A Population of very young Brown Dwarfs and free-floating Planets in Orion

We describe the results of a very deep imaging survey of the TrapeziumCluster in the IJH bands, using the UKIRT high resolution camera UFTI.Approximately 320f the 515 point sources detected are brown dwarf candidates,including several free floating objects with masses below the Deuterium burning(planetary) threshold at 0.013 solar masses, which are detectable because oftheir extreme youth. We have confidence that almost all the sources detectedare cluster members, since foreground contamination is minimal in the 33arcmin^2 area surveyed and the dense backdrop of OMC-1 obscures all backgroundstars at these wavelengths. Extinction is calculated from the (J-H)colours,permitting accurate luminosity estimates and temperatures are derived from thedereddened (I-J) colours. There is some evidence for a cut-off in theluminosity function below the level corresponding to several Jupiter masses,which may represent the bottom end of the IMF. Since star formation is completein the Trapezium this limit could have wide significance, if confirmed.However, it could well be an effect of the dispersal of the molecular cloud bythe central O-type stars, a process whose timescale will vary between starformation regions.