X − Y maps showing the ratio of the vertical velocity dispersion of stars at a given metallicity range to the ISM’s value (rightmost panel of each row, with the σ_z map in grey), and stars with a lower metal content, in bins of 0.1 dex(σ_Z,n, remaining panels). Over-plotted in grey lines are the spiral arm locations, as estimated by Castro-Ginard et al. (2021). Redder (bluer) colours indicate that the lower-metallicity stars have hotter (cooler) kinematics in the considered pixel. The assumed location of the Sun is indicated by a ‘+’ sign. Pixels are 0.5-kpc-wide and considered only if they include more than 200 stars in either selection. Stars with Z_max > 2 kpc have been discarded. One can see that at the outermost radii, stars that are considerably more metal-rich than the ISM tend to be slightly kinematically hotter than more metal-poor stars.