Molecular abundances relative to H₂ against H₂ column densities interpolated within an aperture of diameter equal to the HPBW of each transition. The abundances of the Cha I and III cores are shown as black squares and pink asterisks, respectively. Upper limits (3σ uncertainties) are shown as pink and black downward triangles for Cha III and Cha I, respectively. The N₂H⁺ abundance of the four densest cores in panel g) was derived from the observed peak temperature of the weakest hyperfine component (1_1,0–0_1,1) while the strongest component (1_2,3–0_1,2) was used for all other cores (see Sect. 5.1).