GMM analysis of the proper motion distributions for all the RC stars in the analysed region. The left and right panels show the distribution of the proper motion components parallel (μ_l) and perpendicular (μ_b) to the Galactic plane, respectively. The blue histograms correspond to the data, whereas the orange lines are the total models (solid lines), and each of their Gaussian components (dashed lines). The grey and red shaded areas in the left panel, and the green shaded area in the right panel correspond to the regions analysed in Sect. 4.