Speaker
Description
The deflections of ultra-high energy cosmic rays caused by the Galactic and extragalactic magnetic fields limit the information that can be learned from the arrival directions of particles detected on Earth regarding their potential sources. Recent studies by the Pierre Auger Collaboration have identified an anisotropy in the arrival directions of events exceeding 32 EeV, suggesting that nearby sources may contribute to the clustering of events. A significance of 4$\sigma$ was reported for an analysis that revealed a correlation between the observed arrival directions and a sample of nearby starburst galaxies (SBGs). However, these results were obtained without accounting for the influence of the Galactic Magnetic Field (GMF).
In this study, we explore the impact of Galactic magnetic deflections on cross-correlation analyses with source catalogs, incorporating various realizations of the turbulent field from the GMF model of Jansson $\&$ Farrar (2012), along with the latest GMF models developed by Unger $\&$ Farrar (2023). We demonstrate that, even when magnetic deflections are included into simulated data, the best-fit parameters for a correlation with starburst galaxies, as in the Pierre Auger Collaboration results, can be reproduced with high probability. However, when we search for local overdensities, the simulations reveal structures that are not present in the actual data. We discuss the sensitivity of cosmic-ray observations on the strength of the extragalactic magnetic field, given the prediction of a specific UHECR flux model using the SBG model as an example.
