XXL-derived [0.5 − 2] keV from XXL Paper XX plotted against our aperture [0.5 − 2] keV for the matched groups in our sample, with 1σ uncertainties shown. The colour bar displays the 2D projected sky offset between the GAMA group centre and the XXL X-ray position. The dotted black line denotes a 1:1 match. The two X-ray luminosity measurements are similar in most cases, except when there is a large offset between the XXL source position and the optical group centre. Green stars show re-measured values for groups where a catalogue XXL source overlaps with a prominent non-central GAMA group member (see Sect. 2.3.2 for details). They are connected to the original values by a green line.