Radial-orbit instability in modified Newtonian dynamics

Abstract

The stability of radially anisotropic spherical stellar systems in modified Newtonian dynamics (MOND) is explored by means of numerical simulations performed with the N-body code N-MODY. We find that Osipkov-Merritt MOND models require for stability larger minimum anisotropy radius than equivalent Newtonian systems (ENSs) with dark matter, and also than purely baryonic Newtonian models with the same density profile. The maximum value for stability of the Fridman-Polyachenko-Shukhman parameter in MOND models is lower than in ENSs, but higher than in Newtonian models with no dark matter. We conclude that MOND systems are substantially more prone to radial-orbit instability than ENSs with dark matter, while they are able to support a larger amount of kinetic energy stored in radial orbits than purely baryonic Newtonian systems. An explanation of these results is attempted, and their relevance to the MOND interpretation of the observed kinematics of globular clusters, dwarf spheroidal and elliptical galaxies is briefly discussed.

9 pages, 4 figures, accepted for publication in MNRAS

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Cited by in corpus (22)

• Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions
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• The globular cluster NGC 2419: a crucible for theories of gravity
• Polytropic model fits to the globular cluster NGC 2419 in Modified Newtonian Dynamics
• The Phantom of RAMSES user guide for galaxy simulations using Milgromian and Newtonian gravity
• The dynamical phase transitions of stellar systems and the corresponding kinetimacs
• A Monte Carlo analysis of the velocity dispersion of the globular cluster Palomar 14
• Relaxation of N-body systems with additive r^-α interparticle forces
• Lopsidedness of self-consistent galaxies by the external field effect of clusters
• Radial orbit instability in dwarf dark matter haloes
• Discreteness effects, $N-$body chaos and the onset of radial-orbit instability
• Separable triaxial potential-density pairs in MOND
• Radially anisotropic systems with $r^{-\alpha }$ forces. II: radial-orbit instability
• Application of three-body stability to globular clusters: II. Observed velocity dispersions
• Radially anisotropic systems with $r^{-\alpha }$ forces: equilibrium states
• Gas expulsion in MOND: the possible origin of diffuse globular clusters and ultra-faint dwarf galaxies
• Structure of the equivalent Newtonian systems in MOND N-body simulations. Density profiles and the core-cusp problem
• Simulations of cluster ultra-diffuse galaxies in MOND
• On the problem of deformed spherical systems in Modified Newtonian Dynamics
• Low-mass disc galaxies and the issue of stability: MOND vs dark matter
• The kinematics of star clusters undergoing gas expulsion in Newtonian and Milgromian dynamics
• Testing QUMOND theory with Galactic globular clusters in a weak external field