Reference maps for anisotropy searches with AMS-02
2017 August 16
The measurement of anisotropies in cosmic ray arrival directions requires knowledge of what is expected in case of an isotropic flux. This template can then be used as a reference to search for deviations from isotropy. Two types of anisotropies are commonly cited in the literature: (i) relative anisotropies, where the arrival directions of a cosmic ray sample serve as a reference and (ii) absolute anisotropies, where the reference describes the directional response of the detector to an isotropic flux. Here we discuss the advantages and shortcomings of different techniques to construct such reference maps from data. We introduce a novel method to determine the isotropic reference maps used for the measurement of absolute anisotropies with AMS-02, which can be applied to detectors with any given field of view or any particle species. The performance of this reference map will be presented in several motivated coordinate systems.