Date Published:

December 1, 2015

Abstract:

We present an algorithm that computes the multipole coefficients of thegalaxy three-point correlation function (3PCF) without explicitlyconsidering triplets of galaxies. Rather, centring on each galaxy in thesurvey, it expands the radially binned density field in sphericalharmonics and combines these to form the multipoles without everrequiring the relative angle between a pair about the central. Thisapproach scales with number and number density in the same way as thetwo-point correlation function, allowing run-times that are comparable,and 500 times faster than a naive triplet count. It is exact in angleand easily handles edge correction. We demonstrate the algorithm on theLasDamas SDSS-DR7 mock catalogues, computing an edge corrected 3PCF outto 90 Mpc h^-1 in under an hour on modest computing resources.We expect this algorithm will render it possible to obtain thelarge-scale 3PCF for upcoming surveys such as Euclid, Large SynopticSurvey Telescope (LSST), and Dark Energy Spectroscopic Instrument.

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