Optical image from Hubble/WFC3 observations of the central ∼2′ of NGC 253. Overlays show the apertures used to extract the line fluxes from the different observatories. The apertures from Spitzer/IRS are shown in grey (SH; small rectangle) and black (LH; larger rectangle). The green square shows the footprint of the Herschel/PACS integral-field-unit. The blue circles are the apertures for the SOFIA/FIFI-LS observations of [O III]52 μ m (solid line), [O III]88 μ m (dashed line), [O I]146 μ m (dash-dotted line), and [C II]158 μ m (dotted line), as described in B22. See also Table 2.