A deep photometric survey of the η Chamaeleontis cluster down to the brown dwarf -: planet boundary

We report the outcome of the deep optical/infrared photometric survey of the central region (33 x 33 arcmin(2) or 0.9 pc(2)) of the eta Chamaeleontis (eta Cha) pre-main sequence star cluster. The completeness limits of the photometry are I = 19.1, J = 18.2 and H = 17.6, faint enough to reveal low-mass members down to the brown dwarf and planet boundary of approximate to 13 M-Jup. We found no such low-mass members in this region. Our result combined with a previous shallower (I = 17) but larger area survey indicates that low-mass objects (0.013 < M/M-circle dot < 0.075) were either not created in the eta Cha cluster or lost due to the early dynamical history of the cluster and ejected to outside the surveyed areas.