Do old globular clusters in low mass galaxies disprove modified gravity?

TL;DR

This paper investigates whether the distribution of old globular clusters in low-mass galaxies challenges modified gravity theories, using simulations to explore dynamical friction effects and the influence of galaxy environment.

Contribution

It provides the first self-consistent simulations demonstrating that core stalling and supernova feedback prevent globular clusters from sinking to galaxy centers under modified gravity.

Findings

Core stalling mechanism prevents GCs from settling in galaxy centers.

Supernova explosions in gas-rich dwarfs inhibit GCs' inward migration.

Simulations support that observed GC distributions do not disprove modified gravity.

Abstract

The controversy "dark matter vs. modified gravity" constitutes a major topic of discussion. It was proposed that dynamical friction could be used to discriminate between the two alternatives. Analytic calculations indicate that, with modified gravity, globular clusters (GCs) of low-mass galaxies experience much stronger dynamical friction than in the equivalent system with Newtonian gravity and dark matter. As a result, in modified gravity the old GCs of low mass galaxies should have already settled in the centers of the galaxies. This is not observed. Here we report on our efforts to verify the analytic results by self-consistent simulations with the MOND-type (modified Newtonian dynamics) gravity. The core stalling mechanism, that was not considered in the analytic calculations, prevents GCs to settle in centers of ultra-diffuse galaxies. For isolated dwarf galaxies, which are gas-rich objects, supernova explosions prevent the GCs from settling.