On the dark contents of the Universe: A Euclid survey approach

TL;DR

This paper investigates how relaxing the pressureless dark matter assumption affects dark energy constraints, showing current limitations and future prospects with Euclid and CMB data.

Contribution

It demonstrates the impact of non-pressureless dark matter on dark energy constraints and evaluates how Euclid and CMB data can mitigate degeneracies.

Findings

Current dark energy constraints are degraded without pressureless dark matter assumption.

Adding CMB data recovers constraints similar to pressureless dark matter case.

Future Euclid survey will significantly improve constraints, but degeneracies remain without CMB.

Abstract

In this work we study the consequences of allowing non pressureless dark matter when determining dark energy constraints. We show that present-day dark energy constraints from low-redshift probes are extremely degraded when allowing this dark matter variation. However, adding the cosmic microwave background (CMB) we can recover the $w_{DM} = 0$ case constraints. We also show that with the future Euclid redshift survey we expect to largely improve these constraints; but, without the complementary information of the CMB, there is still a strong degeneracy between dark energy and dark matter equation of state parameters.