The effects of the interactions on the kinematics, stellar population and metallicity of AM2322−821 with Gemini/GMOS

Abstract

We present an observational study of the impacts of the interactions on the kinematics, stellar populations and oxygen abundances of the components of the galaxy pair AM2322−821. A fairly symmetric rotation curve for the companion (AM 2322B) galaxy with a deprojected velocity amplitude of 110 km s−1 was obtained, and a dynamical mass of 1.1–1.3 × 1010M within a radius of 4 kpc was estimated using this deprojected velocity. Asymmetries in the radial velocity field were detected for the companion, very likely due to the interaction between the galaxies. The interaction between the main and companion galaxies was modelled using numerical N-body/hydrodynamical simulations, with the result indicating that the current stage of the system would be about 90 Myr after perigalacticon. The spatial variation in the distribution of the stellar population components in both galaxies was analysed using the stellar population synthesis code STARLIGHT. The companion galaxy is dominated by a very young (t ≤ 1 × 108 yr) population, with the fraction that this population is of the total flux at λ 5870Å increasing outwards in the galaxy disc. On the other hand, the stellar population of AM2322A is heterogeneous along the slit positions observed. Spatial profiles of oxygen abundance in the gaseous phase were obtained using the diagnostic diagram R23 = ([O II]λ 3727 +[O III] λ 4959 +[O III] λ 5007)/Hβ versus [OIII]λ 5007/[O II]λ 3727 where we compared the observed values with the ones obtained from photoionization models. Such gradients of oxygen abundance are significantly flatter for this pair of galaxies than in typical isolated spiral galaxies. This metallicity distribution is interpreted as the gradients having been destroyed by interaction-induced gas flows from the outer parts to the centre of the galaxy.