Spatially resolved gas-phase metallicity at z ∼ 2─3 with JWST/NIRISS
August 2026 • 2026A&A...712A.136A
Abstract • Spatially resolved gas-phase metallicity maps are a crucial element in building our understanding of the chemical evolution of galaxies. We present spatially resolved metallicity maps obtained from NIRISS/WFSS observations in the first work delivering such an analysis of the slitless spectroscopy of multiple galaxies. We investigated the sources of ionization, metallicity, and their relation to star formation in a spatially resolved sense for a sample of eight galaxies: four from JWST-PASSAGE and four from GLASS-JWST ERS. All but one of these galaxies reside in the redshift range 1.9 ≤ z ≤ 2, the outlier being at z = 3.1. Our sample covers a range of 8.0 < log (M⋆/M⊙) < 9.5 in terms of stellar mass, 0.2 < log (SFR M⊙yr−1 ) < 1.1 in the star formation rate (SFR), and 7.8 < 12 + log(O/H) < 9.0 in the global gas metallicity. To resolve the question of the star formation-AGN separation in the absence of resolved Hα +[NII] lines, we present a new SF-demarcation line in the OHNO parameter space, based on MAPPINGS v5.1 publicly available H II region and AGN model grids, with the caveat that these grids partially overlap the OHNO parameter space. We present the mass-metallicity gradient relation for our sample, which show no clear trend with stellar mass. This might be because the high-z galaxies have not yet started their accretion-dominated evolutionary phase. By interpreting the correlation between spatially resolved metallicity and SFR maps as a proxy for effective timescales of metal-transport in galaxies, we find a possible trend that sees this timescale increasing with stellar mass. This is consistent with the picture of more effective feedback in lower mass galaxies and where massive galaxies generally tend to have longer characteristic timescales.
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