Cosmic connections: from cosmic rays to gamma rays, to cosmic backgrounds and magnetic fields

TL;DR

This paper reviews recent advances in understanding cosmic rays, gamma rays, magnetic fields, and background light, highlighting new insights from combined observational data and theories explaining high-energy astrophysical phenomena.

Contribution

It synthesizes recent observational and theoretical developments, proposing a holistic approach to cosmic rays, gamma rays, and magnetic fields in astrophysics.

Findings

New measurements of intergalactic magnetic fields from distant sources

A theory explaining the hard spectra of distant blazars

Discussion of transient galactic sources contributing to ultrahigh-energy cosmic rays

Abstract

Combined data from gamma-ray telescopes and cosmic-ray detectors have produced some new surprising insights regarding intergalactic and galactic magnetic fields, as well as extragalactic background light. We review some recent advances, including a theory explaining the hard spectra of distant blazars and the measurements of intergalactic magnetic fields based on the spectra of distant sources. Furthermore, we discuss the possible contribution of transient galactic sources, such as past gamma-ray bursts and hypernova explosions in the Milky Way, to the observed flux of ultrahigh-energy cosmic-rays nuclei. The need for a holistic treatment of gamma rays, cosmic rays, and magnetic fields is a unifying theme for these seemingly unrelated phenomena.