2007MNRAS.378.1196K

We present measurements of the redshift-space three-point correlation function of 50967 luminous red galaxies (LRGs) from Data Release 3 (DR3) of the Sloan Digital Sky Survey (SDSS). We have studied the shape dependence of the reduced three-point correlation function (Q_z(s, q, θ)) on three different scales, s = 4, 7 and 10h^–1Mpc, and over the range of 1 < q < 3 and 0° < θ < 180°. On small scales (s = 4h^–1Mpc), Q_z is nearly constant, with little change as a function of q and θ. However, there is evidence for a shallow U-shaped behaviour (with θ) which is expected from theoretical modelling of Q_z(s, q, θ). On larger scales (s = 7 and 10h^–1Mpc), the U-shaped anisotropy in Q_z_(with θ) is more clearly detected. We compare this shape dependence in Q_z(s, q, θ) with that seen in mock galaxy catalogues which were generated by populating the dark matter haloes in large N-body simulations with mock galaxies using various halo occupation distributions (HOD). We find that the combination of the observed number density of LRGs, the (redshift-space) two-point correlation function and Q_z(s, q, θ) provides a strong constraint on the allowed HOD parameters (M_min, M₁,α) and breaks key degeneracies between these parameters. For example, our observed Q_z(s, q, θ) disfavours mock catalogues that overpopulate massive dark matter haloes with many LRG satellites. We also estimate the linear bias of LRGs to be b = 1.87±0.07 in excellent agreement with other measurements.