How Different Star-Sorting Methods Change Our View of the Milky Way’s Discs
The paper examines how five different methods for separating Milky Way thin- and thick-disc stars, chemical, age-based, kinematic, and dynamical, lead to different measurements of the discs’ structures. Chemical and age selections give the cleanest separation, while motion-based methods mix the populations. Across all approaches, the thin disc flares with radius, the thick disc stays roughly constant in height, and the thin disc has a longer scale length.
Understanding Galactic Disc Warps: The Influence of Dark Matter and the Sagittarius Dwarf Galaxy
This paper by James Binney explores why spiral galaxies, like the Milky Way, often have warped outer discs. By revisiting and updating earlier models, Binney shows how galactic warps form and evolve, especially under the influence of the Sagittarius Dwarf Galaxy's gravitational pull during close encounters. His model suggests that these interactions cause the Milky Way’s disc to warp temporarily, gradually winding into spiral patterns. This work highlights that such warps provide insight into the dark matter halo’s density and shape, offering a new understanding of galactic dynamics and structure.