Comparison of the Parkes and FAST FRB DM Distribution

TL;DR

This study models and compares the FRB dispersion measure distributions for FAST and Parkes telescopes, highlighting potential observational biases and the ability of FAST to distinguish between different cosmic evolution models.

Contribution

It provides the first comparative analysis of FRB DM distributions between FAST and Parkes, exploring implications for cosmic evolution and IGM ionization.

Findings

Limited low DM FRB events observed, possibly due to statistical or observational factors.

FAST can help differentiate between redshift evolution models.

Current data insufficient to constrain energy distribution in high DM regime.

Abstract

We model the Fast Radio Burst (FRB) dispersion measure (DM) distribution for the Five-hundred-meter Aperture Spherical Telescope (FAST) and compare this with the four FRBs published in the literature to date. We compare the DM distribution of Parkes and FAST, taking advantage of the similarity between their multibeam receivers. Notwithstanding the limited sample size, we observe a paucity of events at low DM for all evolutionary models considered, resulting in a sharp rise in the observed cumulative distribution function (CDF) in the region of $1000\lesssim\mathrm{DM}\lesssim2000$ pc cm$^{-3}$. These traits could be due to statistical fluctuations ($0.12 \le p \le 0.22$), a complicated energy distribution or break in an energy distribution power law, spatial clustering, observational bias or outliers in the sample (e.g., an excessive DM_${HOST}$ as recently found for FRB 20190520B). The energy distribution in this regime is unlikely to be adequately constrained until further events are detected. Modelling suggests that FAST may be well placed to discriminate between redshift evolutionary models and to probe the helium ionisation signal of the IGM.