Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for measuring the build-up of cosmological structure , which depends both on the expansion rate of the Universe and our theory of gravity .
The statistical precision with which redshift space distortions can now be measured demands better control of our theoretical systematic errors .
While many recent studies focus on understanding dark matter clustering in redshift space , galaxies occupy special places in the universe : dark matter halos .
In our detailed study of halo clustering and velocity statistics in 67.5 h ^ { -3 } { Gpc } ^ { 3 } of N -body simulations , we uncover a complex dependence of redshift space clustering on halo bias .
We identify two distinct corrections which affect the halo redshift space correlation function on quasilinear scales ( \sim 30 - 80 h ^ { -1 } Mpc ) : the non-linear mapping between real and redshift space positions , and the non-linear suppression of power in the velocity divergence field .
We model the first non-perturbatively using the scale-dependent Gaussian streaming model , which we show is accurate at the < 0.5 ( 2 ) per cent level in transforming real space clustering and velocity statistics into redshift space on scales s > 10 ( s > 25 ) h ^ { -1 } Mpc for the monopole ( quadrupole ) halo correlation functions .
The dominant correction to the Kaiser limit in this model scales like b ^ { 3 } .
We use standard perturbation theory to predict the real space pairwise halo velocity statistics .
Our fully analytic model is accurate at the 2 per cent level only on scales s > 40 h ^ { -1 } Mpc for the range of halo masses we studied ( with b = 1.4 - 2.8 ) .
We find that recent models of halo redshift space clustering that neglect the corrections from the bispectrum and higher order terms from the non-linear real-to-redshift space mapping will not have the accuracy required for current and future observational analyses .
Finally , we note that our simulation results confirm the essential but non-trivial assumption that on large scales , the bias inferred from real space clustering of halos is the same one that determines their pairwise infall velocity amplitude at the per cent level .