OBSERVATION OF ANISOTROPY IN THE GALACTIC COSMIC-RAY ARRIVAL DIRECTIONS AT 400 TeV WITH ICECUBE

Journal Article · Fri Feb 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/746/1/33· OSTI ID:22011826

Abbasi, R; Aguilar, J A; Andeen, K; Baker, M ^[1]; Abdou, Y ^[2]; Abu-Zayyad, T ^[3]; Ackermann, M; Bazo Alba, J L ^[4]; Adams, J ^[5]; Ahlers, M ^[6]; Allen, M M ^[7]; Altmann, D ^[8]; Auffenberg, J ^[9]; Bai, X ^[10]; Barwick, S W ^[11]; Bay, R ^[12]; Beattie, K ^[13]; Beatty, J J ^[14]; Bechet, S ^[15]; Becker, J K ^[16] ; others, and

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1. Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)
2. Department of Physics and Astronomy, University of Gent, B-9000 Gent (Belgium)
3. Department of Physics, University of Wisconsin, River Falls, WI 54022 (United States)
4. DESY, D-15735 Zeuthen (Germany)
5. Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch (New Zealand)
6. Department of Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP (United Kingdom)
7. Department of Physics, Pennsylvania State University, University Park, PA 16802 (United States)
8. III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen (Germany)
9. Department of Physics, University of Wuppertal, D-42119 Wuppertal (Germany)
10. Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
11. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
12. Department of Physics, University of California, Berkeley, CA 94720 (United States)
13. Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
14. Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)
15. Science Faculty CP230, Universite Libre de Bruxelles, B-1050 Brussels (Belgium)
16. Fakultaet fuer Physik and Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic-ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic-ray-induced muons recorded by the partially deployed IceCube observatory between 2009 May and 2010 May. The data include a total of 33 Multiplication-Sign 10{sup 9} muon events with a median angular resolution of {approx}3 Degree-Sign . A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic-ray median energies of 20 and 400 TeV. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high-energy sky map shows a different anisotropy structure including a deficit with a post-trial significance of -6.3{sigma}. This anisotropy reveals a new feature of the Galactic cosmic-ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

• OSTI ID: 22011826
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 746; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ANISOTROPY
ASTROPHYSICS
COSMIC NEUTRINOS
ENERGY DEPENDENCE
MUONS
SOUTHERN HEMISPHERE
TEV RANGE