Relative proper motion vectors in Sco OB2. The vectors are obtained by subtracting the predicted proper motion of the continuous velocity model from the observed proper motion. The direction of motion of the vector is color-coded as shown in the color wheel. Zero degrees is defined as pointing to the left of the plot, as the x-axis is flipped, and 90 degree pointing to the positive end of the y-axis. The median location of the subgroups is marked by a black circle with the subgroup name.