A new look at lines of sight: using Fourier methods for the wide-angle anisotropic 2-point correlation function

Understand

The anisotropic 2-point correlation function (2PCF) of galaxies measures pairwise clustering as a function of the pair separation's angle to the line of sight.

• The latter is often defined as either the angle bisector of the observer-galaxy-pair triangle or the vector from the observer to the separation midpoint.
• Here we show how to accelerate either of these measurements with Fourier Transforms, using a slight generalization of the Yamamoto et al.
• (2006) estimator in which each member of the pair is used successively as the line of sight.