THE 3-POINT FUNCTION AS A PROBE OF MODELS FOR LARGE-SCALE STRUCTURE

We analyze the consequences of models of structure formation for higher order (n-point) galaxy correlation functions in the mildly nonlinear regime. Several variations of the standard Omega=1 cold dark matter model with scale-invariant primordial perturbations have recently been introduced to obtain more power on large scales, R(p) similar to 20 h(-1) Mpc, e.g., low matter-density (nonzero cosmological constant) models, ''tilted'' primordial spectra, and scenarios with a mixture of cold and hot dark matter. They also include models with an effective scale-dependent bias, such as the cooperative galaxy formation scenario of Bower et al. We show that higher-order (n-point) galaxy correlation functions can provide a useful test of such models and can discriminate between models with true large-scale power in the density field and those where the galaxy power arises from scale-dependent bias: a bias with rapid scale dependence leads to a dramatic decrease of the hierarchical amplitudes Q(J) at large scales, r greater than or similar to R(p). Current observational constraints on the three-point amplitudes Q(3) and S-3 can place limits on the bias parameter(s) and appear to disfavor, but not yet rule out, the hypothesis that scale-dependent bias is responsible for the extra power observed on large scales.