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

THE PIERRE AUGER COLLABORATION, B. WUNDHEILER

ASTROPARTICLE PHYSICS

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2010 p. 314 - 326

0927-6505

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–Kuz’min energy threshold, 6x10^19eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 from the position of an active galactic nucleus within 75 Mpc (using the Véron-Cetty and Véron 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(+7-6)% compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of 69(+11-13)%.