Upper panel: histogram of the projected (i.e., radial) velocity differences between members of galaxy pairs in the UGC pair catalog for a bin width of 40 km s⁻¹. Lower panel: deprojected PDF of the 3D true intervelocities between members of galaxy pairs in the UGC pair Catalog, for the unbiased subsample with blue major axes < 1.2 arcmin. The red continuous curve is obtained by the deprojection method using a moving bin. The dashed black curve represents the result of deprojection by constant bins of width 30 km s⁻¹. Both methods yield a main peak at ≈150 km s⁻¹ and a possible secondary peak at ≈350 km s⁻¹, in agreement with the results from the IGP catalog.