MOND vs. Newtonian dynamics in early-type galaxies. The case of NGC 4649 (M60)

Abstract

Context: Regarding the significant interest in both dark matter and the application of MOND to early-type galaxies, we investigate the MOND theory by comparing its predictions, for models of constant mass-to-light ratio, with observational data of the early-type galaxy NGC 4649. Aims: We study whether measurements for NGC 3379 and NGC 1399 are typical of early-type systems and we test the assumption of a Newtonian constant M/L ratio underlying most of the published models. Methods: We employ the globular clusters of NGC 4649 as a mass tracer. The Jeans equation is calculated for both MOND and constant mass-to-light ratio assumptions. Spherical symmetry is assumed and the calculations are performed for both isotropic and anisotropic cases. Results: We found that both Jeans models with the assumption of a constant mass-to-light ratio and different MOND models provide good agreement with the observed values of the velocity dispersion. The most accurate fits of the velocity 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 of dark matter in the outer parts (beyond 3 effective radii) of this galaxy. We also found that tangential anisotropies are most likely present in NGC 4649.

6 pages, 4 figures

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Cited by in corpus (7)

• Mapping the Dark Side with DEIMOS: Globular Clusters, X-ray Gas, and Dark Matter in the NGC 1407 Group
• Kinematic properties of the field elliptical NGC 7507
• The Geometry Of Modified Newtonian Dynamics
• Study of gravitational fields and globular cluster systems of early-type galaxies
• Dynamics of Elliptical Galaxies with Planetary Nebulae in Modified Newtonian Dynamics
• The massive elliptical galaxy NGC 4649 from the perspective of extended gravity
• The total mass of the early-type galaxy NGC 4649 (M60)