Milky Way potentials in CDM and MOND. Is the Large Magellanic Cloud on a bound orbit?

Abstract

We compute the Milky Way potential in different cold dark matter (CDM) based models, and compare these with the modified Newtonian dynamics (MOND) framework. We calculate the axis ratio of the potential in various models, and find that isopotentials are less spherical in MOND than in CDM potentials. As an application of these models, we predict the escape velocity as a function of the position in the Galaxy. This could be useful in comparing with future data from planned or already-underway kinematic surveys (RAVE, SDSS, SEGUE, SIM, GAIA or the hypervelocity stars survey). In addition, the predicted escape velocity is compared with the recently measured high proper motion velocity of the Large Magellanic Cloud (LMC). To bind the LMC to the Galaxy in a MOND model, while still being compatible with the RAVE-measured local escape speed at the Sun's position, we show that an external field modulus of less than $0.03a_0$ is needed.

Accepted for publication in MNRAS, 13 pages, 7 figures, 3 tables

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• Implications of Recent Measurements of the Milky Way Rotation for the Orbit of the Large Magellanic Cloud
• Populating the Galaxy with pulsars -- II. Galactic dynamics
• Revisiting the Role of M31 in the Dynamical History of the Magellanic Clouds
• N-body simulations for testing the stability of triaxial galaxies in MOND
• Physics of galactic colliders: high speed satellites in LCDM vs MONDian cosmology
• On the nature of faint Low Surface Brightness galaxies in the Coma cluster
• On the MOND External Field Effect in the Solar System
• Galaxy Bulges As Tests of CDM vs MOND in Strong Gravity
• Galactic Sun's motion in the Cold Dark Matter, MOdified Newtonian Dynamics and MOdified Gravity scenarios
• New Analysis of the Proper Motions of the Magellanic Clouds using HST/WFPC2