Primordial magnetic fields and the HI signal from the epoch of reionization

TL;DR

This paper explores how primordial magnetic fields influence the 21cm HI signal during reionization, revealing distinctive signatures and assessing detectability with current and future radio telescopes.

Contribution

It introduces semi-analytic models to analyze magnetic field effects on HI signals, highlighting unique signatures and the potential for detection with SKA.

Findings

Global HI signal appears only in emission in this scenario.

Magnetic fields induce distinctive signatures in the HI two-point correlation function.

Future SKA can detect magnetic field effects within the considered range.

Abstract

The implication of primordial magnetic-field-induced structure formation for the HI signal from the epoch of reionization is studied. Using semi-analytic models, we compute both the density and ionization inhomogeneities in this scenario. We show that: (a) The global HI signal can only be seen in emission, unlike in the standard $\Lambda$CDM models, (b) the density perturbations induced by primordial fields, leave distinctive signatures of the magnetic field Jeans' length on the HI two-point correlation function, (c) the length scale of ionization inhomogeneities is $\la 1 \rm Mpc$. We find that the peak expected signal (two-point correlation function) is $\simeq 10^{-4} \rm K^2$ in the range of scales $0.5\hbox{-}3 \rm Mpc$ for magnetic field strength in the range $5 \times 10^{-10} \hbox{-}3 \times 10^{-9} \rm G$. We also discuss the detectability of the HI signal. The angular resolution of the on-going and planned radio interferometers allows one to probe only the largest magnetic field strengths that we consider. They have the sensitivity to detect the magnetic field-induced features. We show that thefuture SKA has both the angular resolution and the sensitivity to detect the magnetic field-induced signal in the entire range of magnetic field values we consider, in an integration time of one week.