Constraining positron emission from pulsar populations with AMS-02 data

TL;DR

This paper uses extensive simulations of Galactic pulsar populations to evaluate their potential contribution to the positron excess observed by AMS-02, considering various physical and spatial models.

Contribution

It introduces a comprehensive simulation framework for pulsar populations to assess their role in cosmic-ray positron flux, addressing catalog incompleteness and model uncertainties.

Findings

Pulsar populations can explain the AMS-02 positron excess with a few bright sources.

The dominant positron sources are identified as specific pulsars with particular physical parameters.

Different assumptions on pulsar distribution and propagation significantly affect the results.

Abstract

The cosmic-ray flux of positrons is measured with high precision by the space-borne particle spectrometer AMS-02. 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 $\gamma$-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe. In this work we undertake massive simulations of Galactic pulsars populations, adopting different distributions for their position in the Galaxy, intrinsic physical properties, pair emission models, in order to overcome the incompleteness of the ATNF catalog. We fit the $e^+$ AMS-02 data together with a secondary component due to collisions of primary cosmic rays with the interstellar medium. We find that several mock galaxies have a pulsar population able to explain the observed $e^+$ flux, typically by few, bright sources. We determine the physical parameters of the pulsars dominating the $e^+$ flux, and assess the impact of different assumptions on radial distributions, spin-down properties, Galactic propagation scenarios and $e^+$ emission time.