Barred spiral galaxies in modified gravity theories

When bars form within galaxy formation simulations in the standard cosmological context, dynamical friction with dark matter (DM) causes them to rotate rather slowly. However, almost all observed galactic are fast terms of ratio between corotation radius and bar length. Here, we explicitly display an $8\sigma$ tension distribution this that EAGLE simulation at redshift 0. We also compare evolution Newtonian discs embedded DM haloes their three extended gravity theories: Milgromian Dynamics (MOND), a model non-local gravity, scalar-tensor-vector theory (MOG). Although our models start same initial baryonic rotation curve, long-term is different. The instability happens more violently MOND compared other models. There some common features models, particular negligible role played by $-$ which plays key model. Partly for reason, predict weaker faster pattern speeds case. absence strong idealized, isolated observations, they reproduce observational preference `fast' speeds, could not do DM. confirm previous findings apparently `ultrafast' can be due bar-spiral arm alignment leading overestimated length, especially scenarios where already fast.