LATIS: The Stellar Mass–Metallicity Relation of Star-forming Galaxies at z ∼ 2.5

We present the stellar mass–stellar metallicity relation for 3491 star-forming galaxies at 2 ≲ z ≲ 3 using rest-frame far-ultraviolet spectra from the Ly α Tomography IMACS Survey (LATIS). We fit stellar population synthesis models from the Binary Population And Spectral Synthesis code (v2.2.1) to medium-resolution ( R ∼ 1000) and high signal-to-noise (>30 per 100 km s −1 over the wavelength range 1221–1800 Å) composite spectra of galaxies in bins of stellar mass to determine their stellar metallicity, primarily tracing Fe/H. We find a strong correlation between stellar mass and stellar metallicity, with stellar metallicity monotonically increasing with stellar mass at low masses and flattening at high masses ( M * ≳ 10 10.3 M ⊙ ). Additionally, we compare our stellar metallicity measurements with the gas-phase oxygen abundance of galaxies at similar redshift and estimate the average [ α /Fe] ∼ 0.6. Such high α -enhancement indicates that high-redshift galaxies have not yet undergone significant iron enrichment through Type Ia supernovae. Moreover, we utilize an analytic chemical evolution model to constrain the mass loading parameter of galactic winds as a function of stellar mass. We find that as the stellar mass increases, the mass loading parameter decreases. The parameter then flattens or reaches a turning point at around M * ∼ 10 10.5 M ⊙ . Our findings may signal the onset of black-hole-driven outflows at z ∼ 2.5 for galaxies with M * ≳ 10 10.5 M ⊙ .