The authors wish to thank their colleagues A. Hearn and M. Kuperus for many interesting discussions and suggestions. This work was performed as part of the research programme of FOM with financial support from NWO. This work was sponsored by the Stichting Nationale Computerfaciliteiten (National Computing Facilities Foundation, NCF) for the use of supercomputer facilities, with financial support from NWO.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998