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— Cosmic ray density map for the flux-weighted 2MRS galaxies, smoothed with an angular scale σ = 5 ◦ .
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Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an act...
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... corresponding density map is shown on the right panel of the same figure, smoothed with an angular scale σ = 5 ◦ . No isotropic fraction is built into this map to better illustrate the features of the objects in the catalog. We show the density map obtained for the 2MRS catalogue in Fig. 5. Common features can be seen in the two ...
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The origin of ultrahigh energy cosmic rays (UHECRs) is an open question. In this proceeding, we first review the general physical requirements that a source must meet for acceleration to 10-100 EeV, including the consideration that the shock is not highly relativistic. We show that shocks in the backflows of radio galaxies can meet these requiremen...
This paper summarizes the status and the recent measurements from the Pierre
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Observations of cosmic ray arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Véron-Cetty Véron catalog. In this paper we report on the use of three catalog independent methods to search fo...
Citations
... However, to quantify these possibilities we can use a statistical test method to measure the correlation between the detected data in both observatories and a collection of possible sources of some kind. As in [15] we can build a likelihood function that depends on the contribution of the sources of a catalog and an anisotropic background of UHECRs, the likelihood function is: ...
... Given the relatively modest mean free paths of the highest energy cosmic rays, one could expect the ultra-high energy cosmic ray spectrum to be dominated by the nearest radio galaxies. Within this context, it is particularly interesting that the Auger Collaboration has reported a modest excess of events above 55 EeV from directions within ∼20 @BULLET of Cen A (seeFig. 9of Ref.[108], and also Refs.[109][110][111][112][113][114][115]). Although this signal constitutes only a ∼ 2σ excess, it is suggestive within the context of the scenario considered here. ...
Multi-messenger data suggest that radio galaxies (i.e. non-blazar active galaxies) are perhaps the most likely class of sources for the diffuse flux of high-energy neutrinos reported by the IceCube Collaboration. In this study, we consider the gamma-ray spectrum observed from four nearby radio galaxies (Centaurus A, PKS 0625-35, NGC 1275 and IC 310) and constrain the intensity and spectral shape of the emission injected from these sources, accounting for the effects of attenuation and contributions from electromagnetic cascades (initiated both within the radio galaxy itself and during extragalactic propagation). Assuming that this gamma-ray emission is generated primarily through the interactions of cosmic-ray protons with gas, we calculate the neutrino flux predicted from each of these sources. Although this scenario is consistent with the constraints published by the IceCube and ANTARES Collaborations, the predicted fluxes consistently fall within an order of magnitude of the current point source sensitivity. The prospects appear very encouraging for the future detection of neutrino emission from the nearest radio galaxies.
... As a complement to the all-sky analysis, we also search for excesses of unresolved gamma-ray emission around the Cen A and TA hotspot regions. The nearby Cen A radio galaxy is a leading candidate for UHECR acceleration and has shown tentative evidence for an excess of PAO events within 18 • [45]. Additionally, the Telescope Array has observed a statistically significant hotspot of events in a region which stretches at least 20 • in radius in the northern hemisphere [28]. ...
The astrophysical sources responsible for ultra high-energy cosmic rays (UHECRs) continue to be one of the most intriguing mysteries in astrophysics. We present a comprehensive search for correlations between high-energy ($\gtrapprox 1$ GeV) gamma-ray events from the Fermi Large Area Telescope (LAT) and UHECRs ($\gtrapprox 60$ EeV) detected by the Telescope Array and the Pierre Auger Observatory. We perform two separate searches. First, we conduct a standard cross-correlation analysis between the arrival directions of 148 UHECRs and 360 gamma-ray sources in the Second Catalog of Hard Fermi-LAT sources (2FHL). Second, we search for a possible correlation between UHECR directions and unresolved Fermi-LAT gamma-ray emission. For the latter, we use three different methods: a stacking technique with both a model-dependent and model-independent background estimate, and a cross-correlation function analysis. We also test for statistically significant excesses in gamma rays from signal regions centered on Cen A and the Telescope Array hotspot. No significant correlation is found in any of the analyses performed, except a weak ($\lessapprox 2\sigma$) hint of signal with the correlation function method on scales $\sim 1^\circ$. Upper limits on the flux of possible power-law gamma-ray sources of UHECRs are derived.
... Based on the Greisen-Zatsepin-Kuzmin (GZK) suppression (Greisen, 1966;Zatsepin & Kuzmin, 1966); the steep suppression of the spectrum above the energies ∼ 4 × 10 19 eV caused by the interaction of UHECRs with CMB photons; we can restrict candidates for the sources; they would be located within r GZK ∼ 100 Mpc. There have been many attempts to identify the source of UHECRs using correlation tests with astrophysical objects or the matter distribution in the universe (Abbasi et al., 2008;Abreu et al., 2010;Kim & Kim, 2013;Kashti & Waxman, 2008;Takami et al., 2009); however, we have no conclusive correlation results yet. ...
... Thus, the field of view for PAO is −90 • ≤ δ ≤ 24.8 • by Equation (3). In this field of view, the PAO observed 69 UHECR events having energies above 5.5 × 10 19 eV (Abreu et al., 2010). We use this data set for observed UHECR events. ...
The galactic magnetic field (GMF) and the intergalactic magnetic field (IGMF) affect the propagation of ultra-high energy cosmic rays (UHECRs) from the source to us. Here we examine the influences of the GMF/IGFM and the dependence of their sky distribution on galactic latitude, b. We analyze the correlation between the arrival direction (AD) of UHECRs observed by the Pierre Auger Observatory and the large-scale structure of the universe in regions of sky divided by b. Specifically, we compare the AD distribution of observed UHECRs to that of mock UHECRs generated from a source model constructed with active galactic nuclei. Our source model has the smearing angle as a free parameter that reflects the deflection angle of UHECRs from the source. The results show that larger smearing angles are required for the observed distribution of UHECRs in lower galactic latitude regions. We obtain, for instance, a 1{\sigma} credible interval for smearing angle of 0^{\circ}{\leq}{\theta}_s{\leq}72^{\circ} at high galactic latitudes, 60^{\circ}, and of 75^{\circ}{\leq}{\theta}_s{\leq}180^{\circ}, -30^{\circ}{\leq}b{\leq}30^{\circ}, at low galactic latitudes, respectively. The results show that the influence of the GMF is stronger than that of the IGMF. In addition, we can estimate the strength of GMFs by these values; if we assume that UHECRs would have heavier nuclei, the estimated strengths of GMF are consistent with the observational value of a few ?G. More data from the future experiments may make UHECR astronomy possible.
... In 2008, the Pierre Auger experiment reported a weak 1% correlation of their cosmic-ray events above 6 × 10 19 eV with nearby AGNs [9]. However, this significance has decreased since then [10]. In addition, the result is in conflict with their own composition measurements, which prefer a heavy composition (the correlation requires the particles to be protons as heavier nuclei would be deflected too strongly in the magnetic fields), but which have their own problems due to their strong simulation dependency. ...
With the completion of the first cubic-kilometer class neutrino telescopes,
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sources enters into a new phase. The usage of neutrinos as cosmic messengers
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... Some of the earlier studies also point at the UHECR clustering, e.g., [4], while other analyses incline towards a more isotropic distribution (see, e.g. [5,6] for a review of the recent results and [7] for the updated Auger observations, downplaying to some extent the initial anisotropy finding). Notwithstanding the recent advances, the origin of the mysterious UHECRs remains unknown. ...
A mechanism for proton acceleration to ~ 10²¹ eV is suggested. It may operate in accretion flows onto thin dark matter filaments of cosmic structure formation. The flow compresses the ambient magnetic field to strongly increase and align it with the filament. Particles begin the acceleration by E × B drift with the accretion flow. The energy gain in the drift regime is limited by the conservation of the adiabatic invariant p⊥²/B(r). Upon approaching the filament, the drift turns into the gyro-motion around the filament so that the particle moves parallel to the azimuthal electric field. In this `betatron' regime the acceleration speeds up to rapidly reach the electrodynamic limit cpmax = eBR for an accelerator with magnetic field B and the orbit radius R (Larmor radius). The periodic orbit becomes unstable and the particle slings out of the filament to the region of a weak (uncompressed) magnetic field, which terminates the acceleration.
To escape the filament, accelerated particles must have gyro-radii comparable with the filament radius. Therefore, the mechanism requires pre-acceleration that is likely to occur in large scale shocks upstream or nearby the filament accretion flow. Previous studies identify such shocks as efficient proton accelerators, with a firm upper limit ~ 1019.5 eV placed by the catastrophic photo-pion losses. The present mechanism combines explosive energy gain in its final (betatron) phase with prompt particle release from the region of strong magnetic field. It is this combination that allows protons to overcome both the photo-pion and the synchrotron-Compton losses and therefore attain energy ~ 10²¹ eV. A customary requirement on accelerator power to reach a given Emax, which is placed by the accelerator energy dissipation ∝Emax²/Z0 due to the finite vacuum impedance Z0, is circumvented by the cyclic operation of the accelerator.
This article describes the scope and characteristics of the research developed in the state of Puebla, Mexico, whose results have been published in journals indexed in the Web of Science. The analyzed corpus was compiled by the search procedure with the word “puebla” in the organization and address fields, restricted to the period 2008-2012. We observed from the data obtained that the Universidad Autónoma de Puebla and the Instituto Nacional de Astrofísica, Óptica y Electrónica are the most productive institutions of Puebla. Our focus was on the 102 most cited articles of the period. Scientific production of Puebla institutions focuses on the physical and biomedical sciences and this production derives mostly from international collaborations. The multiauthor articles (at least three authors) are the most cited publications, while the individual research papers have little impact according to their number of citations. Finally, we analyze the differences in impact factor across scientific fields.
Trace charge imbalances can explain puzzling cosmological observations such as the large `missing' fraction of electrons in cosmic rays and their contrast to the charge-neutral solar wind, the extreme energy sources that sustain quasars, galactic jets, and active galactic nuclei, the origin and nature of `dark matter' galaxy haloes, and the apparent acceleration of the expansion of the Universe, obviating $\Lambda$CDM. When there are $\sim \num{9e-19}$ amounts of excess $\ce{H3+}$ or $\ce{H-}$ within cold diffuse clouds of $\ce{H2}$, residual repulsive Coulomb forces are comparable to the gravitational attractions between hadrons. This trace-charged dark matter is inert with respect to static electrogravitional self-attractions, but still responds to electromagnetic fields and gravitational attractions with uncharged matter. Residual trace charge is also the ionic catalyst that keeps dark matter in the state of unseen clouds of cold molecular hydrogen plus trace $\ce{H3+}$. Once warm enough to partially ionize, bright matter preferentially expels its net charge to become nearly charge-neutral with respect to surrounding trace-charged dark matter. Planets surrounding stars become charge neutral as they bathe in a charge-neutral stellar wind. In contrast, at AGNs, newly ionized protons along with a significant fraction of entrained dark matter are Coulomb-expelled to relativistic velocities in polar jets that initiate near the event horizon of a trace-charged supermassive black hole. Extrasolar cosmic rays generated by these and from similar speed jets from accreting charged black holes would be strongly proton-dominated, as observed. The original trace charge imbalances could have originated during the Big Bang.
To verify that the active galactic nuclei
(AGN) can be the sources of ultra‐high energy cosmic rays (UHECR), we constructed three test statistics and tested the hypothesis that AGN are the origin of UHECR using the Monte‐Carlo simulation. The observed data from Akeno Giant Air Shower Array (AGASA) and Pierre Auger Observatory (PAO) are used as our UHECR data sets and the AGN list compiled in the 12th edition of Véron‐Cetty and Véron (VCV) catalog is used as our AGN data. Only the UHECR with energies above
5.7×10
19
eV
and AGN within Greisen‐Zatsepin‐Kuzmin (GZK) radius, 100 Mpc, were applied to our statistical tests. We generalized the hypothesis thus it is considered that a certain fraction of the sources is AGN and the rest are isotropic component, coming from the outside of GZK radius. The hypotheses were tested by Kolmogorov‐Smirnov (KS) test in two ways, which are the dependence of fraction and that of smearing angles. The probabilities obtained by KS test are extremely small enough to reject the hypotheses that the UHECR come from the AGN within 100 Mpc totally or come from the completely isotropic distribution for the PAO data. In the case of AGASA, it seems there is no significant correlation with AGN. We look forward to solving the problem of the sources of UHECR using the data observed by Telescope Array (TA) experiment.
The wealth of data collected in the last few years thanks to the Pierre Auger
Observatory and recently to the Telescope Array made the problem of the origin
of ultra high energy cosmic rays a genuinely experimental/observational one.
The apparently contradictory results provided by these experiments in terms of
spectrum, chemical composition and anisotropies do not allow to reach any final
conclusions as yet. Here I will discuss some of the theoretical challenges
imposed by these data: in particular I will discuss some issues related to the
transition from Galactic to extragalactic cosmic rays and how the different
models confront our understanding of Galactic cosmic rays in terms of supernova
remnants paradigm. I will also discuss the status of theories aiming at
describing acceleration of cosmic rays to the highest energies in relativistic
shocks and unipolar inductors.
