Spectroscopic properties and dynamical evolution of the merging system AM 1003-435

Abstract

Aims. We study the system AM 1003-435, which is composed of two strong interacting galaxies. Methods. We obtained long-slit optical spectra of twelve zones of the system, and performed numerical simulations of the encounter between the components following the evolution of their stellar and gaseous contents. Results. The spectrum of the NW nucleus is typical of a starburst, while that of the SE one shows weak emission lines. The highest values of the oxygen and nitrogen abundances are at the NW nucleus. Its derived Hα and Hα + [N II] equivalent widths indicate very intense star formation, in accord to its starburst nature. Indicative ages of the starbursts in the nuclei were obtained. The morphological types of both components derived from their spectral characteristics are in agreement with previous determinations based on photometric parameters. About 70% of the measured Hα luminosity would correspond to the NW component contribution. The IR luminosity of the system is not high (LIR < 10 11 L� ). The estimated star formation rate for AM 1003-435 indicates that its activity is also moderate. The IR radiation, if it has the same origin as the Hα emission, would arise mostly from the NW component. The resulting abundances, burst ages, and masses suggest that the starburst in the SE component, the minor one, started earlier than that of the NW one, and did so in a medium poorer in weighted elements. On the other hand, from a set of N-body simulations of the encounter between both components it was found the time of the perigalacticum, to be comparable to the burst age derived for the SE component, and the star formation in both galaxies would have begun after the perigalacticum. It was also estimated that the central bodies will merge in about 1 Gyr.