Discovery of localized regions of excess 10-TeV cosmic rays

A. A. Abdo, B. Allen, T. Aune, D. Berley, E. Blaufuss, S. Casanova, C. Chen, B. L. Dingus, R. W. Ellsworth, L. Fleysher, R. Fleysher, M. M. Gonzalez, J. A. Goodman, C. M. Hoffman, P. H. Hüntemeyer, B. E. Kolterman, C. P. Lansdell, J. T. Linnemann, J. E. McEnery, A. I. MincerP. Nemethy, D. Noyes, J. Pretz, J. M. Ryan, P. M.Saz Parkinson, A. Shoup, G. Sinnis, A. J. Smith, G. W. Sullivan, V. Vasileiou, G. P. Walker, D. A. Williams, G. B. Yodh

    Research output: Contribution to journalArticlepeer-review


    The 7 year data set of the Milagro TeV observatory contains 2.2×1011 events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of ∼10° has been found in two localized regions of unknown origin with greater than 12σ significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6σ, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at ∼10TeV. Potential causes of these excesses are explored, but no compelling explanations are found.

    Original languageEnglish (US)
    Article number221101
    JournalPhysical Review Letters
    Issue number22
    StatePublished - Nov 24 2008

    ASJC Scopus subject areas

    • General Physics and Astronomy


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