Statistical Analysis of the Correlation between Active Galactic Nuclei and Ultra-High Energy Cosmic Rays

Abstract

We develop the statistical methods for comparing two sets of arrival directions of cosmic rays in which the two-dimensional distribution of arrival directions is reduced to the one-dimensional distributions so that the standard one-dimensional Kolmogorov-Smirnov test can be applied. Then we apply them to the analysis of correlation between the ultra-high energy cosmic rays (UHECR) with energies above $5.7\times 10^{19}$ eV, observed by Pierre Auger Observatory (PAO) and Akeno Giant Air Shower Array (AGASA), and the active galactic nuclei (AGN) within the distance 100 Mpc. For statistical test, we set up the simple AGN model for UHECR sources in which a certain fraction of observed UHECR are originated from AGN within a chosen distance, assuming that all AGN have equal luminosity and smearing angle of UHECR, and the remaining fraction are from the isotropic background contribution. For the PAO data, our methods exclude not only a hypotheses that the observed UHECR are simply isotropically distributed but also a hypothesis that they are completely originated from the selected AGN. But, the addition of appropriate amount of isotropic component either through the background contribution or through the large smearing effect improves the correlation greatly and makes the AGN hypothesis for UHECR sources a viable one. We also point out that restricting AGN within the distance bin of 40-60 Mpc happens to yield a good correlation without appreciable isotropic component and large smearing effect. For the AGASA data, we don't find any significant correlation with AGN.

18 pages, 9 figures, a version published in JCAP

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Cited by in corpus (9)

• The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
• A Bayesian analysis of the 27 highest energy cosmic rays detected by the Pierre Auger Observatory
• Impact of using the ultra-high-energy cosmic ray arrival energies to constrain source associations
• Centaurus A as a point source of Ultra-High Energy Cosmic Rays
• Multilevel Bayesian framework for modeling the production, propagation and detection of ultra-high energy cosmic rays
• Revisit of Correlation Analysis between Active Galactic Nuclei and Ultra-High Energy Cosmic Rays
• Correlation between Ultra-high Energy Cosmic Rays and Active Galactic Nuclei from Fermi Large Area Telescope
• Propagation of ultra-high-energy cosmic rays in the magnetized cosmic web
• Ultra high-energy cosmic rays from beyond the Greisen-Zatsepin-Kuz'min horizon