Dark sectors of the Universe: A Euclid survey approach

TL;DR

This paper explores how relaxing the pressureless dark matter assumption affects dark energy constraints, demonstrating that future Euclid survey data combined with CMB observations can break degeneracies between dark sectors.

Contribution

It introduces generalized dark matter models with constant equation of state and assesses their constraints using current and future observational probes.

Findings

Low-redshift probes cause degeneracy between dark matter and dark energy.

CMB data restores constraints similar to ΛCDM.

Euclid survey can break dark sector degeneracy with weaker dark energy constraints.

Abstract

In this paper we study the consequences of relaxing the hypothesis of the pressureless nature of the dark matter component when determining constraints on dark energy. To this aim we consider simple generalized dark matter models with constant equation of state parameter. We find that present-day low-redshift probes (type-Ia supernovae and baryonic acoustic oscillations) lead to a complete degeneracy between the dark energy and the dark matter sectors. However, adding the cosmic microwave background (CMB) high-redshift probe restores constraints similar to those on the standard $\Lambda$CDM model. We then examine the anticipated constraints from the galaxy clustering probe of the future Euclid survey on the same class of models, using a Fisher forecast estimation. We show that the Euclid survey allows us to break the degeneracy between the dark sectors, although the constraints on dark energy are much weaker than with standard dark matter. The use of CMB in combination allows us to restore the high precision on the dark energy sector constraints.