Adaptive optics imaging of the orion trapezium cluster

We have imaged an area similar to 5 arcmin(2) at the center of the Trapezium cluster in Orion in the K band using the University of Hawaii (UH) adaptive optics system at the UH 2.2 m telescope. Our survey detects 292 stars brighter than K = 18.2 mag and resolves pairs to the 0." 23 diffraction limit of the telescope. The binary fraction in the angular separation range 0." 3-0." 6, corresponding to 132-264 AU at 440 pc, is indistinguishable from that of the solar-like stars in the solar neighborhood. Proplyds are associated with both single stars and visual binaries. About half the stars in our sample have also been measured at V and I by Presser et al.; most of these seem to be about 10(6) yr old, observed through moderate extinction, and having some excess emission at K. The luminosity function turns over before the stellar limit of similar to 13.5 mag, indicating that the cluster does not contain a large population of massive brown dwarfs.