Top panel: continuum subtracted [O III] λ5007 narrowband; contours indicate SB_[OIII] = {5, 12.5, 25}×10⁻¹⁹ erg s⁻¹ cm⁻² arcsec⁻². The cyclic colour map encodes flux densities from 0 to 5 × 10⁻¹⁹ erg s⁻¹ cm⁻² (colour bar) to 5 × 10⁻¹⁷ erg s⁻¹ cm⁻². The image has been smoothed with a Gaussian of 0.4″ FWHM. Bottom panel: continuum subtracted Hβ narrowband. The cyclic colour map encodes flux from 0 to 3 × 10⁻¹⁹ erg s⁻¹ cm⁻² to 3 × 10⁻¹⁷ erg s⁻¹ cm⁻². The image has been smoothed with a Gaussian of 0.95″ FWHM to enhance the visibility of the low-SB Hβ emission.