Kinematics and physical properties of southern interacting galaxies: the minor merger AM 2306–721

We present an observational study about the effects of the interactions in the kinematics, stellar population and abundances of the components of the galaxy pair AM 2306-721. Rotation curves for the main and companion galaxies were obtained, showing a deprojected velocity amplitude of 175 km s −1 and 185 km s −1 , respectively. The interaction between the main and companion galaxies was modeled using numerical N-body/hydrodynamical simulations, with the result indicating that the current stage of the merger wo uld be about 250 Myr after perigalacticum. The spatial variation in the distribution of th e stellar population components in both galaxies was analysed by fitting combinations of stella r population models of different age groups. The central region of main galaxy is dominated by an old (5-10 Gyr) population, while significant contributions from a young (200 Myr) and in termediate (1 Gyr) components are found in the disk, being enhanced in the direction of the t idal features. The stellar population of the companion galaxy is overall much younger, being dominated by components with 1 Gyr or less, quite widely spread over the whole disk. Spatia l profiles of the oxygen abundance were obtained from the a grid of photoionization models using the R23 line ratio. The disk of the main galaxy shows a clear radial gradient, while t he companion galaxy presents an oxygen abundance relatively homogeneous across the disk. The absence of an abundance gradient in the secondary galaxy is interpreted in terms of m ixing by gas flows from the outer parts to the center of the galaxy due to the gravitational int eraction with the more massive primary.