Photometry and dynamics of the minor merger AM 1219−430 with Gemini GMOS-S

Abstract

We present an observational study of the interaction effect on the dynamics and morphology of the minor merger AM1219-430. This work is based on r' and g' images and long-slit spectra obtained with the Gemini Multi-Object Spectrograph at the Gemini South Telescope. We detected a tidal tail in the main galaxy (AM1219A) and a bridge of material connecting the galaxies. In luminosity, AM1219A is about 3.8 times brighter than the secondary (AM1219B). The surface brightness profile of AM1219A was decomposed into bulge and disc components. The profile shows a light excess of ~ 53 % due to the contribution of star-forming regions, which is typical of starburst galaxies. On the other hand, the surface brightness profile of AM1219B shows a lens structure in addition to the bulge and disc. The scale lengths and central magnitudes of the disc structure of both galaxies agree with the average values derived for galaxies with no sign of ongoing interaction or disturbed morphology. The S\'ersic index (n<2), the effective and scale radii of the bulge of both galaxies are typical of pseudo-bulges. The rotation curve of AM1219A derived from the emission line of ionized gas is quite asymmetric, suggesting a gas perturbed by interaction. We explore all possible values of stellar and dark matter masses. The overall best-fitting solution for the mass distribution of AM1219A was found with M/L for bulge and disc of M/L_b=2.8_-0.4^+0.4 and M/L_d=2.4_-0.2^+0.3, respectively, and a Navarro, Frenk and White profile of M_200=2.0_-0.4^+0.5 x10^12 M_sun and c=16.0_-1.1^+1.2. The estimated dynamical mass is 1.6x10^11 M_sun, within a radius of ~ 10.6 kpc.