ANISOTROPY IN COSMIC-RAY ARRIVAL DIRECTIONS IN THE SOUTHERN HEMISPHERE BASED ON SIX YEARS OF DATA FROM THE ICECUBE DETECTOR

Journal Article · Mon Aug 01 04:00:00 EDT 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/0004-637X/826/2/220· OSTI ID:22666006

Aartsen, M. G. ^[1]; Abraham, K. ^[2]; Ackermann, M. ^[3]; Adams, J. ^[4]; Aguilar, J. A.; Ansseau, I. ^[5]; Ahlers, M. ^[6]; Ahrens, M. ^[7]; Altmann, D.; Anton, G. ^[8]; Anderson, T.; Arlen, T. C. ^[9]; Archinger, M.; Baum, V. ^[10]; Arguelles, C. ^[11]; Auffenberg, J. ^[12]; Bai, X. ^[13]; Barwick, S. W. ^[14]; others, and

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1. Department of Physics, University of Adelaide, Adelaide, 5005 (Australia)
2. Technische Universität München, D-85748 Garching (Germany)
3. DESY, D-15735 Zeuthen (Germany)
4. Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)
5. Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels (Belgium)
6. Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, WI 53706 (United States)
7. Oskar Klein Centre and Department of Physics, Stockholm University, SE-10691 Stockholm (Sweden)
8. Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen (Germany)
9. Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)
10. Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz (Germany)
11. Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
12. III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen (Germany)
13. Physics Department, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States)
14. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)

The IceCube Neutrino Observatory accumulated a total of 318 billion cosmic-ray-induced muon events between 2009 May and 2015 May. This data set was used for a detailed analysis of the sidereal anisotropy in the arrival directions of cosmic rays in the TeV to PeV energy range. The observed global sidereal anisotropy features large regions of relative excess and deficit, with amplitudes of the order of 10{sup 3} up to about 100 TeV. A decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole ( ℓ ≤ 4) moments. However, higher multipole components are found to be statistically significant down to an angular scale of less than 10°, approaching the angular resolution of the detector. Above 100 TeV, a change in the morphology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5 PeV, the highest energies currently accessible to IceCube. No time dependence of the large- and small-scale structures is observed in the period of six years covered by this analysis. The high-statistics data set reveals more details of the properties of the anisotropy and is potentially able to shed light on the various physical processes that are responsible for the complex angular structure and energy evolution.

• OSTI ID: 22666006
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 826; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMPLITUDES
ANISOTROPY
COSMIC RADIATION
DECOMPOSITION
DISTRIBUTION
ICECUBE NEUTRINO DETECTOR
MULTIPOLES
MUONS
NEUTRINOS
PEV RANGE
RESOLUTION
SOUTHERN HEMISPHERE
SPHERICAL HARMONICS
STAR EVOLUTION
TEV RANGE
TIME DEPENDENCE