Limit on intergalactic magnetic field from ultra-high-energy cosmic ray hotspot in Perseus-Pisces region

TL;DR

This paper establishes a new upper limit on the intergalactic magnetic field strength in the Taurus void by analyzing ultra-high-energy cosmic ray sources in the Perseus-Pisces supercluster, surpassing previous bounds from radio measurements.

Contribution

It provides the first upper bound on magnetic fields in large-scale voids based on cosmic ray observations, improving previous constraints by an order of magnitude.

Findings

Upper bound on IGMF strength is ~10^{-10} G for correlation length > 70 Mpc.

The bound is an order-of-magnitude stronger than previous radio Faraday rotation limits.

This is the first constraint on magnetic fields in large-scale voids.

Abstract

Telescope Array collaboration has reported an evidence for existence of a source of ultra-high-energy cosmic ray (UHECR) events in Perseus-Pisces supercluster. We show that the mere existence of such a source imposes an upper bound on the strength of intergalactic magnetic field (IGMF) in the Taurus void lying between the Perseus-Pisces supercluster and the Milky Way galaxy. This limit is at the level of 10^{-10} G for a field with correlation length larger than the distance of the super-cluster ~ 70 Mpc. This bound is an order-of-magnitude stronger that the previously known bound on IGMF from radio Faraday rotation measurements and it is the first upper bound on magnetic field in the voids of the Large Scale Structure.