# Modelling the Milky Way's globular cluster system

## TL;DR

This paper develops a detailed dynamical model of the Milky Way's globular cluster system using a Bayesian approach, revealing insights into its structure, rotation, and relation to stellar components.

## Contribution

It introduces a novel action-based distribution function model for the globular cluster system, integrating disc and halo components with Bayesian parameter estimation.

## Key findings

- Model reproduces density profile and rotation velocity of clusters
- Disc and halo parameters align with stellar component estimates
- Identifies potential issues with cluster distance estimates

## Abstract

We construct a model for the Galactic globular cluster system based on a realistic gravitational potential and a distribution function (DF) analytic in the action integrals. The DF comprises disc and halo components whose functional forms resemble those recently used to describe the stellar discs and stellar halo. We determine the posterior distribution of our model parameters using a Bayesian approach. This gives us an understanding of how well the globular cluster data constrain our model. The favoured parameter values of the disc and halo DFs are similar to values previously obtained from fits to the stellar disc and halo, although the cluster halo system shows clearer rotation than does the stellar halo. Our model reproduces the generic features of the globular cluster system, namely the density profile, the mean rotation velocity. The fraction of disc clusters coincides with the observed fraction of metal-rich clusters. However, the data indicate either incompatibility between catalogued cluster distances and current estimates of distance to the Galactic Centre, or failure to identify clusters behind the bulge. As the data for our Galaxy's components increase in volume and precision over the next few years, it will be rewarding to revisit the present analysis.