Can MOND take a bullet? Analytical comparisons of three versions of MOND beyond spherical symmetry

Abstract

A proper test of modified Newtonian dynamics (MOND) in systems of non-trivial geometries depends on modelling subtle differences in several versions of its postulated theories. This is especially true for lensing and dynamics of barely virialized galaxy clusters with typical gravity of scale a0. The original MOND formula, the classical single-field modification of the Poisson equation, and the multifield general relativistic theory of Bekenstein (tensor-vector-scalar, TeVeS) all lead to different predictions as we stray from spherical symmetry. In this paper, we study a class of analytical MONDian models for a system with a semi-Hernquist baryonic profile. After presenting the analytical distribution function of the baryons in spherical limits, we develop orbits and gravitational lensing of the models in non-spherical geometries. In particular, we can generate a multicentred baryonic system with a weak lensing signal resembling that of the merging galaxy cluster 1E 0657-56 with a bullet-like light distribution. We finally present analytical scale-free highly non-spherical models to show the subtle differences between the single-field classical MOND theory and the multifield TeVeS theory. © 2006 RAS.