Ultra-high energy cosmic rays from a finite number of point sources

Abstract

We have calculated the probability that the clustering of arrival directions of ultra-high energy cosmic rays (UHECRs) is consistent with a finite number of uniformly distributed proton sources. The case of a continuous source distribution is reached only for an unrealisticly high source density, $n_s\gg 10^{-2}/Mp{c}^3$. Even for densities as large as $n_s=10^{-3}/Mp{c}^3$, less than half of the observed cluster are on average by chance. For the best-fit value $n_s=(1-3)\times 10^{-5}/Mp{c}^3$ derived from the AGASA data, the probability that at least one observed cluster is from a true point source is larger than 99.97%, while on average almost all observed clusters are true. The best-fit value found is comparable to the density of AGNs and consistent with the recent HiRes stereo data. In this scenario, the Pierre Auger Observatory will not only establish the clustering of UHECRs but also determine the density of UHECR sources within a factor of a few after one year of data taking.

12 pages, 4 figures; v2 matches version to appear

References in corpus (12)

• Ultra-High Energy Cosmic Ray Probes of Large Scale Structure and Magnetic Fields
• The Changing AGN Population
• The Galactic magnetic field and propagation of ultra-high energy cosmic rays
• Mapping deflections of extragalactic Ultra-High Energy Cosmic Rays in magnetohydrodynamic simulations of the Local Universe
• On the Evidence for Clustering in the Arrival Directions of AGASA's Ultrahigh Energy Cosmic Rays
• Study of Small-Scale Anisotropy of Ultrahigh Energy Cosmic Rays Observed in Stereo by HiRes
• The Small Scale Anisotropies, the Spectrum and the Sources of Ultra High Energy Cosmic Rays
• Ultra High Energy Cosmic Rays
• Small Scale Clustering in the Isotropic Arrival Distribution of Ultra-High Energy Cosmic Rays and Implications for Their Source Candidates
• Arrival Distribution of Ultra-High Energy Cosmic Rays: Prospects for the Future
• Hints of Energy Dependences in AGASA EHECR Arrival Directions
• Statistics of cluster multiplicity and the nature of UHE cosmic ray sources

Cited by in corpus (35)

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• The Galactic magnetic field as spectrograph for ultra-high energy cosmic rays
• Reconciling the ultra-high energy cosmic ray spectrum with Fermi shock acceleration
• Search for Anisotropy of Ultra-High Energy Cosmic Rays with the Telescope Array Experiment
• Implications of Ultra-High-Energy Cosmic Rays for Transient Sources in the Auger Era
• Gamma-Ray Constraints on Maximum Cosmogenic Neutrino Fluxes and UHECR Source Evolution Models
• Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory
• The Compton-Getting effect on ultra-high energy cosmic rays of cosmological origin
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• Ultrahigh Energy Nuclei Propagation in a Structured, Magnetized Universe
• Testing large-scale (an)isotropy of ultra-high energy cosmic rays
• Distortion of Ultra-high-energy sky by Galactic Magnetic Field
• Implications to Sources of Ultra-high-energy Cosmic Rays from their Arrival Distribution
• GZK Photons Above 10 EeV
• GZK Photons in the Minimal Ultra High Energy Cosmic Rays Model
• Acceleration and propagation of ultra high energy cosmic rays
• Does Galactic Magnetic Field Disturb the Correlation of the Highest Energy Cosmic Rays with their Sources?
• UHECR observations and lensing in the magnetic field of the Virgo cluster
• Non-Universal Spectra of Ultra-High Energy Cosmic Ray Primaries and Secondaries in a Structured Universe
• Clustering properties of ultrahigh energy cosmic rays and the search for their astrophysical sources
• A global autocorrelation study after the first Auger data: impact on the number density of UHECR sources
• Composition of UHECR and the Pierre Auger Observatory Spectrum
• Selected Topics in Cosmic Ray Physics
• Time Structure of Ultra-High Energy Cosmic Ray Sources and Consequences for Multi-messenger Signatures
• Towards unravelling the structural distribution of ultra-high-energy cosmic ray sources
• Estimation Prospects of the Source Number Density of Ultra-high-energy Cosmic Rays
• Dip in UHECR and Transition from Galactic to Extragalactic Cosmic Rays
• Anisotropies and clustering of extragalactic cosmic rays
• Multiscale autocorrelation function: a new approach to anisotropy studies
• Search for Correlations between Nearby AGNs and Ultra-high Energy Cosmic Rays
• Magnetic deflections and possible sources of the ultra-high-energy cosmic rays in the AGASA-HiRes-Yakutsk cluster
• Anisotropy studies with multiscale autocorrelation function
• Ultra-high energy cosmic ray propagation in the Universe