The bimodality in the mass–metallicity relation in SDSS-MaNGA galaxy pairs

Abstract

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, Σ*, 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.