Left: histogram of the line-of-sight velocities. Member galaxies of the cluster, member galaxies of the high velocity group, and non-member galaxies are in solid (black), dashed (red), and dash-dotted (grey) lines. The arrow shows the cluster redshift. Right: line-of-sight velocity versus projected radius, in which filled blue diamonds and red stars show blue and red member galaxies in the caustic (black curve), and open squares show fore- and background galaxies. The grey curve shows the symmetric boundary by choosing the minimum of the values on both sides of the caustic boundary relative to the cluster redshift. The cluster radii, and , derived from the mass distribution using the caustic method are shown as solid and dashed vertical lines, respectively.