Séminaire Doctoral / Seminar PhD |
| « Secular evolution of stellar discs » |
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Jean-Baptiste FOUVRY |
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Most stars are born in a stellar disc. Mergers destroyed some of these discs quite early in the history of the Universe, but many others have survived to the present day, including the Milky Way of which the Sun is a part. Galactic astronomy has therefore striven to understand the dynamics and evolution of galactic discs over cosmic time. Conversely, the current paradigm of cosmology allows us to assess in detail the statistical impacts of the large-scale environment on these systems. This now puts us in an ideal position to address the pressing question of the respective roles of nature (systems' internal properties) vs. nurture (cosmic environment) in the establishment of the observed properties of these systems.
Indeed, fluctuactions in a stellar disc's gravitational potential cause a long-term evolution of the orbits of the stars. These fluctuations can either originate from an external perturber (e.g. passing-by satellites) or internal (e.g. due to the intrinsic graininess of the system). Secular dynamics intends at studying the long-term effects of such perturbations. To introduce this vast subject, I will detail some key concepts of galactic dynamics required to study such long-term evolutions, such as Boltzmann equation, and angle-action coordinates. By emphasising some crucial physical properties of cold stellar discs, I will finally illustrate how these systems may exhibit non-trivial long-term evolutions. |
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jeudi 5 novembre 2015 - 17:00 Salle Entresol Daniel Chalonge, Institut d'Astrophysique |
| Page web du séminaire / Seminar's webpage |