Arrival distribution of Ultra-High-Energy cosmic rays: prospects for the future.
YOSHIGUCHI H., NAGATAKI S. and SATO K.
Abstract (from CDS):
We predict the arrival distribution of ultra-high-energy cosmic rays (UHECRs) above 4x1019 eV with the event number expected by future experiments in the next few years. We perform event simulations with the source model that is adopted in our recent study and can explain the current Akeno Giant Air Shower Array (AGASA) observation. At first, we calculate the harmonic amplitude and the two-point correlation function for the simulated event sets. We find that significant anisotropy on a large angle scale will be observed when ∼103 cosmic rays above 4x1019 eV are detected by future experiments. The Auger array will detect cosmic rays with this event number in a few years of operation. The statistics of the two-point correlation function will also increase. The angle scale at which the events have strong correlation with each other corresponds to the deflection angle of UHECRs propagating in the extragalactic magnetic field (EGMF), which in turn can be determined by the future observations. We further investigate the relation between the number of events clustered in a direction and the distance of their sources. Despite the limited amount of data, we find that the C2 triplet events observed by the AGASA may originate from a source within 100 Mpc from us at 2 σ confidence level. Merger galaxy Arp 299 (NGC 3690 + IC 694) is the best candidate for their source. If data accumulate, the UHECR sources within ∼100 Mpc can be identified significantly from observed event clusterings. This will provide some kinds of information about poorly known parameters that influence the propagation of UHECRs, such as extragalactic and Galactic magnetic fields and the chemical composition of observed cosmic rays. Also, we will reveal the origin of UHECRs with our method of identifying their sources. Finally, we predict the arrival distribution of UHECRs above 1020 eV that is expected to be observed if the current HiRes spectrum is correct and discuss their statistical features and implications.
ISM: Cosmic Rays - Galaxies: General - ISM: Magnetic Fields - Cosmology: Large-Scale Structure of Universe - Methods: Numerical