Limit on the intergalactic magnetic field from the ultrahigh-energy cosmic ray hotspot in the Perseus-Pisces region

The Telescope Array Collaboration has reported an evidence for existence of a source of ultrahigh energy cosmic ray 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 supercluster (similar to 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 tructure. Our analysis indicates that the source has to be dominated by protons, because heavier nuclei are either photodisintegrated or are too strongly deflected by the Galactic magnetic field.