RR Lyrae Time Capsules: Tracing the Milky Way’s Earliest Assembly
This paper uses a large, homogeneous sample of RR Lyrae stars to trace the early formation of the Milky Way’s halo, thick disk, and thin disk. By combining precise distances, kinematics, and chemical abundances, the authors find a smooth transition from metal-poor, α-enhanced halo stars to more metal-rich, α-poor disk stars. These results support an early, rapid formation of the Galactic spheroid followed by continued assembly through mergers.
Listening to the Milky Way’s Oldest Stars: What RR Lyrae Reveal About the Galactic Halo
This study uses a vast sample of RR Lyrae stars to map the chemistry and motions of the Milky Way’s stellar halo. The authors find strong evidence for a dual halo, with a more metal-rich inner component and a metal-poor outer component. By identifying dynamically tagged groups, they show that many halo stars share common origins from ancient mergers, preserving a record of the Galaxy’s assembly history.
Hidden Clusters in the Dust: Using RR Lyrae Stars to Uncover the Milky Way’s Missing Building Blocks
The paper presents a search for hidden globular clusters in the Milky Way’s dusty plane and bulge using RR Lyrae stars as tracers of old stellar populations. By combining Gaia and near-infrared data with a carefully calibrated clustering algorithm, the authors recover known clusters and identify several compact RR Lyrae groups that may represent previously undiscovered or disrupted clusters.
Tracing Ancient Mergers in the Heart of the Milky Way: RR Lyrae Stars and the Gaia-Enceladus/Sausage in the Inner Stellar Halo
Kunder et al. study RR Lyrae stars in the Milky Way’s inner halo to trace remnants of the ancient Gaia-Enceladus/Sausage merger. They find about 6-9% of these stars show motions and metallicities consistent with GES, less than in the solar neighborhood. Their results match simulations showing GES debris is less concentrated near the Galactic center.