α_CO vs. gas-phase metallicity per pixel, including the pixels of all synthetic CO(1–0) maps for the entire z = 1–3 sample. The color-coding represents the number of pixels per hexbin as shown via a color bar on the right of the figure. The columns again show different redshift bins, whereas the rows indicate the radial position of the clouds within the galaxies with respect to twice the CO(1–0) half-light radius of the galaxy: inner (top), outer (bottom).