Global 21-cm brightness temperature in viscous dark energy models

TL;DR

This paper explores how viscous dark energy models influence the 21-cm brightness temperature, considering various cosmic effects, and derives bounds on model parameters consistent with EDGES observations.

Contribution

It introduces a comprehensive analysis of viscous dark energy effects on 21-cm signals, incorporating multiple cosmic phenomena and providing new constraints on dark matter properties.

Findings

VDE models can explain EDGES excess temperature.

Constraints on dark matter mass and cross-section are modified.

Bounds on VDE parameters are derived from 21-cm data.

Abstract

We investigate the global 21-cm brightness temperature in the context of viscous dark energy (VDE) models. The bulk viscosity of dark energy perturbs the Hubble evolution of the Universe which could cool baryons faster, and hence, alter the 21-cm brightness temperature. An additional amount of entropy is also produced as an outcome of the viscous flow. We study the combined contribution of Hawking radiation from primordial black holes, decay and annihilation of particle dark matter and baryon-dark matter scattering in the backdrop of VDE models towards modification of the 21-cm temperature. We obtain bounds on the VDE model parameters which can account for the observational excess of the EDGES experiment ($-500^{+200}_{-500}$ mK at redshift $14<z<20$) due to the interplay of the above effects. Moreover, our analysis yields modified constraints on the dark matter mass and scattering cross-section compared to the case of the $\Lambda$CDM model.