Observational Constraints on generalized dark matter properties in the presence of neutrinos with the final Planck release

TL;DR

This paper extends the standard cosmological model by allowing dark matter properties to evolve and neutrino parameters to vary, using diverse observational data to constrain these extensions and address the $S_8$ tension.

Contribution

It introduces a generalized dark matter model with evolving equation of state and sound speed, constrained by multiple datasets, and demonstrates compatibility with observations and resolution of the $S_8$ tension.

Findings

Dark matter properties are constrained close to null values.

Tight upper bounds on the sum of neutrino masses.

Lower mean values of $S_8$ that align with large scale structure data.

Abstract

In this paper, we investigate an extension of the standard $\Lambda$CDM model by allowing: a temporal evolution in the equation of state (EoS) of DM via Chevallier-Polarski-Linder parametrization, and the constant non-null sound speed. We also consider the properties of neutrinos, such as the effective neutrino mass and the effective number of neutrino species as free parameters. We derive the constraints on this scenario by using the data from the Planck-2018 cosmic microwave background (CMB), baryonic acoustic oscillation (BAO) measurements, Pantheon+ compilation of Type Ia supernovae (SNe Ia), and some large scale structure (LSS) information from the cosmic shear surveys: Kilo Degree Survey (KiDS)-1000 and Dark Energy Survey (DES). We find constraints on the EoS and sound speed of DM very close to the null value in all the analyses, and thus no significant evidence is found beyond the standard CDM paradigm. In all the analyses, we find the significantly tight upper bounds on the sum of neutrino masses, and significantly lower mean values of $S_8$, which are in agreement with the LSS measurements. Thus, the well-known $S_8$ tension is reconciled in the considered model.