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JADES: Insights on the low-mass end of the mass--metallicity--star-formation rate relation at 3 < z < 10 from deep JWST/NIRSpec spectroscopy Published: 4/17/2023 9:00:01 PM Updated: 9/11/2023 11:55:00 PM

Paper abstract: We analyse the gas-phase metallicity properties of a sample of low stellarmass (log M*/M_sun <= 9) galaxies at 3 < z < 10, observed with JWST/NIRSpec aspart of the JADES programme in its deep GOODS-S tier. By combining this samplewith more massive galaxies at similar redshifts from other programmes, we studythe scaling relations between stellar mass, oxygen abundance (O/H), andstar-formation rate (SFR) for 146 galaxies, spanning across three orders ofmagnitude in stellar mass and out to the epoch of early galaxy assembly. Wefind evidence for a shallower slope at the low-mass-end of the mass-metallicityrelation (MZR), with 12 + log(O/H) = (7.72+-0.02) + (0.17+-0.03) log(M* / 10^8M_sun), in good agreement with the MZR probed by local analogues ofhigh-redshift systems like 'Green Pea' and 'Blueberry' galaxies. The inferredslope is well matched by models including 'momentum-driven' SNe winds,suggesting that feedback mechanisms in dwarf galaxies (and at high-z) might bedifferent from those in place at higher masses. The evolution in thenormalisation is observed to be relatively mild compared to previousdeterminations of the MZR at z~3 (~ 0.1 - 0.2 dex across the explored massregime). We observe a deviation from the local fundamental metallicity relation(FMR) for our sample at high redshift, especially at z > 6, with galaxiessignificantly less enriched (with a median offset in log(O/H) of ~ 0.5 dex,significant at ~ 5 sigma) than predicted given their M* and SFR. Theseobservations are consistent with an enhanced stochasticity in thestar-formation history, and/or with an increased efficiency in metal removalsby outflows, prompting us to reconsider the nature of the relationship betweenM*, O/H, and SFR in the early Universe.