Simulated σ_1D distributions for different parent binary fractions. The vertical dashed line indicates the observed σ_1D for our M 17 sample stars. The median, 0.16 and 0.84 percentiles of the simulated distributions are indicated on the upper part of the graph. The distribution corresponding to f_bin = 0.03 is not shown for clarity; it is almost entirely dominated by the velocity dispersion of the cluster and thus peaks strongly at 2 km s^-1 (≈σ_cl).