Gas fraction f_g vs. halo mass M_500c for Magneticum Box1a/mr non-radiative run (left panel) and full-physics run (right panel). Points are colour-coded by concentration within R_500c. Lines show the average gas fraction for the two quantiles in gas concentration, up to 16% in blue, and from 85% in red, both coloured according to their average concentration. The non-radiative simulation shows a slight dependence of concentration on gas fraction, while full-physics runs show the opposite behaviour: the gas fraction is anti-correlated with concentration. Masses are corrected to WMAP7 Ω_m for consistency with the other results of this study.