Coevolution of metallicity and star formation in galaxies to z=3.7: II.
  A theoretical model
  Recent work suggests that galaxy evolution, and the build-up of stellar mass
(M*) over cosmic time, is characterized by changes with redshift of star
formation rate (SFR) and oxygen abundance (O/H). In a companion paper, we have
compiled a large dataset to study Metallicity Evolution and Galaxy Assembly
(MEGA), consisting of roughly 1000 galaxies to z=3.7 with a common O/H
calibration. Here we interpret the MEGA scaling relations of M*, SFR, and O/H
with an updated version of the model presented by Dayal et al. (2013). This
model successfully reproduces the observed O/H ratio of 80,000 galaxies
selected from the Sloan Digital Sky Survey to within 0.05-0.06 dex. By
extending the model to the higher redshift MEGA sample, we find that although
the specific mass loading of outflows does not change measurably during the
evolution, the accretion rate and gas content of galaxies increase
significantly with redshift. These two effects can explain, either separately
or possibly in tandem, the observed lower metal abundance of high-z galaxies.
