Influence of the cluster environment on Seyfert galaxies

The frequency of Seyfert galaxies in Zwicky clusters has been explored on the basis of a fairly complete sample of 78 objects. No differences have been found between the distributions of Seyferts of type 1 and 2. The distribution of Seyferts members of a cluster as a function of the distance from the cluster center is found consistent with a uniform space density of these objects within a cluster, at variance with the density of normal galaxies. The general Seyfert frequency in clusters of different compactness and in the field is found to be extremely similar to that of late type spirals, and markedly different from those of ellipticals and lenticulars. The suggestion is made that the hosts of Seyferts were originally normal late type spirals, morphologically perturbed by the onset of the nuclear activity. The influence of the cluster environment, in this scheme, would be of indirect, rather than direct nature, acting on the morphological type of the host galaxy rather than on the Seyfert phenomenon itself.