Jul 12 – 23, 2021
Europe/Berlin timezone

The ultra-high-energy cosmic-ray sky above 32 EeV viewed from the Pierre Auger Observatory

Jul 15, 2021, 12:00 PM
1h 30m


Talk CRI | Cosmic Ray Indirect Discussion


Jonathan Biteau (Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France)


The region of the toe in the cosmic-ray spectrum, located at about 45 EeV by the Pierre Auger Collaboration, is of primary interest in the search for the origin of ultra-high energy cosmic rays (UHECRs). The suppression of the flux with increasing energy can be explained by the propagation of UHECRs in intergalactic photon fields, resulting in a shrinking of the observable universe, and/or by the reach of the maximum acceleration potential of astrophysical sources, yielding a sample of UHECRs at presumably high rigidities around the toe. The predominance of foreground sources combined with minimal magnetic bending of UHECR trajectories could thus offer a path towards localizing ultra-high energy accelerators, through the study of UHECR arrival directions.
In this contribution, we present the results of blind and astrophysically-motivated searches for anisotropies with data collected above 32 EeV during the first phase of the Pierre Auger Observatory, i.e. prior to the AugerPrime upgrade, for an exposure of over 100,000 km² yr sr. We have conducted model-independent searches for overdensities at small and intermediate angular scales, correlation studies with several astrophysical structures, and cross-correlation analyses with catalogs of candidate extragalactic sources. These analyses provide the most important evidence to date for an anisotropic distribution of UHECR arrival directions around the toe as measured from a single observatory.


Cosmic ray astronomy; Extragalactic astronomy; Ultra-high-energy cosmic radiation

Collaboration Auger
Subcategory Experimental Results

Primary authors

Jonathan Biteau (Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France) Biteau, for the Pierre Auger Collaboration

Presentation materials