Drivers of disc tilting I: Correlations and possible drivers for Milky
  Way analogues
  The direction of the spin vectors of disk galaxies change over time. We
present the tilting rate of a sample of galaxies in the NIHAO suite of
cosmological hydrodynamical simulations. Galaxies in our sample have been
selected to be isolated and to have well determined spins. We compare the
tilting rates to the predicted observing limit of Gaia, finding that our entire
sample lies above the limit, in agreement with previous work. To test the role
of dark matter and of gas we compare the weighted Pearson's correlation
coefficients between the tilting rates and various properties. We find no
correlation between the dark halo's tilting rate, shape, or misalignment with
respect to the disc, and the tilting rate of the stellar disc. Therefore, we
argue that, in the presence of gas, the dark halo plays a negligible role in
the tilting of the stellar disc. On the other hand, we find a strong
correlation between the tilting rate of the stellar disc and the misalignment
of the cold gas warp. Adding the stellar mass fraction improves the
correlation, while none of the dark matter's properties together with the cold
gas misalignment improves the correlation to any significant extent. This
implies that the gas cooling onto the disc is the principal driver of disc
tilting.
