Bulletin of Taras Shevchenko National University of Kyiv. Astronomy, no. 58, p. 33-36 (2018)

Acceleration and propagation of ultra high energy cosmic rays in the Local Universe

V. Voytsekhovsky, PhD stud.
B. Hnatyk, Dr. Sci., Prof.
Yu. Kudrya, Kand. Sci., Sen. Sci.

Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv


Distribution of matter in the Local Universe (up to ~ 100 Mpc), especially in a Virgo Supercluster region (~20 Mpc) is strongly nonuniform and includes all elements of large scale structure: galaxies and their clusters, superclusters, filaments, sheets and voids. On its smallest scale, our Galaxy and its similar galaxy M31 (Andromeda Nebula) at a distance 770 kpc, together with dozens of dwarf galaxies, form the Local Group of Galaxies. Local group contained in Local Sheet – suchlike pancake concentration of galaxies with radius about 5 Mpc and thickness 1.5 Mpc. This structure is a part of Local Filament – cylindrical region with higher density of matter, that join us to more powerful filament, that concludes Virgo Supercluster and connects two highest matter concentrations in Local Universe – supercluster Great Attractor (70 Mpc) and Perseus-Pisces supercluster (60 Mpc). Extragalactic magnetic field (EGMF) distribution is expected to follow the baryonic matter density distribution. Ultra high energy cosmic rays (UHECRs, E>1018 eV) from extragalactic sources will undergo significant deviations in EGMF, which makes it difficult to search their sources. But for extremely high energy cosmic rays (EHECRs, E>5·1019 eV), that are on the top of cosmic rays energy spectrum (the biggest detected energy of cosmic rays is above 1020 eV), influence of EGMF can be negligible, and their arrival direction can correlate with source position. They carry an important information, about the physics of fundamental interactions beyond the standard model, but still unknown to their origins and mechanisms of acceleration. In addition, a flux of nuclear component of UHECRs decreases in result of nuclear photo-disintegration due to interaction with microwave and infrared background. These processes are significant for protons (hydrogen nuclei), for which the major losses are born of electron-positron pairs and photo-pions reactions. For multi nucleon nucleuses significant process of weakening is photo-disintegration with chemical composition change of main nuclei. In our work we estimate the influence of these factors on the propagation of the UHECRs from sources in the Local Universe, in particular we have investigated the mean free path and magnetic deflection of H(p), He, O, Si and Fe nuclei. For potential sources of UHECRs in the Local Universe, such as Virgo supercluster, Great Attractor and Perseus-Pisces supercluster, we have estimated types and energies of nuclei that can reach the Earth, and, in the same time, can save a connection of arrival directions with source position within 1 rad.

Key words
Large scale structure, Local Universe, intergalactic magnetic fields, ultra high energy cosmic rays, active galactic nuclei, star-burst galaxies

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DOI: https://doi.org/10.17721/BTSNUA.2018.58.33-36