Dendrogram with the hierarchical classification of the stars into groups. The solid line is for the main groups with Ward distance d_W = 6; the dashed line is for the general subgroups with d_W = 3. The dot-dashed line is for the MMR subgroups, established with d_W = 1.3. The end of the dendrogram is truncated with the total number of stars in each branch shown on the x-axis. The numbers that appear on the x-axis are the final groups automatically detected by the dendrogram using the last p non-singleton clusters (p = 24) to facilitate visualisation (for more details, see the algorithm description in the SCIPY package, Virtanen et al. 2020). The number of stars in each MMR subgroup can also be seen in Table 1. Top panel: full dendrogram. Bottom panel: zoomed-in image of dendrogram to display the range 0  ≤  d_W ≤ 10.