The Chemical Evolution of Star-Forming Galaxies Over the Last 11 Billion Years

Understand

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.