Constraints on Galaxy Bias, Matter Density, and Primordial Non-Gaussianity from thePSCzGalaxy Redshift Survey

We compute the bispectrum for the IRAS $\mathrm{PSC}z$ catalog and find that the galaxy distribution displays the characteristic signature of gravity. Assuming Gaussian initial conditions, we obtain galaxy biasing parameters $1/b_1{=1.20\mathrm{}}_{-0.19\mathrm{}}^{+0.18\mathrm{}}$ and $b_2/b_1^2=-0.42\mathrm{}\pm 0.19$, with no sign of scale-dependent bias for $k\le 0.3h{\mathrm{Mpc}}^{-1\mathrm{}}$. These results impose stringent constraints on non-Gaussian initial conditions. For dimensional scaling models with ${\chi }_N^2$ statistics, we find $N>\mathrm{}49\mathrm{}$, which implies a constraint on primordial skewness $B_3<0.35\mathrm{}$.