Astronomy Colloquium

Local star-forming galaxies obey a striking correlation between
stellar mass and metallicity spanning five orders of magnitude in mass and a factor of 300 in metallicity. The gas-phase metallicity of a galaxy reflects its integrated star formation history, modulo inflows and outflows of gas and metals; therefore, the mass-metallicity relation, and its evolution with redshift, serves as a powerful metric of galaxy evolution. We have measured the mass-metallicity relation at 0.011. However, we have identified an intriguing population of luminous/massive metal-poor galaxies at z~0.7 that must trace a much more rapid
chemical enrichment history to reach the present-day mass-metallicity relation. Finally, I compare these results to observations of star-forming galaxies at z=1-2, and discuss the challenges of extending metallicity measurements to lower mass/luminosity and higher redshift.