New full-sky studies of the distribution of ultra-high-energy cosmic-ray arrival directions

TL;DR

This paper updates full-sky anisotropy analyses of ultra-high-energy cosmic rays by combining data from Auger and TA, introducing new methods and galaxy catalog comparisons to better understand cosmic-ray distribution.

Contribution

It presents new combined full-sky anisotropy results, including a novel harmonic space analysis and extended galaxy catalog comparisons, advancing cosmic-ray distribution studies.

Findings

Indications of large- and medium-scale anisotropies in cosmic-ray arrival directions.

Introduction of a new harmonic space analysis for auto- and cross-correlation measurements.

Extended galaxy catalog comparisons to explore source correlations.

Abstract

Ground-based full-sky studies of the angular distribution of arrival directions of ultra-high-energy cosmic rays require combining data from different observatories, such as the Pierre Auger Observatory (Auger) and the Telescope Array (TA), because no single array can cover all declinations. A working group comprising members from the Auger and TA collaborations has been tasked with performing such studies for more than a decade and has found several indications of full-sky anisotropies. Here, we update the results for the large- and medium-scale anisotropy analyses using the latest data from TA, which include corrections for daily and yearly atmospheric effects in data for large-scale anisotropies and looser selection criteria in data for medium-scale anisotropies. We extend the latter one by considering two more galaxy catalogues, consisting of jetted or all AGNs. Finally we also introduce a new angular harmonic space analysis that allows us to measure both the auto-correlation and cross-correlation with all catalogues for all multipoles independently ($\ell_\text{max} = 20$ in this work) and scanning the energy threshold.