The SAMI Galaxy Survey: Stellar and gas misalignments and the origin of
  gas in nearby galaxies
  Misalignment of gas and stellar rotation in galaxies can give clues to the
origin and processing of accreted gas. Integral field spectroscopic
observations of 1213 galaxies from the SAMI Galaxy Survey show that 11% of
galaxies with fitted gas and stellar rotation are misaligned by more than 30
degrees in both field/group and cluster environments. Using SAMI morphological
classifications and Sersic indices, the misalignment fraction is 45+/-6% in
early-type galaxies, but only 5+/-1% in late-type galaxies. The distribution of
position angle offsets is used to test the physical drivers of this difference.
Slower dynamical settling time of the gas in elliptical stellar mass
distributions accounts for a small increase in misalignment in early-type
galaxies. However, gravitational dynamical settling time is insufficient to
fully explain the observed differences between early- and late-type galaxies in
the distributions of the gas/stellar position angle offsets. LTGs have
primarily accreted gas close to aligned rather than settled from misaligned
based on analysis of the skewed distribution of PA offsets compared to a
dynamical settling model. Local environment density is less important in
setting the misalignment fractions than morphology, suggesting that mergers are
not the main source of accreted gas in these disks. Cluster environments are
found to have gas misalignment driven primarily by cluster processes not by gas
accretion.
