Speaker
Description
Studying the nature of the spiral arms is essential for understanding the intricate structure of the Milky Way disc. In recent years, The Gaia has provided groundbreaking observational data, revealing the detailed kinematical features of stars in the Milky Way. However, so far, the nature of spiral arms remains unresolved.
In this talk I will present the stellar kinematics traced by the classical Cepheids around the Perseus and Outer arms in the Milky Way, enabled by cross-matching Gaia DR3 data with the classical Cepheid catalogue. Precise distance estimates based on the period-luminosity relation of Cepheid variable stars provide broad observational coverage of the Galactic disk and, for the first time, reveal the kinematics of both the Perseus and Outer arms.
Our analysis shows that these two arms exhibit opposite kinematical properties from each other: the Cepheids in the Perseus arm have a positive correlation between their radial and azimuthal velocities, whereas those in the Outer arm display a negative correlation. Furthermore, comparisons with a Milky Way-like N-body/hydrodynamic simulation indicate that the observed stellar motion structure around the Perseus arm is seen in the disrupting spiral arms, while that of the Outer arm aligns with growing spiral arms. These findings suggests that two neighbouring spiral arms in distinct evolutionary phases - one growing and the other disrupting - coexist in the Milky Way.
