(T_e, n_e) and abundance profiles along the RA direction in the observed mid-eastern region of NGC 6781, designated as Cen1-Cen5 and Rim1-Rim5 as shown in Table 6. (Top left) [N ii] 122 μm line map from Fig. 11. (Middle left) log T_e profiles. (Bottom left) log n_e profiles. (Top right) relative ionic abundance profiles. (Middle right) relative elemental abundance profiles (where log N_H = 12). (Bottom right) C/O and N/O profiles. The legend of symbols is given in each panel; filled circle: T_e or n_e based on [O iii], open circle: T_e or n_e based on [N ii], triangle: C⁺, log (C/H) + 12, and C/O, circle: N⁺ (open), N²⁺ (filled), log (N/H) + 12, and N/O, square: O²⁺ and log (O/H) + 12. The vertical gray line associated with each symbol represents uncertainties, while the vertical downward arrows indicate upper limits (all of the values at Rim1 and Rim2). Note that these values are exclusively of the H ii region of NGC 6781 (see Sect. 3.3.3). The vertical dashed gray lines indicate boundaries between stratified regions discussed in Sect. 3.3.5.