The ATLAS$^{\rm{3D}}$ project - XXV: Two-dimensional kinematic analysis
  of simulated galaxies and the cosmological origin of fast and slow rotators
  We present a detailed two-dimensional stellar dynamical analysis of a sample
of 44 cosmological hydrodynamical simulations of individual central galaxies
and their satellites. Kinematic maps of the stellar line-of-sight velocity,
velocity dispersion, and higher-order Gauss-Hermite moments $h_3$ and $h_4$ are
constructed for each central galaxy and for the most massive satellites. The
amount of rotation is quantified using the $\lambda_{\mathrm{R}}$-parameter.
The velocity, velocity dispersion, $h_3$, and $h_4$ fields of the simulated
galaxies show a diversity similar to observed kinematic maps of early-type
galaxies in the ATLAS$^{\rm{3D}}$ survey. This includes fast (regular), slow,
and misaligned rotation, hot spheroids with embedded cold disk components as
well as galaxies with counter-rotating cores or central depressions in the
velocity dispersion. We link the present day kinematic properties to the
individual cosmological formation histories of the galaxies. In general, major
galaxy mergers have a significant influence on the rotation properties
resulting in both a spin-down as well as a spin-up of the merger remnant. Lower
mass galaxies with significant in-situ formation of stars, or with additional
gas-rich major mergers - resulting in a spin-up - in their formation history,
form elongated fast rotators with a clear anti-correlation of $h_3$ and
$v/\sigma$. An additional formation path for fast rotators includes gas poor
major mergers leading to a spin-up of the remnants. This formation path does
not result in anti-correlated $h_3$ and $v/\sigma$. The galaxies most
consistent with the rare class of non-rotating round early-type galaxies grow
by gas-poor minor mergers alone. In general, more massive galaxies have less
in-situ star formation since $z \sim 2$, rotate slower and have older stellar
populations. (shortened)
