The effect of large-scale structure on the SDSS galaxy three-point correlation function

Abstract

We present measurements of the normalized redshift-space three-point correlation function (3PCF) (Q(z)) of galaxies from the Sloan Digital Sky Survey (SDSS) main galaxy sample. These measurements were possible because of a fast new N-point correlation function algorithm (called npt) based on multiresolutional k-d trees. We have applied npt to both a volume-limited (36 738 galaxies with 0.05 = 10 h(-1)Mpc). If we exclude this supercluster, our observed Q(z) is in better agreement with that obtained from the 2-degree Field Galaxy Redshift Survey (2dFGRS) by other authors, thus demonstrating the sensitivity of these higher order correlation functions to large-scale structures in the Universe. This analysis highlights that the SDSS data sets used here are not 'fair samples' of the Universe for the estimation of higher order clustering statistics and larger volumes are required. We study the shape dependence of Q(z)(s, q, theta) as one expects this measurement to depend on scale if the large-scale structure in the Universe has grown via gravitational instability from Gaussian initial conditions. On small scales (s 10 h(-1)Mpc, we see considerable shape dependence in Q(z). However, larger samples are required to improve the statistical significance of these measurements on all scales.