Synthetic emission maps in CO(J = 1 → 0) (left) and [CII] at 158 μm (right). The solid contour marks the assumed 0.4 K km s^-1 detection threshold for CO, the dashed contour marks the position of the line centre optical depth τ_CO = 1, and the dotted contour marks the position of the molecular transition f_H2 = 1/2. Grey areas are outside of the computational domain.