U_LSR − V_LSR velocity diagram for the interacting planetary nebulae sample. The dotted ellipses are the 1σ and 2σ contours. The objects located outside the 2σ contour belong to the thick-disk populations, those inside the 1σ contour are thin-disk populations, and those between the 1σ and 2σ contours are classified as thin or thick populations. The error bars are defined as in Fig. 1.