The Milky Way Halo in Action Space
G. C. Myeong (1), N.W. Evans (1), V. Belokurov (1), J.L. Sanders (1),, S. Koposov (1,2) ((1) IoA, Cambridge, (2) CMU, Pittsburgh)

TL;DR
This study analyzes the Milky Way's stellar halo in action space using Gaia data, revealing distinct populations with different metallicities, kinematics, and possible origins, including a newly observed low-metallicity resonant component.
Contribution
It provides a detailed characterization of the local stellar halo in action space, identifying new components and their properties, especially a low-metallicity resonant population not previously observed.
Findings
Metal-rich stars are more radially extended in action space.
Metal-poor stars are more evenly distributed and have higher prograde rotation.
A low-metallicity resonant component with outward radial velocity was discovered.
Abstract
We analyse the structure of the local stellar halo of the Milky Way using 60000 stars with full phase space coordinates extracted from the SDSS--{\it Gaia} catalogue. We display stars in action space as a function of metallicity in a realistic axisymmetric potential for the Milky Way Galaxy. The metal-rich population is more distended towards high radial action as compared to azimuthal or vertical action, or . It has a mild prograde rotation km s), is radially anisotropic and highly flattened with axis ratio . The metal-poor population is more evenly distributed in all three actions. It has larger prograde rotation km s), a mild radial anisotropy and a roundish morphology (). We identify two further components of the halo in action space.…
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