JADES: the chemical enrichment pattern of distant galaxies -- enhancement, silicon depletion, and iron enhancement
arXiv:2509.18055
Abstract
We present gas-phase abundances of carbon (C), -elements (O, Ne, Si, and Ar) and iron (Fe) obtained from stacked spectra of high- 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 [C/O], moderate [Ne/O], and low [Ar/O] values at a low gas-phase metallicity of (), suggesting dominant yields of core-collapse supernovae evolved from massive stars. The detection of a weak SiIII] emission line in our stacked spectrum provides a silicon-to-oxygen abundance ratio of [Si/O], which is lower than that of stars in the Milky Way disc and lower than expected by chemical evolution models, suggesting silicon depletion onto 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 , SFR, specific SFR (sSFR), and ultra-violet (UV) continuum slope , we identify [FeIII] 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- star-forming galaxies, while raising the possibility of anomalous, selective Fe/O enhancement at the very early epoch of star formation.
Accepted for publication in MNRAS