Radial variation of the SB of the LAB (black dots; distance in physical kpc). The red line is a least-squares fit of a power law to the data. The average profile of the 17 nebulae associated with radio-quiet QSOs (B16) is shown as a purple line. The yellow line represents the Slug Nebula (Cantalupo et al. 2014), the dashed part of it is polluted by the QSO light. Correcting the observed SB for redshift dimming would bring the yellow curve very close to the purple curve, but would slightly increase the distance between the red and purple curves. The upper limit of the gray area corresponds to the 2σ noise on the profile.