Studying cosmic ray sources using intergalactic electromagnetic cascades

TL;DR

This paper explores how intergalactic electromagnetic cascades can be used to investigate cosmic ray sources, revealing potential new source subclasses and setting limits on exotic black holes.

Contribution

It introduces a novel method combining cosmic ray, gamma-ray, and neutrino data to study particle acceleration near supermassive black holes.

Findings

Identification of a new subclass of sources contributing to gamma-ray and neutrino emissions

Derived upper limits on the number of exotic supermassive black holes with strong magnetic fields

Demonstrated the use of the TransportCR code for cosmic ray propagation simulations

Abstract

In this paper intergalatic electromagnetic cascades are used as a probe of cosmic ray sources. This is achieved as follows. In extragalactic space cosmic rays initiate electromagnetic cascades in which gamma-ray and neutrino emission arises. We used the joint analysis of cosmic ray data, along with extragalactic gamma-ray and neutrino emission, to study particle acceleration in the vicinity of supermassive black holes. Particle injection spectra depend on processes of particle acceleration, and here we discuss models with various injection spectra. The computation of the propagation of cosmic rays in space were performed using the publicly avaliable TransportCR code. It was found that a new subclass of sources might exist that does not contribute to the particle flux on Earth, instead to gamma-ray and neutrino emissions arising in electromagnetic cascades. In addition, the upper limit of the relative number of 'exotic' supermassive black holes surrounded by a superstrong magnetic field is derived.