New constraints on MOND from galaxy clusters

We revisit the application of Modified Newtonian Dynamics (MOND) to galaxy clusters. We confront the high quality X-ray data for eight clusters of galaxies observed by the XMM-Newton satellite with the predictions of MOND. We obtain ratios of the Newtonian dynamical mass to the MOND mass of Md/Mm = 1.09 ± 0.08 at r ∼ 0.1 Rvir increasing to Md/Mm = 1.57± 0.24 in the outer parts (i.e r ∼ 0.5 Rvir), in the concordance cosmological model. We confirm that the MOND paradigm lowers the discrepancy between the binding mass with the baryonic mass in clusters to a factor of ∼ 1.6 at about half the virial radius, that as pointed out by Sanders (2003), necessitates a component of dark baryons or neutrinos in the cluster core. However application of the new data requires a much larger discrepancy of ∼ 4.5 (increasing to 5.1 when only hot systems are considered, i.e kT > 3.5 keV) at large radii that MOND cannot explain without introducing further ad hoc assumptions.