2D distribution of the azimuthal or rotational velocity of all stellar particles in Romeo, R < 40 kpc and |z| < 10 kpc, as a function of age (left panel) and metallicity [Fe/H] (right panel), with the median trend shown in red. The green, blue, and purple lines depict the median trend of the stellar population in the high-α, bridge and low-α discs, respectively. In the left panel, the dashed vertical lines indicate the inferred period at which the MW’s stellar disc settles (see Sect. 3.2), while the dashed black line in the right panel shows the inferred trend for the MW as in Belokurov & Kravtsov (2022).