Z_max as a function of R_max. The density plot corresponds to GUMS stars that follow the selection function of the PGS VMP sample (below [Fe/H] = –1.7) in ℓ, b, ϖ and apparent G magnitude. The red solid line corresponds to the 66% contour line of each GUMS sample, while the yellow solid line is the 66% contour line of PGS VMP stars ([Fe/H] < –1.7). The red dashed line corresponds to the 66% contour line of each highly prograde (V_ϕ > 180 km.s⁻¹) GUMS subsample; the yellow dashed line is the 66% contour line of PGS VMP highly prograde stars. The orange solid horizontal line corresponds to Z_max = 2 kpc. Left panel: GUMS thin disc. Middle panel: GUMS thick disc. Right panel: GUMS halo.