# Exploring the epoch of hydrogen reionization using FRBs

Paz Beniamini, Pawan Kumar, Xiangcheng Ma, Eliot Quataert

Research output: Contribution to journalArticlepeer-review

## Abstract

We describe three different methods for exploring the hydrogen reionization epoch using fast radio bursts (FRBs) and provide arguments for the existence of FRBs at high redshift (z). The simplest way, observationally, is to determine the maximum dispersion measure (DMmax) of FRBs for an ensemble that includes bursts during the reionization. The DMmax provides information regarding reionization much like the optical depth of the cosmic microwave background to Thomson scattering does, and it has the potential to be more accurate than constraints from Planck, if DMmax can be measured to a precision better than 500 pccm-3. Another method is to measure redshifts of about 40 FRBs between z of 6 and 10 with ${\sim}10{{\ \rm per\ cent}}$ accuracy to obtain the average electron density in four different z-bins with ${\sim}4{{\ \rm per\ cent}}$ accuracy. These two methods do not require knowledge of the FRB luminosity function and its possible redshift evolution. Finally, we show that the reionization history is reflected in the number of FRBs per unit DM, given a fluence limited survey of FRBs that includes bursts during the reionization epoch; we show using FIRE simulations that the contribution to DM from the FRB host galaxy and circumgalactic medium during the reionization era is a small fraction of the observed DM. This third method requires no redshift information but does require knowledge of the FRB luminosity function.

Original language English (US) 5134-5146 13 Monthly Notices of the Royal Astronomical Society 502 4 https://doi.org/10.1093/mnras/stab309 Published - Apr 1 2021

## All Science Journal Classification (ASJC) codes

• Astronomy and Astrophysics
• Space and Planetary Science

## Keywords

• H ii regions
• dark ages, reionization, first stars