Speaker
Description
Using hydrodynamical cosmological simulations, we show that the gas discs
of most gas-rich dwarf galaxies are not in equilibrium, challenging a foundational
assumption in rotation curve analysis. The observed diversity of rotation curves
and inner mass deficits (‘cores’) are longstanding tensions with ΛCDM predic-
tions in the dwarf regime. However, if non-equilibrium effects are “masked” by
projection and azimuthal averaging, current observational methods may create
the illusion of diversity in central mass concentration. Analysing 10^10 − 10^11M⊙
haloes from the COLIBRE simulations, and employing SPH techniques to re-
construct the (hydro-)dynamical state of the gas, we find that nearly all galaxies
in this regime are not in a steady state, with non-equilibrium effects significantly
enhanced in the inner regions. As a result, the gas rotational velocity generally
fails to trace the underlying gravitational potential, often leading to an under-
estimation of the inner mass content. Moreover, clear harmonic patterns in the
non-equilibrium component of the motions may provide a way to link them to
their physical causes, and identify them in observations.
