Stellar halo streams in the Solar neighbourhood

TL;DR

This paper reviews the discovery and analysis of stellar halo streams in the Solar neighborhood, emphasizing how phase-space data reveals the Galaxy's hierarchical formation history and the importance of upcoming Gaia data for future research.

Contribution

It provides a comprehensive overview of the current state of stellar halo stream research and discusses strategies for identifying these structures in the Milky Way.

Findings

Large-scale surveys have revealed thousands of halo stars with full phase-space data.

Stellar streams retain chemical and kinematic signatures of their origins.

Future Gaia data will enable more precise disentangling of Galactic building blocks.

Abstract

The phase-space structure of our Galaxy holds the key to understand and reconstruct its formation. The Lambda-CDM model predicts a richly structured phase-space distribution of dark matter and (halo) stars, consisting of streams of particles torn from their progenitors during the process of hierarchical merging. While such streams quickly loose their spatial coherence in the process of phase mixing, the individual stars keep their common origin imprinted into their kinematic and chemical properties, allowing the recovery of the Galaxy's individual "building blocks". The field of Galactic Archeology has witnessed a dramatic boost over the last decade, thanks to the increasing quality and size of available data sets. This is especially true for the solar neighborhood, a volume of 1-2 kpc around the sun, where large scale surveys like SDSS/SEGUE continue to reveal the full 6D phase-space information of thousands of halo stars. In this review, I summarize the discoveries of stellar halo streams made so far and give a theoretical overview over the search strategies imployed. This paper is intended as an introduction to researchers new to field, but also as a reference illustrating the achievements made so far. I conclude that disentangling the individual fragments from which the Milky Way was built requires more precise data that will ultimately be delivered by the Gaia mission.