Galaxy Mergers and the Mass-Metallicity Relation: Evidence for Nuclear
  Metal Dilution and Flattened Gradients from Numerical Simulations
  Recent results comparing interacting galaxies to the mass-metallicity
relation show that their nuclear oxygen abundances are unexpectedly low. We
present analysis of N-body/SPH numerical simulations of equal-mass mergers that
confirm the hypothesis that these underabundances are accounted for by radial
inflow of low-metallicity gas from the outskirts of the two merging galaxies.
The underabundances arise between first and second pericenter, and the
simulated abundance dilution is in good agreement with observations. The
simulations further predict that the radial metallicity gradients of the disk
galaxies flatten shortly after first passage, due to radial mixing of gas.
These predictions will be tested by future observations of the radial
metallicity distributions in interacting galaxies.
