Fig. 3: The stellar mass–metallicity relation and the ionization diagnostic diagram.
From: A luminous and young galaxy at z = 12.33 revealed by a JWST/MIRI detection of Hα and [O iii]
Left: position of GHZ2 in the stellar mass–metallicity plane in comparison to lower-redshift galaxies at z ≈ 4–9 (black dots for individual galaxies and purple line for best-fitting relationship38) and the z = 10–13 galaxies from the JADES survey14 (green points; metallicity estimated from fitting the SED). Error bars represent 1σ uncertainties in the stellar mass values and the range of allowed values for the metallicities. None of the z > 10 galaxies, including GHZ2, are on the lower-redshift relationship38, suggesting an evolution towards lower metallicities at earlier epochs. The predictions from the FIRE80 (golden line) and ASTRAEUS81 (grey region) simulations at z ≈ 10 are in broad agreement with the current constraints, whereas the IllustrisTNG82 simulations (blue region) predict slightly higher metallicities, although still consistent within the error bars. Despite being at very high redshifts, none of these galaxies show pristine (close-to-zero) metallicities, implying a rapid metal enrichment in the early Universe. Right: [N ii]/Hα versus [O iii]/Hβ diagram along with predictions from a stellar photoionization model20 assuming four different metallicities and six ionization parameters in steps of 0.5 dex (symbol sizes increase with ionization parameter). Note that models with Z ≲ 0.01 Z⊙ would lie below the dashed line. The observational constraints on the R3 value (formally a lower limit derived under the assumption of zero dust attenuation) implies high ionizing conditions, with \(\log (U) > -2.0\).
