Encircling the dark: constraining dark energy via cosmic density in spheres

TL;DR

This paper introduces a new method using cosmic density within spheres to accurately estimate dark energy parameters, offering a promising tool for future large-scale surveys like Euclid.

Contribution

It develops a maximum likelihood estimator based on the analytic density PDF to constrain dark energy evolution with improved accuracy.

Findings

Achieves a few percent accuracy on dark energy parameters wp and wa.

Provides a publicly available code for density PDF calculations.

Demonstrates the estimator's effectiveness for Euclid-like surveys.

Abstract

The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few percent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical collapse dynamics is made available online so as to provide straightforward means of testing the effect of alternative dark energy models and initial power-spectra on the low-redshift matter distribution.