Speaker
Description
The Pierre Auger Observatory spans $3\,000\,\text{km}^2$ near Malargüe, Argentina, and serves as the only facility in the southern hemisphere to observe ultra-high-energy cosmic rays (UHECRs), the most energetic particles known. Three triangular arrays of water Cherenkov detectors spaced by $1\,500\,$m, $750\,$m and $433\,$m are used to measure the extensive air showers initiated by primaries with energies above $10^{16}\,$eV. The field of view of the Observatory covers all declinations up to $+44.8^\circ$, containing both the Galactic center and the supergalactic plane. After 20 years of data-taking and with an angular resolution of approximately $1^\circ$, the Observatory has yielded discoveries offering insight into the origin of UHECRs. Above $8\,$EeV, a dipole inconsistent with the Galactic plane is observed at $6.8\,\sigma$ significance, strongly suggesting an extragalactic origin for the highest-energy cosmic rays. At energies above $38\,$EeV, a medium-scale excess centered on Centaurus A is measured at $4\,\sigma$ post-trial significance using a $27^\circ$ top-hat smearing window. No other excess coinciding with the structure of the local Universe is found. Finally, a $3\,\sigma$ deficit in the isotropic flux due to the shadowing of on average $7\times10^{17}$-eV cosmic rays by the Moon and the Sun enables the verification of the pointing and the average angular resolution of the detector arrays.