A Bayesian analysis of the 27 highest energy cosmic rays detected by the Pierre Auger Observatory

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Title: A Bayesian analysis of the 27 highest energy cosmic rays detected by the Pierre Auger Observatory
Authors: Watson, LJ
Mortlock, DJ
Jaffe, AH
Item Type: Journal Article
Abstract: It is possible that ultrahigh energy cosmic rays (UHECRs) are generated by active galactic nuclei (AGNs), but there is currently no conclusive evidence for this hypothesis. Several reports of correlations between the arrival directions of UHECRs and the positions of nearby AGNs have been made, the strongest detection coming from a sample of 27 UHECRs detected by the Pierre Auger Observatory (PAO). However, the PAO results were based on a statistical methodology that not only ignored some relevant information (most obviously the UHECR arrival energies, but also some of the information in the arrival directions), but also involved some problematic fine-tuning of the correlation parameters. Here we present a fully Bayesian analysis of the PAO data (collected before 2007 September), which makes use of more of the available information, and find that a fraction FAGN= 0.15+0.10−0.07 of the UHECRs originate from known AGNs in the Veron-Cetty and Veron (VCV) catalogue. The hypothesis that all the UHECRs come from VCV AGNs is ruled out, although there remains a small possibility that the PAO–AGN correlation is coincidental (FAGN= 0.15 is 200 times as probable as FAGN= 0.00).
Issue Date: 21-Nov-2011
Date of Acceptance: 19-Jul-2011
ISSN: 0035-8711
Publisher: Oxford University Press (OUP)
Start Page: 206
End Page: 213
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 418
Issue: 1
Copyright Statement: © 2011 The Authors. Monthly Notices of the Royal Astronomical Society © 2011 RAS.
Sponsor/Funder: Science and Technology Facilities Council (STFC)
Funder's Grant Number: ST/G001901/1
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
methods: statistical
cosmic rays
galaxies: active
0201 Astronomical And Space Sciences
Publication Status: Published
Online Publication Date: 2011-11-10
Appears in Collections:Physics
Faculty of Natural Sciences

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