Top and middle panels: C¹⁸O (2–1) (left) and N₂H⁺ (1–0) emission (right) according to the time dependent model, 300 yr (top panel) and 1000 yr (middle panel) after the burst. Both panels show comparisons of the observations (contours) with the synthetic maps based on the respective models (color background). Integration intervals and the contour spacing are the same as in Fig. 1. The scaling of the maps can be understood in comparison with the cuts in the bottom panel. Bottom panel: vertical cuts for C¹⁸ O (left) and N₂H⁺ (right) 300 (red lines) and 1000 yr (blue lines) after the burst. Gray lines show the data.