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.
@article{arxiv.1601.07761,
title = {Correlations between kinematics and metallicity in the Galactic bulge: a review},
author = {Carine Babusiaux},
journal= {arXiv preprint arXiv:1601.07761},
year = {2016}
}