MOND plus classical neutrinos are not enough for cluster lensing |
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| Authors: | Priyamvada Natarajan Hongsheng Zhao |
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| Institution: | Department of Astronomy, Yale University, P. O. Box 208101, New Haven CT 06511-208101, USA;Department of Physics, Yale University, P. O. Box 208120, New Haven CT 06520-208120, USA;School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS;Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark |
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| Abstract: | Clusters of galaxies offer a robust test bed for probing the nature of dark matter that is insensitive to the assumption of the gravity theories. Both Modified Newtonian Dynamics (MOND) and General Relativity (GR) would require similar amounts of non-baryonic matter in clusters as MOND boosts the gravity only mildly on cluster scales. Gravitational lensing allows us to estimate the enclosed mass in clusters on small (～20–50 kpc) and large (～several 100 kpc) scales independent of the assumptions of equilibrium. Here, we show for the first time that a combination of strong and weak gravitational lensing effects can set interesting limits on the phase-space density of dark matter in the centres of clusters. The phase-space densities derived from lensing observations are inconsistent with neutrino masses ranging from 2–7 eV, and hence do not support the 2 eV-range particles required by MOND. To survive, the most plausible modification for MOND may be an additional degree of dynamical freedom in a covariant incarnation. |
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| Keywords: | cosmology: theory dark matter large-scale structure of Universe |
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