  Nuclear inflows of metal-poor interstellar gas triggered by galaxy
interactions can account for the systematically lower central oxygen abundances
observed in local interacting galaxies. Here, we investigate the metallicity
evolution of a large set of simulations of colliding galaxies. Our models
include cooling, star formation, feedback, and a new stochastic method for
tracking the mass recycled back to the interstellar medium from stellar winds
and supernovae. We study the influence of merger-induced inflows, enrichment,
gas consumption, and galactic winds in determining the nuclear metallicity. The
central metallicity is primarily a competition between the inflow of
low-metallicity gas and enrichment from star formation. An average depression
in the nuclear metallicity of ~0.07 is found for gas-poor disk-disk
interactions. Gas-rich disk-disk interactions, on the other hand, typically
have an enhancement in the central metallicity that is positively correlated
with the gas content. The simulations fare reasonably well when compared to the
observed mass-metallicity and separation-metallicity relationships, but further
study is warranted.
