Radial [Fe/H] distribution (left: as a function of Galactocentric distance R_Gal, right: w.r.t. the guiding radius R_g) over the extent of the Galactic disc (4−14 kpc range). As in Fig. 2, the CoRoGEE sample is shown in blue, the Bergemann et al. (2014) stars in red, and the Bensby et al. (2014) sample in orange. Again, hexagons and stars represent the young [α/Fe]-enhanced stars defined in Fig. 1. The locations of Galactic cepheids (black; data from Genovali et al. 2014) are also indicated.