The Physics of Pulsar Halos: Research Progress and Prospect

TL;DR

This paper reviews recent progress in understanding pulsar halos, their observational evidence, theoretical models, and implications for cosmic-ray physics and gamma-ray emissions in our galaxy.

Contribution

It provides a comprehensive overview of the physics, observations, and models of pulsar halos, highlighting their significance in cosmic-ray and gamma-ray astrophysics.

Findings

Extended TeV gamma-ray emissions are linked to pulsar halos.

Pulsar halos are a distinct class of nonthermal sources.

Implications for cosmic-ray positron excess are discussed.

Abstract

Diffusive TeV gamma-ray emissions have been recently discovered extending beyond the pulsar wind nebulae of a few middle-aged pulsars, implying that energetic electron/positron pairs are escaping from the pulsar wind nebulae and radiating in the ambient interstellar medium. It has been suggested that these extended emissions constitute a distinct class of nonthermal sources, termed "pulsar halos". In this article, I will review the research progress on pulsar halos and discuss our current understanding on their physics, including the multiwavelength observations, different theoretical models, as well as implications for the origin of cosmic-ray positron excess and Galactic diffuse gamma-ray emission.