MOND vs. Newtonian dynamics in early-type galaxies. The case of NGC 4649 M60 - AstrophysicsReport as inadecuate

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Abstract: Context: Regarding the significant interest in both dark matter and theapplication of MOND to early-type galaxies, we investigate the MOND theory bycomparing its predictions, for models of constant mass-to-light ratio, withobservational data of the early-type galaxy NGC 4649.Aims: We study whether measurements for NGC 3379 and NGC 1399 are typical ofearly-type systems and we test the assumption of a Newtonian constant M-L ratiounderlying most of the published models.Methods: We employ the globular clusters of NGC 4649 as a mass tracer. TheJeans equation is calculated for both MOND and constant mass-to-light ratioassumptions. Spherical symmetry is assumed and the calculations are performedfor both isotropic and anisotropic cases.Results: We found that both Jeans models with the assumption of a constantmass-to-light ratio and different MOND models provide good agreement with theobserved values of the velocity dispersion. The most accurate fits of thevelocity dispersion were obtained for the mass-to-light ratio in the B-band,which was equal to 7, implying that there is no need for significant amounts ofdark matter in the outer parts beyond 3 effective radii of this galaxy. Wealso found that tangential anisotropies are most likely present in NGC 4649.

Author: S. Samurovic, M. M. Cirkovic


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