Photometry and dynamics of the minor mergers AM 1228-260 and AM 2058-381

Abstract

We investigate interaction effects on the dynamics and morphology of the galaxy pairs AM 2058-381 and AM 1228-260. This work is based on r images and long-slit spectra obtained with the Gemini Multi-Object Spectrograph at the Gemini South Telescope. The luminosity ratio between the main (AM 2058A) and secondary (AM 2058B) components of the first pair is a factor of ∼ 5, while for the other pair, the main (AM 1228A) component is 20 times more luminous than the secondary (AM 1228B). The four galaxies have pseudobulges, with a S´ersic index n < 2. Their observed radial velocities profiles (RVPs) present several irregularities. The receding side of the RVP of AM 2058A is displaced with respect to the velocity field model, while there is a strong evidence that AM 2058B is a tumbling body, rotating along its major axis. The RVPs for AM 1228A indicate a misalignment between the kinematic and photometric major axes. The RVP for AM 1228B is quite perturbed, very likely due to the interaction with AM 1228A. NFW halo parameters for AM 2058A are similar to those of the Milky Way and M 31. The halo mass of AM 1228A is roughly 10 per cent that of AM 2058A. The mass-to-light (M/L) of AM 2058 agrees with the mean value derived for late-type spirals, while the low M/L for AM 1228A may be due to the intense star formation ongoing in this galaxy.