Séminaire / Seminar GReCO |
| « Gravity does it all: A Top-Down Multiscale Analysis of the Cosmic Emergence of Thin Galactic Discs » |
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Christophe Pichon |
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Thin stellar discs dominate the star-forming population of the Universe, yet their remarkable stability and efficiency remain among the most persistent puzzles in galaxy formation. I will suggest that thin discs emerge and persist naturally through dynamical self-regulation, driven by the interplay between gravitational wakes, coherent gas inflows, and star formation. ?Once a stellar disc becomes sufficiently massive to resist disruption, it enters a homeostatic state where orbital heating—driven by perturbations—is precisely balanced by cooling from new stars formed on nearly circular orbits. This loop maintains discs close to marginal gravitational stability, enabling them to remain thin, long-lived, and highly efficient at converting gas into stars.This self-regulated attractor state explains the ubiquity, resilience, and tightness of observed galaxy scaling relations, such as the Tully-Fisher and Kennicutt-Schmidt laws, without recourse to any finely tuned feedback prescriptions.
While high-resolution simulations excel at showing ‘what’ happens in a specific galactic realisation, the corresponding kinetic theory is designed to reveal ‘why’ it happens, by providing analytical insight into the underlying physical mechanisms. Cf https://www.dropbox.com/scl/fi/g7ilwutdsdjja8m1fa0fz/Cargese-oct-2025.pdf?rlkey=p2t7tllrgq70prpkvq3etwjbt&st=09qbiocg&dl=0 |
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lundi 10 novembre 2025 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |