The bimodality in the mass-metallicity relation in SDSS-MaNGA galaxy
  pairs
  Aims: Interacting galaxies show a metallicity dilution compared to isolated
galaxies of similar masses in the mass-metallicity space at the global scale.
We investigate the spatially resolved mass-metallicity relation (MZR) of galaxy
pairs in the SDSS-MaNGA survey to confirm that the local relation between the
stellar mass surface density and the metallicity is consistent with the MZR at
the global scale. Methods: We investigate the relationship between the stellar
mass surface density and the metallicity abundance, 12+log (O/H), for
star-forming spaxels belonging to 298 galaxy pairs identified using visual and
kinematic indicators in the SDSS-MaNGA survey. We also investigate if a)the
location of a spaxel relative to the galaxy centre and b)the galaxy pair
separation have any effect on the local MZR. Results: We find that the
correlation between mass and metallicity holds for interacting galaxies at the
local level. However, we find two peaks in spaxel distribution, one peak with
enriched metallicity and the other with diluted metallicity. We find that the
spaxels belonging to the galaxy central regions (i.e. at lower R/Reff) are
concentrated close to the two peaks. We also find that the metallicity-diluted
spaxels belong to galaxy pairs with closer projected separations and that
spaxels with enriched metallicity belong to galaxy pairs with greater projected
separations. Conclusions: We find two discrete peaks in the spatially resolved
MZR for star-forming spaxels that belong to galaxy pairs. The peaks are likely
related to the galaxy projected separation or the stage of the interaction
process of a galaxy pair.
