Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

Journal Article · Tue Jun 01 04:00:00 EDT 2010 · Astropart.Phys.34:314-326,2010

DOI:https://doi.org/10.1016/j.astropartphys.2010.08.010· OSTI ID:986986

Abreu, P; Aglietta, M; Ahn, E J; Allard, D; Allekotte, I; Allen, J; Alvarez Castillo, J; Alvarez-Muniz, J; Ambrosio, M; Aminaei, A; Anchordoqui, L

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuzmin energy threshold, 6 x 10{sup 19} eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1{sup o} from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is (38{sub -6}{sup +7})%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of (69{sub -13}{sup +11})%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL
• Sponsoring Organization: USDOE
• DOE Contract Number: AC02-07CH11359
• OSTI ID: 986986
• Report Number(s): FERMILAB-PUB-10-220-A-TD; arXiv eprint number arXiv:1009.1855
• Journal Information: Astropart.Phys.34:314-326,2010, Journal Name: Astropart.Phys.34:314-326,2010; ISSN 0927-6505
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
Astrophysics
CEN
GALAXIES
NUCLEI
SKY