Insights into the Galactic Bulge Chemodynamical Properties from Gaia Data Release 3

Abstract

We explore the chemodynamical properties of the Galaxy in the azimuthal velocity V _ϕ and metallicity [Fe/H] space using red giant stars from Gaia Data Release 3. The row-normalized V _ϕ –[Fe/H] maps form a coherent sequence from the bulge to the outer disk, clearly revealing the thin/thick disk and the Splash. The metal-rich stars display bar-like kinematics, while the metal-poor stars show dispersion-dominated kinematics. The intermediate-metallicity population (−1 − 1 dex, with the Splash not participating in the bar formation and growth. Moreover, with a set of isolated evolving N -body disk simulations, we confirm that a nonrotating classical bulge can be spun up by the bar and develop cylindrical rotation, consistent with the observations for the metal-poor stars.

Keywords

• Galactic bulge
• Galaxy bulges
• Milky Way evolution