Polytropic model fits to the globular cluster NGC 2419 in Modified Newtonian Dynamics

TL;DR

This study tests polytropic models of the globular cluster NGC 2419 within Modified Newtonian Dynamics (MOND) and finds that these models are inconsistent with observed data, favoring Newtonian gravity instead.

Contribution

The paper provides the first detailed comparison of polytropic models in MOND with high-quality observational data of NGC 2419, demonstrating their inadequacy.

Findings

MOND polytropic models are ruled out by data

Newtonian models fit the data significantly better

Results challenge the validity of MOND for this cluster

Abstract

We present an analysis of the globular cluster NGC 2419, using a polytropic model in Modified Newtonian Dynamics (MOND) to reproduce recently published high quality data of the structure and kinematics of the system. We show that a specific MOND polytropic model of NGC 2419 suggested by a previous study can be completely ruled out by the data. Furthermore, the highest likelihood fit polytrope in MOND is a substantially worse model (by a factor of approximately 5000) than a Newtonian Michie model studied in an earlier contribution by Ibata et al. (2011). We conclude that the structure and dynamics of NGC 2419 favor Newtonian dynamics and do indeed challenge the MOND theory.