A joint 2- and 3-point clustering analysis of the VIPERS PDR2 catalogue at z~1: breaking the degeneracy of cosmological parameters

TL;DR

This study combines 2- and 3-point galaxy correlation functions from VIPERS data to effectively break degeneracies among key cosmological parameters, providing measurements consistent with Planck cosmology.

Contribution

It introduces a joint analysis of 2- and 3-point correlation functions with nonlinear modeling, validated on realistic mocks, to improve constraints on cosmological parameters at z~1.

Findings

Successfully breaks degeneracy between _8, bias, and growth rate.

Provides measurements of f(z) and _8 consistent with Planck.

Validates modeling approach down to 10 h^{-1} Mpc scales.

Abstract

We measure the galaxy 2- and 3-point correlation functions at $z=[0.5,0.7]$ and $z=[0.7, 0.9]$, from the final data release of the VIPERS survey (PDR2). We model the two statistics including a nonlinear 1-loop model for the 2-point function and a tree-level model for the 3-point function, and perform a joint likelihood analysis. The entire process and nonlinear corrections are tested and validated through the use of the 153 highly realistic VIPERS mock catalogues, showing that they are robust down to scales as small as 10 $h^{-1} \, \mathrm{Mpc}$. The mocks are also adopted to compute the covariance matrix that we use for the joint 2- and 3-point analysis. Despite the limited statistics of the two (volume-limited) sub-samples analysed, we demonstrate that such a combination successfully breaks the degeneracy existing at 2-point level between clustering amplitude $\sigma_8$, linear bias $b_1$ and the linear growth rate of fluctuations $f$. For the latter, in particular, we measure $f(z=0.61)=0.64^{+0.55}_{-0.37}$ and $f(z=0.8)=1.0\pm1.0$, while the amplitude of clustering is found to be $\sigma_8(z=0.61)=0.50\pm 0.12$ and $\sigma_8(z=0.8)=0.39^{+0.11}_{-0.13}$. These values are in excellent agreement with the extrapolation of a Planck cosmology.