Cluster accretion shocks as possible acceleration sites for ultra-high-energy protons below the greisen cutoff

Hyesung Kang, Dongsu Ryu, T. W. Jones

Research output: Contribution to journalArticlepeer-review

125 Scopus citations

Abstract

Three-dimensional hydrodynamic simulations of large-scale structure in the universe have shown that accretion shocks form during the gravitational collapse of one-dimensional caustics, and that clusters of galaxies formed at intersections of the caustics are surrounded by these accretion shocks. Estimated speed and curvature radius of the shocks are 1000-3000 km s-1 and about 5 Mpc, respectively, in the Ω = 1 cold dark matter universe. Assuming that energetic protons are accelerated by these accretion shocks via the first-order Fermi process and modeling particle transport around the shocks through Bohm diffusion, we suggest that protons can be accelerated up to the Greisen cutoff energy near 6 × 1019 eV, provided the mean magnetic field strength in the region around the shocks is at least of order 1 μG. We have also estimated the proton flux at Earth from the Virgo Cluster. Assuming that a few (1-10) percent of the ram pressure of the infalling matter would be transferred to the cosmic rays, the estimated flux for E ∼ 1019 eV is consistent with observations, so that such clusters could be plausible sources of the ultrahigh-energy cosmic rays.

Original languageEnglish (US)
Pages (from-to)422-427
Number of pages6
JournalAstrophysical Journal
Volume456
Issue number2 PART I
DOIs
StatePublished - 1996

Keywords

  • Acceleration of particles
  • Cosmic rays
  • Hydrodynamics
  • Large-scale structure of universe
  • Methods: Numerical

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