Contribution of pulsars to cosmic-ray positrons in light of recent observation of inverse-Compton halos

The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron (e+) cosmic-ray flux has been consolidated after the observation of a γ-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe, and at GeV energies for Geminga at a much larger extension. The γ-ray halos around these PWNe are interpreted as due to electrons (e-) and e+ accelerated and escaped by their PWNe, and inverse Compton scattering low-energy photons of the interstellar radiation fields. The extension of these halos suggests that the diffusion around these PWNe is suppressed by 2 orders of magnitude with respect to the average in the Galaxy. We implement a two-zone diffusion model for the propagation of e+ accelerated by the Galactic population of PWNe. We consider pulsars from source catalogs and build up simulations of the PWN Galactic population. In both scenarios, we find that within a two-zone diffusion model, the total contribution from PWNe and secondary e+ is at the level of AMS-02 data, for an efficiency of conversion of the pulsar spin-down energy in e± of η∼0.1. For the simulated PWNe, a 1σ uncertainty band is determined, which is of at least 1 order of magnitude from 10 GeV up to few TeV. The hint for a decreasing e+ flux at TeV energies is found, even if it is strongly connected to the chosen value of the radius of the low diffusion bubble around each source.