Effects of Galactic magnetic field on the UHECR anisotropy studies

Abstract

We estimate 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. We simulate the mock event datasets with a set of assumptions for the starburst galaxy (SBG) source model (Aab et al. 2018), coherent deflection by a GMF model (Jansson & Farrar 2012a,b), and the mixed-mass composition Heinze & Fedynitch (2019), then conducted a maximum-likelihood analysis with ignorance of the GMF in the same manner as previous studies. We find that the anisotropic fraction f ani is estimated systematically lower than the true value. We estimate the true parameters which are compatible with the best-fit parameters reported in Aab et al. (2018). We find that except for a narrow region with a large anisotropic fraction and small separation angular scale wide parameter space is still compatible with the experimental results. We also develop the maximum-likelihood method with consideration of the GMF model and confirm that the estimated parameters would be improved.