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Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube

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Abstract
Between 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.
Keywords
astroparticle physics, cosmic rays, MILAGRO HOT-SPOTS, AIR-SHOWER ARRAY, ENERGY-SPECTRUM, INTENSITY, TELESCOPE, ASTRONOMY

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Citation

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Chicago
Abbasi, R, Yasser Abdou, T Abu-Zayyad, J Adams, JA Aguilar, M Ahlers, D Altmann, et al. 2011. “Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube.” Astrophysical Journal 740 (1).
APA
Abbasi, R., Abdou, Y., Abu-Zayyad, T., Adams, J., Aguilar, J., Ahlers, M., Altmann, D., et al. (2011). Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube. ASTROPHYSICAL JOURNAL, 740(1).
Vancouver
1.
Abbasi R, Abdou Y, Abu-Zayyad T, Adams J, Aguilar J, Ahlers M, et al. Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube. ASTROPHYSICAL JOURNAL. 2011;740(1).
MLA
Abbasi, R, Yasser Abdou, T Abu-Zayyad, et al. “Observation of Anisotropy in the Arrival Directions of Galactic Cosmic Rays at Multiple Angular Scales with IceCube.” ASTROPHYSICAL JOURNAL 740.1 (2011): n. pag. Print.
@article{2146317,
  abstract     = {Between 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.},
  articleno    = {16},
  author       = {Abbasi, R and Abdou, Yasser and Abu-Zayyad, T and Adams, J and Aguilar, JA and Ahlers, M and Altmann, D and Andeen, K and Auffenberg, J and Bai, X and Baker, M and Barwick, SW and Bay, R and Alba, JLB and Beattie, K and Beatty, JJ and Bechet, S and Becker, JK and Becker, KH and Benabderrahmane, ML and BenZvi, S and Berdermann, J and Berghaus, P and Berley, D and Bernardini, E and Bertrand, D and Besson, DZ and Bindig, D and Bissok, M and Blaufuss, E and Blumenthal, J and Boersma, DJ and Bohm, C and Bose, D and Boser, S and Botner, O and Brown, AM and Buitink, S and Caballero-Mora, KS and Carson, Michael and Chirkin, D and Christy, B and Clem, J and Clevermann, F and Cohen, S and Colnard, C and Cowen, DF and D'Agostino, MV and Danninger, M and Daughhetee, J and Davis, JC and De Clercq, C and Demirors, L and Denger, T and Depaepe, O and Descamps, Freija and Desiati, P and De Vries-Uiterweerd, Garmt and DeYoung, T and Diaz-Velez, JC and Dierckxsens, M and Dreyer, J and Dumm, JP and Ehrlich, R and Eisch, J and Ellsworth, RW and Engdegard, O and Euler, S and Evenson, PA and Fadiran, O and Fazely, AR and Fedynitch, A and Feintzeig, J and Feusels, Tom and Filimonov, K and Finley, C and Fischer-Wasels, T and Foerster, MM and Fox, BD and Franckowiak, A and Franke, R and Gaisser, TK and Gallagher, J and Gerhardt, L and Gladstone, L and Glusenkamp, T and Goldschmidt, A and Goodman, JA and Gora, D and Grant, D and Griesel, T and Gross, A and Grullon, S and Gurtner, M and Ha, C and Haj Ismail, Abd Al Karim and Hallgren, A and Halzen, F and Han, K and Hanson, K and Heinen, D and Helbing, K and Herquet, P and Hickford, S and Hill, GC and Hoffman, KD and Homeier, A and Hoshina, K and Hubert, D and Huelsnitz, W and Hulss, JP and Hulth, PO and Hultqvist, K and Hussain, S and Ishihara, A and Jacobsen, J and Japaridze, GS and Johansson, H and Joseph, JM and Kampert, KH and Kappes, A and Karg, T and Karle, A and Kenny, P and Kiryluk, J and Kislat, F and Klein, SR and Kohne, JH and Kohnen, G and Kolanoski, H and Kopke, L and Kopper, S and Koskinen, DJ and Kowalski, M and Kowarik, T and Krasberg, M and Krings, T and Kroll, G and Kurahashi, N and Kuwabara, T and Labare, M and Lafebre, S and Laihem, K and Landsman, H and Larson, MJ and Lauer, R and Lunemann, J and Madajczyk, B and Madsen, J and Majumdar, P and Marotta, A and Maruyama, R and Mase, K and Matis, HS and Meagher, K and Merck, M and Meszaros, P and Meures, T and Middell, E and Milke, N and Miller, J and Montaruli, T and Morse, R and Movit, SM and Nahnhauer, R and Nam, JW and Naumann, U and Niessen, P and Nygren, DR and Odrowski, S and Olivas, A and Olivo, M and O'Murchadha, A and Ono, M and Panknin, S and Paul, L and de los Heros, CP and Petrovic, J and Piegsa, A and Pieloth, D and Porrata, R and Posselt, J and Price, CC and Price, PB and Przybylski, GT and Rawlins, K and Redl, P and Resconi, E and Rhode, W and Ribordy, M and Rizzo, A and Rodrigues, JP and Roth, P and Rothmaier, F and Rott, C and Ruhe, T and Rutledge, D and Ruzybayev, B and Ryckbosch, Dirk and Sander, HG and Santander, M and Sarkar, S and Schatto, K and Schmidt, T and Schonwald, A and Schukraft, A and Schultes, A and Schulz, O and Schunck, M and Seckel, D and Semburg, B and Seo, SH and Sestayo, Y and Seunarine, S and Silvestri, A and Slipak, A and Spiczak, GM and Spiering, C and Stamatikos, M and Stanev, T and Stephens, G and Stezelberger, T and Stokstad, RG and Stossl, A and Stoyanov, S and Strahler, EA and Straszheim, T and Stur, M and Sullivan, GW and Swillens, Q and Taavola, H and Taboada, I and Tamburro, A and Tepe, A and Ter-Antonyan, S and Tilav, S and Toale, PA and Toscano, S and Tosi, D and Turcan, D and van Eijndhoven, N and Vandenbroucke, J and Van Overloop, Arne and van Santen, J and Vehring, M and Voge, M and Walck, C and Waldenmaier, T and Wallraff, M and Walter, M and Weaver, C and Wendt, C and Westerhoff, S and Whitehorn, N and Wiebe, K and Wiebusch, CH and Williams, DR and Wischnewski, R and Wissing, H and Wolf, M and Wood, TR and Woschnagg, K and Xu, C and Xu, XW and Yodh, G and Yoshida, S and Zarzhitsky, P and Zoll, M},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  language     = {eng},
  number       = {1},
  pages        = {17},
  title        = {Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube},
  url          = {http://dx.doi.org/10.1088/0004-637X/740/1/16},
  volume       = {740},
  year         = {2011},
}

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