Application of the IPTW method to B5 simulation. Top: bar major axis at ϕ_b = 163.5°, as in the original snapshot and shown in Fig. 1. Bottom: after applying a rotation of Δϕ = 16.5° to put the bar major axis along the x-axis. Left: surface density where the bar region (obtained using Dehnen method) is indicated by the green dashed circle. A scatter plot representing the value of ⟨x⟩ for each slice in y is overlapped. The scatter plot varies its colour as function of the distance to the centre in the y-axis, being the red points close to the centre and the green close to the external parts of the galaxy. Right: scatter plot of the Tremaine-Weinberg integrals ⟨x⟩ and ⟨v_y⟩ for the different slices in the y-axis. The colour of the scatter plot is the same in both left and right panels. In the right panel, the points with a black circle are inside of the bar region and, therefore, the only considered for fitting Ω_p.