Optimal extraction of [C ii] (top), [O i] (middle), and [O iii] (bottom). For each line the top panel shows the observed footprint (with crossed spaxels indicating non-detection) and the template footprint (chosen from a library of precomputed projected PSFs). The footprint is shown as a regular grid for display purposes only; in reality, the spaxels are not uniform in size and one row is shifted with respect to the others. The bottom panel shows the spaxel fluxes ordered by flux. Observed values are indicated in orange. The theoretical distribution from the template footprint is shown with the black curve. The 3 brightest spaxels suffice to locate the peak.