Search for EeV Protons of Galactic Origin

Abstract

Cosmic rays in the energy range $10^{18.0}$ - $10^{18.5}$ eV are thought to have a light, probably protonic, composition. To study their origin one can search for anisotropy in their arrival directions. Extragalactic cosmic rays should be isotropic, but galactic cosmic rays of this type should be seen mostly along the galactic plane, and there should be a shortage of events coming from directions near the galactic anticenter. This is due to the fact that, under the influence of the galactic magnetic field, the transition from ballistic to diffusive behavior is well advanced, and this qualitative picture persists over the whole energy range. Guided by models of the galactic magnetic field that indicate that the enhancement along the galactic plane should have a standard deviation of about 20${}^{\circ }$ in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50${}^{\circ }$ in galactic longitude, we use the data of the Telescope Array surface detector in $10^{18.0}$ to $10^{18.5}$ eV energy range to search for these effects. The data are isotropic. Neither an enhancement along the galactic plane nor a deficit in the galactic anticenter direction is found. Using these data we place an upper limit on the fraction of EeV cosmic rays of galactic origin at 1.3% at 95% confidence level.

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• Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory
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• High-Energy Galactic Cosmic Rays (Astro2020 Science White Paper)
• Magnetic diffusion and interaction effects on Ultrahigh Energy Cosmic Rays: protons and nuclei
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• 2022 report from the Auger-TA working group on UHECR arrival directions
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• Using Deep Learning to Enhance Event Geometry Reconstruction for the Telescope Array Surface Detector
• Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review
• Anisotropies of Diffusive Ultra-high Energy Cosmic Rays in $f(R)$ Gravity Theory
• Leptonic or Hadronic Emission: X-Ray Radiation Mechanism of Large-scale Jet Knots in 3C 273
• Status of the Yakutsk air shower array and future plans
• Zenith angle distribution of cosmic ray showers measured with the Yakutsk array and its application to analysis of arrival directions in equatorial coordinates
• The Knee and the Second Knee of the Cosmic-Ray Energy Spectrum
• Magnetic Suppression of Cosmic Rays' Flux in $\mathbf{f}(\mathbf{R})$ and $\mathbf{f}(\mathbf{Q})$ Theories of Gravity
• On the Hadronic Origin of High Energy Emission of $\gamma$-ray Loud Narrow-Line Seyfert 1 PKS 1502+036
• Past, Present and Future of UHECR Observations
• Analysing Ultra High Energy Cosmic Rays' Anisotropy in $\mathbf{f}(\mathbf{R},\mathbf{T})$ Gravity Theory
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