A wavelet-based approach to UHECR arrival direction analysis

• Main Authors: A A Ivanov, A D Krasilnikov, M I Pravdin, Yu G Shafer
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Yakutsk
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1073.4295; http://www-rccn.icrr.u-tokyo.ac.jp/icrc2003/PROCEEDINGS/PDF/86.pdf

Abstract A Mexican Hat wavelet is used to analyze the arrival directions of ultra-high energy cosmic rays (UHECRs) detected with the Yakutsk array. The purpose is a search for possible deviation from expected isotropic distribution in right ascension and on the celestial sphere. Necessary limitations are discussed in order to adapt an unbounded wavelet to a circle and sphere. As a result, significant anisotropy is found in the energy range between 10 19 and 3.16 × 10 19 eV: the chance probability for the isotropic distribution to have the wavelet amplitude exceeding observed one is less than 0.5%. The wavelet center is (2.3±1.3) h in right ascension, 52.5 0 ± 7.5 0 in declination; 10 0 < R < 20 0 are the scale parameter limits. The result relevance is stressed by coincident evidences of anisotropy in the same energy range drawn from the Yakutsk array data using different methods of analysis -wavelet, harmonic and galactic latitude distribution.