The diversity of rotation curves of simulated galaxies with cusps and cores by Finn A. Roper et al. on Wednesday 30 November

We use $\Lambda$CDM cosmological hydrodynamical simulations to explore the

kinematics of gaseous discs in late-type dwarf galaxies. We create

high-resolution 21-cm 'observations' of simulated dwarfs produced in two

variations of the EAGLE galaxy formation model: one where supernova-driven gas

flows redistribute dark matter and form constant-density central 'cores', and

another where the central 'cusps' survive intact. We 'observe' each galaxy

along multiple sight lines and derive a rotation curve for each observation

using a conventional tilted-ring approach to model the gas kinematics. We find

that the modelling process introduces systematic discrepancies between the

recovered rotation curve and the actual circular velocity curve driven

primarily by (i) non-circular gas orbits within the discs; (ii) the finite

thickness of gaseous discs, which leads to overlap of different radii in

projection; and (iii) departures from dynamical equilibrium. Dwarfs with dark

matter cusps often appear to have a core, whilst the inverse error is less

common. These effects naturally reproduce an observed trend which other models

struggle to explain: late-type dwarfs with more steeply-rising rotation curves

appear to be dark matter-dominated in the inner regions, whereas the opposite

seems to hold in galaxies with core-like rotation curves. We conclude that if

similar effects affect the rotation curves of observed dwarfs, a late-type

dwarf population in which all galaxies have sizeable dark matter cores is most

likely incompatible with current measurements.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2203.16652v3