Cosmology with cosmic web environments II. Redshift-space auto and cross power spectra

TL;DR

This paper demonstrates that combining environment-dependent power spectra in redshift space significantly improves constraints on cosmological parameters, including neutrino mass, by breaking degeneracies and utilizing information across scales.

Contribution

It introduces a method to use environment-dependent power spectra in redshift space to enhance cosmological parameter constraints beyond traditional matter statistics.

Findings

Combination of environment-dependent spectra tightens parameter constraints by up to 5.5 times.

Environment-based spectra provide additional information at all studied scales from 0.1 to 0.5 h/Mpc.

Information saturation occurs in matter statistics, but environment spectra continue to improve constraints.

Abstract

Degeneracies among parameters of the cosmological model are known to drastically limit the information contained in the matter distribution. In the first paper of this series, we shown that the cosmic web environments; namely the voids, walls, filaments and nodes; can be used as a leverage to improve the real-space constraints on a set of six cosmological parameters, including the summed neutrino mass. Following-upon these results, we propose to study the achievable constraints of environment-dependent power spectra in redshift space where the velocities add up information to the standard two-point statistics by breaking the isotropy of the matter density field. A Fisher analysis based on a set of thousands of Quijote simulations allows us to conclude that the combination of power spectra computed in the several cosmic web environments is able to break some degeneracies. Compared to the matter monopole and quadrupole information alone, the combination of environment-dependent spectra tightens down the constraints on key parameters like the matter density or the summed neutrino mass by up to a factor of $5.5$. Additionally, while the information contained in the matter statistic quickly saturates at mildly non-linear scales in redshift space, the combination of power spectra in the environments appears as a goldmine of information able to improve the constraints at all the studied scales from $0.1$ to $0.5$ $h$/Mpc and suggests that further improvements are reachable at even finer scales.