Average metallicity variations among 1G stars, ⟨δ[Fe/H]_1G⟩, as a function of the radial distance from the cluster center. The gray points correspond to the average δ[Fe/H] of 1G stars within each analyzed field, whereas the thick and thin error bars indicate the uncertainties associated with ⟨δ[Fe/H]_1G⟩ and the dispersions, respectively. On the bottom axis, the distance from the cluster center is normalized to the half-light radius from Baumgardt & Hilker (2018, r_hl = 2.78 arcmin). On the top axis, instead, the radial coordinate is converted to parsec by adopting a distance of 4.41 kpc (Baumgardt & Hilker 2018). The horizontal bars mark the extension of each radial interval.