Revisiting primordial magnetic fields through 21-cm physics: bounds and forecasts

Article Type

Research Article

Publication Title

Journal of Cosmology and Astroparticle Physics

Abstract

Primordial magnetic fields (PMFs) may significantly influence 21-cm physics via two mechanisms: (i) magnetic heating of the intergalactic medium (IGM) through ambipolar diffusion (AD) and decaying magnetohydrodynamic turbulence (DT), (ii) impact on the star formation rate density (SFRD) through small-scale enhancement of the matter power spectrum. In this analysis, we integrate both of these effects within a unified analytical framework and use it to determine upper bounds on the parameter space of a nearly scale-invariant non-helical PMF in the light of the global 21-cm signal observed by EDGES. Our findings reveal that the joint consideration of both effects furnishes constraints of the order B 0 ⋦Ô(10-2) nG on the present-day magnetic field strength, which are considerably tighter compared to earlier analyses. We subsequently explore the prospects of detecting such a magnetized 21-cm power spectrum at the upcoming SKA-Low mission. For the relevant parameters of the PMF (B 0 and n B) and the excess radio background (ϵ), SNR estimation and Fisher forecast analysis indicate that it may be possible to constrain these three parameters with relative 1σ uncertainties ⋦ 10% and an associated SNR ≳10 at SKA-Low. This also leads to possible correlations among these three parameters, thus revealing intriguing trends of interplay among the various physical processes involved.

DOI

10.1088/1475-7516/2025/01/089

Publication Date

1-1-2025

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