Y_x and gas fraction relations at r₅₀₀. Top left: M − Y_x relation. Top right: L_x − Y_x relation. Lower left: M_g − M relation. Lower right: f_g − T relation. Filled circles are groups, open circles are HIFLUGCS clusters (gas masses from Zhang et al. 2011), and asterisks are the groups from Sun et al. (2009). The dot-dashed line with shaded error regions is the cosmic baryon fraction from WMAP5 (Dunkley et al. 2009).