Relation between gas fraction and halo mass within r_500,MT for the XXL-100-GC sample. Left: the red line and the red shaded area show the best-fit relation and its uncertainty. The data points show the individual f_gas estimates obtained using the M−T relation. The WMAP9 cosmic baryon fraction is displayed in the grey shaded area, whereas the dashed magenta line indicates the cosmic baryon fraction corrected by the depletion factor Y_b = 0.85 at r₅₀₀ (Planelles et al. 2013). Right: same as in the left panel. For comparison, the solid curves show similar relations obtained using hydrostatic masses (yellow, Sun et al. 2009; blue, Ettori 2015; green, Lovisari et al. 2015).