Dynamical Models of the Galactic Center

TL;DR

This paper reviews various dynamical models to explain the unusual distribution of old stars in the Milky Way's center, highlighting the current lack of a definitive explanation for the core versus cusp structure.

Contribution

It provides a comprehensive discussion of potential models for the old star distribution in the Galactic Center, emphasizing the unresolved nature of the core-cusp conundrum.

Findings

Old stars form a core, not a cusp, in the Galactic Center.

Unrelaxed nucleus may reflect the distribution of faint stars and remnants.

Interactions with unseen populations could explain the deficit of bright giants.

Abstract

The distribution of late-type (old) stars in the inner parsec of the Milky Way is very different than expected for a relaxed population around a supermassive black hole. Instead of a density cusp, there is a 0.5 pc core. This article discusses what sorts of dynamical models might explain this "conundrum of old age." A straightforward interpretation is that the nucleus is unrelaxed, and that the distribution of the old giants reflects the distribution of fainter stars and stellar remnants generally in the core. On the other hand, a density cusp could be present in the unobserved populations, and the deficit of bright giants could be a result of interactions with these objects. At the present time, no model is clearly preferred.