Zahid, H. Jabran, Geller, Margaret J., Kewley, Lisa J., Hwang, Ho Seong, Fabricant, Daniel G., and Kurtz, Michael J. 2013. "The Chemical Evolution of Star-forming Galaxies over the Last 11 Billion Years." Astrophysical Journal Letters 771:L19. https://doi.org/10.1088/2041-8205/771/2/L19
We calculate the stellar mass-metallicity relation at five epochs ranging to z ~ 2.3. We quantify evolution in the shape of the mass-metallicity relation as a function of redshift; the mass-metallicity relation flattens at late times. There is an empirical upper limit to the gas-phase oxygen abundance in star-forming galaxies that is independent of redshift. From examination of the mass-metallicity relation and its observed scatter, we show that the flattening at late times is a consequence of evolution in the stellar mass where galaxies enrich to this empirical upper metallicity limit; there is also evolution in the fraction of galaxies at a fixed stellar mass that enrich to this limit. The stellar mass where metallicities begin to saturate is ~0.7 dex smaller in the local universe than it is at z ~ 0.8.