Date Published:

January 1, 2016

Abstract:

Though Fourier transforms (FTs) are a common technique for findingcorrelation functions, they are not typically used in computations ofthe anisotropy of the two-point correlation function (2PCF) about theline of sight in wide-angle surveys because the line-of-sight directionis not constant on the Cartesian grid. Here we show how FTs can be usedto compute the multipole moments of the anisotropic 2PCF. We also showhow FTs can be used to accelerate the 3PCF algorithm of Slepian &Eisenstein. In both cases, these FT methods allow one to avoid thecomputational cost of pair counting, which scales as the square of thenumber density of objects in the survey. With the upcoming large datasets of Dark Energy Spectroscopic Instrument, Euclid, and Large SynopticSurvey Telescope, FT techniques will therefore offer an importantcomplement to simple pair or triplet counts.

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