Mon. Not. R. Astron. Soc., 364, 654-658 (2005/December-1)
New constraints on modified Newtonian dynamics from galaxy clusters.
POINTECOUTEAU E. and SILK J.
Abstract (from CDS):
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 a ratio of the MOND dynamical mass to the baryonic mass of Mm/Mb= 4.94±0.50 in the outer parts (i.e. r∼ 0.5Rvir), in the concordance cosmological model where the predicted asymptotic ratio, if any baryons are present, is 7.7+1.4–1.1(at r≥ 0.3Rvir). We confirm that the MOND paradigm lowers the discrepancy between the binding mass and the baryonic mass in clusters by a factor of ∼1.6 at about half the virial radius. However, at this radius about 80 per cent of the mass is still missing, and as pointed out by Sanders, this necessitates a component of dark baryons or neutrinos in the cluster core. Concerning the neutrino hypothesis, application of the new data requires a minimum neutrino mass of mν> 1.74±0.34 eV to fill this gap. The corresponding 2σ lower limit of mν> 1.06 eV is marginally inconsistent with the current constraints from the cluster number counts, and from the cosmic microwave background and large-scale structure data. MOND must invoke neutrinos to represent the main component that account for the missing mass problem in clusters.