The quasi-linear nearby Universe

TL;DR

This paper introduces a new method to reconstruct quasi-linear matter density and velocity fields in the local Universe using galaxy peculiar velocities, enabling detailed analysis of structures like clusters, superclusters, and voids.

Contribution

A novel reconstruction technique combining constrained simulations and observational data to map the quasi-linear matter distribution in the nearby Universe.

Findings

Robust reconstruction of key cosmic structures.

Demonstration of non-linear bias in galaxy luminosity-weighted density fields.

Bias reduces in the linear regime.

Abstract

The local Universe provides a unique opportunity for testing cosmology and theories of structure formation. To facilitate this opportunity we present a new method for the reconstruction of the quasi-linear matter density and velocity fields from galaxy peculiar velocities and apply it to the Cosmicflows-2 data. The method consists of constructing an ensemble of cosmological simulations, constrained by the standard cosmological model and the observational data. The quasi-linear density field is the geometric mean and variance of the fully non-linear density fields of the simulations. The main nearby clusters (Virgo, Centaurus, Coma), superclusters (Shapley, Perseus-Pisces) and voids (Dipole Repeller) are robustly reconstructed. Galaxies are born biased with respect to the underlying dark matter distribution. Using our quasi-linear framework we demonstrate that the luminosity-weighted density field derived from the 2M++ redshift compilations is non-linearly biased with respect to the matter density field. The bias diminishes in the linear regime.