Notes. We display their hierarchical clustering (HC) classification number (i.e. MMR subgroup number, adopted throughout this paper) and colour associated in all plots, and age fitting results (both for log(t) and t) retrieved from UNIDAM. For the ages, we display the median of and , i.e. 50th percentile for each; 16th and 84th percentiles (corresponding to ∓1σ interval) for , and maximum and minimum values for and , respectively. The order displayed is with increasing ⟨[Fe/H]⟩. ^( * )Groups 6 and 7 have, respectively, 2 and 3 outliers of younger age, which we remove from the analysis (as well as from this table); see Fig. A.2.