Histograms of the different velocity groups in X coordinates. The red histograms represent stars with RA proper motion along the X direction and the green histograms represent stars with RA proper motion opposite from the X coordinates. The region between two blue dash lines indicates the Double Cluster core region (Kharchenko et al. 2013). To show the histogram of stars belonging to cluster cores, halo stars were excluded whose position happens to be the locus of the core region in X coordinates (the region enclosed by the blue vertical lines).