JADES: the chemical enrichment pattern of distant galaxies – α enhancement, silicon depletion, and iron enhancement

Journal article

We present gas-phase abundances of carbon (C), -elements (O, Ne, Si, and Ar), and iron (Fe) obtained from stacked spectra of high-z star-forming galaxies with the deep Near Infrared Spectrograph medium-resolution data from the James Webb Space Telescope Advanced Deep Extragalactic Survey. Our 564 sources at –7 have a median stellar mass of and a median star-formation rate of , placing them close to the star-formation main sequence. We find that the stacked spectrum of all our 564 sources has relatively low , moderate , and low values at a low gas-phase metallicity of (), suggesting dominant yields of core-collapse supernovae evolved from massive stars. The detection of a weak [Si iii] emission line in our stacked spectrum provides a silicon-to-oxygen abundance ratio of , which is lower than that of stars in the Milky Way disc and lower than expected by chemical evolution models, suggesting silicon depletion on to dust grains. Likewise, this Si/O value is lower than that we newly derive for two individual galaxies (GN-z11 and RXCJ2248) with negligible dust attenuation. By performing spectral stacking in bins of , star-formation rate (SFR), specific SFR (sSFR), and ultraviolet continuum slope , we identify [Fe iii] line detections in the high-sSFR bin and the blue- bin, both of which exhibit supersolar Fe/O ratios, while their C/O, Ar/O, and Si/O ratios are comparable to those of the all-sources stack. Our findings support a chemically young gas composition with rapid dust depletion in the general population of high-z star-forming galaxies, while raising the possibility of anomalous, selective Fe/O enhancement at the very early epoch of star formation.

Authors: Isobe, Y; Maiolino, R; Ji, X; D’Eugenio, F; Simmonds, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 547
• Issue: 3
• Pages: stag123
• Article number: stag123
• Publication date: 2026-01-19
• Acceptance date: 2026-01-12
• DOI: 10.1093/mnras/stag123
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: active; ISM: abundances; galaxies: high-redshift; galaxies: star formation