GMF model dependence of correlations between BL Lacs and ultra high energy cosmic rays

Abstract

Some studies suggested that there exists a correlation between locations of BL Lacertae objects (BL Lacs) and arrival directions of ultra high energy cosmic rays (UHECRs). Especially by assuming the primary particles charged +1 and using a galactic magnetic field (GMF) model to calculate deflections of the UHECRs, the significance of correlation can be improved. A new GMF model is constructed by incorporating all progresses in the GMF measurements in recent years and use it to a thorough study of the deflections of the UHECRs measured by the AGASA experiment. Compared with other models, the GFM model dependence of the correlation between the UHECRs and the selected BL Lacs is studied. It turns out that only specific one of those GMF models makes the correlation significant, even if the GMF models are not very different. The UHECR deflections are also different depending on which GMF model is used. It indicates that the significance of the correlation, suggested in those studies, is strongly depending on GMF models. Great improvement in statistics may help to suppress the sensitivity to GMF models.