Brown Dwarfs in the Pleiades II. A deep optical and near-infrared survey
  The brown dwarf population in the Pleiades cluster has been probed in a deep 850 arcmin2 RIJK survey. The survey is complete to I=21.4 in 76% of the area and to I=20.2 in the remaining 24%. Photometry of 32 previously known members is presented together with 8 new candidates, four of which are below the brown dwarf limit. The faintest one is the lowest mass brown dwarf candidate found hitherto in the Pleiades (I=20.55, 0.04Msun). The derived Pleiades luminosity function is compared to the most recent theoretical mass-luminosity relations and is consistent with a power-law index in the mass function between 0 and 1 to the limit of this survey. 
Leif Festin