Data from the literature were obtained with the Lyon Meudon Extragalactic database (LEDA), supplied by the LEDA team at CRAL-Observatoire de Lyon (France). We thank Raphaïl Moreno (IRAM) and the staff of OHP for assistance at the telescopes. We thank the referee, I. Shlosman, for fruitful comments.
© European Southern Observatory (ESO) 1997
Online publication: July 8, 1998