JWST Census for the Mass-Metallicity Star-Formation Relations at z=4-10 with the Self-Consistent Flux Calibration and the Proper Metallicity Calibrators

TL;DR

This study uses JWST/NIRSpec data to analyze the evolution of the mass-metallicity and SFR-metallicity relations at high redshifts z=4-10, revealing small metallicity evolution and a potential break in equilibrium at z>8.

Contribution

It provides a self-consistent flux calibration method and robust metallicity measurements for high-redshift galaxies, extending the MZ and SFR-MZ relations to z=10.

Findings

Small evolution of MZ relation from z~2-3 to z=4-10

No evolution of SFR-MZ relation up to z~8

Significant decrease in SFR-MZ relation at z>8

Abstract

We present the evolution of the mass-metallicity (MZ) relations at z=4-10 derived with 135 galaxies identified in the JWST/NIRSpec data taken from the three major public spectroscopy programs of ERO, GLASS, and CEERS. Because there are many discrepancies between flux measurements reported by early ERO studies, we first establish our NIRSpec data reduction procedure for reliable emission-line flux measurements and errors successfully explaining Balmer decrements with no statistical tensions via thorough comparisons of the early ERO studies. Applying the reduction procedure to the 135 galaxies, we obtain emission-line fluxes for physical property measurements. We confirm that 10 out of the 135 galaxies with [OIII]4363-lines have electron temperatures of (1.1-2.3)*10^4K, similar to lower-z star-forming galaxies, that can be explained by heating of young massive stars. We derive metallicities of the 10 galaxies by the direct method and the rest of the galaxies with strong lines by the metallicity calibrations of Nakajima et al. (2022) applicable for these low-mass metal-poor galaxies, anchoring the metallicities with the direct-method measurements. We thus obtain MZ relations and star-formation rate (SFR)-MZ relations over z=4-10. We find that there is a small evolution of the MZ relation from z~2-3 to z=4-10, while interestingly that the SFR-MZ relation shows no evolution up to z~8 but a significant decrease at z>8 beyond the error. This SFR-MZ relation decrease at z>8 may suggest a break of the metallicity equilibrium state via star-formation, inflow, and outflow, while further statistical and local-baseline studies are needed for a conclusion.