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

TL;DR

The bispectrum for the IRAS PSCz catalog is computed and it is found that the galaxy distribution displays the characteristic signature of gravity, imposing stringent constraints on non-Gaussian initial conditions.

Abstract

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 $1/b_1=1.20^{+0.18}_{-0.19}$ and $b_2/b_1^2=-0.42\pm0.19$, with no sign of scale-dependent bias for $k\leq 0.3$ h/Mpc. These results impose stringent constraints on non-Gaussian initial conditions. For dimensional scaling models with $χ^2_N$ statistics, we find N>49, which implies a constraint on primordial skewness $B_3<0.35$.

Figures (3)

• Figure 1: $Q$ from the PSC$z$ survey vs. $k = k_1$ for triangles with ratio of sides $k_2/k_1$ separated by angle $\theta$. Panels show bands in triangle shape, from nearly collinear (upper left) to open (lower right). Triangles, squares, and circles show results for $k_2/k_1=0.25$--0.5, 0.5--0.75, 0.75--1.0. The dashed lines in each panel show the median and 68% range of the points.
• Figure 2: $Q$ from the PSC$z$ survey vs. $\theta$ for triangles with $0.2 \leq k_1 \leq 0.4\, h \, {\rm Mpc}^{-1}$ and with sides of ratio $k_2/k_1=0.4-0.6$ separated by angle $\theta$. The solid curve shows $Q$ in redshift space averaged over many 2LPT realizations of the $\Lambda$CDM model. The dashed curve shows the prediction for $\Lambda$CDM with the best--fit bias parameters $1/b_1 = 1.20$, $b_2/b_1^2=-0.42$.
• Figure 3: Likelihood contours for bias parameters $b_1$ and $b_2$ from the PSC$z$ survey for $k_{\rm max}=0.3\, h \, {\rm Mpc}^{-1}$, assuming Gaussian initial conditions and a linear power spectrum with $\Gamma=0.21$. The contours denote $68\%$, $90\%$ and $95\%$ confidence levels.