Star-gas misalignment in galaxies: I. The properties of galaxies from
  the Horizon-AGN simulation and comparisons to SAMI
  Recent integral field spectroscopy observations have found that about 11% of
galaxies show star-gas misalignment. The misalignment possibly results from
external effects such as gas accretion, interaction with other objects, and
other environmental effects, hence providing clues to these effects. We explore
the properties of misaligned galaxies using Horizon-AGN, a large-volume
cosmological simulation, and compare the result with the result of the
Sydney-AAO Multi-object integral field spectrograph (SAMI) Galaxy Survey.
Horizon-AGN can match the overall misalignment fraction and reproduces the
distribution of misalignment angles found by observations surprisingly closely.
The misalignment fraction is found to be highly correlated with galaxy
morphology both in observations and in the simulation: early-type galaxies are
substantially more frequently misaligned than late-type galaxies. The gas
fraction is another important factor associated with misalignment in the sense
that misalignment increases with decreasing gas fraction. However, there is a
significant discrepancy between the SAMI and Horizon-AGN data in the
misalignment fraction for the galaxies in dense (cluster) environments. We
discuss possible origins of misalignment and disagreement.
