Our determination of the best NFW model is illustrated. We simulate 20 NFW profiles with scale lengths ranging r_s = 0.02−1.0 Mpc, for each of which 20 Monte Carlo realizations are created to account for centroiding errors and beamsize. Left: the uncorrected mean surface brightness profile from the mean_unmasked stacks (white circles) in the 3.6 |$\, \mu$|m band is shown for the 1.0 < z ≤ 1.3 clusters. Corrections are then applied based on these models to restore its intrinsic profile (the blue lines). The corrected profile is then compared to the underlying profile (the red line) to obtain the goodness-of-fit |$\chi _\nu ^2$|⁠. Mean and standard deviation of 20 different realizations are indicated on bottom left corner. We also show van der Burg et al. (2014) measurements for cluster galaxies at z ∼ 1 (the grey triangles), which are in good agreement with our corrected profile realizations (the blue lines). All profiles are normalized at r_norm = 0.35 Mpc as indicated by a vertical dotted line. Right: The computed reduced chi-square values for the 3.6 μm band are shown as filled circles at 20 different r_s values. Highly concentrated NFW profiles in the range of r_s ≈ 0.1–1.5 Mpc are strongly preferred. The W1-band measurements yield similarly low r_s values (the open triangles).