The Metallicity Evolution of Star-Forming Galaxies from Redshift 0 to 3:
  Combining Magnitude Limited Survey with Gravitational Lensing
  We present a comprehensive observational study of the gas phase metallicity
of star-forming galaxies from z ~ 0 -> 3. We combine our new sample of
gravitationally lensed galaxies with existing lensed and non-lensed samples to
conduct a large investigation into the mass-metallicity (MZ) relation at z > 1.
We apply a self-consistent metallicity calibration scheme to investigate the
metallicity evolution of star-forming galaxies as a function of redshift. The
lensing magnification ensures that our sample spans an unprecedented range of
stellar mass (3*10^{7}-6*10^{10} M_sun). We find that at the median redshift of
z=2.07, the median metallicity of the lensed sample is 0.35 dex lower than the
local SDSS star-forming galaxies and 0.18 dex lower than the z ~ 0.8 DEEP2
galaxies. We also present the z ~ 2 MZ relation using 19 lensed galaxies. A
more rapid evolution is seen between z ~ 1->3 than z ~ 0 -> 1 for the high-mass
galaxies (10^{9.5-11} M_sun), with almost twice as much enrichment between z ~
1 -> 3 than between z ~ 1 -> 0. We compare this evolution with the most recent
cosmological hydrodynamic simulations with momentum driven winds. We find that
the model metallicity is consistent with the observed metallicity within the
observational error for the low mass bins. However, for higher masses, the
model over-predicts the metallicity at all redshifts. The over-prediction is
most significant in the highest mass bin of 10^{10-11} M_sun.
