Figure 39

Figure 39: The baryonic mass–X-ray temperature relation for rich clusters (gray triangles [359, 389]) and groups of galaxies (green triangles [12]). The solid line indicates the prediction of MOND: the data are reasonably consistent with the slope (M ∝ T 2), but not with the normalization. This is the residual missing baryon problem in MOND: there should be roughly twice as much mass (on average) as observed. Also shown is the scaling relation expected in ΛCDM (dashed line [137]). This is in better (if not perfect) agreement with the normalization of the data for rich clusters, but not the slope. The difference is sometimes attributed to preheating of the gas [496], which might also occur in MOND.