We thank Magda Arnaboldi and Linda Sparke for the useful discussion about the case of AM 2020-504. We are indebted to Bradley Whitmore for kindly proving us the image of NGC 4672 we used in Fig. 1. Marc Sarzi acknowledges the Max-Planck-Institut für Astronomie in Heidelberg for the hospitality while this paper was in progress. This research has made use of the Lyon-Meudon Extragalactic Database (LEDA) and of the NASA/IPAC Extragalactic Database (NED).
© European Southern Observatory (ESO) 2000
Online publication: August 17, 2000