The impact of galaxy formation on satellite kinematics and
  redshift-space distortions
  Galaxy surveys aim to map the large-scale structure of the Universe and use
redshift space distortions to constrain deviations from general relativity and
probe the existence of massive neutrinos. However, the amount of information
that can be extracted is limited by the accuracy of theoretical models used to
analyze the data. Here, by using the L-Galaxies semi-analytical model run over
the MXXL N-body simulation, we assess the impact of galaxy formation on
satellite kinematics and the theoretical modelling of redshift-space
distortions. We show that different galaxy selection criteria lead to
noticeable differences in the radial distributions and velocity structure of
satellite galaxies. Specifically, whereas samples of stellar mass selected
galaxies feature satellites that roughly follow the dark matter, emission line
satellite galaxies are located preferentially in the outskirts of halos and
display net infall velocities. We demonstrate that capturing these differences
is crucial for modelling the multipoles of the correlation function in redshift
space, even on large scales. In particular, we show how modelling small scale
velocities with a single Gaussian distribution leads to a poor description of
the measure clustering. In contrast, we propose a parametrization that is
flexible enough to model the satellite kinematics, and that leads to and
accurate description of the correlation function down to sub-Mpc scales. We
anticipate that our model will be a necessary ingredient in improved
theoretical descriptions of redshift space distortions, which together could
result in significantly tighter cosmological constraints and a more optimal
exploitation of future large datasets.
