A repeating fast radio burst associated with a persistent radio source

TL;DR

This paper reports the discovery and localization of a repeating fast radio burst (FRB 20190520B) with an associated persistent radio source, highlighting the complex local environment and implications for using FRBs to probe the intergalactic medium.

Contribution

It presents the first localization of a repeating FRB with a high host galaxy dispersion measure and associated persistent radio source, revealing a dense local environment.

Findings

FRB 20190520B is co-located with a persistent radio source.

The host galaxy has a high dispersion measure (~903 pc cm$^{-3}$).

The host galaxy is a dwarf with high star formation rate.

Abstract

The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium, which is assumed to dominate the total extragalactic dispersion. While the host galaxy contributions to dispersion measure (DM) appear to be small for most FRBs, in at least one case there is evidence for an extreme magneto-ionic local environment and a compact persistent radio source. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific star formation rate at a redshift $z=0.241\pm0.001$. The estimated host galaxy DM $\approx 903^{+72}_{-111}$ pc cm$^{-3}$, nearly an order of magnitude higher than the average of FRB host galaxies, far exceeds the DM contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host galaxy identifications.