Advances in Constraining Intrinsic Alignment Models with Hydrodynamic
  Simulations
  We use galaxies from the IllustrisTNG, MassiveBlack-II and Illustris
hydrodynamic simulations to investigate the behaviour of large scale galaxy
intrinsic alignments. Our analysis spans four redshift slices over the
approximate range of contemporary lensing surveys $z=0-1$. We construct
comparable weighted samples from the three simulations, which we then analyse
using an alignment model that includes both linear and quadratic alignment
contributions. Our data vector includes galaxy-galaxy, galaxy-shape and
shape-shape projected correlations, with the joint covariance matrix estimated
analytically. In all of the simulations, we report non-zero IAs at the level of
several $\sigma$. For a fixed lower mass threshold, we find a relatively strong
redshift dependence in all three simulations, with the linear IA amplitude
increasing by a factor of $\sim 2$ between redshifts $z=0$ and $z=1$. We report
no significant evidence for non-zero values of the tidal torquing amplitude,
$A_2$, in TNG, above statistical uncertainties, although MassiveBlack-II
favours a moderately negative $A_2\sim-2$. Examining the properties of the TATT
model as a function of colour, luminosity and galaxy type (satellite or
central), our findings are consistent with the most recent measurements on real
data. We also outline a novel method for constraining the TATT model parameters
directly from the pixelised tidal field, alongside a proof of concept exercise
using TNG. This technique is shown to be promising, although the comparison
with previous results obtained via other methods is non-trivial.
