Accreted Globular Clusters in External Galaxies: Why Adaptive Dynamics is not the Solution

TL;DR

This paper demonstrates that the adaptive dynamics method, which assumes similar orbits for accreted globular clusters, fails to accurately determine the gravitational potential in galaxy simulations.

Contribution

The study critically tests the adaptive dynamics approach using realistic galaxy simulations and shows its limitations for modeling accreted globular clusters.

Findings

Minimizing action deviations does not constrain the true potential.

Adaptive dynamics cannot reliably model accreted GCs.

Actions of accreted stellar particles evolve unpredictably.

Abstract

Many astrophysical and galaxy-scale cosmological problems require a well determined gravitational potential which is often modeled by observers under strong assumptions. Globular clusters (GCs) surrounding galaxies can be used as dynamical tracers of the luminous and dark matter distribution at large (kpc) scales. A natural assumption for modeling the gravitational potential is that GCs accreted in the same dwarf galaxy merger event move at the present time on similar orbits in the host galaxy and should therefore have similar actions. We investigate this idea in one realistic Milky Way like galaxy of the cosmological N-body simulation suite Auriga. We show how the actions of accreted stellar particles in the simulation evolve and that minimizing the standard deviation of GCs in action space, however, cannot constrain the true potential. This approach known as adaptive dynamics does therefore not work for accreted GCs.