Detecting Triaxiality in the Galactic Dark Matter halo through Stellar Kinematics

TL;DR

This paper proposes a method to detect the triaxial shape of the Milky Way's dark matter halo by analyzing long-lasting stellar kinematic fossils, which reflect the halo's shape and assembly history.

Contribution

It introduces a novel approach to identify stellar kinematic groups as indicators of dark matter halo triaxiality, linking stellar dynamics to dark matter shape.

Findings

Kinematic fossils can reveal dark matter halo shape.

Stellar groups may dominate from single accretion events.

Detection supports cosmological galaxy formation models.

Abstract

Assuming the dark matter halo of the Milky Way as a non-spherical potential (i.e. triaxial, prolate, oblate), we show how the assembling process of the Milky Way halo, may have left long lasting stellar halo kinematic fossils only due to the shape of the dark matter halo. In contrast with tidal streams, associated with recent satellite accretion events, these stellar kinematic groups will typically show inhomogeneous chemical and stellar population properties. However, they may be dominated by a single accretion event for certain mass assembling histories. If the detection of these peculiar kinematic stellar groups is confirmed, they would be the smoking gun for the predicted triaxiality of dark halos in cosmological galaxy formation scenarios.