Jabran Zahid, Margaret Geller, Lisa Kewley, Ho Seong Hwang, Daniel Fabricant, Michael Kurtz
We measure the stellar mass-metallicity relation at five epochs ranging to z~2.3. We quantify, for the first time, 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. These observations provide a benchmark for theoretical and observational studies of the chemical evolution of star-forming galaxies.
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http://arxiv.org/abs/1303.5987
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