Dumbbell Galaxies and Multiple Nuclei in Rich Clusters: Radio Data (Poster paper)

Summary

ABSTRACT

We present preliminar results of radio observations of 78 southern rich clusters, whose brightest member is a dumbbell galaxy or a multiple nucleus. We identified 41 radio sources with the cluster brightest member: 23 of the 44 observed have a multiple nucleus, and 18 of the 34 mapped have a dumbbell galaxy.

INTRODUCTION

In many galaxy clusters, the first–ranked galaxy is not a single isolated object but has two or more components. Such galaxies show a wide range of morphologies, from dumbbell systems (two galaxies of roughly equal brightness (Δm < 1 – 2) inside a common halo) to galaxies with multiple nuclei (two or more condensations visible within the image of a single galactic spheroid, with each secondary nucleus at least two magnitudes fainter than the main system).

It is likely that in some multiple systems the companions are gravitationally bound to the central galaxy (often a cD) and may eventually be cannibalized; while in others we see unbound galaxies whose eccentric orbits in the cluster potential well bring them close to the cluster center where the cD is located (Tonry 1985).

Since many active galaxies are located in dense environments and show signs of interaction, it has often been suggested that gravitational interactions between galaxies may trigger nuclear activity.