Correlations between kinematics and metallicity in the Galactic bulge: a review

TL;DR

This review discusses the complex relationship between metallicity and kinematics in the Galactic bulge, highlighting recent survey findings that reveal a metal-poor component with unique kinematic properties and uncertain origins.

Contribution

It synthesizes recent survey data to clarify the correlations between metallicity and kinematics in the Galactic bulge, emphasizing the need to understand the metal-poor component.

Findings

Bulge exhibits cylindrical rotation indicating a disky origin.

A metal-poor component with distinct kinematics has been identified.

The origin and properties of the metal-poor component remain uncertain.

Abstract

Recent large scale surveys of galactic bulge stars allowed to build a detailed map of the bulge kinematics. The bulge exhibits cylindrical rotation consistent with a disky origin which evolved through bar driven secular evolution. However correlations between metallicity and kinematics complicate this picture. In particular a metal-poor component with distinct kinematic signatures has been detected. Its origin, density profile and link with the other Milky Way stellar populations are currently still poorly constrained.