Early Dark Energy Effects on the 21cm Signal

TL;DR

This paper investigates how early dark energy influences the 21cm cosmic signal and assesses HERA's potential to detect or constrain EDE parameters, offering a new observational approach to address the Hubble tension.

Contribution

It provides the first detailed analysis of EDE effects on the 21cm signal and forecasts HERA's capability to distinguish EDE models from $ mf extLambda$CDM.

Findings

EDE significantly alters the 21cm signal evolution.

HERA can differentiate EDE from $ mf extLambda$CDM within 2 years.

HERA is sensitive to EDE fractional energy density $f_{EDE}$ within 2$\sigma$ after 100 days.

Abstract

Early dark energy (EDE) is one of the leading models proposed to resolve the perplexing Hubble tension. Despite extensive scrutiny and testing against various observables, conclusive constraints remain elusive as we await new data. In this paper, we study the impact of EDE on the 21cm signal, a powerful probe of cosmic dawn, and the epoch of reionization. First, we examine the signatures of the shift in cosmological parameters and the new EDE parameters on the evolution of the 21cm signal compared to $\Lambda$CDM. We then focus on the implications of these signatures for upcoming radio interferometer telescopes, such as the Hydrogen Epoch of Reionization Array (HERA), and their ability to differentiate between EDE and $\Lambda$CDM. Finally, we forecast HERA's sensitivity to the fractional energy density of EDE, $f_{\rm EDE}$, assuming a fiducial EDE model. We find significant modifications to the 21cm signal due to the presence of EDE. Furthermore, our analysis suggests that HERA, operating in its designed configuration, is poised to differentiate between the models and be sensitive to $f_{\rm EDE}$ within $2\sigma$ after $\mathcal{O}(100)$ days of observation and $5\sigma$ after 2 years.