Research
Breathing motion and spiral arms
Gaia DR3 data reveals a distinct pattern of compressing breathing motion a coherent, antisymmetric vertical motion of stars around the Milky Way's mid-plane aligned with the Local arm. Comparison with an N-body simulation suggests that this pattern indicates the Local arm is in a growth phase, while the expanding breathing motion observed near the Perseus arm may indicate it is in a disruption phase. These findings suggest that the Milky Way harbours dynamic spiral arms in various evolutionary phases.
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Bar resonances
The Gaia data reveal complex stellar velocity-space structures, such as the Hercules stream, which cannot be explained by axisymmetric models. Using an N-body simulation of a Milky Way-like galaxy, Asano et al. (2020, 2022) demonstrated that these substructures, including the Hercules stream, arise from bar resonances. We employed the Kullback-Leibler divergence to analyze the spatial and temporal variations of velocity-space distributions, finding that Hercules-like substructures are most prominent in specific regions in the bar's rotating frame, highlighting the dynamic influence of bar resonances on the stellar distribution.
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