Title

Anisotropies and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

Authors

P. Abreu, Instituto Superior Técnico
M. Aglietta, Università degli Studi di Torino
E. J. Ahn, Fermi National Accelerator Laboratory
I. F.M. Albuquerque, Universidade de São Paulo
D. Allard, APC - AstroParticule et Cosmologie
I. Allekotte, Instituto Balseiro
J. Allen, New York University
P. Allison, The Ohio State University
J. Alvarez Castillo, Universidad Nacional Autónoma de México
J. Alvarez-Muñiz, Universidad de Santiago de Compostela
M. Ambrosio, Università degli Studi di Napoli Federico II
A. Aminaei, Radboud Universiteit
L. Anchordoqui, University of Wisconsin-Milwaukee
S. Andringa, Instituto Superior Técnico
T. Anticic, Institute Ruder Boskovic
A. Anzalone, INAF Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo
C. Aramo, Università degli Studi di Napoli Federico II
E. Arganda, Universidad Complutense de Madrid
F. Arqueros, Universidad Complutense de Madrid
H. Asorey, Instituto Balseiro
P. Assis, Instituto Superior Técnico
J. Aublin, Laboratoire de Physique Nucléaire et de Hautes Energies
M. Ave, Karlsruher Institut für Technologie, Campus Süd
M. Avenier, Laboratoire de Physique Subatomique et de Cosmologie de Grenoble
G. Avila, Comision Nacional de Energia Atomica Argentina
T. Bäcker, Universität Siegen
M. Balzer, Karlsruher Institut für Technologie, Campus Nord
K. B. Barber, The University of Adelaide
A. F. Barbosa, Centro Brasileiro de Pesquisas Físicas
R. Bardenet, Laboratoire de l'Accélérateur Linéaire
S. L.C. Barroso, Universidade Estadual do Sudoeste da Bahia
B. Baughman, The Ohio State University
J. Bäuml, Karlsruher Institut für Technologie

Document Type

Conference Proceeding

Publication Date

1-1-2011

Abstract

The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5×1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrative values of Z = 6, 13, 26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.

Publication Source (Journal or Book title)

Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011

First Page

137

Last Page

140

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