Illustration of the two substructure removal methods introduced in Sect. 4: (a) Method 1: median technique applied to spheroidal clusters of increasing ellipticity (ϵ = 0, 0.3 and 0.6). With no substructures and assuming spherical symmetry. The relative residuals are computed as: (median–mean)/median. (b) Method 2: effect of the threshold value Xσ on the projected gas density of the cluster CL135: the isocontours are shown in red for X = 3.5 and in white for X = 2. The black circles indicate 0.2 R₅₀₀, R₅₀₀ and R₂₀₀. The units are expressed in [M_⊙ Mpc⁻³]; (c) relative residuals between the profiles obtained with these two methods, computed as (Method 1−Method 2)/Method 1, for different threshold Xσ values (X = 1, 2, 3.5 and 4).