The origin of kinematically distinct cores and misaligned gas discs in
  galaxies from cosmological simulations
  Integral field spectroscopy surveys provide spatially resolved gas and
stellar kinematics of galaxies. They have unveiled a range of atypical
kinematic phenomena, which require detailed modelling to understand. We present
results from a cosmological simulation that includes stellar and AGN feedback.
We find that the distribution of angles between the gas and stellar angular
momenta of galaxies is not affected by projection effects. We examine five
galaxies ($\approx 6$ per cent of well resolved galaxies) that display atypical
kinematics; two of the galaxies have kinematically distinct cores (KDC), while
the other three have counter-rotating gas and stars. All five form the majority
of their stars in the field, subsequently falling into cosmological filaments
where the relative orientation of the stellar angular momentum and the bulk gas
flow leads to the formation of a counter-rotating gas disc. The accreted gas
exchanges angular momentum with pre-existing co-rotating gas causing it to fall
to the centre of the galaxy. This triggers low-level AGN feedback, which
reduces star formation. Later, two of the galaxies experience a minor merger
(stellar mass ratio $\sim1/10$) with a galaxy on a retrograde orbit compared to
the spin of the stellar component of the primary. This produces the KDCs, and
is a different mechanism than suggested by other works. The role of minor
mergers in the kinematic evolution of galaxies may have been under-appreciated
in the past, and large, high-resolution cosmological simulations will be
necessary to gain a better understanding in this area.
