Parameter space used for the radiative transfer modeling of CN in the region at the western side of the bubble. The first row shows results for the excitation temperature. The color bar shows values of excitation temperature, T_ex for the grid of volume densities (x-axis), line widths (y-axis) and column densities (each panel) for fixed electron fraction. The second row shows results for opacity, τ, and the third row shows the peak temperature, T_peak. The last row shows the χ² minimization of the modeled peak temperature and the observed value computed from the CN(1−0) spectra.