Top panel: PPD radius distribution versus ambient stellar density. Squares, triangles, stars, and crosses correspond to ONC sources, T-Tauri stars, Herbig stars, and YSOs, respectively. Dotted lines represent the theoretical truncation for ages of 0.3 (top) and 1 Myr (bottom). Bottom panel: KS test p_KS-values for the PPD radii at that density to be consistent with the sample at lower densities, using { 6,7,8 }  (triangles, squares, diamonds) objects per density bin (see text). The grey thick line shows the p_KS-value for ONC PPDs only when dividing the subsample in two at the indicated density. The horizontal dashed line and grey area indicate the median p_KS and its 1σ dispersion retrieved from 30 000 Monte Carlo experiments to verify the significance of the results (see text). Dotted lines mark 95% (top) and 99% (bottom) confidence levels.