3 Conclusions

We have imaged about 1deg² in the central region of the Pleiades young cluster using IZ broad-band filters, and identified more than 40 brown dwarf candidates with I magnitudes ranging from 17.5 to 22 (completeness is given by $I \sim 21$mag). This corresponds to a mass interval starting roughly at the substellar mass limit down to 0.03$M_{\odot}$ according to recent non-dusty evolutionary models by Chabrier et al. (1996). Follow-up IR and spectroscopic observations of seven of these candidates (Zapatero Osorio et al. 1997a) have revealed that they are very likely to be cluster brown dwarfs. Further data for the remaining candidates should definitely establish or refute cluster membership in the Pleiades. These studies will provide a solid foundation for deriving the cluster substellar mass function.

Acknowledgements

We thank the referee, J. Stauffer, for his valuable comments. We also thank the Comité Científico Internacional for awarding 25% of the International Time at the Observatories of the Canary Islands to this project in 1996-97. Partial financial support was provided by the Spanish DGES project no. PB95-1132-C02-01. A. M. acknowledges a NATO-CNR senior fellowship.