Identification of Sagittarius stream members in Angular Momentum space with Gaussian mixture techniques

TL;DR

This study applies Gaussian mixture models to Gaia and SEGUE data to identify Sagittarius stream members in angular momentum space, revealing new stream segments and substructures across the Milky Way.

Contribution

It introduces a novel application of Gaussian mixture techniques to dynamical stellar data for stream identification, expanding the known extent of the Sagittarius stream.

Findings

Identified 925 probable Sagittarius stream members.

Detected multiple dynamical components in the Milky Way halo.

Mapped the Sagittarius stream across approximately 800 degrees on the sky.

Abstract

This paper uses Gaussian mixture techniques to dissect the Milky Way (MW) stellar halo in angular momentum space. Application to a catalogue of 5389 stars near the plane of the Sagittarius (Sgr) stream with full 6D phase-space coordinates supplied by Gaia EDR3 and SEGUE returns four independent dynamical components. The broadest and most populated corresponds to the `smooth' MW halo. The narrowest and faintest contains 40 stars of the Orphan stream. We find a component with little or no angular momentum likely associated with the GSE substructure. We also identify 925 stars and 7 Globular Clusters with probabilities $>90\%$ to be members of the Sgr stream. Comparison against $N$-body models shows that some of these members trace the continuation of the leading/trailing tails in the Southern/Northern hemispheres. The new detections span $\sim 800^\circ$ on the sky, thus wrapping the Galaxy {\it twice}.