Constraints on Galaxy Bias, Matter Density, and Primordial Non--Gausianity from the PSCz Galaxy Redshift Survey

We compute the bispectrum for the \IRAS PSCz catalog and find that the galaxy distribution displays the characteristic signature of gravity. Assuming Gaussian initial conditions, we obtain galaxy biasing parameters $1\mathrm{/}{b}_1=1.20_{-0.19}^{+0.18}$ and $b_2\mathrm{/}{b}_1^2=-0.42\pm 0.19$, with no sign of scale-dependent bias for $k\le 0.3$ h/Mpc. These results impose stringent constraints on non-Gaussian initial conditions. For dimensional scaling models with ${\chi }_N^2$ statistics, we find N>49, which implies a constraint on primordial skewness $B_3<0.35$.