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arXiv · 2512.18708

Towards Unveiling the Origins of the Milky Way Bulge through Multi-band-Messenger Sky Surveys

Hai-Feng Wang·Xiao Han·Giovanni Carraro·Martin Lopez-Corredoira·Yuan-Sen Ting·Guan-Yu Wang
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Abstract

We analyze the structure and chemo-dynamical properties of the Galactic bulge using ab-type RR Lyrae stars (RRabs) from OGLE-IV and giant stars from APOGEE and Gaia. Orbital integration of 1,879 RRab variables reveals three populations: central bulge, inner bulge, and halo/disk contaminants. Inner bulge RRabs display bar-like kinematics, whereas central bulge stars show slower rotation and lower dispersion. APOGEE data for 28,188 stars confirm these kinematic trends and reveal a bimodal chemical distribution, indicating distinct formation pathways. Our results support a pseudo-bulge origin of the inner bulge through disk instability, with the overall morphology better described as boxy rather than X-shaped. Through the integration of multi-messenger, multi-band data, our collaboration aims to provide deeper insights into the physical properties and evolutionary history of the Galactic bulge.

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Hai-Feng Wang, Xiao Han, Giovanni Carraro, Martin Lopez-Corredoira, Yuan-Sen Ting, Guan-Yu Wang. 2025-12-21. Towards Unveiling the Origins of the Milky Way Bulge through Multi-band-Messenger Sky Surveys. https://arxiv.org/abs/2512.18708

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