Probing the Metallicity Dependence of Fast Radio Burst Progenitors with CHIME/FRB Outrigger Dwarf Host Galaxies

arXiv:2609.28629 · astro-ph.HE, astro-ph.GA · Submitted 2026-09-23 · Read on arXiv

astro-ph.HE, astro-ph.GA

Submitted: 2026-09-23

Updated: 2026-09-23

Comments: Submitted to ApJ. 32 pages, 10 figures, and 6 tables

Code: https://github.com/CIERA-Transients/POTPyRI

License: http://creativecommons.org/licenses/by/4.0/

The gist: Using the fast radio bursts (FRBs) localized with the CHIME/FRB Outriggers between February and October 2025, we conduct a systematic search for dwarf host galaxies.

Terminology

Abstract

Using the fast radio bursts (FRBs) localized with the CHIME/FRB Outriggers between February and October 2025, we conduct a systematic search for dwarf host galaxies. We identify and characterize eight host galaxies for one repeating and seven apparently non-repeating FRBs, newly classifying five hosts as dwarfs with stellar masses of (M/M) about 8.1-9.1. We measure their gas-phase metallicities and, when combined with hosts from the literature, finding that repeating and non-repeating FRBs have statistically distinct metallicity distributions. Non-repeating FRBs inhabit relatively metal-rich environments (12 + log(O/H) 8.35) across the full observed mass range, while repeating FRBs have significant preference for dwarf galaxies with 12 + log(O/H) 8.35. Almost all repeaters associated with persistent radio sources (PRSs) are in dwarfs with 12 + log(O/H) 8.15, suggesting a connection between repeaters in metal-poor dwarf environments and PRS formation. We also calculate the host dispersion measure (DM host), Faraday rotation measure (RM host), and scattering timescale (τ host,1 GHz) for 54, 37, and 24 FRBs, respectively, including both our sample and FRBs in the literature. We find no significant (>3σ) correlation between host metallicity and DM host, RM host, or τ host,1 GHz. The distinct host metallicities of apparently non-repeating and repeating FRBs may reflect metallicity-dependent massive-star evolution, with repeating FRBs and PRSs requiring more extreme magnetar birth spins than the predominantly non-repeating FRB population.

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