Structure and kinematics of the interacting group NGC 5098/5096

Context. Most galaxies in the Universe are found in groups that have various morphologies and dynamical states. Studying how groups evolve is an important step for our understanding of both large-scale structure formation and galaxy evolution. Aims. We analysed a system composed of two groups at z ≃ 0.037, NGC 5098, a group dominated by a pair of elliptical galaxies, and NGC 5096, a compact system that appears to be interacting with NGC 5098. We describe its current dynamical state in order to investigate how it fits in our current cosmological framework. Methods. Our analysis is based on deep Canada-France-Hawaii Telescope (CFHT/MegaCam) g and r imaging, archival Chandra X-ray data, and publicly available data of the galaxy redshift distribution. We modelled the surface brightness of the 12 brightest galaxies in the field of view and investigated the diffuse intragroup light that we detected. With a redshift sample of 112 galaxies, we studied the dynamical states of both groups. Results. We detected low surface brightness diffuse light associated with both galaxy–galaxy interactions and a possible group–group collision. The substructure we found in velocity space indicates a past interaction between the two groups. This is further corroborated by the X-ray analysis. Conclusions. We conclude that NGC 5098 and NGC 5096 form a complex system that may have collided in the past, thus producing a sloshing observed in X-rays and a large-scale diffuse component of intragroup light as well as some important tidal debris.