Testing modified gravity with globular cluster velocity dispersions

TL;DR

This paper evaluates a modified gravity theory (MOG) against globular cluster velocity dispersions, showing MOG aligns with Newtonian predictions for GCs, unlike MOND, and suggests future observations could distinguish these theories.

Contribution

It demonstrates that MOG predicts globular cluster velocity dispersions consistent with Newtonian gravity, providing a potential test to differentiate between MOG and MOND.

Findings

MOG predicts velocity dispersions independent of galactic center distance.

Newtonian gravity and MOG agree with observed GCs.

Future observations of distant GCs can test gravitational theories.

Abstract

Globular clusters (GCs) in the Milky Way have characteristic velocity dispersions that are consistent with the predictions of Newtonian gravity, and may be at odds with Modified Newtonian Dynamics (MOND). We discuss a modified gravity (MOG) theory that successfully predicts galaxy rotation curves, galaxy cluster masses and velocity dispersions, lensing, and cosmological observations, yet produces predictions consistent with Newtonian theory for smaller systems, such as GCs. MOG produces velocity dispersion predictions for GCs that are independent of the distance from the galactic center, which may not be the case for MOND. New observations of distant GCs may produce strong criteria that can be used to distinguish between competing gravitational theories.