Implications of \textit{SARAS3} data for Coulomb-like interacting dark matter

TL;DR

This study uses SARAS3 21-cm data to constrain Coulomb-like dark matter interactions, modeling their effects on gas cooling and structure formation, and finds no significant preference for interacting dark matter over standard models.

Contribution

It provides the first joint Bayesian analysis of SARAS3 data considering both gas cooling and structure suppression in interacting dark matter models.

Findings

SARAS3 data disfavors deep 21-cm absorption features at z=23.6

No significant statistical preference for interacting dark matter over CDM

Sets an upper bound on the amplitude of the global 21-cm signal in IDM models

Abstract

The 21-cm signal from cosmic dawn is a potentially sensitive probe of interactions between dark matter (DM) and baryons. We investigate the implications of the SARAS3 non-detection in the 55.5-84.4 MHz band for Coulomb-like interacting DM (IDM). In contrast to earlier constraint analyses that focused primarily on baryon cooling, we model the interaction self-consistently by including both excess cooling of the gas and the suppression of structure formation, which delays the onset of star formation and hence suppresses the Ly$\alpha$, X-ray, and ionizing backgrounds at early times. We perform a joint Bayesian fit of a global 21-cm signal model and a flexible foreground model to the SARAS3 antenna temperature, and find that the signal parameters remain weakly constrained after marginalizing over the foregrounds. The null result is nonetheless informative: the data disfavour deep absorption features within the observed band, with the strongest bound at $z = 23.6$ ($\nu \approx 57.7$ MHz), where $T_{21} \gtrsim -277.6$ mK at $3\sigma$. Comparing the IDM and standard cold dark matter scenarios, we find no statistically significant preference for IDM (Bayes factor $B \approx 1.7$). While we do not constrain the strength of baryon-DM interactions, the SARAS3 non-detection places a meaningful upper bound on the amplitude of the global 21-cm signal in this class of models.