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

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.