Abstract
We have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly’s Eye experiment and active galactic nuclei (AGN) visible from its northern hemisphere location. No correlations, other than random correlations, have been found. We report our results using search parameters prescribed by the Pierre Auger collaboration. Using these parameters, the Auger collaboration concludes that a positive correlation exists for sources visible to their southern hemisphere location. We also describe results using two methods for determining the chance probability of correlations: one in which a hypothesis is formed from scanning one half of the data and tested on the second half, and another which involves a scan over the entire data set. The most significant correlation found occurred with a chance probability of 24%.
Highlights
The search for the sources of the highest energy cosmic rays is an important topic in physics today
We report on searches for correlations between the pointing directions of ultrahigh energy cosmic rays observed stereoscopically by the High Resolution Fly’s Eye (HiRes) experiment and Active Galactic Nuclei (AGN) from the Veron-Cetty and Veron (VCV) catalog, 12th edition [18]
We have searched for correlations between the pointing directions of HiRes stereo events with AGN from the the Veron-Cetty Veron catalog using three different methods
Summary
The search for the sources of the highest energy cosmic rays is an important topic in physics today. These reports of anisotropy in the northern sky await confirmation or rejection by the Telescope Array experiment [8] Another method for searching for anisotropy is to search for correlations in pointing directions of cosmic rays with known astrophysical objects that might be sources. We report on searches for correlations between the pointing directions of ultrahigh energy cosmic rays observed stereoscopically by the HiRes experiment and AGN from the Veron-Cetty and Veron (VCV) catalog, 12th edition [18]. One property of the search method in (θmax, Emin, zmax) is that the large size of the catalog and the size of the correlation angle circles determine that one can scan over only a narrow range of θmax and zmax To illustrate this using simulated events with isotropically distributed pointing directions, Figure 2 shows that the number of random pairings with AGN is determined by the. As θmax and zmax are increased, the number of random pairings increases, rapidly overcoming any real correlations between cosmic rays and AGN
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