  The evolution of the metal content of galaxies and its relations to other
global properties [such as total stellar mass (M*), circular velocity, star
formation rate (SFR), halo mass, etc.] provides important constraints on models
of galaxy formation. Here we examine the evolution of metallicity scaling
relations of simulated galaxies in the Galaxies-Intergalactic Medium
Interaction Calculation suite of cosmological simulations. We make comparisons
to observations of the correlation of gas-phase abundances with M* (the
mass-metallicity relation, MZR), as well as with both M* and SFR or gas mass
fraction (the so-called 3D fundamental metallicity relations, FMRs). The
simulated galaxies follow the observed local MZR and FMRs over an order of
magnitude in M*, but overpredict the metallicity of massive galaxies (log M* >
10.5), plausibly due to inefficient feedback in this regime. We discuss the
origin of the MZR and FMRs in the context of galactic outflows and gas
accretion. We examine the evolution of mass-metallicity relations defined using
different elements that probe the three enrichment channels (SNII, SNIa, and
AGB stars). Relations based on elements produced mainly by SNII evolve weakly,
whereas those based on elements produced preferentially in SNIa/AGB exhibit
stronger evolution, due to the longer timescales associated with these
channels. Finally, we compare the relations of central and satellite galaxies,
finding systematically higher metallicities for satellites, as observed. We
show this is due to the removal of the metal poor gas reservoir that normally
surrounds galaxies and acts to dilute their gas-phase metallicity (via
cooling/accretion onto the disk), but is lost due to ram pressure stripping for
satellites.
