Dark Matter reconstruction from stellar orbits in the Galactic Centre

TL;DR

This paper introduces a flexible, model-agnostic method to reconstruct the distribution of dark matter and other matter in the Galactic Centre using stellar orbit data, aiming to improve unbiased density profile constraints.

Contribution

It develops a spherical shell model that fits a wide range of density profiles without prior assumptions, tested on mock data of star S2.

Findings

Discriminates between different density profiles with large, precise data sets.

Current and near-future instruments have limited ability to distinguish profiles.

Future observations can constrain total enclosed mass unbiasedly.

Abstract

Context. Current constraints on distributed matter in the innermost Galactic Centre (such as a cluster of faint stars and stellar remnants, Dark Matter or a combination thereof) based on the orbital dynamics of the visible stars closest to the central black hole, typically assume simple functional forms for the distributions. Aims. We take instead a general model agnostic approach in which the form of the distribution is not constrained by prior assumptions on the physical composition of the matter. This approach yields unbiased - entirely observation driven - fits for the matter distribution and places constraints on our ability to discriminate between different density profiles (and consequently between physical compositions) of the distributed matter. Methods. We construct a spherical shell model with the flexibility to fit a wide variety of physically reasonable density profiles by modelling the distribution as a series of concentric mass shells. We test this approach in an analysis of mock observations of the star S2. Results. For a sufficiently large and precise data set, we find that it is possible to discriminate between several physically motivated density profiles. However, for data coming from current and expected next generation observational instruments, the potential for profile distinction will remain limited by the precision of the instruments. Future observations will still be able to constrain the overall enclosed distributed mass within the apocentre of the probing orbit in an unbiased manner. We interpret this in the theoretical context of constraining the secular versus non-secular orbital dynamics.