Distortion of Ultra‐High‐Energy Sky by Galactic Magnetic Field

Abstract

We investigate the deflections of UHE protons by Galactic magnetic field (GMF) using four conventional GMF models in order to discuss the positional correlation between the arrival distribution of UHECRs and their sources. UHE protons coming from the direction around the Galactic center are highly deflected above 8° by the dipole magnetic field during their propagation in Galactic space. However, in bisymmetric spiral field models, there are directions in which the deflection angle is below 1°. One of these directions is toward Centauras A, the nearest radio-loud active galactic nucleus that is a possible UHECR source candidate. On the other hand, UHE protons arriving from the direction of the Galactic anticenter are generally less deflected, especially in bisymmetric spiral field models. Thus, the Northern Hemisphere, not including the Galactic center, is suitable for studies of correlation with sources. The dependence on model parameters is also investigated. The deflection angles of UHE protons are dependent on the pitch angle of the spiral field. We also investigate distortion of the supergalactic plane by the GMF. Since the distortion in the direction around the Galactic center strongly depends on the GMF model, we can obtain information on the GMF around the Galactic center if Pierre Auger Observatory finds significant positional correlation around the supergalactic plane. © 2008. The American Astronomical Society. All rights reserved.