The MOSDEF Survey: The Evolution of the Mass-Metallicity Relation from z = 0 to z 3.3

We investigate the evolution of galaxy gas-phase metallicity (O/H) over the range z = 0-3.3 using samples of ~300 galaxies at z ~ 2.3 and ~150 galaxies at z ~ 3.3 from the MOSDEF survey. This analysis crucially utilizes different metallicity calibrations at z ~ 0 and z > 1 to account for evolving interstellar medium (ISM) conditions. We find significant correlations between O/H and stellar mass (M_*) at z ~ 2.3 and z ~ 3.3. The low-mass power-law slope of the mass-metallicity relation (MZR) is remarkably invariant over z = 0-3.3, such that O/H ∝ ${M}_{* }^{0.30}$ at all redshifts in this range. At fixed M_*, O/H decreases with increasing redshift as dlog(O/H)/dz = -0.11 ± 0.02. We find no evidence that the fundamental metallicity relation between M_*, O/H, and star formation rate evolves out to z ~ 3.3. We employ analytic chemical evolution models to place constraints on the mass and metal loading factors of galactic outflows. The efficiency of metal removal increases toward lower M_* at fixed redshift and toward higher redshift at fixed M_*. These models suggest that the slope of the MZR is primarily set by the scaling of the outflow metal loading factor with M_*, not by the change in gas fraction as a function of M_*. The evolution toward lower O/H at fixed M_* with increasing redshift is driven by both higher gas fraction (leading to stronger dilution of ISM metals) and higher metal removal efficiency. These results suggest that the processes governing the smooth baryonic growth of galaxies via gas flows and star formation hold in the same form over at least the past 12 Gyr. ^* Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W.M. Keck Foundation.