Constraining coupled quintessence with the 21 cm signal

The 21 cm line probes the evolution of matter perturbations over a wide range of redshifts, from the dark ages to the completion of reionization, and down to the present-day Universe. Observing the 21 cm 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 21 cm signal and fluctuations in coupled quintessence, we simulate cosmological volumes of the 21 cm 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 upcoming 21 cm line surveys like SKA and a fiducial global 21 cm signal experiment, we perform a Fisher matrix analysis to constrain the coupling Q and the dark matter density parameter Omega(dm). The results indicate that SKA will be able to place a 68% upper limit of 0.04 on vertical bar Q vertical bar. At the same time, our fiducial global 21 cm detector constrains the dark matter density parameter Omega(dm) with a predicted error of Delta Omega(dm) approximate to 0.005, whereas SKA sets a weaker constraint of Delta Omega(dm) approximate to 0.1. These constraints are comparable to those already obtained from the cosmic microwave background, but explore an entirely different redshift range.