Towards unravelling the structural distribution of ultra-high-energy cosmic ray sources

TL;DR

This study explores how future ultra-high-energy cosmic ray observations can reveal their local astrophysical source distribution by simulating their propagation and comparing arrival directions to source models.

Contribution

It introduces a realistic model of structured extragalactic magnetic fields and source distribution to assess the potential of UHECRs in unveiling local cosmic structures.

Findings

UHECRs above 10^19.8 eV are optimal for source identification.

Approximately 500 detected events are needed to map local structures.

Five years of Pierre Auger Observatory data could achieve this.

Abstract

We investigate the possibility that near future observations of ultra-high-energy cosmic rays (UHECRs) can unveil their local source distribution, which reflects the observed local structures if their origins are astrophysical objects. In order to discuss this possibility, we calculate the arrival distribution of UHE protons taking into account their propagation process in intergalactic space i.e. energy losses and deflections by extragalactic magnetic field (EGMF). For a realistic simulation, we construct and adopt a model of a structured EGMF and UHECR source distribution, which reproduce the local structures actually observed around the Milky Way. The arrival distribution is compared statistically to their source distribution using correlation coefficient. We specially find that UHECRs above $10^{19.8}$eV are best indicators to decipher their source distribution within 100 Mpc, and detection of about 500 events on all the sky allows us to unveil the local structure of UHE universe for plausible EGMF strength and the source number density. This number of events can be detected by five years observation by Pierre Auger Observatory.