Constraints on Galaxy Bias, Omega_m, and Primordial Non-Gaussianity from the PSCz Survey Bispectrum

We compute the bispectrum $B(k_1,k_2,k_3)$, the three-point correlation function in Fourier space, for the IRAS-PSCz galaxy catalog and show that it agrees well with gravitational instability predictions in a universe dominated by cold dark matter. Assuming a local bias model, we find linear and quadratic bias parameters $1/b_1=1.20^{+0.18}_{-0.19}$ and $b_2/b_1^2=-0.42^{+0.19}_{-0.19}$ for these galaxies. We find no sign of scale-dependent bias for wave-numbers $ k\leq 0.3 \kMpc$ and that Eulerian biasing is preferred over Lagrangian biasing. We also consider constraints from the bispectrum on non-Gaussian initial conditions. For a class of dimensional scaling models with $\chi^2_N$ statistics (which become Gaussian as $N\to\infty$), we find that $N>49$. This implies that dimensional scaling models are constrained to have a primordial dimensionless skewness $B_3 < 0.35$.