Left: redshift diagram showing the selected cluster members (red dots, coincident with those in the main structure identified in Sect. 6) and the caustics (purple solid lines). Right: caustic-ELG mass profile (purple circles) computed by integrating the squared caustic amplitude profile; NFW-best-fit mass profile to the weak-lensing mass from Kneib et al. (2003; black dashed line); caustic analysis of the catalog from Diaferio et al. (2005; red squares). The vertical and horizontal lines are M₂₀₀ and r₂₀₀ of the caustic-ELG (purple) and weak-lensing (grey) mass profiles.