Probing the Intergalactic Medium with Fast Radio Bursts

TL;DR

Fast radio bursts (FRBs) can serve as powerful probes of the intergalactic medium, providing insights into cosmic reionization, magnetic fields, and microlensing effects through their dispersion and rotation measures.

Contribution

This paper introduces analytical expressions for dispersion and rotation measures of FRBs as functions of redshift and explores their sensitivity to IGM properties and microlensing effects.

Findings

Dispersion and rotation measures depend on redshift and IGM properties.

Microlensing by stellar-mass objects leaves detectable spectral imprints.

Large FRB samples can enable detailed IGM studies.

Abstract

The recently discovered fast radio bursts (FRBs), presumably of extra-galactic origin, have the potential to become a powerful probe of the intergalactic medium (IGM). We point out a few such potential applications. We provide expressions for the dispersion measure and rotation measure as a function of redshift, and we discuss the sensitivity of these measures to the HeII reionization and the IGM magnetic field. Finally we calculate the microlensing effect from an isolate, extragalctic stellar-mass compact object on the FRB spectrum. The time delays between the two lensing images will induce constructive and destructive interference, leaving a specific imprint on the spectra of FRBs. With a high all-sky rate, a large statistical sample of FRBs is expected to make these applications feasible.