Ultra-High Energy Cosmic Rays Detected by Auger and AGASA:Corrections for Galactic Magnetic Field Deflections, Source Populations, and Arguments for Multiple-Components
The origin and composition of Ultra-High Energy Cosmic Ray Events (UHECRs) are under debate. Here we improve constraints on the source population(s) and compositions of UHECRs by accounting for UHECR deflections within existing Galactic magnetic field models (GMFs). We used Monte Carlo simulations for UHECRs detected by the Pierre Auger Observatory and AGASA in order to determine their outside-the-Galaxy arrival directions, and compared these with Galactic and extragalactic sources. The simulations, which used UHECR compositions from protons to Iron and seven models of the ordered GMF, include uncertainties in the GMF and a turbulent magnetic field. The correlation between UHECRs and nearby extended radiogalaxies (Nagar & Matulich 2008) remains valid, even strengthened, within several GMF models. Both the nearest radiogalaxy CenA, and the nearest radio-extended BL Lac, CGCG 413-019, are likely sources of multiple UHECRs. The correlation appears to be linked to the presence of the extended radio source rather than a tracer of an underlying population. It is possible, but unlikely, that all UHECRs originate in the nearby radiogalaxy CenA. For light UHECRs about a third of UHECRs can be "matched" to nearby galaxies with extended radio jets. The remaining UHECRs could also be explained as originating in extended radiogalaxies if one has at least one of: a large UHECR mean free path, a high cluster and/or intergalactic magnetic field, a heavy composition for two-thirds of the detected UHECRs. Several UHECRs have trajectories which pass close to Galactic magnetars and/or microquasars.
If extended radiogalaxies are, or trace, UHECR sources, the most consistent models for the ordered GMF are the BS-S and BS-A models; the GMF models of Sun et al. 2008 are acceptable if a dipole component is added.
In this work, direct measurements of the muon density at $1000\,\textrm{m}$ from the shower axis obtained by the Akeno Giant Air Shower Array (AGASA) are analysed. The selected events have zenith angles $θ\leq 36^{\textrm{o}}$ and reconstructed energies in the range $18.83\,\leq\,\log_{10}(E_{R}/\textrm{eV})\,\leq\,19.46$. These are compared to the predictions corresponding to proton, iron, and mixed composition scenarios obtained by using the high-energy hadronic interaction models EPOS-LHC, QGSJetII-04, and Sibyll2.3c. The mass fractions of the mixed composition scenarios are taken from the …
Ultra-high energy cosmic ray correlations with Active Galactic Nuclei in the world dataset
Pierre Auger合作组最近提出了最高能量宇宙射线的到达方向与活动星系核（AGN）子集相关的假说。我们使用雅库茨克、AGASA和HiRes实验收集的公开事件集对活动星系核假说进行了盲检验。程序的一致性要求事件能量朝向共同能量标度归一化。所得数据集中相关事件的数量为21个中的3个，这与预期的随机背景一致。
We present a new approach for the identification of ultra-high energy cosmic rays from sources using dynamic graph convolutional neural networks. These networks are designed to handle sparsely arranged objects and to exploit their short- and long-range correlations. Our method searches for patterns in the arrival directions of cosmic rays, which are expected to result from coherent deflections in cosmic magnetic fields. The network discriminates astrophysical scenarios with source signatures from those with only isotropically distributed cosmic rays and allows for the identification of cosmic …
The images of ultrahigh-energy cosmic ray sources get distorted, in an energy dependent way, by the effects of Galactic and extragalactic magnetic fields. These deflections can also affect the observed cosmic ray spectrum, specially when the sources are transient. We study scenarios in which one or a few nearby extragalactic sources, such as CenA or M81/M82, provide the dominant contribution to the cosmic ray flux above the ankle of the spectrum. We discuss the effects of the angular dispersion induced by the turbulent extragalactic magnetic fields, and the coherent deflections caused by the r…
This work presents a scenario of ultra-high energy cosmic ray source distribution where a nearby source is solely responsible for the anisotropies in arrival directions of cosmic rays while the rest of the sources contribute only isotropically. An analytical approach focused on large-scale anisotropies, which are influenced by deflections in a Kolmogorov-type turbulent magnetic field, is employed to provide more general results. When the recent Pierre Auger Observatory angular power spectrum above 8 EeV is used the restricted model gives, under the assumption of the small angle approximation, …
The distribution of ultra-high-energy cosmic-ray arrival directions appears to be nearly isotropic except for a dipole moment of order $6 \times (E/10~\mathrm{EeV})$ per cent. Nonetheless, at the highest energies, as the number of possible candidate sources within the propagation horizon and the magnetic deflections both shrink, smaller-scale anisotropies might be expected to emerge. On the other hand, the flux suppression reduces the statistics available for searching for such anisotropies. In this work, we consider two different lists of candidate sources: a sample of nearby starburst galaxi…
We interpret the correlation between local star-forming galaxy positions and ultra-high-energy cosmic ray (UHECR) directions, recently detected by the Pierre Auger Observatory (PAO), in terms of physical parameters: the local density of sources and the magnetic fields governing the UHECR propagation. We include a Galactic magnetic field model on top of a random extragalactic magnetic field description to determine the level of UHECR deflections expected from an ensemble of source positions. Besides deflections in magnetic fields, we also take into account energy losses with background photon f…
On the astrophysical origin of cosmic rays: Constraining the Ultra-High-Energy Cosmic Ray Horizon through Nearby Galaxy Distributions
Instituto de Astronomía Teórica y Experimental (IATE), CONICET, Observatorio Astronómico de Córdoba（理论与实验天体物理研究所（IATE），阿根廷国家科学研究委员会，科尔多瓦天文台）；Gabinete de Astronomía Extragaláctica, Departamento de Geofísica, Astronomía y Física, CONICET, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de San Juan（河外天文研究室，地球物理学、天文学与物理系，阿根廷国家科学研究委员会，理学院，圣胡安国立大学）；Observatorio Astronómico de Córdoba, UNC（科尔多瓦天文台，科尔多瓦大学）
Tipler has shown that if we assume that the particle physics Standard Model and DeWitt-Wheeler quantum gravity (equivalent to Feynman-Weinberg quantum gravity) are a Theory of Everything, then in the very early universe, the Cosmic Background Radiation (CBR) could not have coupled to right handed electrons and quarks. Tipler further showed that if this property of CBR has continued, the Sunyaev-Zel'dovich (SZ) effect would be observed to be too low by a factor of two. WMAP and PLANCK observed this. Tipler showed that this CBR property would also mean the Ultra High Energy Cosmic Rays (UHECR) w…
Active galactic nuclei (AGNs) are considered to be one of the most appropriate sources of ultra high energy cosmic rays (UHECRs, $E \gtrsim 10^{18} \mathrm{~eV}$). Radiogalaxy Virgo A (M87) in the centre of a cluster of galaxies Virgo Cluster (VC) can be a prominent source of UHECRs. We investigate the possible contribution of Virgo A and the VC to the flux of events with trans-GZK energies - extremely high energy cosmic rays (EHECRs) - from the recent Auger and Telescope Array (TA) data sets ($E > 52 \mathrm{~EeV}$ and $E > 57 \mathrm{~EeV}$, respectively). We simulate EHECR propagation from …
Ultrahigh energy cosmic rays are the most energetic of any subatomic particles ever observed in nature. The quest for their mysterious origin is currently a major scientific challenge. Here we explore the possibility that these particles originate from nearby starburst galaxies, a scenario that matches the recent observation by the Telescope Array experiment of a cosmic-ray hotspot above 57~EeV not far from the direction of the starburst galaxy M82. Specifically, we study the stochastic propagation in space of ultrahigh energy cosmic rays through the state-of-the-art simulation framework CRPro…
We investigate the implications of the current data regarding large scale anisotropies, and examine to what extent they can be used to constrain the origin of UHECRs and the astrophysical parameters of the source scenarios. We discuss the possibility of observing an associated anisotropy of the composition, the potential benefit of the separation of the different nuclear components and the interest of observing the UHECR sky with larger exposure future observatories. We simulate UHECR sky maps for various astrophysical scenarios satisfying the current observational constraints, taking into acc…
The IceCube Neutrino Observatory has recently found compelling evidence for a particular blazar producing high-energy neutrinos and $\mathrm{PeV}$ cosmic rays, however the sources of cosmic rays above several $\mathrm{EeV}$ remain unidentified. It is believed that the same environments that accelerate ultra-high-energy cosmic rays (UHECRs) also produce high-energy neutrinos via hadronic interactions of lower-energy cosmic rays. Two out of three joint analyses of the IceCube Neutrino Observatory, the Pierre Auger Observatory and the Telescope Array yielded hints for a possible directional corre…
Rome University “La Sapienza”（罗马大学）；MIFP, Rome, Italy（MIFP）；National University of Oil and Gas «Gubkin University»（国立石油天然气大学古布金大学）；Institute of Physics, Southern Federal University（南联邦大学物理研究所）
The origin and nature of the cosmic rays is still uncertain. However, a big progress has been achieved in recent years due to the good quality data provided by current and recent cosmic-rays observatories. The cosmic ray flux decreases very fast with energy in such a way that for energies $\gtrsim 10^{15}$ eV, the study of these very energetic particles is performed by using ground based detectors. These detectors are able to detect the atmospheric air showers generated by the cosmic rays as a consequence of their interactions with the molecules of the Earth's atmosphere. One of the most impor…
Ultra-high-energy cosmic rays (UHECRs) are atomic nuclei from space with vastly higher energies than any other particles ever observed. Their origin and chemical composition remain a mystery. As we show here, the large- and intermediate-angular-scale anisotropies observed by the Pierre Auger Observatory are a powerful tool for understanding the origin of UHECRs. Without specifying any particular production mechanism, but only postulating that the source distribution follows the matter distribution of the local Universe, a good accounting of the magnitude, direction and energy dependence of the…
Ultra-high energy cosmic rays (UHECRs) are the most energetic particles observed and serve as a probe of the extreme universe. A key question to understanding the violent processes responsible for their acceleration is identifying which classes of astrophysical objects (active galactic nuclei or starburst galaxies, for example) correlate to their arrival directions. While source clustering is limited by deflections in the Galactic magnetic field, at the highest energies the scattering angles are sufficiently low to retain correlation with source catalogues. While there have been several studie…
Despite deflections by Galactic and extragalactic magnetic fields, the distribution of ultra-high energy cosmic rays (UHECRs) over the celestial sphere remains a most promising observable for the identification of their sources. Thanks to a large number of detected events over the past years, a large-scale anisotropy at energies above 8 EeV has been identified, and there are also indications from the Telescope Array and Pierre Auger Collaborations of deviations from isotropy at intermediate angular scales (about 20 degrees) at the highest energies. In this contribution, we map the flux of UHEC…
The sources of ultra-high energy cosmic rays (UHECRs) are still one of the main open questions in high-energy astrophysics. If UHECRs are accelerated in astrophysical sources, they are expected to produce high-energy photons and neutrinos due to the interaction with the surrounding astrophysical medium or ambient radiation. In particular, neutrinos are powerful probes for the investigation of the region of production and acceleration of UHECRs since they are not sensitive to magnetic deflections nor to interactions with the interstellar medium. The results of three different analyses that corr…
We search for signals of magnetically-induced effects in the arrival directions of ultra-high-energy cosmic rays detected at the Pierre Auger Observatory. We apply two different methods. One is a search for sets of events that show a correlation between their arrival direction and the inverse of their energy, which would be expected if they come from the same point-like source, they have the same electric charge and their deflection is relatively small and coherent. We refer to these sets of events as "multiplets". The second method, called "thrust", is a principal axis analysis aimed to detec…
