Integrated oH₂D⁺(1₁₀ − 1₁₁) N₂H⁺(4 − 3), and DCO⁺(5 − 4) maps from a model where the grain radius is assumed to be a = 0.3 µm. This model approximately reproduces the observed oH₂D⁺ and N₂H⁺ line intensities but underpredicts the DCO⁺ intensity. In the core model shown in the figure, the fractional DCO⁺ abundance is multiplied by 4. The simulation times are shown in the titles of the images.