Séminaire/Seminar Galaxies |
| « Assembly theory of the Milky Way galaxy » |
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Sergey Khoperskov |
| How did the Milky Way assemble its present-day disc, bar, and bulge, and what imprint did that history leave on the chemo-dynamical structure we observe today? In this talk, I present a complete picture of the Galaxy’s assembly based on a novel orbit-superposition reconstruction of the Milky Way constrained by APOGEE DR17. The method first establishes that orbit-based modelling can recover the stellar density, kinematics, and chemical-abundance structure of the Galaxy despite the incomplete spatial coverage of the Galactic surveys, and then uses this framework to infer the large-scale organisation of the disc and bulge as well as the spatially resolved star-formation history of the disc. The emerging picture is that of a Galaxy shaped by coupled secular evolution and long-term inside-out growth: the disc exhibits coherent chrono-chemo-kinematic structure, including azimuthal metallicity variations in the 6–8 kpc region that peak along the bar major axis, while the inner radial metallicity profile is flattened by an old, metal-poor, high-a population that contributes a substantial fraction of the stellar mass (~40%). In the bulge, chemically distinct components map onto the X-shaped and boxy structures, and the absence of a single universal metallicity gradient supports a bulge built primarily out of disc material through bar-driven evolution. Finally, the reconstructed star-formation history implies that the Milky Way was a compact system at early times, experienced its main star-formation peak 9-10 Gyr ago, and subsequently grew to its present size through inside-out disc formation, with a later episode establishing the outer, metal-poor low-a disc. Together, these results outline a physically connected assembly narrative for the Milky Way, linking present-day orbital structure to the Galaxy’s formation history. |
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jeudi 30 avril 2026 - 11:30 Salle Entresol Daniel Chalonge Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |