Title of the HDR
Numerical Simulation and Galaxy Modeling.
Composition of the jury
- Joshua BARNES, Institute for Astronomy, University of Hawaii at Manoa, Rapporteur
- Alain BLANCHARD, Institut de Recherche en Astrophysique et Planétologie, Rapporteur
- Annie ROBIN, Université Marie et Louis Pasteur, Rapporteur
- Jacques LASKAR, Observatoire de Paris, Président du jury
- Rodrigo IBATA, Observatoire Astronomique de Strasbourg, Examinateur
- Gary MAMON, Institut d’Astrophysique de Paris, Examinateur
- François HAMMER, Observatoire de Paris, Examinateur
Abstract
This thesis investigates galactic dynamics through the combined use of multi-scale numerical simulations and comparisons with observational data. The central objective is to clarify the physical processes that govern galaxy formation and evolution across a wide mass range, from massive disk galaxies to faint dwarf systems. The methodological framework relies on the development and application of efficient simulation techniques capable of capturing the coupled effects of gravity, gas dynamics, star formation, and stellar feedback. Several key results are obtained from this work. First, merger simulations within the IMAGES framework show that gas-rich major mergers can drive the formation of disk galaxies and provide a physically grounded explanation for the Hubble sequence. A well-constrained major-merger model reproduces the main structural properties of the Andromeda galaxy, offering a coherent reference for its bulge, bar, disk, stellar streams in the halo. In parallel, simulations and analytical modeling focused on the Milky Way’s circumgalactic medium (CGM) show that ram-pressure processes play a central role in shaping nearby dwarf systems. An analytical ram-pressure solver, extended to dissipative dwarf interactions, enables efficient reconstruction of the Magellanic Clouds’ orbital history and provides robust initial conditions for hydrodynamical modeling of the Magellanic Stream, supporting a ram-pressure origin rather than tidal stripping. Consistently, simulations of dwarf galaxies indicate that dwarf spheroidals around the Milky Way may originate as gas-rich systems undergoing first infall, with their rapid evolution driven by ram-pressure stripping from the CGM. When combined with N-body and analytical modeling, their kinematics can be explained by the combined effects of tidal forces, gas removal, and turbulence within the hot halo, challenging the traditional view of long-lived, dark-matter-dominated satellites. This picture is further supported by the discovery of young stellar populations and extended low-density stellar halos in classical dwarf spheroidals. Moreover, simulations show that ram-pressure stripping by the intergalactic medium can account for gas loss in dwarf irregular galaxies such as WLM, highlighting the broader importance of environmental processes. Overall, this work demonstrates that detailed dynamical modeling provides a powerful and direct approach to understanding galaxy-scale processes, complementing cosmological simulations. Future efforts will focus on expanding simulation capabilities and building a comprehensive library of galaxy merger models and dwarf galaxy interactions with the CGM and IGM, covering a wide range of masses, orbital parameters, and configurations. The long-term goal is to integrate these tools with artificial intelligence methods to develop a community-oriented, AI-assisted framework for galaxy dynamics.
