“Dynamics of galaxies as probes to constrain gravity models“
In this thesis, we test cosmological and gravitational models (ΛCDM and MOND) using idealized galaxy simulations. Ultra-diffuse galaxies (UDGs) in the Coma cluster exhibit higher velocity dispersions than MOND predicts. Our MOND simulations show that tidal heating from the cluster cannot account for this but that UDGs on a first radial infall can maintain high velocity dispersions without destruction until their first pericentric passage. In the ΛCDM context, we simulate disc galaxies with varying dark matter halo properties, gas masses, disc kinematics, and bulges. We find that massive halos, bulges, and hot stellar discs inhibit bar formation, while different halo concentrations affect bar strength. Using three instability criteria (Toomre Q, ELN, and baryonic force fraction fb), we construct parameter spaces to assess bar susceptibility. These criteria allow to highlight the roles of different components in bar dynamics.