A multiplicity survey of the ρ Ophiuchi molecular clouds

We present a volume-limited multiplicity survey with magnitude cutoff ({m}_K≤ 10.5 mag) of 158 young stellar objects located within or in the vicinity of the ρ Ophiuchi Dark Cloud. With exception of eleven already well observed objects, all sources have been observed by us in the K-band with 3.5 m telescopes by using speckle techniques. The separation range covered by our survey is 0.13''≤θ≤ 6.4'', where the lower limit is given by the diffraction limit of the telescopes and the upper limit by confusion with background stars. The multiplicity survey is complete for flux ratios ≥ 0.1 (Δ{m}_K≤ 2.5) at the diffraction limit. After taking the background density into account the degree of multiplicity is 29.1%± 4.3% and thus only marginally higher than the value 23.5%± 4.8 % derived for the given separation range for the main-sequence solar-like stars in the solar neighbourhood (Duquennoy & Mayor 1991). We discuss the implications of these findings.