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Opis: The Pierre Auger Observatory has developed various activities along the last year in the field of education and dissemination of astrophysics and high-energy astroparticle physics. Since 1999 different approaches and improvements of the tools used to explain what cosmic rays are have been implemented, tested, and redesigned based on public feedback in its headquarters in Malargüe city. This presentation highlights the Observatory's engagement with the community, focusing on the new initiatives. The open data policy, master classes for middle-level students and teachers, the design of innovative activities that involve the community, and the presence of the Observatory in special events with the participation of students are also described.
Ključne besede: open data policy, ultra-high-energy cosmic rays, Pierre Auger Observatory, education
Objavljeno v RUNG: 16.05.2025; Ogledov: 373; Prenosov: 5
Celotno besedilo (8,89 MB)
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Opis: Cosmic ray detectors like the 3000 sq. km surface array of the Pierre Auger Observatory are capable of observing high-energy photons in the range of 10[sup]18 to 10[sup]20 eV if the flux is sufficiently high. However, no clear candidates for ultra-high-energy photons have been identified yet, so simulations must be used to study typical trigger patterns and observables for discriminating photons from hadrons, e.g., with neural networks. Thinning algorithms are applied to keep the computation time and file sizes in a manageable range since the simulation of ultra-high-energy particle showers is computationally expensive. In CORSIKA, particles with energies below a certain fraction of the primary energy, the thinning level, are exposed to thinning. In the case of thinning, only one of the particles emerging from an interaction is tracked. By assigning a corresponding weight, this particle then represents a number of its siblings. However, the weights of particles that originate from electromagnetic interactions can be 100 times larger than for hadronic interactions. In contrast to hadronic showers, where a major part of the signal in a surface detector is produced by muons, photon showers are almost purely electromagnetic. Using simulations of photon-induced showers with two different thinning levels, the influence on different observables used for photon-hadron discrimination is investigated. Effects deriving from both statistical sampling and detector simulations are considered. Possible influences on station-level as well as event-level observables are probed. With this study, we are reassured that the optimal thinning parameters determined for hadron-induced showers are also sufficient for photon-induced showers.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, extensive air showers, CORSIKA air-shower simulator
Objavljeno v RUNG: 16.05.2025; Ogledov: 369; Prenosov: 5
Celotno besedilo (3,18 MB)
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Opis: The flux of ultra-high-energy cosmic rays (UHECRs) is remarkably uniform across all directions in the sky. The only anisotropy detected with a significance greater than 5σ is a large-scale dipolar modulation in right ascension for energies above 8 EeV. To enhance our sensitivity to potential anisotropies, which may be obscured by significant deflections by magnetic fields, two strategies can be employed: (1) focusing on large-scale anisotropies, such as the dipole and quadrupole moments across various energy intervals, which are anticipated to be more resilient to magnetic deflections; or (2) focusing on the highest energies, where the background from distant sources is more attenuated. The unique aspect of our research is achieving full-sky coverage by combining data for the Pierre Auger Observatory and the Telescope Array, which would not be possible with a single detector array. This comprehensive coverage enables the application of analysis techniques that would otherwise require specific assumptions with partial sky coverage. Accounting for potential systematic effects in energy reconstruction is crucial to avoid spurious north–south anisotropies; the overlapping sky region observed by both arrays allows us to address this in an entirely data-driven manner. In this contribution, we present the latest results using the largest UHECR dataset collected to date, with events detected until December 2022 at the Pierre Auger Observatory and until May 2024 at the Telescope Array. It is shown that the dipolar modulation is the only anisotropy that is significantly (4.6σ) identified in the angular power spectrum. The hypothesis of correlations with the starburst galaxies is supported at the significance of 4.4σ.
Ključne besede: ultra-high-energy cosmic rays, Pierre Auger Observatory, UHECR arrival directions, UHECR large-scale anisotropies, UHECR medium-scale anisotropies, full-sky coverage, Telescope Array
Objavljeno v RUNG: 05.05.2025; Ogledov: 470; Prenosov: 4
Celotno besedilo (2,00 MB)
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Opis: The origin of Ultra-High-Energy Cosmic Rays (UHECRs) is one of the biggest mysteries in modern astrophysics. Since UHECRs are deflected by Galactic and extragalactic magnetic fields, their arrival directions do not point to their sources. Previous analyses conducted on the arrival directions of high-energy events (E ≥ 32 EeV) recorded by the Surface Detector of the Pierre Auger Observatory have not shown significant anisotropies. The largest excess found in the first 19 years of data - at the 4.0 sigma level - is in the region around Centaurus A, and it is also the driving force of a correlation of UHECR arrival directions with a catalog of Starburst Galaxies, which is at the 3.8 sigma level. Since UHECRs are mostly nuclei, the lightest ones (least charged) are also the least deflected. While the mass of the events can be estimated better using the Fluorescence Detector of the Pierre Auger Observatory, the Surface Detector provides the necessary statistics needed for astrophysical studies. The introduction of novel mass-estimation techniques, such as machine learning models and an algorithm based on air-shower universality, will help identify high-rigidity events in the Surface Detector data of the Pierre Auger Observatory. With this work, we present how event-per-event mass estimators can help enhance the sensitivity in the search for anisotropies in the arrival directions of UHECRs at small and intermediate angular scales using simulations.
Ključne besede: ultra-high-energy cosmic rays (UHECRs), extensive air showers, Pierre Auger Observatory, UHECR propagation, UHECR arrival directions, UHECR mass composition, Centaurus A radio galaxy, starburst galaxies, air-shower universality
Objavljeno v RUNG: 30.04.2025; Ogledov: 545; Prenosov: 6
Celotno besedilo (2,03 MB)
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Opis: We use a new method to estimate the injected mass composition of ultrahigh cosmic rays (UHECRs) at energies higher than 10 EeV. The method is based on comparison of the energy-dependent distribution of cosmic ray arrival directions as measured by the Telescope Array (TA) experiment with that calculated in a given putative model of UHECR under the assumption that sources trace the large-scale structure (LSS) of the Universe. As we report in the companion Letter, the TA data show large deflections with respect to the LSS which can be explained, assuming small extragalactic magnetic fields (EGMF), by an intermediate composition changing to a heavy one (iron) in the highest energy bin. Here we show that these results are robust to uncertainties in UHECR injection spectra, the energy scale of the experiment and galactic magnetic fields. The assumption of weak EGMF, however, strongly affects this interpretation at all but the highest energies E > 100 EeV, where the remarkable isotropy of the data implies a heavy injected composition even in the case of strong EGMF. This result also holds if UHECR sources are as rare as 2 × 10[sup]−5 Mpc[sup]−3, that is the conservative lower limit for the source number density.
Ključne besede: ultrahigh energy cosmic rays, large-scale structure, extragalactic magnetic fields, UHECR propagation, Telescope Array, UHECR mass composition, UHECR arrival directions
Objavljeno v RUNG: 23.04.2025; Ogledov: 398; Prenosov: 2
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