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Anisotropy studies of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory
Josina Schulte, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: Measurements of anisotropic arrival directions of ultra-high-energy cosmic rays provide important information for identifying their sources. On large scales, cosmic rays with energies above 8 EeV reveal a dipolar flux modulation in right ascension with a significance of 6.9 deg., with the dipole direction pointing 113◦ away from the Galactic center. This observation is explained by extragalactic origins. Also, model-independent searches for small- and intermediate-scale overdensities have been performed in order to unveil astrophysically interesting regions. On these scales, no statistically significant features could be detected. However, intermediate-scale analyses comparing the measured arrival directions with potential source catalogs show indications for a coincidence of the measured arrival directions with catalogs of starburst galaxies and the Centaurus A region. In this contribution, an overview of the studies regarding anisotropies of the arrival directions of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory on different angular scales is presented and the current results are discussed.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, UHECR anisotropy studies, UHECR sources
Published in RUNG: 24.01.2024; Views: 673; Downloads: 5
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With AugerPrime to the phase II of the Pierre Auger Observatory
Daniele Martello, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: AugerPrime, the upgrade of the Pierre Auger Observatory, is nearing completion and the Observatory is now prepared to collect physics data after the commissioning of the new components. The Pierre Auger Observatory has demonstrated, based on the data collected thus far, the existence of the cutoff in the spectrum with high accuracy. However, the origin of this cutoff remains incompletely understood. The upgraded Observatory is designed to address the unresolved questions regarding the nature of the cosmic ray flux cutoff thanks to its capability to disentangle the muon and electromagnetic components of extensive air showers. Furthermore, the measurement of the muon component at ground level can verify the accuracy of hadronic interaction models currently used. This presentation will provide an overview of the status of the Observatory and the accurate commissioning done before the start of the physics run. Furthermore, we will present the initial data from Phase II data mainly dedicated to proving the continuity of operation of the Observatory from Phase I to Phase II.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, AugerPrime detector upgrade, Pierre Auger data
Published in RUNG: 24.01.2024; Views: 674; Downloads: 6
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8.
Advances on the Pierre Auger outreach and education program
Gabriella Cataldi, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: The Pierre Auger Observatory has implemented a novel method of astroparticle detection that combines various techniques and has an open data policy. The dissemination of information about the different astroparticle detection methods, ranging from surface water-Cherenkov detectors to underground scintillator detectors, is now possible due to access to specialized tools for data analysis. This allows for the introduction of the topic of astroparticles to teachers and students at different educational levels. This marks a significant moment for the Observatory. In this work, we will discuss the diverse outreach initiatives undertaken by the Observatory, which have facilitated interaction among members of the international collaboration and enabled collaborative actions between the permanent staff of the Observatory in Malargüe and other institutions worldwide through synchronous meetings. These programs provide visitors with the opportunity to explore the environment of secondary particle cascades produced by cosmic rays, leading to a record number of monthly visitors since the opening of the Observatory 25 years ago.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, Pierre Auger Outreach and Education program
Published in RUNG: 24.01.2024; Views: 613; Downloads: 8
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9.
Astrophysical interpretation of energy spectrum and mass composition of cosmic rays as measured at the Pierre Auger Observatory
Eleonora Guido, Andrej Filipčič, Jon Paul Lundquist, Shima Ujjani Shivashankara, Samo Stanič, Serguei Vorobiov, Danilo Zavrtanik, Marko Zavrtanik, 2023, published scientific conference contribution

Abstract: The combined interpretation of the spectrum and composition measurements plays a key role in the quest for the origin of ultra-high-energy cosmic rays (UHECRs). The Pierre Auger Observatory, thanks to its huge exposure, provides the most precise measurement of the energy spectrum of UHECRs and the most reliable information on their composition, exploiting the distributions of the depth of maximum of the showers in the atmosphere. A combined fit of a simple astrophysical model of UHECR sources to the spectrum and mass composition measurements is used to evaluate the constraining power of the data measured by the Pierre Auger Observatory on the source properties. We find that our data across the “ankle” feature are well reproduced if two extragalactic populations of sources are considered, one emitting a very soft spectrum which dominates the region below the ankle, and the other taking over at energies above the ankle, with an intermediate mixed composition, a hard spectrum and a low rigidity cutoff. Interestingly, similar results can also be obtained if the medium-mass contribution at lower energy is provided by an additional galactic component.
Keywords: Pierre Auger Observatory, ultra-high energy cosmic rays, UHECR energy spectrum, UHECR mass composition
Published in RUNG: 24.01.2024; Views: 637; Downloads: 7
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10.
Investigation of multi-messenger properties of FR0 radio galaxy emitted ultra-high energy cosmic rays
Jon Paul Lundquist, Lukas Merten, Serguei Vorobiov, Margot Boughelilba, Albert Reimer, Paolo Da Vela, F. Tavecchio, G. Bonnoli, C. Righi, 2023, published scientific conference contribution

Abstract: Low luminosity Fanaroff-Riley type 0 (FR0) radio galaxies are amongst potential contributors to the observed flux of ultra-high energy cosmic rays (UHECRs). Due to FR0s’ much higher abundance in the local universe than more powerful radio galaxies (e.g., about five times more ubiquitous at redshifts z≤0.05 than FR1s), they could provide a substantial fraction of the total UHECR energy density. In the presented work, we determine the mass composition and energy spectrum of UHECRs emitted by FR0 sources by fitting simulation results from the CRPropa3 framework to the recently published Pierre Auger Observatory data. The resulting emission spectral characteristics (spectral indices, rigidity cutoffs) and elemental group fractions are compared to the Auger results. The FR0 simulations include the approximately isotropic distribution of FR0s extrapolated from the measured FR0 galaxy properties and various extragalactic magnetic field configurations, including random and large-scale structured fields. We predict the fluxes of secondary photons and neutrinos produced during UHECR propagation through cosmic photon backgrounds. The presented results allow for probing the properties of the FR0 radio galaxies as cosmic-ray sources using observational high-energy multi-messenger data.
Keywords: ultra-high energy cosmic rays, UHECRs, Pierre Auger Observatory, UHECR propagation, UHECR interactions, UHECR energy spectrum, UHECR mass composition, UHECR sources, Fanaroff-Riley (FR) radio galaxies, FR0 galaxies
Published in RUNG: 24.01.2024; Views: 581; Downloads: 10
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