Maximum Likelihood method for ultrahigh energy cosmic ray cross correlations with astrophysical sources

TL;DR

This paper enhances the Maximum Likelihood method to better identify and rank astrophysical sources of ultrahigh energy cosmic rays, demonstrating a significant correlation with known BLLacs.

Contribution

The paper introduces a modified likelihood approach that accounts for source luminosities and enables ranking of sources based on their correlation likelihood.

Findings

Identified 9 true correlations between UHECRs and BLLacs.

Estimated probability of chance correlation is 6×10^-5.

Method validated through simulations across various scenarios.

Abstract

We extend the Maximum Likelihood method used by HiRes to study cross correlations between a catalog of candidate astrophysical sources and Ultrahigh Energy Cosmic Rays (UHECRs), to allow for differing source luminosities. Our approach permits individual sources to be ranked according to their likelihood of having emitted the correlated UHECRs. We test both old and new method by simulations for various scenarios. We conclude that there are 9 true correlation between HiRes UHECRs and known BLLacs, with a 6*10^-5 probability of such a correlation arising by chance.