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

TL;DR

This study investigates how galaxy interactions affect the kinematics, stellar populations, and metallicity distribution in the galaxy pair AM2322-821, revealing interaction-induced gas flows and recent star formation activity.

Contribution

It provides detailed observational analysis and modeling of the impact of galaxy interactions on kinematics, stellar populations, and metallicity gradients, using Gemini/GMOS data and simulations.

Findings

Companion galaxy shows symmetric rotation with 110 km/s velocity amplitude.

Interaction likely occurred about 90 million years ago.

Metallicity gradients are flatter than in isolated spiral galaxies.

Abstract

We present an observational study about the impacts of the interactions in the kinematics, stellar populations, and oxygen abundances of the components of the galaxy pair AM\,2322-821. 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 \times 10^{10} M_{\sun}$ 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 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 perigalacticum. The spatial variation in the distribution of the stellar-population components in both galaxies was analysed using the stellar population synthesis code {\sc STARLIGHT}. The companion galaxy is dominated by a very young (t $ \leq 1\times10^{8}$ yr) population, with the fraction of this population to the total flux at $\lambda\, 5\,870\, \AA$, increasing outwards in the galaxy disc. On the other hand, the stellar population of AM\,2322A is heterogeneous along the slit positions observed. Spatial profiles of oxygen abundance in the gaseous phase were obtained using the diagnostic diagram R23 vs. [OIII]/[OII], 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