Column density map (with 37′′ resolution) of the interface between the Rosette molecular cloud and the H ii region around NGC 2244. The DisPerSe skeleton is drawn in white, and each part of the dense layer is labelled from 1 to 4. The pillar is identified as a segment with one side connected by a triple point to the dense fronts 3 and 4, and the opposite side is disconnected and points toward the ionizing sources. The parts of the skeleton used for the profiles in Fig. 3 are indicated with the green dashed lines. The position of the main ionizing sources (O stars) are indicated with the white crosses.