The orientations of galaxies and haloes in cosmological hydrodynamical simulations
Using a cosmological hydrodynamical simulation in a box of size
200 h^{−1} Mpc , we address the issue of the alignments of galaxies and
haloes with respect to cosmic web. We also analyse the angular momentum
profiles of galaxies in the inner parts of haloes with respect to the outer parts.
The angular momenta of stars in the inner regions (∼ 0.25 rvir) of haloes do
not seem to be well-aligned with the angular momentum of halo as a whole.
The angle between the specific angular momentum of gas in the inner parts
of the halo, and the specific angular momentum of the total halo, has a
median of ∼ 29 degrees. For the case of stars , this angle is of 42 degrees.
We also find that specific angular momenta of gas and stars in the inner
parts of halo tend to align with the vorticity of the velocity field but show
random distribution with the shear tensor of the velocity field. These
alignments increase as we consider bigger inner regions.