Effect of distance and extinction on the sample completeness. Top left: cumulative extinction at Z = 0, computed from the Lallement et al. (2022) dust map. Top right: predicted apparent G magnitude for a red clump star, assuming an intrinsic M_G = 0.5 mag. Bottom left: selection function S_Gaia chem(X, Y, Z) plotted for b = 0. Bottom right: XY distribution of red clump stars with |Z|< 15 pc in our RC-GSP-Spec sample (Sect. 2.2.2). The Galactic centre is to the right in every panel.