"Galaxy metallicity measurements at high redshift: probing galaxy growth over the past 12 billion years"
The scaling of galaxy gas-phase metallicity with stellar mass and star-formation rate is a sensitive probe of the cycle of baryons and galaxy growth. Characterizing the redshift evolution of these metallicity scaling relations provides a way to assess whether key processes governing galaxy growth (gas inflows, outflows, and star formation) proceed similarly throughout cosmic history. Accurately determining metallicity at high redshifts (z>1) is crucial to this approach, but the translation between strong emission-line ratios and metallicity is non-trivial. I will discuss the issues surrounding metallicity measurements at high redshifts, and detail the progress that has been made in this area using direct-method metallicities based on electron temperature measurements at z~1-3. I will present the mass-metallicity relation and fundamental metallicity relation (i.e., mass-SFR-metallicity) at z~2-3 based on both direct-method and strong-line ratio metallicities, and discuss the implications for baryon cycling.