Constraining coupled quintessence with the 21cm signal

TL;DR

This paper investigates how 21cm cosmological observations can constrain coupled quintessence models, focusing on the effects of dark matter-dark energy coupling during reionization and assessing the potential of upcoming surveys like SKA.

Contribution

It introduces simulations of the 21cm signal including dark matter-quintessence coupling and performs Fisher analysis to forecast constraints from future observations.

Findings

SKA can constrain the coupling parameter |Q| to less than 0.04

Global 21cm experiments can measure dark matter density parameter with an uncertainty of about 0.005

Constraints from 21cm observations are comparable to those from CMB but probe different redshifts

Abstract

The 21cm line probes the evolution of matter perturbations over a wide range of redshifts, from the dark ages down to the completion of reionization. Observing the 21cm cosmological signal will extend our understanding of the evolution of the Universe and it is thus important to investigate the predictions of different cosmological models. In this paper we focus on the prospect of constraining coupled quintessence models during the Epoch of Reionization both for global signal experiments and for intensity mapping surveys. To derive the all-sky 21cm signal and fluctuations in coupled quintessence, we simulate cosmological volumes of the 21cm signal including the coupling between dark matter and the quintessence field, where the strength of the coupling is labeled by the parameter $Q$. We show that the coupling between dark matter and quintessence modifies structure formation and expedites the process of reionization. For the upcoming 21cm line surveys like SKA and a fiducial global 21cm signal experiment, we perform a Fisher matrix analysis to constrain the coupling $Q$ and the dark matter density parameter $\Omega_\mathrm{dm}$. The results indicate that SKA will be able to place a 68% upper limit $0.04$ to $|Q|$. At the same time, such a global 21cm detector provides a constraint on the dark matter density parameter $\Omega_\mathrm{dm}$ around $\Delta\Omega_{\rm dm}\approx 0.005$, whereas SKA sets a quite weaker constraint around $\Delta\Omega_{\rm dm}\approx0.1$. These constraints are comparable to those already obtained from the cosmic microwave background, but explore an entirely different redshift range.