Simulating Redshift-Space Distortions for Galaxy Pairs with Wide Angular
  Separation
  The analysis of Redshift-Space Distortions (RSD) within galaxy surveys
provides constraints on the amplitude of peculiar velocities induced by
structure growth, thereby allowing tests of General Relativity on extremely
large scales. The next generation of galaxy redshift surveys, such as the
Baryon Oscillation Spectroscopic Survey (BOSS), and the Euclid experiment will
survey galaxies out to z=2, over 10,000--20,000 sq deg. In such surveys, galaxy
pairs with large comoving separation will preferentially have a wide angular
separation. In standard plane-parallel theory the displacements of galaxy
positions due to RSD are assumed to be parallel for all galaxies, but this
assumption will break down for wide-angle pairs. Szapudi 2004 and Papai &
Szapudi 2008 provided a methodology, based on tripolar spherical harmonics
expansion, for computing the redshift-space correlation function for all
angular galaxy pair separations. In this paper we introduce a new procedure for
analysing wide-angle effects in numerical simulations. We are able to separate,
demonstrate, and fit each of the effects described by the wide-angle RSD
theory. Our analysis highlights some of the nuances of dealing with wide-angle
pairs, and shows that the effects are not negligible even for relatively small
angles. This analysis will help to ensure the full exploitation of future
surveys for RSD measurements, which are currently confined to pair separations
less than \sim80 Mpc/h out to z\simeq 0.5.
