On the Energy Dependence of the ARGO-YBJ Anisotropy Data in the TeV Range

Abstract We apply the Liouville mapping method to anisotropy maps produced by the ARGO-YBJ experiment to remove the effects of the heliosphere and the isolatitudinal normalization employed by the experimental team. We investigate seven energy bands between ∼ 1 and 30 TeV. Although the quality of the model fit is limited in a few energy channels, we are able to extract from the anisotropy maps the energy dependence of their Legendre polynomial amplitudes and of the cosmic-ray density gradient components perpendicular to the local interstellar magnetic field. The result shows that the interstellar spectral powers and the density gradient components tend to decrease with energy. The pitch-angle distributions of several energy bands exhibit a rapid increase in particle intensity around a pitch-angle of zero, i.e., along the magnetic field direction, supporting the presence of focusing by an inhomogeneous local interstellar magnetic field. The directions of the density gradients inferred from our models suggest that there is an increase in TeV cosmic rays coming from the general direction of the Geminga pulsar.