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The star-forming regions in Chamaeleon are one of the nearest (distance ~165pc) and youngest (age ~2 Myrs) conglomerates of recently formed stars and theideal target for population studies of star formation. We investigate a totalof 16 Cha targets, which have been suggested, but not confirmed as binaries ormultiple systems in previous literature. We used the adaptive optics instrumentNaos-Conica (NACO) at the Very Large Telescope Unit Telescope 4 of the ParanalObservatory, at 2-5 different epochs, in order to obtain relative and absoluteastrometric measurements, as well as differential photometry in the J, H, and Kband. On the basis of known proper motions and these observations, we analysethe astrometric results in our "Proper Motion Diagram" (PMD: angular separation/ position angle versus time), to eliminate possible (non-moving) backgroundstars, establish co-moving binaries and multiples, and search for curvature asindications for orbital motion. All previously suggested close components areco-moving and no background stars are found. The angular separations rangebetween 0.07 and 9 arcseconds, corresponding to projected distances between thecomponents of 6-845 AU. Thirteen stars are at least binaries and the remainingthree (RX J0919.4-7738, RX J0952.7-7933, VW Cha) are confirmed high-ordermultiple systems with up to four components. In 13 cases, we found significantslopes in the PMDs, which are compatible with orbital motion whose periodsrange from 60 to 550 years. However, in only four cases there are indicationsof a curved orbit, the ultimate proof of a gravitational bond. Massive primarycomponents appear to avoid the simultaneous formation of equal-mass secondarycomponents. (abridged)

Astrometric confirmation of young low-mass binaries and multiple systems in the Chamaeleon star-forming regions