The spectrum has been smoothed with a 3 × 3 pixel (0.57 arcsec × 118 km s⁻¹) boxcar filter. The intensity is denoted by a combined contour/grey level plot. The outermost contiguous contour corresponds to a flux density 1.25 × 10⁻²⁰ erg cm⁻² s⁻¹ Å⁻¹, the average flux density in the emission ridges is 5 × 10⁻²⁰ erg cm⁻² s⁻¹ Å⁻¹. For comparison, the 1σ noise per pixel prior to smoothing is 2.7 × 10⁻²⁰ erg cm⁻² s⁻¹ Å⁻¹.