Volume 358 - 36th International Cosmic Ray Conference (ICRC2019) - CRI - Cosmic Ray Indirect
Anisotropies of the Highest Energy Cosmic-ray Events Recorded by the Pierre Auger Observatory in 15 years of Operation
L. Caccianiga
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Pre-published on: 2019 July 22
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Abstract
To understand the origin of ultra-high energy cosmic rays (UHECRs), the study of the distribution of their arrival directions has always been of capital importance, despite the difficulties that arise from the deflection they suffer due to magnetic fields. In particular, the highest-energy region, above a few tens of EeV, which extends beyond the observed flux suppression, is of particular interest because of the high rigidities and the suppression of distant sources. We present here the latest results of searches for anisotropies in the arrival directions of the UHECRs detected by the Pierre Auger Observatory. The dataset used for this work is the largest ever recorded from a single observatory at these energies: with nearly 15 years of data, it covers the sky up to a declination of $45^\circ$, with an exposure now exceeding $100,000 \; \mathrm{km}^2 \; \mathrm{sr} \; \mathrm{yr}$. The study of large-scale anisotropy indicates an extragalactic origin for the sources of UHECRs with energies larger than 8 EeV. A search for anisotropies at small to intermediate angular-scales is presented, which enables a model-independent study of flux patterns at the highest energies. We also study the arrival directions of UHECRs against the distribution of nearby extragalactic matter traced by different catalogs of candidate sources. We discuss the most striking features characterized by the Pierre Auger Observatory, which include the most significant indication of anisotropy in the arrival directions of the highest energy cosmic rays.
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