Exploring parameter space using RADEX-MCMC “corner plot” showing the distribution of T_kin, n(e⁻), n(H), and N(HeH⁺) (in the log₁₀ scale) within the prior intervals [3:4.3], [4:6], [3:6], and [10:13], respectively, in the diagonal panels and the correlation between any pair of them (off-diagonal panels). The central dashed, vertical line in each diagonal panel shows the most likely parameters based on the χ² likelihood (the other vertical lines show the 16% and 84% quantiles). The contours of the corner plot (2D plots) represent the 1 σ and 2σ levels at the 39.3% and 86.4% confidence levels.