Rotational velocity, V_ϕ, as a function of the metallicity, [Fe/H], color coded by density scale, for the thin disc selections (top row). Thin-disc stars are shown in red scale overplotted over the rest of the sample in grey scale. Contour plots of the 50%, 75%, 90%, 99%, and 99.9% (the latter only for the metal-poor thin disc) are overplotted following the same color code. Second row: V_ϕ distributions of thin-disc stars at four different ranges of metallicity (from dark blue to white, [Fe/H] < −0.5, [Fe/H] < −1, [Fe/H] < −1.5, [Fe/H] < −2), normalized to the maximum number of stars and multiplied by a factor to help the visualization (from dark blue to white, ×10, ×5, ×2 and ×1). Third and fourth rows: same as middle panels but for |Z_max| and R_guide distributions, respectively. From left to right we display the Gaia DR3 RVS, GALAH and APOGEE stellar samples.