A. A. Abdo, B. T. Allen, T. Aune, D. Berley, S. Casanova, C. Chen, B. L. Dingus, R. W. Ellsworth, L. Fleysher, R. Fleysher, M. M. Gonzalez, J. A. Goodman (+21 others)
2009 Astrophysical Journal  
Results are presented of a harmonic analysis of the large scale cosmic-ray anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy pro jections in right ascension generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico. With a high duty cycle and large field-of-view, Milagro is an excellent instrument for
more » ... nt instrument for measuring this anisotropy with high sensitivity at TeV energies. The analysis is conducted using a seven year data sample consisting of more than 95 billion events, the largest such data set in existence. We observe an anisotropy with a magnitude around 0.1% for cosmic rays with a median energy of 6 TeV. The dominant feature is a deficit region of depth (2.49 +/- 0.02 stat. +/- 0.09 sys.)x10^(-3) in the direction of the Galactic North Pole centered at 189 degrees right ascension. We observe a steady increase in the magnitude of the signal over seven years.
doi:10.1088/0004-637x/698/2/2121 fatcat:5qtkbgbnxjdjna24dls65o7psm