Constraints on the Intergalactic Transport of Cosmic Rays

Abstract

Motivated by recent experimental proposals to search for extragalactic cosmic rays (including anti-matter from distant galaxies), we study particle propagation through the intergalactic medium (IGM). We first use estimates of the magnetic field strength between galaxies to constrain the mean free path for diffusion of particles through the IGM. We then develop a simple analytic model to describe the diffusion of cosmic rays. Given the current age of galaxies, our results indicate that, in reasonable models, a completely negligible number of particles can enter our Galaxy from distances greater than $\sim 100$ Mpc for relatively low energies ($E$ $<10^6$ GeV/n). We also find that particle destruction in galaxies along the diffusion path produces an exponential suppression of the possible flux of extragalactic cosmic rays. Finally, we use gamma ray constraints to argue that the distance to any hypothetical domains of anti-matter must be roughly comparable to the horizon scale.

arXiv comment24 pages, AAS LaTex, 1 figure, accepted to ApJ

References in corpus (3)

• A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects
• Cosmic Ray Protons and Magnetic Fields in Clusters of Galaxies and their Cosmological Consequences
• The arrival directions of the most energetic cosmic rays

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• Review of the theoretical and experimental status of dark matter identification with cosmic-ray antideuterons
• Measurement of the Cosmic-Ray Antiproton to Proton Abundance Ratio between 4 and 50 GeV
• Cosmic-ray Antinuclei as Messengers of New Physics: Status and Outlook for the New Decade
• CHAMP Cosmic Rays
• Probing the EBL evolution at high redshift using GRBs detected with the Fermi-LAT
• The Ultimate Fate of Cosmic Rays from Galaxies and their Role in the Intergalactic Medium