A search for anisotropy in the arrival directions of ultra high energy cosmic rays recorded at the Pierre Auger Observatory

Journal Article · Sun Apr 01 00:00:00 EDT 2012 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2012/04/040· OSTI ID:22280133

Abreu, P.; Andringa, S. ^[1]; Aglietta, M. ^[2]; Ahlers, M. ^[3]; Ahn, E. J. ^[4]; Albuquerque, I. F.M. ^[5]; Allard, D. ^[6]; Allekotte, I. ^[7]; Allen, J. ^[8]; Allison, P. ^[9]; Almela, A. ^[10]; Castillo, J. Alvarez ^[11]; Alvarez-Muñiz, J. ^[12]; Ambrosio, M.; Aramo, C. ^[13]; Aminaei, A. ^[14]; Anchordoqui, L. ^[15]; Antici'c, T. ^[16]; Arganda, E. ^[17]; others, and

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1. LIP and Instituto Superior Técnico, Technical University of Lisbon (Portugal)
2. Istituto di Fisica dello Spazio Interplanetario (INAF), Università di Torino and Sezione INFN, Torino (Italy)
3. University of Wisconsin, Madison, WI (United States)
4. Fermilab, Batavia, IL (United States)
5. Universidade de São Paulo, Instituto de Física, São Paulo, SP (Brazil)
6. Laboratoire AstroParticule et Cosmologie (APC), Université Paris 7, CNRS-IN2P3, Paris (France)
7. Centro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche (Argentina)
8. New York University, New York, NY (United States)
9. Ohio State University, Columbus, OH (United States)
10. Universidad Tecnológica Nacional - Facultad Regional Buenos Aires, Buenos Aires (Argentina)
11. Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)
12. Universidad de Santiago de Compostela (Spain)
13. Università di Napoli 'Federico II' and Sezione INFN, Napoli (Italy)
14. IMAPP, Radboud University Nijmegen (Netherlands)
15. University of Wisconsin, Milwaukee, WI (United States)
16. Rudjer Boškovi'c Institute, 10000 Zagreb (Croatia)
17. IFLP, Universidad Nacional de La Plata and CONICET, La Plata (Argentina)

Observations of cosmic ray arrival directions made with the Pierre Auger Observatory have previously provided evidence of anisotropy at the 99% CL using the correlation of ultra high energy cosmic rays (UHECRs) with objects drawn from the Véron-Cetty Véron catalog. In this paper we report on the use of three catalog independent methods to search for anisotropy. The 2pt–L, 2pt+ and 3pt methods, each giving a different measure of self-clustering in arrival directions, were tested on mock cosmic ray data sets to study the impacts of sample size and magnetic smearing on their results, accounting for both angular and energy resolutions. If the sources of UHECRs follow the same large scale structure as ordinary galaxies in the local Universe and if UHECRs are deflected no more than a few degrees, a study of mock maps suggests that these three methods can efficiently respond to the resulting anisotropy with a P-value = 1.0% or smaller with data sets as few as 100 events. Using data taken from January 1, 2004 to July 31, 2010 we examined the 20,30,...,110 highest energy events with a corresponding minimum energy threshold of about 49.3 EeV. The minimum P-values found were 13.5% using the 2pt-L method, 1.0% using the 2pt+ method and 1.1% using the 3pt method for the highest 100 energy events. In view of the multiple (correlated) scans performed on the data set, these catalog-independent methods do not yield strong evidence of anisotropy in the highest energy cosmic rays.

• OSTI ID: 22280133
• Journal Information: Journal of Cosmology and Astroparticle Physics, Vol. 2012, Issue 04; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ANGULAR DISTRIBUTION
ANISOTROPY
ASTROPHYSICS
CORRELATIONS
COSMIC RADIATION
COSMOLOGY
EEV RANGE
ENERGY RESOLUTION
GALAXIES
UNIVERSE