Self-Generated Cosmic-Ray Turbulence Can Explain the Morphology of TeV Halos

TL;DR

This paper proposes that self-generated turbulence from cosmic-ray streaming can explain the observed size and morphology of TeV halos around pulsars, addressing previous underpredictions of cosmic-ray confinement.

Contribution

The study revisits self-confinement models, correcting prior underestimations and demonstrating their ability to account for TeV halo features with enhanced cosmic-ray confinement.

Findings

Self-generated turbulence can significantly inhibit cosmic-ray diffusion in TeV halos.

Corrected models align better with observed halo sizes and morphologies.

Including supernova remnant contributions enhances confinement effects.

Abstract

Observations have shown that spatially extended "TeV halos" are a common (and potentially generic) feature surrounding young and middle-aged pulsars. However, their morphology is not understood. They are larger than the "compact" region where the stellar remnant dominates the properties of the interstellar medium, but smaller than expected in models of cosmic-ray diffusion through the standard interstellar medium. Several explanations have been proposed, but all have shortcomings. Here, we revisit a class of models where the cosmic-ray gradient produced by the central source induces a streaming stability that "self-confines" the cosmic-ray population. We find that previous studies significantly underpredicted the degree of cosmic-ray confinement and show that corrected models can significantly inhibit cosmic-ray diffusion throughout the TeV halo, especially when similar contributions from the coincident supernova remnant are included.