR trend relative to the local FMR, favoring stochastic gas cycling, while two EMPG candidates are also Little Red Dots with broad Hα and prominent Lyα, linking near-pristine conditions to early black-hole growth.

Key figures to inspect

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• Figure 3. Figure recommendations could not be made reliably because no figure captions were supplied, and I am not willing to invent figure numbers without a caption list.