Photometric decomposition results using lenstronomy. (1) HST/ACS HRC F330W flux map with saturated pixels replaced. Grey lines show surface brightness contours of Σ_mol. (2) F330W flux map after subtracting the PSF model, revealing a diffuse component near the centre. Dashed contours show the initial guess of the single-Sérsic model fit to this structure. (3) F330W residual image after subtracting both the PSF and best-fit single-Sérsic model. (4) Residual map normalized by uncertainty. (5) Same as (3) but subtracting a 90°-rotated PSF from the original image. (6) Similar to (4) but the single-Sérsic model was not subtracted. The detection of the diffuse component near the AGN does not depend on the PSF subtraction (2 vs 5). Aside from compact UV emission from star-forming clumps in the single-arm spiral, no extended UV emission is left over when a single-Sérsic model is subtracted.