Strong Hydrogen Absorption at Cosmic Dawn: the Signature of a Baryonic Universe

TL;DR

The paper suggests that the unexpectedly strong 21cm absorption signal at cosmic dawn can be explained by a universe composed solely of baryonic matter, challenging standard cosmological models.

Contribution

It introduces a baryonic universe model that accounts for the strong 21cm absorption signal observed at high redshift, contrasting with the predictions of the standard bLambdabCDM model.

Findings

Observed 21cm absorption is stronger than bLambdabCDM predictions.

A baryonic universe model naturally explains the strong absorption signal.

Standard cosmology cannot easily account for the observed signal strength.

Abstract

The recently reported detection of redshifted 21cm absorption at $z \approx 17$ is a significant advance in the exploration of the cosmic dark ages. The observed signal ($T_{\mathrm{21}} \approx -0.5$ K with the limit $T_{\mathrm{21}} < -0.3$ K at 99\% c.l.) is anomalously strong for $\Lambda$CDM, which predicts at most $-0.24$ K. Here I show that the strong observed signal is expected in a purely baryonic universe.