No Evidence for Galactic Latitude Dependence of the Fast Radio Burst Sky Distribution

TL;DR

This study analyzes the distribution of Fast Radio Bursts across the sky and finds no evidence of dependence on Galactic latitude, supporting the hypothesis that FRBs originate from an isotropic extragalactic population.

Contribution

It provides the first comprehensive statistical analysis of FRB sky distribution using CHIME/FRB data, confirming isotropy and ruling out Galactic latitude dependence.

Findings

FRB distribution is consistent with isotropy across the sky.

Statistical tests show no significant Galactic latitude dependence.

Results support extragalactic origin of FRBs.

Abstract

We investigate whether the sky rate of Fast Radio Bursts depends on Galactic latitude using the first catalog of Fast Radio Bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst (CHIME/FRB) Project. We first select CHIME/FRB events above a specified sensitivity threshold in consideration of the radiometer equation, and then compare these detections with the expected cumulative time-weighted exposure using Anderson-Darling and Kolmogrov-Smirnov tests. These tests are consistent with the null hypothesis that FRBs are distributed without Galactic latitude dependence ($p$-values distributed from 0.05 to 0.99, depending on completeness threshold). Additionally, we compare rates in intermediate latitudes ($|b| < 15^\circ$) with high latitudes using a Bayesian framework, treating the question as a biased coin-flipping experiment -- again for a range of completeness thresholds. In these tests the isotropic model is significantly favored (Bayes factors ranging from 3.3 to 14.2). Our results are consistent with FRBs originating from an isotropic population of extragalactic sources.