The black line shows the requirement for the two KMM subclusters to be gravitationally bound, as computed from the Newtonian criterion; the grey shading indicates 1σ uncertainties on this requirement, which depends on the projected distance and line-of-sight velocity difference of the two subclusters. The red line indicates the sum of the measured masses for these subclusters; the orange shading indicates 1σ uncertainties on this sum. On the x-axis, the angle between the axis connecting the KMM-main and KMM-sub subclusters is defined with respect to the plane of the sky (90 degrees corresponds to a line-of-sight collision). The KMM subclusters are gravitationally bound for an angle between ~35 and ~75 degrees, if we take into account both the uncertainties on our mass estimates and the uncertainties on the Newton criterion requirements.