Initial density structure from XMM-Newton data, which gives the best fit of the 1420-MHz contours of CTB 109 and the Lobe region after 8000 yr. The position of the SN explosion is marked with a black star and the position of the AXP with a magenta star, which is almost completely covered by the black star. The elliptically shaped cloud (n_cloud = 20 cm^-3), which resembles the Lobe region after its encounter with the shock wave, is located at (ℓ,b) = (109.1545°,−1.0078°).