Statistical measurements of dispersion measure fluctuations of FRBs

TL;DR

This paper analyzes dispersion measure fluctuations of FRBs using the CHIME catalog, revealing large fluctuations and potential inhomogeneities in intergalactic electron density, but with significant uncertainties.

Contribution

It provides a detailed statistical analysis of DM fluctuations in a large FRB sample, highlighting the need for more data to confirm intergalactic turbulence.

Findings

Large DM fluctuations similar to previous studies

No clear evidence of large-scale turbulence in the larger sample

Indications of density inhomogeneities on scales around 100 Mpc

Abstract

Extragalactic Fast Radio Bursts (FRBs) have large dispersion measures (DMs) and are unique probes of intergalactic electron density fluctuations. By using the recently released First CHIME/FRB Catalog, we reexamined the structure function (SF) of DM fluctuations. It shows a large DM fluctuation similar to that previously reported in Xu & Zhang (2020), but no clear correlation hinting towards large scale turbulence is reproduced with this larger sample. To suppress the distortion effect from FRB distances and their host DMs, we focus on a subset of CHIME catalog with DM $<500$ pc cm$^{-3}$. A trend of non-constant SF and non-zero correlation function (CF) at angular separations $\theta$ less than $10^\circ$ is seen, but with large statistical uncertainties. The difference found between SF and that derived from CF at $\theta \lesssim 10^\circ$ can be ascribed to the large statistical uncertainties or the density inhomogeneities on scales on the order of $100$ Mpc. The possible correlation of electron density fluctuations and inhomogeneities of density distribution should be tested when several thousands of FRBs are available.