Azimuthally averaged radial surface brightness profile of the Mg II nebula centered on galaxy A (blue data points). For comparison the profile of the Mg II continuum (±20 000 km s⁻¹ around the Mg II doublet) shown in black is also rescaled (gray) to the Mg II SB at the location of galaxy C (where Mg II absorption is unlikely, see Appendix D). The positions of the group members are indicated with vertical dashed lines. The radial profiles have been calculated using unsmoothed Mg II and continuum images after masking the pixels outside the 1σ significance level approximated with an elliptical contour as shown in the inset (left). Middle and right panels: radial profiles after masking the pixels above and below the [A,B,C] axis, respectively. In the insets, we also show the two-pixel annuli used to construct the profiles as white circles.