Density structure of CTB 109, obtained by converting the mean ¹²CO emission in the eastern part with n₀ = 0.155 cm^-3 from XMM-Newton data. Overlaid black contour lines display the 1420-MHz continuum emission for 8 K, 15 K, 21 K, 29 K, and 100 K (Tian et al. 2010). The current position of the associated AXP 1E 2259+586 is marked with a magenta star. The circumference of a foreground cloud fragment, which was removed for the calculations, is marked as a blue ellipse.