# Insight into primordial magnetic fields from 21-cm line observation with EDGES experiment

## TL;DR

This paper uses EDGES 21-cm observations to place new constraints on primordial magnetic fields, showing they must be weaker than 10^{-10} G to be consistent with the observed cool IGM gas at redshifts 15-20.

## Contribution

It provides the first detailed numerical analysis linking EDGES 21-cm data to limits on primordial magnetic fields, improving previous constraints.

## Key findings

- Primordial magnetic fields must be weaker than 10^{-10} G.
- Magnetic energy dissipation can significantly heat the IGM.
- EDGES results strongly constrain primordial magnetic field strength.

## Abstract

The recent observation of the 21-cm global absorption signal by EDGES suggests that the intergalactic medium (IGM) gas has been cooler than the cosmic microwave background during $15 \lesssim z \lesssim 20$. This result can provide a strong constraint on heating sources for the IGM gas at these redshifts. In this paper we study the constraint on the primordial magnetic fields (PMFs) by the EDGES result. The PMFs can heat the IGM gas through their energy dissipation due to the magnetohydrodynamic effects. By numerically solving the thermal evolution of the IGM gas with the PMFs, we find that the EDGES result gives a stringent limit on the PMFs as $B_{1\mathrm{Mpc}} \lesssim 10^{-10}$ G.