The variance of dispersion measure of high-redshift transient objects as a probe of ionized bubble size during reionization

TL;DR

This paper proposes using the variance in dispersion measures of high-redshift transient objects to infer the size distribution of ionized bubbles during the Epoch of Reionization, providing a new observational probe.

Contribution

It introduces a simple model linking DM variance to ionized bubble sizes, enabling estimation of bubble sizes from a few hundred sources at a single redshift.

Findings

DM variance reflects bubble size distribution

Measurement of DM variance can determine typical bubble size

Few hundred sources suffice for precise measurement

Abstract

The dispersion measure (DM) of high-redshift $(z \gtrsim 6)$ transient objects such as Fast Radio Bursts can be a powerful tool to probe the intergalactic medium during the Epoch of Reionization. In this paper, we study the variance of the DMs of objects with the same redshift as a potential probe of the size distribution of ionized bubbles. We calculate the DM variance with a simple model with randomly-distributed spherical bubbles. It is found that the DM variance reflects the characteristics of the probability distribution of the bubble size. We find the variance can be measured precisely enough to obtain the information on the typical size with a few hundred sources at a single redshift.