Emissivity map calculated from the excess counts associated to the cocoon in Fig. 5 (right panel). The dashed contours correspond to the 8 µm emission from MSX data at 1.85 × 10⁻⁶ W m⁻² sr−¹. The contours correspond to the peak column density of the ionised gas template at 3.5 × 10²¹ H cm⁻². The circle and the dashed circle correspond to the position and r₆₈ of FCES G78.83+3.57 and FCES G78.74+1.56 respectively.