Discriminating local sources of high-energy cosmic electrons and positrons by current and future anisotropy measurements

Using 7 yr of data, the Fermi Large Area Telescope (LAT) has detected no significant anisotropy of cosmic ray (CR) electrons and positrons (e^- + e⁺). This provides the strongest restriction to the e^- + e⁺ anisotropy up to now. As a next-generation CR observatory, the high-energy cosmic-radiation detection (HERD) facility is expected to be better capable of detecting anisotropy than the Fermi-LAT. In this paper, we discuss several models that aim to explain the AMS-02 data using present and future anisotropy measurements. We find that the upper limits of the Fermi-LAT disfavour the Vela supernova remnant as the dominant source in sub-TeV, while other cases that remain safe under the constraints of the Fermi-LAT are expected to be distinguished from each other by the HERD. We also discuss the possibilities of remarkable TeV spectral features, and we test the corresponding anisotropies. We find the conditions under which the TeV model can have a prominent spectral feature and can avoid the constraints of the Fermi-LAT at the same time. Furthermore, the expected performance of the HERD is sensitive enough to detect the anisotropies of all these TeV models, and even for the case of a featureless TeV spectrum. Thus, the HERD might play a crucial part in the study of the origin of cosmic electrons and positrons.