The Multi-object Spectroscopy Observation of Seven Interacting Galaxy Pairs: Metallicity Gradients and Star Formation Distributions

Abstract

We use the Multi-Object Spectroscopy system of Xinglong 2.16 m telescope to study the gradients of gas-phase oxygen abundance and the distributions of star formation activities of seven nearby interacting galaxy pairs. On the basis of emission line luminosities and flux ratios, we estimate the gas-phase metallicities (log(O/H)), excitation mechanisms, and star formation rates (SFRs) of different regions in each galaxy. The average radial slope of log(O/H) from linear fitting of galaxy pairs in our sample is significantly flatter than that of isolated disk galaxies, also the central metallicity is much lower for interacting galaxies. This supports the predictions and results of previous theoretical numerical simulations and observational works which show the cold gas inflows induced by galaxy interactions can dilute the central metallicity. From the analysis of the radial distribution of SFR surface densities (ΣSFR), we find that, in our sample, galaxies in Spiral–Spiral (S+S) pairs have peak ΣSFR at the center region and lower SFRs at the outer parts than that at the center. On the other hand, for two spirals in Spiral-Elliptical (S+E) pairs (Arp142 and J0338+2120), they both have relatively higher (ΣSFR) in their off-nuclei regions. This may hint a dependence of star formation distributions for paired galaxies on their companion morphologies.