Anisotropies of ultrahigh-energy cosmic rays in a scenario with nearby sources

TL;DR

This paper investigates how nearby extragalactic sources and magnetic fields influence the anisotropies and observed patterns of ultrahigh-energy cosmic rays, considering source contributions, magnetic deflections, and composition effects.

Contribution

It introduces a detailed analysis of magnetic field effects on cosmic ray anisotropies from nearby sources, including source imaging and contributions to observed dipoles and hot spots.

Findings

Magnetic deflections significantly affect cosmic ray source images.

Nearby sources can explain observed anisotropies and hot spots.

Source composition influences the anisotropy patterns.

Abstract

The images of ultrahigh-energy cosmic ray sources get distorted, in an energy dependent way, by the effects of Galactic and extragalactic magnetic fields. These deflections can also affect the observed cosmic ray spectrum, specially when the sources are transient. We study scenarios in which one or a few nearby extragalactic sources, such as CenA or M81/M82, provide the dominant contribution to the cosmic ray flux above the ankle of the spectrum. We discuss the effects of the angular dispersion induced by the turbulent extragalactic magnetic fields, and the coherent deflections caused by the regular Galactic magnetic field, with the associated multiple imaging of the sources. We consider the possible contribution from those sources to the dipolar distribution discovered by the Pierre Auger Observatory above 8 EeV, as well as to the hot spots hinted in the observations by the Pierre Auger and Telescope Array observatories at higher energies, taking into account the mixed nature of the cosmic ray composition.