Estimation and reduction of the biases by the galactic magnetic field on the UHECR correlation studies

¹ Astrophysical Big Bang Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
² Institute for Cosmic Ray Research, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582, Japan
³ Osaka Metropolitan University, 3-3-138 Sugimoto Sumiyoshi-ku, Osaka-shi, 558-8585, Japan

^* Corresponding author: ryo.higuchi@riken.jp

Published online: 28 April 2023

Abstract

The correlation studies between ultrahigh-energy cosmic ray (UHECR) anisotropy and source candidates are keys to understand the origin of UHECRs. Especially, studies with consideration of source models, magnetic fields, and mass compositions are necessary. We estimated the biases caused by the coherent deflection due to the galactic magnetic field (GMF) in the previous maximum-likelihood analysis for searching the UHECR sources (Aab et al. 2018, Abbasi et al. 2018). In our work with simulated mock datasets, we find that the anisotropic fraction f_ani is estimated systematically lower than the true value when we ignore the effect caused by the GMF. We also develop the maximum-likelihood method which includes the GMF model and confirm that the estimated parameters would be improved. We apply the method to the observational datasets obtained from the Telescope Array and Auger experiments.