Maps of the key quantities employed by CWT98: DCO⁺ deuteration level (top-left panel), CO depletion factor (top-right), electronic fraction (bottom-left), and ζ₂ (bottom-right). Note that the colour scales for the last two quantities are in units of 10⁻⁶ and 10⁻¹³ s⁻¹, respectively. These maps assume the molecular column density and total gas column density derived in run 2. The mean uncertainties are 2.6 × 10⁻⁴ (R_D), 0.3 (f_D), 3 × 10⁻⁶ $\left(x_{{\text{e}}^{-}}\right)$, and 1.5 × 10⁻¹³ s⁻¹ (ζ₂). The beam size and scalebar are shown in the bottom-left panel. The contours show N(H₂), as in Fig. 2.